The Jolie Brise has an overlapping foresail with two sheets leading aft either side of the mast.
Has anybody seen this done on a scale boat?
See my on-line calculators at Jolie Brisefor
Deck crown,
Lead ballast - volumn/weight,
Wind/sail area - sheet load/travel
Drum servo sheet load/travel - turns/torque
Arm servo sheet load/travel - angle/torque
Tony
On most boats with a jib & main we use a single sailwinch with a double arm to control two sails at once. The arm is centered on the aervo with equal lengths so you get equal sheet payout.
I have thought about this at length. I was conceptualizing an overlapping job for a scale sloop, here are some of the problems that have to be overcome. When the port sheet takes control the starboard sheet should be at full extension until it takes over on the next tack (and vice versa). This requires that the sheets attach to the control that is attached to the winch with some sort of sliding mechanism. Secondly, think of the jib cars on a big boat. As you sheet the jib out, in order to get the best performance, the cars should be moved aft. I did not over come the jib car issue, but I think it is possible. I also beleive that if you have a winch strong enough, you could modify a drum so that the main was controlled also. That poses another problem, that when tacking, if you are going from close hauled to close hauled, both the jib and the main would have to go to fully sheeted out back to the position required which even with a fast winch will require some time and it may be hard to keep the long sheets from fouling. Those are all problems that may not be figured out until it is actually built. Good Luck.
BTW, this was for a drum winch, I hadn’t thought about using an arm style.
-Andrew
I saw a bit on video on You Tube of an overlapping headsail. It worked very well and looked cool. Here are some links.
http://www.youtube.com/watch?v=APo9uLq7Q00
http://www.youtube.com/watch?v=rUSkCdCnQCg
I don’t think you can do it on a single servo unless you build a complex gearbox/clutch. The problem is that the sheet being cast off, needs to be released quickly as the boat passes head to wind. At that moment, the system is asymmetric. The old sheet needs to be longer than the new sheet as the clew of the jib moves out to the new leeward side. The old sheet has to pass around the mast and out to the clew.
So you need a way to fully release the old sheet quickly (like a clutch being released) so that the sheet can run free. Meanwhile, the clutch for the new sheet engages and begins to pull in the new sheet.
If you could use a drum where one side spools off line while the other side winds it in and it works . . then go for it.
The other issue with an overlapping genao is that it will not be as effective downwind as a jib on a boom. The genoa curves in and is blanketed by the mainsail.
Instead of having two sheets from the clew of the foresail why not move the jib sheeting position (i.e. the jib car) from one side of the boat to the other? When I get a chance I’ll sketch it out. It would need two servos/winches though.
Ray
A quick sketch of my suggestion above. It is illustrative only.
Ray
Doesn’t the vortex ordinarily use a string eating winch?
http://www.rcgroups.com/forums/showthread.php?t=719601&page=2
Have a look and a read.
Hope this is useful.
Andrew :zbeer: