Bruce Was Right
Back in the 70’s, Edmond Bruce was cobbling together wind tunnels and test tanks out of duct tape and bailing wire, conducting sailing experiments that were published in the Amateur Yacht Research Society newsletter. Think of him as the ‘Doc Brown’ of sailing and you won’t be too far off. The guy was a genius, one of those who could think “Fourth Dimensionally”.
His primary claim to fame is the invention of an inclined hydrofoil designed to counteract the heeling force of the sail, replacing lead ballast or even “live buoyancy to leeward” with the same kind of dynamic energy as the sail. He saw the sailboat as a yin-yang kind of thing, a delicate balancing act of dual forces that almost alchemically combined to permit transport when properly aligned.
Edmond inspired a lot of people back in the day, and one was Jean Louis Pelou who has kindly sent pix of his Bruce foil equipped proa Epicemar, originally built in 1980, and still sailing today. Epicemar is 40’ (12m) flying 270 sq. ft. (25 sq. m) of sail. The twin, 45 degree daggerboards counteract the force of the twin sails.
These days, all the cool kids sport lifting foils in their lee hulls, though they seldom call them Bruce foils anymore.
More pix after the jump.
What an interesting rig. Both sails seem to have two booms AND two masts! I imagine the stayed, canted, leeward masts are to keep the rig up when caught aback? As for the booms, I don’t know much about wishbone booms, but I’ve never seen a sail that uses both wishbones and a conventional boom. Can someone enlighten me?
Hi Jonathan,
I’m no guru, and have never seen this boat before, so am only making guesses here….
I think you’ll find the second masts you are referring to actually to windward not leeward.
As for the wishbone, well looking at the 1st photo, the traditional boom goose neck is almost at deck level and there doesn’t seem to be any kind of boom vang, so perhaps thats the purpose of the wishbones. It could also be to bend the masts without having back stays. See (http://en.wikipedia.org/wiki/Wishbone_boom) for the claimed advantages of the wishbone boom. Iv’e never used one so am only speculating.
I would love more details though.
Dave.
Thanks Dave.
I definitely misspoke on the secondary masks being to leeward. I was thinking about a proa being caught aback, at which point they would be to leeward (though hopefully only temporarily!). After all, if they were always to windward, they would never be loaded in compression, and a traditional wire stay would do the job.
Regarding the wishbone boom, wouldn’t you get all of those advantages without the traditional boom? Why use both?
Jonathan,
Seems like having both boom and whishbone would make reefing the sails easier, and you could run the sheets to the lower booms at a better angle than you could get to the end of the whishbones.
Micha,
I thought WB booms were supposed to make reefing easier? but you could be right.
Jonathan,
When I first saw your comment, I though maybe something to do with sheeting angle, but when I look again at the photos there is no reason the sheets couldn’t be attached to the WB boom. It could be something as simple as the traditional boom was the original rig and the WB was an afterthought or mod, and they just left the original boom? I guess we’ll never know unless the owner/designer tells us.
Dave.
Here is an example of this setup: http://www.sponbergyachtdesign.com/Wobegon.htm
I love this design. Not being much of a proa aficionado I cannot comment too much, however the lines and rig in the first photo of the post are just beautiful.
I’ve often played with similar rig designs in my head, but never seen a double wishbone. Thank you for writing this great post!
I ame the owner of this proa and i have seen several comments regarding booms + wishbones. At the beginning there was only wishbones and the sails were designed for wishbones. In order to facilitate the reefinf of the sails I decide to replace the wishbones by booms, but some diificulties appeared with sails tension and boom angle, and one solution was to join the booms and wishbones, so, Dave is riht : replace the booms vangs and make easier the sails reefing.