Question details:

 What equipment is optional for an A Class boat when racing?

This question is especially relevant to the Q&A concerning whether the boat may weigh less than the certified weight (less the tolerance).



Class Rule C.4.2 states that the boat shall sail with the hull, hull appendages, ballast, mast spar and main boom spar relating to the certificate. CR C.8.3 states the mainsail shall be set when racing. C.9.2 states rc equipment, if temporarily removed,  shall be replaced by items of similar weight in the same position. C.9.3 states the owner's flag is mandatory. CR F.1 states the rig shall consist of no more than one mast, one headsail luff spar, one main boom, one headsail boom, standing rigging, running rigging, wind indicators and owner's flag. CR G.1 states the sail plan shall consist of one mainsail and, optionally, one headsail.

From the above it is clear that the mandatory equipment comprises:

  • hull
  • hull appendages
  • ballast
  • mast spar
  • main boom spar
  • rc equipment of similar weight and position
  • mainsail

And the remaining equipment is optional comprising:

  • headsail luff spar
  • headsail boom
  • standing rigging
  • running rigging
  • wind indicators
  • replacement of rc equipment of similar weight and position
  • headsail

Question details:

When an A Class boat is raced without optional equipment on board, does it comply with the class rules when its weight is below the lower limit for boat weight because optional equipment is omitted?


The full text of the discussion and conclusion, under the 2017 CR and previous CR, will be posted here as a download. For the sake of brevity the conclusion is posted here:

The CR permit several items of the rig that shall be on board for certification control to be omitted for racing. The CR do not require sails to be on board during certification control. Further the CR permit the headsail to be omitted when racing.

It follows that the weight of the boat when racing is permitted to be lighter than the certified weight less the tolerance.

It follows that the weight of the boat when racing is permitted to be heavier than the certified weight plus the tolerance if the sails used weigh 200 grams or more.

At an event for A Class after 30th June 2016

At an event for A Class after 30th June 2016 the 2016 CR apply. Section C of the 2016 CR applies to all boats so this (discussion and) conclusion applies equally to boats competing under certificates issued under previous class rules.

Question details:

Why should a different gauge used for draught restriction than for length restriction (relevant to Marblehead, RG65 and Nano class)?


Use of the length restriction gauge adapted to also restrict the draught of the Marblehead class was proposed when the draught limit was introduced in that class (late 1990s).

The conclusion at the time was that use of a combined gauge would have major disadvantages –

  • it would not restrict the draught of a boat as accurately/effectively as a transverse draught restriction gauge does
  • it would be easy to get more draught by lowering the bow and stern of the boat into the water
  • it would tend to encourage boats that were not manoeuvrable

The following notes expand on this. In the time leading up to the Marblehead rule change the major section, relative to the true waterplane, of all available M designs were placed on a single piece of paper#. There was a spot on the 'hulls' about 50 mm off the centreline that all the sections passed through with a + or - 3 mm variation. This + or – 3 mm range is a very small variation from the average value being + or - 0.5% of the overall draught figure.

The bow and stern profiles of the same designs were all plotted, relative to the true waterplane, in the same way and there was a large vertical range at the 'measurement points' created by the ledges in the length restriction gauge. A + or - 10 mm range, or more, was found.

This test indicates that, in a mature class, the transverse draught restriction gauge is approximately three times better/more effective for controlling draught than the length restriction gauge.

It was also considered how the different restriction methods could be exploited to gain additional draught.

Using the transverse draught restriction gauge

The section shape of a hull near midships could be altered to increase draught marginally. However the change that is necessary would have the following effects:

  • increased wetted surface area
  • increased form drag (due to distorted section shape)
  • decreased prismatic coefficient (or beam, or waterline length) for the same displacement

These effects were all counterproductive and would tend to discourage such changes or negate them if tried.

Using the length restriction gauge

The bow and stern profile of a hull could be altered to increase draught markedly. The change would have the following effects:

  • longer waterline length (if not already maximised)
  • increased prismatic coefficient (or decreased beam or decreased hull depth)
  • marginally increased wetted surface area for same displacement
  • decreased manoeuvrability

The first and second might be viewed as positively useful. The third of these effects was the only one that directly adversely affected straight line speed but was marginal in size. The fourth, which may not be considered as a problem, was probably the most serious negative factor.

Based on the data and brief analysis above the conclusion at the time was that the transverse draught restriction gauge would be the better choice for the following reasons:

  • It controlled draught several times better than a combined gauge
  • With a transverse gauge any exploitation of section shape could give marginally increased draught but created three disincentives and no clear benefit
  • With a combined gauge any exploitation of profile shape could give a marked increase in draught, had two potential benefits and only one negative factor which might not be recognised as such.
  • It would be unwise to use a draught restriction system that might encourage designs of boats that were not manoeuvrable.
  • Dedicated length and draught restriction gauges are smaller, easier to handle and transport than a combined gauge

For the same reasons the Marblehead system is proposed for the RG65 and NANO class rules.


Question details:

Should the 2016 software should be used when ownership of a boat first certified to the previous class rule changes?


No. Use of the software for certification under the previous class rules should be used. Change of ownership causes the certificate to become invalid but it does not cause the boat to cease to comply with the class rules.


A.12.1 A hull may be issued with a new certificate, showing dates of re-certification and initial certification as applicable:

(a) when a certificate becomes invalid upon change of ownership

by application of the new owner to the certification authority in the country where the hull is to be registered. The application shall include the old certificate and re-certification fee if required. In the case of an imported hull the certification authority shall request the measurement form(s) from the previous certification authority and a new hull registration number shall be issued,.

In this case there is no requirement to apply the procedure in A.9 (which describes how a hull is certified). Use of the software for certification under the previous class rules should be used.

Question details:

Should the 2016 software should be used when the owner of a boat first certified to the previous class rule elects to have his boat re-certified


A boat with a certificate first issued to previous versions of the class rules may have one or more alternative certificates issued using the process identified in CR A.12.1 (c).


A.12.1 A hull may be issued with a new certificate, showing dates of re-certification and initial certification as applicable:

(c) when one or more alternative certificates are requested to be valid concurrently with an existing certificate

by application of the procedure in A.9.

A.9 is the standard procedure for certification and no variation is necessary for a boat with a previous certificate.

Question details:

What is the point of the NANO class?


The advent of 3D printing fittings and other parts for rc boats raises the possibility of a class where the hulls and other parts are largely constructed by 3D printing and, probably, by the end user. Although this may well work in the existing RG65 and FOOTY classes, those class rules permit conventional moulded carbon fibre for the hull and deck structures and this confers a large weight/stiffness advantage to boats built using ‘hi tech’ methods

A new class rule devised specifically to cater for those who want to create their own boat, primarily by printing it themselves, would seem to be a logical step for the sport.

Such a class is an ideal one in which students of all ages can test their design and build skills. Perfect for craft, design and technology projects. The possibility of designing the boat on Friday and going racing on Saturday has become a reality.

Importantly the class raises the possibility of readily available low cost boats within an open class that is ideal for those starting the sport of rc sailing. You do not have to choose a one design with no freedom to experiment. 

Objectives of NANO class

  • Sailors are quite likely to be able to design and build the majority of their own boat
  • Hull and associated structural parts may only be made by 3D printing
  • No hull/boat certification process
  • No sail area measurement
  • Event measurement only
  • Draught/length ratio not so large that fin technology rules – 0.45 length maximum
  • Tightly controlled rig size and number

Provisional class rules have been launched in May 2017. It is anticipated that feedback from users may assist with refinement of the class rules, if required, to help achieve the desired objectives.

Question details:

To what extent are hollows permitted in the profile of a Marblehead hull?


The relevant rule is D.2.3 (b) (2).


(b)         Except for the trunking for hull appendages, the hull shall not have:

(2)         hollows in the plan view and/or the profile under the datum waterplane that exceed 3 mm,

The drawing shows a hollow in the profile under the datum waterplane. There is a difference between the true waterline (waterplane) and the datum waterplane referred to in the class rules. The class rules use a length restriction gauge of a specified design to determine the datum waterplane.

The drawing shows a hull with a hollow in the profile at the stern. It also shows the length restriction gauge and the datum waterplane. The hollow found when a straight edge is placed to touch the hull at A and D is greater than 3 mm. However D.2.3 (b) (2) applies to hollows under the datum waterplane. When a straight edge is placed touching the hull at B and C, the hollow is less than or equal to 3 mm. The hull, therefore, complies with D.2.3 (b) (2).

marblehead hollows in profile

Question details:

Can a sail be used on more than one boat where each boat has different parent sail areas?


Any sail can be checked against the certificate of any boat for compliance. If the sail is found compliant the measurer can mark the area of the parent sail on it. There is no limit to the number of boats that a reduced size sail can be used with, subject to it complying with the certificates of those boats.


Please see the realted Q&A

Why is the measured area of a parent sail required to be marked on smaller sails?

Question details:

Why is the measured area of a parent sail required to be marked on smaller sails?



It is useful for race committees and competitor sailors to be re-assured that reduced size sails used by a competitor comply with his boat’s certificate. Prior to 2016 the class rules required reduced size sails to ‘fit inside’ the profile of the largest (measured) sails.

Although this was an apparently simple rule it was impossible for sails genuinely made to the same measured dimensions to comply with the rule if their luff curve (or leech length) differed from the largest (measured) sail. No marks identifying any sail with any boat were required.

The 2016 class rules require each sail to comply with the boat’s certificate. This is straightforward to establish using the sail measurement system and works for sails that are of maximum size but have a different luff curve. To show that reduced size sails have been checked against a boat’s certificate and have been found to comply, the measurer is required to add the area of the parent sail to reduced size sails.


Please see the realted Q&A

Can a sail be used on more than one boat where each boat has different parent sail areas?

Question details:

Will there be a method of producing a certificate/sail measurement for the provisional class?



The sail measurement system is identical in concept to the 2016 10 Rater measurement system that has many advantages compared to the previous 10R system.

Apart from being very simple to use it produces very repeatable results and is not type forming (does not tend to encourage one partcular sail profile shape).

Currently some edits are being made to the 10R certificate/sail measurement software that will give more useful information to the measurer, certification aithority and sail maker. When these have been refined and tested the certificate will be released and the same material will be used for the provisional IRSA RG65.

Question details:

What steps were taken to consult RG65 ICA and others before release of the provisional class rules?


Log of actions over the last 15 months up to March 2017 concerning the dialog between the RG65 ICA, others and IRSA :

Dec 2015             Based on the interest of some National Members the IRSA TC develops a first rule to discuss within the Technical Committee of IRSA

Feb 2016             First contact of IRSA TC with Fredo Vollmer (RG65 ICA Chairman) by Gerd Mentges (Vice Chairman TC) and explaining the wish of IRSA to develop the RG65 class in a way that is acceptable for both IRSA and ICA. IRSA explained that this action is in no way an unfriendly act but an action which IRSA wants to make in conjunction with the RG65 ICA.

March 2016         First draft of a rule text send to Fredo Vollmer

March 2016         First draft send to the RG65 representative of USA

March 2016         First draft send to the German representative of RG65 ICA

May 2016             Discussion of the text (input from different parties, amongst others Fredo Vollmer, Earl Bobert, Graham Bantock)

June 2016            Sketches with possible faults using the current RG65 sail measurement rule send to Earl Bobert (USA)

June 2016            Survey from Fredo Vollmer send to all RG ICA countriesr recommending rejection of IRSA approach. Results in rejection of IRSA approach

June 2016            Advantages for the RG65 sailors sent to Fredo. Answer to his question concerning possible cost - there is no fee to be paid to IRSA

July 2016             IRSA did not give up the attempt of working together and sent a proposal to Fredo Vollmer for an official working group of IRSA and RG65 representatives

Sept 2016            Answer from Fredo Vollmer with some questions concerning the proposal and reply from Gerd Mentges

Oct. 2016             IRSA proposal for a personal meeting with Fredo Vollmer and ICA representatives to improve any cooperation.

Oct. 2016             Skype meeting Fredo Vollmer with Harry Drenth (RG representative for the Netherlands). Harry repeated the proposal for a meeting.

Nov 2016             Skype meeting Fredo Vollmer with Gerd Mentges. Announcement of publishing a "provisional rule” to progress the discussion and for public information.

Nov 2016             Gerd Mentges sent a DSV (German national WS and IRSA member) proposal for organization of a collaboration between a national RG community and an IRSA national member to Fredo Vollmer. 

This proposal shows opportunities of sailing together even if someone is not a member of the national organization.

Fredo Vollmer found this being a very good solution and mentions to translate it and send it to all RG national representatives.

Dec 2016             Transmission of the accompanying text to the provisional rule to Fredo Vollmer with the request to comment on it.

Jan 2017              Fredo Vollmer answers that the RG ICA has a lot of experts to take part in the proposed working group.

March 17             IRSA is still waiting for nominations of RG ICA representatives for the proposed working group.

March 17             Provisional RG65 class rule posted on IRSA website


Question details:

How large can the sail maker label be on sails? Or the manufacturer label on other items of equipment? The class rules do not restrict this?


The relevant rules are contrained in the World Sailing Advertising Code, also known as Regulation 20.

Clause 20.7.1 states that the display of manufacturer's and sailmaker's marks is permitted at all times as detailed in Table 2 but not in areas that area reserved for Event Advertising. For radio controlled boats the area reserved for Event Advertising is 40% of the hull length on each side of the hull from the foremost point on the hull. No Event Advertising is permitted on the boom(s), backstay or sails.

20.7.2 tells us a manufacturer's mark may include the name, logo or other identification marks of the designer or manufacturer of the equipment.

20.7.3 tells us that a sailmaker's mark may include the name, logo or other identification marks of a sailmaker or of the sail cloth manufacturer or the pattern or model of the sail.

Table 2 – Manufacturer’s and Sailmaker’s Marks

Radio-controlled boat

Hull  - On each side of the hull, and may include the name or mark of the designer or builder - One mark to fit within a rectangle measuring 15% of hull length x 150mm                     

Spars and Equipment - On each side of spars and on each side of other equipment - One mark not exceeding 50mm length                    

Sails - On each side of sails and kites - One mark to fit within a 50mm diameter circle






Question details:

How does A Class rule G.3.2 (e) work where there are no batten pockets or battens?



G.3.2 (e) requires the batten pocket point to be found.

The batten pocket point is defined in the class rules as

"the intersection of the extended centreline of the batten pocket, or batten if there is no batten pocket, and the leech."

This case is much the same as a missing limit mark on the mast. If there is no batten pocket or batten the point cannot be found and the measurement cannot be taken. The official measurer should decline to sign the measurement forms (signing would indicate he had completed the task satisfactorily) or report that the measurement of the mainsail is incomplete on the measurement form and the certification authority will refuse to issue a certificate.

In practice the owner should be asked to add something that resembles a batten pocket (tape) or a batten (self adhesive glass sheet) in an appropriate place and the measurement (and in G.3.3) can be taken successfully.

Question details:

Template to assist measurement of Marblehead sails and rigs


Daniel Kohler (FRA) was seen using this simple but useful template at the 2016 Marblehead Championship in France. The design is by Michel Brun (do you have a CAD file please, Michel, that we can add as a download?).

It seemed to be laser cut or CNC cut from aluminium alloy. The dimensions of the cuts outs etc are used as follows:

900 mm radius - control of upper and lower regions of leech

105 mm - maximum batten length

40 mm - top width of pocket luff mainsails, mast spar cross section below lower point, combined boom spar cross section where two boom spars are joined, boom spar cross section within 100 mm of one end

25 mm - top width of mainsail that has a luff rope

20 mm - mast spar cross section above lower point, headboard width and top width for mainsail

13 mm - minimum bumper length

3 mm - minimum limit mark width

PLEASE NOTE - The 40 x 40 and 20 x 20 cut outs DO NOT imply that the mast and/or boom may be square sections in those regions. The class rules make it clear that the limit is on any cross section - a 40 mm diameter or 20 mm diameter are effectively the maximum sections permitted.  

M Measurement Jig    P1040043s

Question details:

Is there a size limit for primary and/or secondary reinforcement on Marblehead Class sails? Is the material used for primary and/or secondary reinforcement restricted in any way?


Primary or secondary reinforcement used on Marblehead Class sails is un-restricted in size.

Class Rule G.2.5 (a) requires sails to be soft sails.

ERS G.1.4 (c) defines a soft sail as one where the body of the sail is capable of being folded flat in any direction without damaging the ply other than by creasing.

ERS G.1.4 (a) tells us the body of the sail is the sail excluding areas where parts are added e.g. (ERS G.1.1) sail reinforcements.

Therefore sail reinforcements do not have to comply with the soft sail test.

ERS G.6.1 tells us that primary reinforcement is an unrestricted number of additional layers of ply of permitted material and that secondary reinforcement is not more than two layers of ply of permitted material not thicker than the body of the sail. As there are no restrictions on size the maker is free to use any reinforcement that complies with the restriction on primary reinforcement.

The only requirement is that reinforcement consists of ply of permitted material (there are no restrictions so any material is permitted subject to it being a ply).

ERS G.1.4 (b) defines a ply as a sheet of sail material (which may be made up of a number of layers).

Provided the reinforcement is made up of sail material it is compliant with the Marblehead class rules.




Question details:

Is it permitted to use deck spreaders?

These are sometimes referred to as outriggers and can be seen on IMOCA 60 Class boats. The inboard end is close to or on the deck and they have standing rigging going down from the outboard end to the hull and standing rigging going up to support the mast.


A deck spreader is defined in the ERS F1.4 (c)(iii) as a hull spar extending transversely to attach standing rigging. A hull spar is defined in ERS F.1.4 (c) as a spar attached to the hull. The spars permitted on a Marblehead rig are limited to one mast spar, one headsail luff spar and four boom spars.

A deck spreader is not permitted.

If the spreader is attached only to the mast, and not to the deck, then it no longer falls within the definition of a deck spreader. Instead it is a spreader defined in ERS F.1.5 as equipment used to brace a spar, attached at one end to the spar and the other end to rigging and working in compression when in use. It is effectively the same as any other spreader, normally placed higher up the mast.

A spreader, if not attached to the hull, is permitted.

Question details:

What does a race committee do when a boat has sail marks that are not clearly legible or compliant with the RRS?


A little history first - going back a couple of decades the sail identification marks rules were in the class rules and measurers were required to check that marks complied with those rules. In principle this ensured boats had compliant sail identification marks. But in practice, for various reasons, a proportion of boats had marks that did not comply.

Race committees and juries tended to avoid pressing the issue - it was a measurement issue not a racing rules issue and, therefore, not their problem. Taking the sail marks (except for the insignia) out of the class rules solved several problems - most importantly, compliance with the sail marks rules was a racing rules issue and was clearly something the race committee and jury had full and sole responsibility and authority for dealing with. Other problems solved were harmonisation across the classes, the possibility of sail certification (measurement) without application of the numbers and letters, a saving of measurer time when certifying (measuring) sails, and the freedom for the owner to change the sail numbers without having to engage the measurer (something that was rarely done anyway).

A boat that has marks that are not clearly legible infringes RRS App G1.1. There are several other ways that marks may fail to comply with this rule and App E - please see the Q&A under Sail Identification for some examples. In either case the race committee may be affected because it may have difficulty identifying the boat in question during a recall or when finishing. Competitors, umpires and judges may be affected when attempting to protest the boat. This is a fairness issue and, therefore, one which an international jury can be asked to advise on by the race committee (see App N2.1).

In the first instance the race committee, or an equipment inspector or technical committee at a major event, should advise the sailor that his sail marks do not comply with the RRS and that the boat will be protested if it races without suitable amendment to the marks. Hopefully he will respond appropriately. Provision of a black marker pen may help him comply. Provision of acetone to remove inked marks may also be useful. With average care self adhesive numbers can be removed without damaging sails and no are excuse for non-compliance.

If the sailor fails to respond in an appropriate way the race committee or technical committee can (and should) proceed as soon as the boat races as it would for any other breach of the RRS by making a protest against the boat under RRS 60.2/60.4.

When a protest committee finds that a boat has sail identification marks that are not compliant it shall either warn her and give her time to comply or penalise her. See App G4. As the penalty is not prescribed by the RRS it is one that is discretionary i.e. it can be scaled to suit the specific case. International juries will be familiar with the Discretionary Penalties guide - there is one in preparation for RC sailing.











Question details:

Are the sail marks shown below compliant with the RRS as modified by Appendix E?


RRS Appendix E8 G1.4 (a) requires national letters to be in 'capital letters'. The 'K' in this set of letters does not look like a capital letter in the same type face as the 'U' and 'R' so these do not comply.



RRS Appendix E8 G1.4 (a) requires marks to be of the 'same colour'. It also requires them to be 'clearly legible'. These numbers are formed by infilling a black outline with green so they do not comply with the requirement to be of the same colour. They may also fail on legibility because the green is not as opaque/dark as other colours.



This set of national letters fail to comply for the same reason.



RRS Appendix E8 G1.4 (a) requires marks to be 'clearly legible'. Where the body of the sail is a mix of materials of different colours there can be problems choosing a colour for the sail marks that will meet the 'clearly legible' requirement.

Here the owner has used white marks instead of black. Are they 'clearly legible'? Would black sail marks be more 'clearly legible'? If the appointed equipment inspector at an event reports this to the race committee they shall bring a protest against the boat which the jury will decide on. 



RRS Appendix E8 G1.4 (a) requires marks to be 'clearly legible'. The race committee at the world championships in Lake Garda, 2016, complained about marks that had strokes that were relatively thin because they were not very legible at a distance.

The same or better legibility than Helveitica is acceptable. Assuming the standard (not bold, narrow or condensed) font is meant by this the ratio of stroke thickness to height for Helvetica is between 12 and 14% of the height. The example below looks less than this and is likely to be less 'clearly legible'.

P1030960        22


This set of national letters probably fail to comply for the same reason. The gaps created by the use of a stencil do not help.



The vertical spacing of marks is controlled by RRS Appendix E8 G1.5 (a). Where there is sufficient space available on the sail this is currently a minimum of 60 mm.

The example here does not meet that requirement.



The height of marks is controlled by RRS Appendix E8 G1.4 (b) which specifies the height of numbers to be 100 mm mimimum and 110 mm maximum. The variation in these is greater than the permitted variation.

The spacing of marks is controlled by RRS Appendix E8 G1.5 (b) which specifies the spacing of numbers to be 20 mm mimum and 30 mm maximum. The spacing in these is less than 20 mm.



Question details:

How might a rc foiling class take off?


There are not many such boats around so, even if they did all meet the criteria suggested for an international class, it seems unlikely that fleets large enough for a meaningful race would exist for a while. However, if the boats met the suggested criteria a comparison of speed, perhaps around an agreed size and format of course, becomes a useful comparison of achievement level.

A 'speed week-end' where boats gather and are timed around a course might be an interesting starting point too.

Question details:

Class rules for an international foiling class? What may be useful restrictions in a class rule for a foiling class that might become an international class? 


There seems to be some interest in creating foiling multihulls for rc sailing. It may be useful for those developing such boats to be contrained by some restrictions so that the boats may fit within a 'class'. Comparisons of performance, whether measured by speed, foiling ability, manoeuvrability or some other criterion, then become meaningful. For this reason, and to assist those who are experimenting with such boats to move more quickly towards an international class should they wish to form one, a sub-committee of the IRSA TC led by Ian Holt has considered what restrictions might apply.

They can be summarised as:

  • The Mini40, MultiOne classes may be suitable starting points
  • Alternatively a 1 metre x 1 metre box may be a suitable restriction for the hull(s)
  • Foils should be permitted to extend outboard of the hulls but that restriction should be limited to a modest figure, say 100 mm
  • Automation of control should be permittted
  • The type of course might be prescribed in the class rules
  • Rig height should be restricted
  • Measurement of sail area may be unnecessary *
  • A minimum weight (without rig) might be useful **
  • A maximum draft of not more than 700 mm ***

 To expand a little on these:

The speed of a foiling boat can be high and is not linked to length as in monohull keelboats. A small hull size helps with transportability and construction.

It has been found easier to add foils to the outside of hulls but their extension should be restricted so that RRS 11 can be complied with easily.

On board computing that imparts a degree of autonomous control (height, pitch etc) much like that given to a drone, and for sail/rig control, would make sailing the boats easier.

Windward ability may be limited and class rules that prescribe a short beat and long reaches may be preferred to the traditional rc sailing course.

All the other international rc sailing classes now restrict the maximum rig height/mainsail luff length in some way - this is useful as it keeps rigs small enough to fit into a modest size car and permits them to be transported economically by plane. A minimum rig height (no smaller than for an IOM) would ensure no problem with placement of RRS App E size sail marks. It also sets a virtual upper limit to wind speed used for racing and a clear boundary so sailors can be properly prepared for the 'worst' conditions they will need to cope with.

*   Ian Holt noted that sail area was not really an important speed limiting factor except a very low wind speeds.

**   I suggest a minimum weight (sailing condition less rig) might serve to constrain how hi-tech construction methods need become in the longer term in order to keep the class open to those whose building techniques are not of the highest levels. An important factor if the class is to be open to many.

*** IRSA regulations precribe that a class may choose a maximum draught of not more than 700 mm. This is so that a race committee can ensure sufficient water depth for all boats over the course area for their event.


Question details:

How is the area of the mast measured when the mast passes the deck at two points? This is relevant where the mast is supported in a mast gate, usually above the gooseneck and main boom, and the gooseneck andkicking strap is below the level of the foredeck.


Class rule J.2 Measured Rig Area states:

"The measured rig area is the sum of the area of the components of the largest rig excluding (certain stated parts)."

The mast below the mast gate (the upper deck level) and above deck level is not one of the excluded parts so its area shall be included in the Measured Rig Area. Where the mast crosses the deck more than once the area is measured to the lowest point where the mast crosses the deck.

Section K.4 is referenced as the method for measuring the mast area and the diagram L.1 shows the lowest spar cross width, m0, taken at deck level.

No rules restrict the shape of the deck in the vicinity of the mast. It is for the owner to specify where the mast deck level shall be taken. If the measurer disagrees with the choice of that point he shall report his opinion in the comment box provided on the measurement form. The Certification Authority shall not issue a certificate and may ask for an interpretation on the specific case.

 j2 figure

Question details:

Is the area of a fitting that has a faired section included in the measured rig area?


CR J.1(c)  states:

Fittings faired into a spar and/or bigger than reasonably required for their purpose shall be considered to be part of the spar.

The class rule requires that a fitting that is faired into the spar (or bigger than reasonably required) shall be taken as part of the spar. The requirement is not met by a fitting that has a faired section. If the fitting is not faired into the adjacent spar then it is not faired in regardless of whether its section is a faired shape or not.

Builders and measurers should be aware that if a fitting is faired into the spar any hollows created in the profile of the spar are to be bridged for the purpose of measurement. CR K.4.2 (h) refers. The additional measured rig area may be far larger than the profile area of the fitting.

Question details:

Are rotating mast fittings included in the measured rig area? For example, mainsail head attachment fitting, backstay crane, shroud attachments,


Mast fittings attached to the mast spar are component of the rig but are not spars according to the ERS definition F.1.1. They are not rigging, spreaders or corrector weights so the conclusion is that they are fittings. Whether they rotate or not with respect to the mast spar, providing fittings are not larger than necessary and are not faired into a spar (CR J.1 (b) ) there is no requirement to include their area in the measured rig area.

IMAG3621s     IMAG3622s


Question details:

Is the area of a mast stub (and any gooseneck mounted on it) included in the measured rig area?


A combined stub mast item and gooseneck that supports the mast spar is a component of the rig but it is not a spar according to the ERS definition F.1.1. It is not rigging, spreaders or corrector weights so the conclusion is that the mast stub and the gooseneck are fittings. Providing fittings are not larger than necessary and are not faired into a spar (CR J.1 (b) ) there is no requirement to include their area in the measured rig area.


Question details:

Does the Certification Authority have to use an official stamp in the relevant place when issuing a certificate?


There is no prescribed requirement for the size or style of ‘official stamp’. At an event the person inspecting the official stamp on a certificate has no means of knowing if it is the correct one or not. The important thing is that the issuing Certification Authority will recognise it at some future stage should the certificate be referred back to it for any reason.

Any size or style of official stamp will suffice providing the CA is happy that it can recognise it as authentic at a later stage.

Question details:

What has happened to the previous interpretations? There were many interpretations to the previous versions of the Marblehead, Ten Rater and A Class Rules. Where are they now?


IRSA regulations restrict the life of an interpetation to two years - after that time any interpretation ceases to be valid. The reason for this is that it is expected that the class rules will be changed during the two year period to make the interpretation unnecessary.

Where the new class rules require equipment to comply with the current class rules, if the class rules incorporate the effect of the earlier interpretation(s), then clearly the intrerpretation(s) is no longer needed. This explains why some interpetations are no longer needed and have been removed.

Where the new class rules permit equipment to comply with earlier versions of the class rules (usually known as 'grandfathering') then the earlier interpretation, although expired, remains relevant and is retained for information. A few such interpretations are retained.

Many other interpretations that were issued in the period before 2014 have been revised and are presented here in the form of Q&As (see Q&A on the difference between an interpretation and a Q&A). Again, this explains why many earlier interpetations are no longer needed and have been removed.

Question details:

Can the aft QBL measurement points be on the transom?


1994 Class Rule

The 1994 A CR 3.2.4. states that "QUARTER BEAM MEASUREMENT POINTS are located on the surface of the hull one tenth of the waterline beam above the waterline and one quarter of the waterline beam from the centreline". The question is whether the transom is a part of the hull? Transom is a part of the hull according to the Equipment Rules of Sailing. Before the transom was included in the ERS definition of hull there was an interpretation in the Ten Rater Class that concluded the transom was part of the hull. There is, therefore, no reason to think that the definition of the hull in the Equipment Rules of Sailing, although not applicable for the 1994 A CR, should be unfamiliar to the average measurer/ builder/designer.

Quarter Beam Measurement Points may be located on the transom in accordance with requirements of A CR 3.2.4. Attention is drawn to the requirements of A CR 3.3.3 – the restriction on hollows in the surface of the hull apply equally to the transom.

2016 Class Rule

The QBL measurement points are required to be on the external surface of the hull shell (CR H.5.9). In ERS D.1.1 the hull is defined as 'The shell including the transom,.....'.

Question details:

Under the 2002 CR was it permitted to use a 'square' boom spar cross section 20 mm wide x 20 mm deep?


The 2002 CR restricted the boom spar cross section to 20 mm. The ERS definitions referred to vertical boom spar cross section and transverse boom spar cross section which led to the unfounded belief that the Marblehead boom spars were restricted in a vertical sense and a transverse sense thus permitting 20 mm 'square' section boom spars. As the term boom spar cross section was not itself defined in the ERS - the class rules effectively permitted a maximum boom spar cross section equal to a 20 mm diameter circle. A square section could be used but would have a maximum side of 14.1 mm.

The 2016 CR revert to the term 'cross section' and a diagram indicates how the limit is applied.

Boats in the class shall have rigs that comply with the 2016 CR even if initially certified before the 2016 CR came into effect.


In other words, do you have a particular skill or experience that can help with the operation of the IRSA?

The IRSA is an association that serves over 30 National Organisations that maintain and promote Radio Controlled Sailing in their countries. Through these national bodies, the IRSA also serves the RC community as a whole, particularly being focused on the Internationally Recognised classes (10R, Marblehead, A-Class and IOM) and assisting emerging international classes. IOM sailors are served by their own international class association (ICA) called IOMICA, which is affiliated to the IRSA under a contract.

So you want to help?

There are many different aspects of the IRSA work that needs keen, skilled and enthusiastic people.

  1. Treasury and finance. 
  2. Interpretation and changes to the Racing Rules of Sailing. 
  3. Supporting the logistics of running World and Continental events
  4. Interpretation and changes to the class rules and measurement procedures.
  5. Development of international classes for those classes that are spread across the globe and can be indentified as being truely international.
  6. Organisation of the IRSA structure, in terms of ongoing analysis of the constitution and the various rules and regulations that direct the operations.
  7. And, there are other ongoing and sporadic needs.

Speaking of the Executive, the IRSA is divided into distinct working groups.

  1. The Executive Committee. This group are nominated and elected by the national bodies and IOMICA every two years. Each has their own job, so to speak, and often come together to discuss and sometimes vote on matters on the Executive Forum.
  2. The Committees. These assist in the development of various rules, interpretations and advice as matters turn up. They are invaluable to help the committee chairmen (who sit on the Executive) to bring quality and well thought through matters to the Executive for ratification or revision.

So where could a keen volunteer fit in?

If you wish to be part of the Executive, you will have to wait until the next General Assembly in April 2018. Apply to your national organisation to be nominated to the position you feel you can bring some solid expertise to.

If you wish to be part of a committee in the areas outlined in 1-6 above, and feel you have the experience and background to bring quality advice to these committees, then please don’t hesitate.... apply to your national body to be nominated. ​

The nomination does not mean you will automatically be involved. The nomination will be reviewed by the Committee Chairman and then the Executive and you will be required to supply information like sailing background and experience in the area you are applying for. There is no limit to the number of committee members, but you are required to be very proactive when the need arrives.

Please note.

IRSA does not take nominations directly from individuals, only the member national bodies. So all applications need to be forwarded through the national member of your country. Also, there is a limit of two volunteers per committee per country.

Looking forward to you joining a dedicated group wanting to put back into this beautiful sport and continue the considerable momentum already built up.  

Question details:

How are sails checked at an event (equipment inspection) for compliance with the certificate.



At an event the equipment inspector (measurer) checks a sail by placing it on the measurement grid with the head point and tack point on the vertical grid line. The clew point is placed on the datum grid line.

The following dimensions are then compared with the certificate values:

  • luff perpendicular
  • cross widths at 200 mm intervals up the sail
  • height of the sail above the uppermost grid line that the sail cuts
  • heights from the datum grid line to the sail foot

This process is described in detail in CR Section K. Sails with values that are the same or less than on the certificate are compliant.

If the sail is a reduced height sail it is likely that it will not have heights from the datum grid line to the sail foot that are compliant with this procedure. However Section C contains rules that apply at and event and Section C.8.1 (b) tells us that sails may be moved vertically when carrying out equipment inspection.



An event can be run using "single certificates"

If it is considered desirable at a particular event to ensure a sailor cannot choose the best configuration to suit the prevailing conditions, the event organiser can issue a Notice of Race, and a Sailing Instruction, requiring a certificate to be lodged at some prescribed time ahead of the event and to use the boat in that configuation. This also prevents owners of multiple boats from choosing which boat to use at the time of the race.



Starting in around February 2015, class rule changes were introduced and discussed within the IRSA Technical Committee. The proposed rule changes were circulated to IRSA Designated National Members (DNMs) around December 2015 and January 2016. A number of DNMs responded with comments, and these were addressed by the TC Chairman. The proposed revised class rules were then brought to the Executive Committee by the TC Chairman in March 2016, which the EC formally voted on and approved. The rules, and an explanation of the changes, were published in April 2016, and came into effect in July 2016 after minor errors were found and edits made. This is the process which has been used in the previous decades of rule changes by the IMYRU, ISAF-RSD, and now IRSA.  


It is inevitable that a new set of class rules may have a rule which is thought to be in error or in need of amendment. Suggest a rule change to your DNM. If it agrees, or if you are the DNM, send it to the TC Chairman for further discussion. Please read carefully our regulations and Q&A to avoid unnecessary work before you send any suggestions to the TC. Proposals for rule changes should be based on meaningful technical evidence and not on loud repetitions.  


IRSA would like to see the RG65 class form a class committee within the IRSA structure. Although currently organised on a regional structure of representation, IRSA is in the process of re-structuring into a class based organisation. When any class committee becames self-sufficient, IRSA policy is that it should split off to become an independent ICA in the same way as IOMICA. 


That pathway would be: 

  • Use the revised class rules 
  • Achieve sufficient registered boats in sufficient countries and continents 
  • Apply to IRSA for International Status 
  • Apply to hold a world championship. 


Of course, but it may take longer to arrive at a result that is satisfactory to IRSA. 


The draught limit is to ensure all boats at an event can be guaranteed to be able to sail. From an IRSA point of view it is imperative that the race committee of an IRSA event does not find itself embarrassed because some competitors with class rule compliant boats cannot compete.  


Briefly: 

  • The class rules would be written in the WS SCR format using terms defined in the ERS. 
  • The sail measurement system would be specified 
  • Ballast materials denser than lead would be prohibited 
  • A draught limit would be introduced 
  • Sail marks rules would be rationalised with those in Appendix E of the RRS 
  • The rules for racing will be specified as the RRS. 
  • Changing the fin/ballast unit after each day’s racing could either be facilitated by the class rules or, alternatively, prohibited. 
  • Measurement and certification of boats would be by independent official measurers 
  • Each national association would keep a register of officially certified boats


An issue that would prevent the RG65 achieving international status is the tradition that the boats are measured by the owners with no independent checking. A complicating factor here is a lack of a prescribed system for measuring sail area.

Another tradition in the class, that of being able to replace the fin/ballast unit after each day’s racing, is not permitted either by the current class rules or the Racing Rules of Sailing.

The current lack of restriction on the material used for the ballast means that Tungsten (also known as Wolfram) and other exotic high density materials are permitted. The unwelcome cost implications of this in the long term are clear.

The concept of having only three rigs in the class is a sound principle that works well in the IOM class. Whereas the IOM class has several safeguards to keep cost down (no exotic materials in the hull, minimum hull weight, wood or aluminium spars only, one design sails) there are no such restrictions in the RG65 class and construction costs are higher than they would be otherwise. It is probably too late to introduce some of these concepts into the RG65 class – as “the horse has already bolted”. But there are some things that can easily be achieved that will help keep the class popular in the long term and restrict escalation of costs. 


Class rules written using the WS SCR format ensure that as far as possible the language used and the measurement methods employed by the class rules are harmonised across the classes. Designers, builders, sail makers and measurers can then be confident of having a common understanding of class rules.

Commonly used words like ‘boat’, ‘hull’, ‘hull appendage’ and a vast number of other similar boat part names are all very precisely defined in the Equipment Rules of Sailing (ERS) which is a stand-alone document available as a download from the WS and IRSA websites. 


To gain international class status some straightforward, but important, standards have to be achieved. 

  • The class has to have a certain number of boats across a certain number of continents and countries. 
  • The class rules have to be written to a common standard, the WS Standard Class Rules (SCR) format.

Whereas the numerical requirements are met, it is clear the requirement for WS SCR format class rules is not.


The class appeals to a large number of builders because they can exploit exotic construction methods without the problems associated with larger scale building projects. Construction can be as convenient as on a kitchen table. Sail making can be accomplished in a relatively small space. The class is a ‘development’ or ‘open’ class so builders have freedom to improve performance that is deliberately blocked in ‘one design’ or ‘closed’ classes.

The boat with all its rigs will comfortably fit into a well designed pack not much bigger than a box used to transport an IOM hull. The prospect of travelling by public transport, as well as by plane without having to pay for excess baggage, is a realistic one. The restriction on the number of rigs serves to restrict cost and complexity, and the boats can be sailed in a space as small as an Olympic swimming pool. A well set up RG65 performs remarkably well, so it is easy to see why the class is popular.

It is consistent with IRSA’s constitutional object to develop the sport of rc sailing throughout the world to lend support to any class that is popular internationally.

Given the opportunity to hold world championships the class would inevitably attract greater numbers of participants and the level of competition in the class would increase enormously. It is essential that robust class rules are in place before that happens so that continued participation in the class does not become prohibitively expensive.  

Wtih well designed and managed class rules there is no reason why the class cannot become an international class and hold a world championship in the near future leading to even greater numbers being attarcted to the class - for this reason IRSA is interested in the class. 


Not as it exists at present.

Some time back WS delegated responsibility for the international administration of radio sailing to IRSA and it is through this affiliation that IRSA is able to grant the right to run WORLD championships in the rc international classes. WS protects the right to call a sailing event a world championship – claiming an event is one when it is not sanctioned by WS or IRSA is a breach of the WS rules and can result in competitors being excluded from legitimate sailing events.

IRSA is the international class association for the Marblehead, Ten Rater and A Classes. The International One Metre has its own independent international class association, IOMICA, that is responsible for the administration of the IOM class and which is affiliated to IRSA. All these international classes hold world championships from time to time and the events are run under the guidance of IRSA’s & IOMICA’s regulations using the well known Appendix E of the Racing Rules of Sailing (RRS).

In order that the RG65 class may hold any event titled ‘world championship’ it has to have international class status given by IRSA.

Question details:

Under what rules are sails certified for a 10R certified before 1st July 2016?

If a boat certified prior to 1st July 2016 has new sails, which rules apply for the certification of those sails?


Section C 8.1 (c) of the class rules tells us that for hulls and sails certified before 1st July 2016 the profile of each alternative sail shall fit within the profile of the sails recorded on the certificate. These class rules continue to apply to a hull and sails certified before 1st July 2016.

New sails fall under Section G 1.1 which tells us that sails shall comply with the class rules relating to the certificate, or with the 2016 class rules. For a hull certified before 1st July 2016 the previous class rules continue to apply.


Question details:

Use of boats with certificates issued by sources other than IRSA affiliated bodies?

Is it possible to enter an event described in the NoR and SIs as for boats of an international class (IOM,. M, 10R or A Class) with a certificate other than an IRSA certificate issued by a body affiliated to IRSA?



The IRSA international classes are distinct from classes using the same name but which are not administered (ultimately) by IRSA. For example the Naviga administered One Metre, Marblehead and Ten Rater classes are different classes and the certificates issued under those rules are not valid for IRSA events (world or continental championships) or events normally organised by IRSA affiliated bodies. The same is true for the Marblehead class administered by the American Model Yachting Association which uses class rules different to the international class rules.

The owner of a boat in one of those classes can obtain a certificate for the international class after having his boat measured to the IRSA class rule. To do this he should find an official measurer (please see the Equipment Rules of Sailing) and then contact his certification authority (normally the body in his country that administer rc sailing and is affiliated to IRSA). If he is a member of a body affiliated to his World Sailing Member National Authority (the body responsible for the administration of SAILING in his country) he will then be eligible to take part in events for the international class.

Question details:

A Ten Rater has its largest sails measured for the purpose of establishing its rating. Those sail sizes are entered on the measurement form and are recorded on the certificate. The same is true for an A Class boat and for a Marblehead (usually the largest of A rig, of B rig and of C rig). Is it necessary to have smaller sails measured and certified?



The smaller sails are measured to ensure they are indeed smaller and that they meet the other requirements and restrictions. Then they are certified (usually by the measurer signing the sails) to show that this porocess has bene completed satisfactorily.

Question details:

Does an alternative sail have to fit within the profile of the 'largest' measured sail?

The 2002 class rules C.8.1 Limitations stated: "The profile of each alternative sail shall fall within the profile of the sails recorded on the certificate."

Is this no longer a requirement in the 2016 class rules?




Diff Profilesgb1No. Under the 2002 class rules it is required that 'alternative' sails shall fall within the profile of the sails recorded on the certificate. The 2016 class rules do not require this.

Sail makers will be aware that sails are 3D objects and small changes to the inbuilt shape at the seams will have an effect on the profile of the sail. Although apparently simple in its requirements, the 2002 class rule creates several problems. Unless the sailmaker knows the leech length of a sail he is replacing he is unable to make a sail of the same profile (even if it is a purely 2D object). Even 1 mm more, or 1 mm less, leech length or luff curve results in the profile of the replacement sail not matching the original. It is not smart to have a class rule that does not allow the owner to replace his equipment and easily meet the class rules. Further, unless the sails measured and recorded on the certificate are retained by the owner when he has replacement sails they, and the other 'alternative' sails cannot be checked according to the class rules.

The 2016 class rules no longer require alternative sails to fall within the profile of the sails recorded on the certificate but treat the issue in a slightly different way that solves the problems mentioned above and gives other benefits. How?

The way in which the 'largest' sail is placed on the measurement grid has been revised marginally - the head and tack are placed on a line perpendicular to the transverse grid lines with the clew placed on a grid line. At and above the clew the cross widths are taken as usual (but at 200 mm intervals instead). Below the clew the depths are taken at 50 mm intervals. The dimensions are recorded on the certificate.

'Alternative' sails are checked by placing them on the grid in the same way and checking that their dimensions (measured in the same way) are equal to or less than the certificate dimensions.

There is no requirement for these 'alternative' sails to fall within the profile of the 'largest'. This introduces freedom to have sails made with different luff curves (or fullness/camber for example) but which comply with the certificate. Any width added at the luff needs to be removed at the leech. Provided the cross widths measured at all grid lines remain less than or equal to the certifiate values, the sail complies. See the diagram above.

The sail maker has all the information he needs to make sails that comply with the class rules as extended by the boat's certificate without asking for more. At equipment inspection there need be no difficulty in establishing a sail's compliance under the 2016 class rules.

This freedom exists for boats with certificates to the 2016 class rules only. Boats measured to the 2002 class rules and any new sails made for them shall continue to comply with those class rules. 



Question details:

At what point, on change of ownership, does the certificate become invalid?


The certificate becomes invalid upon a change of ownership. The change of ownership is the important criterion – not the signing of the certificate by the new owner – not the issue of the new certificate in the new owner’s name.

However, while the concept of ownership is normally well understood between any two people it may be that the law of the land becomes relevant in particular cases and this may vary depending on the contract involved and where the ‘transaction’ takes place.

The view is that IRSA class rules are not intended to, nor do they, shed any light on ownership or when it changes hands.

Question details:

When the foot of a double luff sail falls below the lower limit mark, does it comply with the class rules?


The class rules (Marblehead and A Class) require that the tack point shall not be set below the upper edge of the lower limit mark. The tack point is normally aft of the mast spar but on a double luff sail (specifically a pocket luff sail) it may be forward of the mast spar. In this case it may be that the foot of the sail overlaps the lower limit mark (as shown on the diagram). There is no requirement in either class rule that the foot of the sail shall be above the lower limit mark.

A sail set as shown in the diagram complies with the class rules.

tack point_and_lower_limit_mark

Question details:

What is the difference between a Q&A and a Class Rules Interpretation?


An interpretation is requested when it is not clear (to a designer, builder, measurer, class association or certification authority) how a class rule shall be interpreted. When an interpretation is issued it should be kept in mind that the interpretation is valid until the class rules are changed or for two years maximum only. The purpose of this last rule is that two years gives sufficient time to consider if the effect of the interpretation is a) desirable or b) undesirable. Depending on the decision or choice (a or b, by the IRSA TC or the class depending on whether there is an independent class organisation or not) the class rules can be revised accordingly.

Thus, when drafting any interpretation, it should be kept in mind how the class rules should/could be revised to make the original interpretation request redundant.

It follows that, if no revised class rule can be written, there is no need to issue an interpretation. Where no interpretation is required, but only an explanation of the effect of the class rules, it follows that it would be appropriate to deal with the original request by issuing a Q&A to be published on the IRSA website and elsewhere as appropriate.

This is the guiding principle used by the IRSA Technical Committee when considering any question about the class rules whether it is a formal request for an interpretation or not.



The ERS is a document maintained by the ISAF which is a revised on the same 4 year cycle as the Racing Rules of Sailing. The current version may be found on the ISAF website and there are several versions in translation listed there too.

Question details:

Section C of the class rules requires the hull registration number to be displayed legibly on the external surface of the hull with a minimum height of 20 mm.

Section D of the class rules requires the hull registration number to be permanently marked on a non-removable part of the hull surface.

Can a single set of hull registration numbers satisfy both rules?


Yes. Providing the hull registration number digits are of minimum height 20 mm, are clearly legible, are easily visible, are painted, engraved, bonded in or moulded in, and are on a non-removable part of the hull then both rules are satisfied by a single set of numbers.

However, it is often more convenient and attractive to use vinyl numbers on the deck to satisfy the Section C rule and some more convenient method on an inside area to satisfy the Section D rule.

Bear in mind the purpose of the rules: the Section C rule is for the benefit of the race committee and other competiors at an event to help identify a boat when it does not have it's rig in place; the Section D rule is to permanently and uniquely identify a boat so that it may be grandfathered, if needed, at a later date. In 50+ year's time the number will also add value and interest to any boat that has survived that long.

Question details:

Why are boat weights and lengths not required to be checked at certification control (measurement)?


It used to be normal for class rules to require all equipment to be checked for compliance with the class rules. It was also normal for the certificate or class rules to state that alterations would invalidate the certificate. Yet it was commonplace for owners to make alterations to their boat/equipment without returning to the measurer to have it re-checked. This made it tedious for scrupulous owners to enjoy the freedom to develop their boats in the same way that less scrupulous owners did.

Clearly, when a boat competes at an event it is important that it complies with the class rules in all aspects. However at certification control (measurement) it makes no sense to check the overall length or draught of a boat because those dimensions necessarily depend on the weight of the boat and its flotation which are in turn affected by the weight and placement of removable items (rudder, fin, ballast, rc equipment). By removing those checks from certification control a tank and accurate scales are not required before a certificate can be issued. Only at an event when those items are in place need, and can, those dimensions be checked. If a tank and accurate scales are available at certification control measurers are encouraged to monitor those checks if owners wish. But owners need to be made aware of their continuing responsibilities after the certificate has been issued.

The freedom granted to the owners to alter equipment is balanced by their responsibility to ensure that their boat complies with the class rules when competing at an event. It follows that equipment inspection at an event (always difficult when flotation has to be checked) is the only way to monitor correct compliance with the class rules. At an event a tank can be used to check all the boats, far more efficient than at each boat's certification control. 

Should a boat be found not to comply with the weight and dimensional limits the responsibility lies clearly and solely with the owner for failing to ensure compliance. Altering the boat and failing to take steps to ensure continued compliance with the class rules might be taken as a breach of RRS 69 by a jury.


Question details:

Why is the waterline length not required to be checked at certification control (measurement)?


Prior to the 1994 version of the class rules it was required to determine the waterline endings, measure the length between them and use that figure to determine the rating. The waterline endings were not marked with limit marks and no data was recorded that might determine those points. According to the certificate any alterations to the boat that affected the rating would invalidate the certificate.

However it was commonplace for owners to alter the fittings, mast position, spars, sails, on board rc equipment etc and not repeat the measurement process. Note that even a weight reduction would alter the rating thus rendering the certificate invalid.

In 1994 the requirement to add limit marks was introduced and it became permitted for the first time to alter the boat without the certificate becoming invalid. 

The purposes of this change:

  • to permit owners to freely modify their boats (which they did anyway) but for the first time within the class rules
  • with suitable equipment the measurer (certification measurer or equipment inspector at an event) can easily dry measure between the marks to establish the rated waterline length
  • with a tank, or any piece of calm water, the owner/measurer/sailor can float the boat and establish that the waterline endings are inside the limit marks without the need to precisely determine the waterline ending positions
  • there is the possibility that other sailors can judge whether a boat is floating to its marks or not

The new freedom granted to the owners was balanced by their new responsibility to ensure that their boat complies with the class rules and certificate when competing at an event. It follows that equipment inspection at an event (always difficult when flotation has to be checked) is the only way to monitor correct compliance with the class rules. But there is nothing new about this - it has always been so.

Should a boat be found to float with the waterline endings beyond the limit marks at an event the responsibility lies clearly and solely with the owner for failing to ensure it floats correctly. Altering the boat and failing to take steps to ensure continued compliance with the class rules might be taken as a breach of RRS 69 by a jury.

The 2016 CR have followed the same logic but have introduced some further safeguards. Boat weight is determined at certification control and is recorded on the certificate. At an event the boat may not weigh more than 0.05 kg more than this figure. The waterline limit marks shall be long enough to be visible when afloat.

Question details:

When a boat with a reverse sloping transom (retrousee transom) has a waterline limit mark placed at the waterline, but where the transom/stern of the boat extends beyond the limit mark under the water, what is the correct treatment under the class rules?


The class rule C.4.1 (c) requires that no part of the underwater hull extends beyond the waterline limit marks.

C.4.1 (c)   submerged parts of the hull shall not extend beyond the inboard edges of the waterline limit marks.

In the case described a part of the underwater hull does extend beyond the waterline limit mark (which is correctly placed). The boat does not comply with C.4.1 (c) and therefore is not eligible to compete in competition.

The owner needs to find some way to place the limit mark so that the boat complies with the class rules.


Question details:

Where the deck is irregularly shaped near the mast, where is the correct place for the deck limit mark?


The IOM class rules do not seek to restrict the shape of the deck near the mast. It would be complex to do so and the point to which rig height is measured is taken to be relatively non-critical.

A deck limit mark shall be displayed on the hull centreplane near to the mast position. The mark shall be a minimum of 5 mm in diameter.

It is for the owner to decide where to place the mark.

Once the mark is placed the measurer can carry out his measurements.

Equipment inspectors (event measurers) carrying out pre-race checks may wish to make the deck limit mark 'permanent' by signing over the top.

Question details:

A recent ruling for the IOM class says the certification authority for the hull is the DNM of the country where the owner is resident.  Does this apply to the M, 10R, and A Classes too?



The IOM, Marblehead, Ten Rater and A Class class rules indicate the certification measurement forms (measurement forms) are sent to the certification authority in the country where the hull is to be registered. This seems to give the owner some choice over where his hull is to be registered.  However, ERS C.3.1 defines the certification authority as 'the MNA of the owner'. Where the term certification authority is used it shall be understood to be the certification authority in the country where the owner is resident or in the country of which the owner is a national. This is normally the DNM (Delegated National Member for radio sailing) in the country.

Question details:

Who issues a certificate for any of the IRSA classes?






The certification authority issues the certificate. As of 1st July 2016 all the IRSA classes have the same administrative section. It is A.9 that indicates it is the certification authority that issues a certificate.

The term 'certification authority' is defined in the ERS as:

For the hull: the ISAF, the MNA of the owner or their delegates.

For other items: the ISAF, the MNA of the country where the certification shall take place, or their delegates.

The members of IRSA are the bodies to which the administration of RC sailing has been delegated (if not the MNA of the country itself) and which are known as the DNMs. So, for the hull it is the IRSA DNM of the owner.

For other items it will usually be the same but it could be the MNA or delegate of MNA in another country where the emasurement took place. This would apply where, for example, sails were certified in house by a sailmaker who had been delegated the authority to do that.

See also the related Q&A concerning who is the certification authority, or DNM, for an owner.

Question details:

Where there are multiple deck limit marks, how should the measurer chose which one to measure to?


The Marblehead class rules do not seek to restrict the shape of the deck near the mast. It would be complex to do so and the point to which rig height is measured is taken to be relatively non-critical.

A deck limit mark for each rig/sail group shall be displayed on the hull centreplane near to the relevant mast position. The limit marks shall be a minimum of 5 mm in diameter.

It is for the owner to decide where to place each limit mark. If there is any lack of clarity regarding which limit mark applies to a rig/sail group the owner should be asked to identify the limit mark(s) accordingly.

Once the limit marks are identified the official measurer can carry out his measurements.

Equipment inspectors (event measurers) carrying out pre-race checks may wish to make deck limit marks 'permanent' by signing over the top.

Question details:

Is a rotating mast head fitting (approx. 10 x 20 mm) that supports the head of the mainsail permitted?


If the size is no bigger than is necessary, yes.

The 2016 CR require rigs to comply with the 2016 CR. The rule relevant to the design of rig fittings has changed marginally. A rotating fitting or a fitting attached to a rotating spar shall be no bigger than is necessary.

Question details:

Is it permitted to have a hull with a beam less than 100 mm?



For a hull certified to the 2002 CR, if the maximum beam of the hull is less than 100 mm it will not be possible to use the depth gauge in the prescribed way to test compliance with C.5.2.

If the hull beam is 100 mm or more it will be able to meet class rule C.5.2 but this may impose restrictions on the design of the hull appendages, as on a 100 mm wide hull the gauge may touch the hull at only one section and will have to rotate about a single point of contact.

For a hull certified under the 2016 CR, D.2.4 specifiies a minimum hull beam of 100 mm.

Question details:

  1. Is a spar that is attached to the hull and extending from the mast and along the foredeck a part of the rig for measurement purposes and should it be included in the measured area?
  2. Is a spar that is attached to the mast of a swing rig and extending forward to support a headsail boom to be included in the measured area?


  1. If it is part of the rig (if it is removed when the rig is removed then it is a part of the rig rather than a part of the hull) then it shall comply with the class rules for the rig. One boom with a boom spar cross section not exceeding 22 mm is permitted to extend the tack and/or clew of each sail without being included in the measured rig area. If the spar described is in addition to a headsail boom then one or the other of these shall be included in the measured rig area. If it has a boom spar cross section greater than 22 mm it shall be included in that area anyway.
  2. Yes. See the answer A1 above.

Same for 2002 and 2016 CR.

Question details:

  1. qa2Would a hull with an open central section of the aft overhang (fig 1), extending from the transom forward to a short distance aft of the aft waterline ending, comply with the class rules?
  2. Does the presence of a deck across the top of and joining the twin overhangs (fig 2) make any difference?
  3. Does the width of the open section (fig 3) make any difference?
  4. Does leaving the twin overhangs un-decked (i.e. each is no more than just the thin skin of the primary hull moulding) (fig 5) make any difference?


  1. No. The open section is a hollow in the surface of the hull (see definition of hollow below). Since hollows in the external surface of the hull are prohibited less than 40mm above the datum waterplane and more than 15 mm from the centreplane, the proposed feature clearly falls outside the rule D 2.4(b) and the hull does not comply with the class rules.
    Hollow is undefined in CR, ERS and RRS. The Oxford English Dictionary definition of the noun ‘hollow’ is: “a hole or depression in something”.
  2. No. The presence of a deck does not change the presence of hollows in the external surface of the hull to be tested under D 2.4 (b).
  3. Yes. D 2.4(b) (3) makes an exception for hollows within 15mm of the centreplane which are permitted. The reason for this exception is to permit the hollows that are formed by the presence of the keel and rudder where they join, or are faired into, the hull. If the hollows are entirely within this region they are permitted.
  4. No. In this arrangement the upper surface of the overhangs are “inset transom and upper surface of deck” and thereby, any concavity in that upper surface is not prohibited by D2.4(b) 5).
    The absence of a deck or any other structure apart from the hull shell does not change the presence of hollows in the external surface of the hull to be tested under D 2.4 (b).

The 2002 CR have the same effect.

Question details:

For the purpose of initial certification control (measurement), is it possible to take the largest cross widths of two or more sails and use these to create dimensions for a ‘virtual’ sail that is recorded on the certificate?


For boats certified to the 2002 CR, no. The Ten Rater class rules I.2 and J.2 refer to the measured rig area and measured sail area of the largest rig. It follows that the largest rig and sails to be used shall be presented to the measurer and be certified.

The Ten Rater class rule does not require that the largest rig and sails be used at any event. However, alternative sails are mentioned in Section C and in order to certify those sails the measurer shall check that they fall within the profile of the largest sails (the dimensions of which are recorded on the certificate). This check cannot be made unless those largest sails are present.

For boats certified to the 2016 CR, yes. The concepts of measuring the largest suit of sails and alternative sails having to fit within the profile of those sails no longer apply. It is possible that the dimensions of 'virtual' sails could be placed on the measurement form and sails checked against those dimensions for compliance.

Question details:

Under the 2002 CR and where a hull design has plumb (vertical) ends and the waterline endings extend to the extreme ends of the hull, may the waterline limit marks be placed around the bow and/or on the transom?


No. The class rules require the waterline limit marks to be placed on the undersurface of the hull.

A waterline limit mark placed around the bow some distance up from the LWL is not on the undersurface of the hull although it may be across the centreplane of the hull. Similarly with the waterline limit mark placed on the transom. These waterline limit marks would not comply with Class Rule D.2.1.

It is suggested you add a short extension(s) to the hull, where appropriate, that may carry the required waterline limit mark(s) that are on the underside of the hull as in the diagram below.

limit mark_on_10R_vertical_bow

The 2016 CR contain different wording and this issue is effectively resolved.

Figure L.4._Variation_1gb1  Figure L.4._Variation_2gb1  

Question details:

Is it necessary to float a Ten Rater at the time of certification control (measurement) to establish the correct placement of the waterline limit marks?


No. The true waterline length is not a measurement that is required at certification control (measurement) or at any other time unless the purpose of the measurement is to determine compliance with the certificate (equipment inspection).

What is required is placement of the waterline limit marks and measurement of the distance between them. Class rule C.4.1 shall be complied with when the boat is racing and, providing the boat complies fully with the class rules when racing, no rule is broken if the boat has not been floated at the time of initial certification control.

The requirement in the 2002 CR to have the waterline endings no more than 30 mm inboard of those limit marks no longer applies.

Question details:

What sail identification marks shall be displayed when a hull holds a certificate in more than one class.


When a boat races it shall carry the appropriate sail identification marks for that class. Providing they do not affect the legibility of the marks, alternative class insignia may remain on the sails.


No. C.6.3 prevents the movement, articulation, retraction or extension of hull appendages (including the ballast). Additionally RRS 51, which is not excluded by Appendix E of the RRS, states that movable ballast ‘for the purpose of changing trim or stability’ is not allowed.

1994 CR 4.1.1 prevents movement of the ballast fore and aft and canting keels per se are not prohibited. However, when a race is un using the RRS and RRS 51 is not cancelled the effect is the same.

The same logic applies to the other classes too.


Yes. Class rule C.7.2 applies to the spars, which may not be replaced unless lost or damaged beyond repair, and does not apply to the rigging or fittings on the mast and main boom.

The 1994 A Class rules do not use the ERS definitions so the requirement to use the original mast and/or main boom should be understood to apply to their spars i.e. the structural members to which fittings and rigging may be added.

Owners are reminded that the boat shall still comply with other class rules (weight, flotation etc) that may be affected when rigging is changed.


Except when the original mast spar or main boom spar are damaged, no. CR C.7.2  permits that the mast spar and main boom spar, when lost or damaged beyond repair, may be replaced with the approval of the race committee.

C.4.2 requires the boat to sail with the mast spar and main boom spar used when the boat was measured for the certificate in use at the event.

The clear implication of C.4.2 is that if the mast spar or main boom spar are replaced then the boat shall be re-measured. If the boat complied with its certificate (and the dimensions on it) no further action is required. If it does not comply with its certificate then the necessary adjustments shall be made to the boat and/or the measurements forms and a new certificate shall be issued.

The 1994 class rule has the same effect.

Question details:

Is it permitted to have a small raised area of deck to house mast partners and a mast ram at the mast point and a small recessed area just aft of that point?


Yes. D.2.3 (d) (1994 CR 6.3.5) allows for a limited amount of transverse deck round, being 1/24th of the beam at any point. The class rules do not place any fore and aft or transverse restrictions on deck camber, only that it shall not exceed the permitted amount.

Question details:

Is the extension fitted to the sails in the photograph to be considered as part of the sail or as a halyard? If the extension is part of the sail then:

  1. Do these sails comply with G.3.2 (b) (1994 CR 6.3.1)?
  2. Where is the head point?
  3. How are the "correct positions" of the battens to be found for clause G.3.3 (1994 CR 6.3.2)?
  4. Do these sails satisfy the requirements of measurement form item 10 (1994 MF item13)?



a      Yes. The upper part of each sail is clearly not separable from the remainder of the sail and is therefore part of the sail. Taking the individual points raised above in turn:
The class rules are open class rules and therefore anything which is not specifically prohibited is permitted. CR G 3.2 (b) requires the mainsail to be trilaterial and bounded by the luff, foot and leech. There is no rule which prohibits a concave leech but hollows shall be bridged as described by ERS H.5.2. For the 1994 class rules the IYRU SMR describe how to handle measurement of a sail with a hollow leech. The sail is not a quadrilateral sail and has the three required edges. Restrictions are placed on the shape and size of the sail elsewhere in the CR and the sail shall comply with those restrictions.

b      The head point is defined in the ERS G.4.2 and is found as the intersection of the luff, extended as necessary, and the line through the highest point of the sail at 90 degrees to the luff. For the 1994 CR the IYRU SMR apply but the effect is the same. The design of the sails referred to does not affect this measurement.

c      The batten position is limited as in G.3.3 (1994 CR 6.3.2). The design of the sails referred to does not affect this measurement.

d      Yes. See (a) above.

Question details:

Can a boat with a certificate in one class also hold a valid certificate in another class?


There is no rule in any of the International One Metre, Marblehead, Ten Rater or A Class class rules which prevents a boat from having a valid certificate for another class.

Question details:

Where a mainsail has a pocket luff over only a part of the luff, how are the luff perpendicular, quarter width, half width, three-quarter width and head width to be taken?


qa3The ERS G.1.4 (g) defines a double luff sail as “….a sail with more than one luff or a sail passing round a spar and attached back on itself.”

The sail does pass round the spar and attaches back on itself so it is a double luff sail and shall be measured as prescribed even where the double luff is not present. The class rule G.2.4 (b)(1) prescribes that the luff perpendicular and cross widths shall be taken to the luff, or to the fore edge of the spar, whichever gives the greater dimension.

The ERS G.4.2 shows how the head point of the mainsail is found at the intersection of the luff, extended as necessary, and the line through the highest point of the sail at 90 degrees to the luff. When the luff is extended in this way, the head point will be a point at the forward edge of the mast spar.

Where the sail has a series of short luff sleeves, each like a double luff, in total no more than 10% of the luff in length and no one of them more than twice as long as the shortest, then the sail ceases to be a pocket luff sail. The widths shall all be taken to the luff excluding the luff sleeves which are discontinuous attachments. Class rule G.2.4 (b)(5) refers.