Which spars of a Ten Rater swing rig can be excluded from the certified rig area?

10R 
Question Details

Which spars of a Ten Rater swing rig can be excluded from the certified rig area?

Answer

Relevant rules

Ten Rater Class Rules 2018

Section J – Rig Area

J.1         GENERAL

(a)       One boom spar with a maximum boom spar cross section not exceeding 22 mm may be used to extend the tack and/or clew of each sail without being included in the certified rig area.

(b)      A fitting shall be considered to be part of the spar when:

                        (1) it is faired into the spar; or

                        (2) it is bigger than is reasonably required for its purpose.

J.2         CERTIFIED RIG AREA

J.2.1         The certified rig area is the sum of the areas of the rig components of the largest rig, excluding the items listed in J.2.2,       

                  where if the sum of the area of the components does not exceed 10% of the maximum permitted sail area, the area of each component shall be found as in J.3 and/or J.4, or otherwise

                  where the area of each component shall be found as in K.3

J.2.2         (a) spars as in J.1(a).

                  (b) fittings as in J.1(b)

                  (c) spreaders.

                  (d) rigging with a maximum cross section of less than 2 mm.

ERS

F.1.4        Spar Types

                  (b)       BOOM

                  A spar attached at one end to a mast spar or a hull and on which the clew of a sail is set and on which the tack and/or foot of the sail may be set. Includes its rigging, fittings and any corrector weights, but not running rigging, running rigging blocks and/or any kicking strap/strut arrangement.

NB          The class rules use the defined term spar instead of the ERS defined term spar. A spar does not include the fittings and corrector weights. A spar does include fittings and corrector weights.

Discussion

CR J.2.1 makes it clear that the certified rig area is the sum of the area of the component parts excluding certain, specified, parts.

Excluded items include spars as in J.1(a). Specifically one boom spar with a maximum boom spar cross section not exceeding 22 mm may be used to extend the tack and/or clew of each sail without being included in the certified rig area.

Note that there are several requirements for such spars to be excluded from the certified rig area. These requirements are:

The spar shall be a boom spar – therefore:

               It shall be attached at one end to a mast spar or the hull

               It shall be used to set the clew

No more than one per sail

With a maximum boom spar cross section not exceeding 22 mm

Application

Form A

picA

The most common form of swing rig comprises the following spars in addition to the mast spar:

Item 1   A spar cantilevered aft from the mast spar to which the main clew is set – this is a boom spar

Item 2   A spar cantilevered forward from the mast spar – this is not a boom spar

Item 3   A spar to which the headsail clew and tack is set – this is not a boom spar

Of the above spars items only item 1 meets the ERS definition of boom spar. Items 2 and 3 do not meet that definition.

CR J.1(a) permits item 1 to be excluded from the certified rig area if its depth does not exceed 22 mm, but because items 2 and 3 are not booms, their spar area shall be included in the certified rig area.

Form B

PicBAn alternative version of the swing rig comprises items 1 and 2 from Form A and item 4.

Item 4   A near vertical spar attached at its upper end to the mast spar and at its lower end to the headsail clew – this is a boom spar. It also meets the ERS definition of whisker pole which is categorised in the ERS as an OTHER SPAR even though it meets the definition of a boom.

Therefore the area of Item 4 may be omitted from the certified rig area as it meets the ERS definition of a boom, but item 2 shall be measured for area.

Form C

picCAn alternative version of the swing rig is similar to Form B but has a spar, item 3, connected to item 2 at their fore ends and to item 4 at its aft end.

Item 4   A near vertical spar attached at its upper end to the mast spar and at its lower end to the aft end of a spar onto which the headsail is set this is not a boom spar.

Therefore the area of Items 2, 3 and 4 shall be measured for area.

End