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.