Marblehead Opions Sought on Battens

Mar 17, 2021

Australia's IMCA Marblehead Representative is seeking feedback/opinions on batten limitations for the Marblehead class.

An enquiry about the compliance of an IOM sail that had a large patch (just within the leech stiffening zone template) of heavy sail film at a batten has led the IRSA TC to consider the wider problem of trying to limit the ‘effective’ size of battens in the Marblehead and A Classes.

In the Marblehead and A Classes there are no limitations on the thickness of material used for the body of the sail or their reinforcements. The body of the sail is required to comply with the requirement to be a soft sail. The ERS definition tells us a soft sail is where the body of the sail is capable of being folded flat in any direction without damaging any ply other than by creasing.

The films typically used for sails of rc sail boats will be damaged only by creasing when folded as required. The snag with this is that it effectively permits Mylar film (and other plastics) of quite high thickness to comply with the requirement to be soft sail material. Mylar film is available in thicknesses up to 350 and 500 micron, both well in excess of what is used for most battens.

It is clear that the restriction on the size and placement of stiffening (battens) becomes relatively meaningless when the body of the sail itself can be made as stiff or stiffer anywhere. Therefore the IRSA Technical Committee has considered how the class rules might be changed to maintain what has been the traditional understanding of how sails shall be constructed e.g. a soft sail with stiffening added where required/permitted.

One approach considered is to limit the thickness of the material used in the body of the sail. This would also require the reinforcement to be limited in size, otherwise the addition of thicker material at strategic points would not be prevented. A problem with this approach is that some scrim/laminate materials have an overall thickness considerably higher than their mean thickness (because of the presence of fibres laminated onto/into the film). Any minimum thickness limit would have to be high enough to permit these materials and that would work contra to the attempt to limit the thickness of pure films that can be used.

An alternative approach is to de-restrict all limitations on the size and placement of stiffening. This removes the basic problem by avoiding having to distinguish between the body of the sail and any stiffening.

IRSA is considering this matter because it is felt useful to deal with it before there is a serious outcome i.e. a protest at a major event. The above discussion is limited to the Marblehead and A Classes only – the 10 Rater class avoids the issue by having no limitations on stiffening or the material used for the body of the sail – the IOM class, via IOMICA, may arrive at its own solution.

Your views on the idea of removing the limitations on stiffening in the Marblehead and A Class are sought. If the idea is unwelcome then it would be especially useful to have your proposal for an alternative method of resolving the problem.

All comments can be sent to Australia's IMCA Marblehead Representative


Category: Australia
Posted by: ARYA Publicity