Having read the recently posted (16/11/10) interpretation regarding wing sails written 12 August 2010 I came away with the feeling it was most probably at odds with ISAF reccommendations for measuring sail area that you can find here: http://www.sailing.org/tools/documents/GuideSailArea-[941].pdf .
The great oddity of the class interpretation is considering the forward element of the wing sail the mast and the rear element the sail. This allows for the deduction of the 90mm mast allowance which implies that a two element rig will be substantially bigger than the current enclosed luff sail. It gets odder: a one element sail - twistable or not does not get the 90mm mast allowance and might(???) even be illegal. Same for 3 or more element sails.
ISAF would suggest that the entire area of a wing be measured. Furthermore it would suggest as would common sense that there is no difference between a one, two or three element sail. A slot is unmeasured area. One flapped wing is still one wing regardless the flap configuration - a biplane or triplane configuration is something very different. A flapped wing does not a multiple sail configuration create. The fact that a sloop rig can be analyzed as a slotted foil does not imply the converse (a dog is a mammal but a mammal is not a dog). In any case even if we were to accept that false argument any slot in the wing sail should be banned (including a slotted two element sail) but the number of mechanical elements and amount of inducible camber would be left free as long as all slots were sealed.
The apparent discrimination in favour of a two element wing sail at this point in time when we have no experience is nonsensical. It could very well be that a three element sail when broken down is more transportable.Equally, there is no reason to descriminate against slots, a multiple slot configuration may be sailable in a wider range of conditions. More critically the sail area bonus allotted to the wing (in the two element configuration) which should be an inherently more powerful and efficient rig hardly seems fair. Especially since it clashes with ISAF sail area measurement prescriptions.
Soon the class will be voting on the wing. The current interpretation of the rule might influence that vote - perhaps not for the best. It's hard to support the logic of the current interpretation.....
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ReplyDeletehmm,
ReplyDeletei had been thinking along the lines that as the rules interpretation or revisions evolve what would be the class direction?
Should "fair" mean that a wing should be of smaller size but of equivalent performance to the soft sail as it has been these past few years ( Adam's original smaller wing comments and intention are relevant here),
OR
should "fair" mean "a wing with the same 'sail area' ( whatever that means) as the soft sail?
So far, the focus has tended toward the latter and perhaps this is in lieu of any better general information about the relative performance of the wing and the soft sail.
It seems to me that discussion on the rules objective should first be nailed down, then from that baseline position determine how the interpretation(s) / revision(s) should proceed.
Is the objective of the class "fair" racing between wings and softsails, or is it "fair" engineering (i.e anything goes ) inside a "fair" (i.e. well known) measurement norm ( like the "box rule" on hull dimensions).
That debate should precede any rule interpretation.
Very well put, but the Interpretation is not based on anything except the Class Rules as they are written, specifically the one sail rule. It was done by the IMCA executive in March without Adam May who had a vested interest having just built the first wing rig.
ReplyDeleteThe referred ISAF document was once part of the Class rules but ISAF lost it for a period (Last printed by IYRU about 1980 but not posted by ISAF until about 2008) and its reference was deleted from our rules, so while its a good system its not specified for moths.
Whether slots make the rig more than one sail needs to be decided and ruled much more definitively, but maybe the one sail rule is no longer needed anyway. I think this will be determined by IMCA members in 2011.
There is a current and heated debate in progress amoungst the Exec and measurers as to what is legal for Belmont.
Where is this extra sail area?
ReplyDeleteFront element is the mast, it does not enclose the mast. The part that doesn't fit through a 90mm ring is measured as sail area.
Aft element is a sail. Measure as "normal".
The sum must be less than 8 square metres.
Think of a traditional wing mast and soft sail combo. You are not allowed to build a 500mm chord mast and put an 8sqm bolt rope sail on the back of it. That would give you an effective sail area of 10.6sqm (8 + 2.6). You are allowed to build a 90mm chord wing mast and not have it counted to sail area.
None of the wing sails published yet have a first element with a chord of less than 90mm. There is no area to be gained.
If it looks like a dog and barks like a dog its probably a dog.
ReplyDeleteI think one of the most problematic things about this interpretation is that two elements of a single, two-element wing constitute a mast and a sail. This is basically forcing a square peg into a round hole; applying a rule that simply did not anticipate a solid sail to solid sails only generates needless complexity.
ReplyDeleteIf the rule did not anticipate wings, it is more sensible to simply state that the rule does not address wings, propose a logical method of measuring them, set an area limit, and proceed from there until a new or modified rule is available.
Measuring successive girths along the span and using these to generate a planform area is accurate and straightforward. I suspect all parties with wings in Belmont would agree to 8sqm limit by this method.
There is still the two sail rule.
ReplyDeleteWhat if a BOR style wing pops up with numerous trailing elements independently sheeted?