Thanks for the comments to my previous entry – I posted my further thoughts here to make them more easily readable: The present IMCA sail area rule follows the principle of measuring sail area according to ISAF guidelines. It attempts to measure the area contributing to driving force. That is why the luff sleeve/ mast is not measured since it contributes more drag than lift. The exception is area of wing masts in excess of 90mm X mast length. This is understandable and presumably written because it was estimated that a sufficiently wide wing mast (in excess of 90mm) would contribute to driving force. The 90mm number is probably an educated guess but even if it is not spot on it agrees with the concept of attempting to measure area contributing to driving force
The IMCA wing sail interpretation does not follow the principle of measuring area that produces driving force. The wing in its entirety produces lift and therefore the entire wing needs to be measured if ISAF guidelines are to be followed. The interpretation is at odds with ISAF general principles as well as specific recommendations for measuring wings. As such it is not even consistent with our Rules and their present application which do follow ISAF guidelines when it comes to conventional rigs or wingmast/softsail rigs.
I believe an interpretation not in agreement with ISAF principles will not stand up in appeal. Ultimately it is the rules which are the defining element. At the end of the day the real bone of contention is whether a multi element wing is one sail or not. I would argue that it most certainly is when slots are sealed. I would also argue that it is one sail when slotted but the point can be debated. If all elements can be sheeted together then it is probably one sail.
I think the matter should be cleared up urgently to safeguard the fantastic PR asset we have in the wing sail. The first step in moving the issue forward is to is to draft a new and more robust interpretation that takes into account ISAF guidelines. As of now there is no firm grounding for a reasoned discussion. If it is true that there is still doubt about what will be allowed at Belmont then the situation needs to be righted.
Subscribe to:
Post Comments (Atom)
Hi Giovanni,
ReplyDeletethe 90mm ring rule is quite an old one. It dates back to the days when moths had unstayed wooden masts, which were quite fat at height of the deck.
Cheers
Burkh
Interesting, originally was the 90MM dimension just a max diameter rule? Or was there a provision for oversize dimensions to count as sail area? Or did that happen later when someone thought of a wing mast of sorts?
ReplyDeleteI think this was a downwind issue originally. As was with the booms. The rule was not intended as a max diameter but just to prevent cheating.
ReplyDeleteWhen I started moth sailing there was a guy who in light conditions lifted the centreboard out of its case and fixed it under the boom on downwinds. Those were the days...
:-)
Burkh
So if the 90mm thing is an "old rule" ( i.e. vestigial in some way) and perhaps in fact the rules-as-they-are were built with only soft sails in mind are rapidly approaching "old rule " status then stretching the rules (or more accurately stretching the rule interpretations) to cover wings is a mistake.
ReplyDeleteIf wings are ok by the majority of the class, then a new rule is needed for these wings. When writing the rule the objective should first be to align an equivalence between the definitions of "what is a wing?" and "what is a soft sail?"
then determine relevant maximum areas of each, and the means of measuring these.
After all if we had never had soft sails, then the motivation would be to create a rule that says "a moth wing is a legal wing if X."; and the class would select in the rule the parameters of "X" such that no one felt one wing was intrinsically better than another.
Just as we do with sails, legal "wing equivalence" should be an objective in any new wing rule. I.e. My wing and your wing are "the same" in these dimensions, and are therefore legal, and "fair" for competition.
So should there then be an understood equivalence (or at least an objective of an equivalence) between existing sails and any new wing rule?
Not sure whether a single sheet controlling a slotted sail is One Sail. How about the aero rig?
ReplyDeletehttp://www.john-shuttleworth.com/Articles/52images/aerorig3.jpg