Sunday, December 26, 2010

What needs to be fixed.

We are almost there in the tedious process of deciding if Bora can use his wing.

How did we get in such a mess?
This week ISAF decided our current rules did not cover mesurement of wings so they could not be measured. Why?
Its only our current rules which do not cover wings because before that the rule read:

Sails

1.

The boat shall carry only one sail. No extra sail shall be on board when racing.

2.

The sails and spars shall be measured in accordance with ISAF "Measurement and Calculation of Sail Area". The ISAF Sail Measurement Instructions shall not apply. The measured and calculated area shall not exceed 8.00 m2, except that:

i.

Clause 3.2.5(b) of the ISAF Measurement and Calculation of Sail Area shall not apply.

ii.

Only the area of that part of the spars that will not pass through a ring 90 mm internal diameter shall be included.

iii.

For a sail which encloses the mast, an area equivalent to the length of the luff multiplied by 50 mm shall be excluded.

iv.

For a sail which encloses the boom, an area equivalent to the length of the foot multiplied by 90 mm shall be excluded.


When we ammended our rules in 2005 to measure true area rather than the 3 offset simpsons rule method (Clause 3.2.5(a)), we deleted the above reference to the "ISAF Measurement and Calculation of sail area.. MCSA" which is what the CCats use to measure their wings and which Bora found still contains a reference to its applicability to the Moth class.

If we had retained that reference ISAF this year could not have made that decision. There are other matters of ambiguity, like how we apply luff length limits, mast length limits and the one sail rule, but we could have measured the area.

So in 2005 we inadvertantly banned something which the rules had specifically previously allowed. Its important that in 2011 we do not inadvertantly write new rules which prevent development in any new direction.

I am advocating strongly to reinstate the ISAF MCSA as our standard for area measurement. But we also need to decide a few more very basic things.
1. Do we want to ban all solid sails? Not just complex ones like Bora's.
2. Do we need the one sail rule or how do we apply it to multi panel wings.
3. How do we measure luff length of wings, or can we replace luff limits with a rig height limit.

My personal choice is to accept wing development as the class did pre 2005. They will get better, cheaper, simpler, more packable and faster.
I do not really care about the one sail rule, but if we delete it we have one less thing to argue about.
The simplest method of controlling aspect ratio is to limit total rig height to a distance above the keel of the hull. This is at present about 6.3m, which would be a good number to choose.

If we adopt the ISAF MCSA then we might as well get rid of the two other inconsistancies and measure total area of all exposed sails, wings and spars, ie delete the luff pocket allowance and the 90mm free mast area . We would have to increase the total to 8.3sqm to match existing rigs.

Please consider carefully we must not make mistakes this time which will cause dramas in the future.

3 comments:

Karl said...

No real need for a rig height limit; after a certain point it is counterproductive and the class generally settles upon one length after awhile, like the A-cats. One more unnecessary rule to discard.

Giovanni Galeotti said...

I do not want to see a change in the way we measure soft sails that renders our current soft sail rigs obsolete with respect to new soft sail rigs.

Phil Stevenson said...

Giovanni, The measurement proposal does not make any existing rig obsolete. The height limit would match existing rigs and the increase in area will cover the luff pocket or bolt rope mast. All existing rigs would be treated equitably.
Karl, the class fought strongly against Dave Lister' wing mast proposal which was 100% consistant with the wording of the extisting rules but because it used all of the 6.25m height limit was deemed against the spirit and was so banned before it was built. This strong emotion will ensure that some control of aspect ratio will remain.