In looking at recent pictures am I imagining things or are footy rigs getting larger? My first racing last fall was done with rigs in the range of 150-180 square inches (0.097-0.116m2). My rigs were as large or larger than any I raced against.
I know Scott mentioned rigs of 190-210 square inches (0.123-0.136m2) on his boat. Current races I’ve been in have seen rigs larger than mine as well. What range of sail plans are people going to the pond with? What about you guys and gals across the pond?
Brent, yes you are right, in the UK we have recently two meetings where there were some very light airs. Now skippers are building BIG rigs
thanks for the info you sent hope you got my reply and attachments
Yesterday we had 3 Footies racing in light winds, with the following rigs:
McRig…21"…17"…260 Very large roach
Swing rig…28"…16"…224 minimal roach
Sloop rig…29…19"…280 minimal roach
Nobody had a problem with controllability, but we all had fat hulls, and the wind was never more than 4 knots.
Thanks for the input. Do you guys have any pictures posted anywhere? I’d like to see some of these sailplans. Your rigs definitely have proportionally more foot than I’m currently using. I may have to try a new profile.
My 180 square inch fathead swing rig has a 23" luff and 11" total foot. My next two planned rigs are:
- 210 square in, 11.5" total foot with 26 inch luff
- 240 square in, 12" total foot with 29 inch luff
Please do not be led astray by what other people (like me) are doing. The rationale for the low aspect ratio sails is to get more sail area down low, where it contributes less heeling moment and less submarining moment. There is probably a limit where it becomes impractical, but I have been racing Sunfish for many years, where the boom is as long as the luff, and they go to windward reasonably well. However, there is usually more wind at higher elevations above the surface, so there is obviously a trade-off.
I don’t have any good pictures on line to show you, but you can get a general idea of large-footed sails by looking at Scott Spacie’s rigs, which appear on several of the “race results” pages on the main Footy website, and also on a page called “Huntington Footies” in the Pictures section of this newsgroup. He has built all kinds of Footy sails, and has spent a lot of time optimizing them.
As someone who likes to put numbers to theories I think I have convinced myself that - for Footy sized rigs - a low centre of sail area/pressure wins out over more wind at higher levels. I say this because :-
Ref. http://findarticles.com/p/articles/mi_m0QRG/is_27/ai_n11836129 suggests that if we assume that :-
Req’d Speed = Datum Speed x ( Req’d Height/ Datum Height )^(some power)
where the Datum Speed, Datum Height and the power are obtained from testing and are effectively ;-
Datum Speed = 1 unit - say mph
Datum Height = 43 feet - because the tests were done on big boats
Power = .14
. . . . then it can be shown that the difference in wind speed between a 700 mm and a 500 mm high triangular Footy rig is about 3%.
However, the difference in centre of pressure height between these two rigs will be closer to 40%. This means that the heeling moment will be 40% lower on the shorter mast, although you will have to increase the foot length in order to recover the full sail area in order to have a comparable apples to apples sail force.
This works for two reasons :-
At Footy rig heights the curve of wind speed at a height is almost flat
Although you are having to increase the lower rig’s area to keep the same force, it can be done by increasing the sail foot length which doesn’t feature in the heeling moment calculation.
I will niow retire to my bunker before the flack comes over.