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Launch of new Core Sound 20


brigait1

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Hi all,

Well, we finally managed to wrap things up and get the boat launched this Labor Day weekend. There were only a few minor snags and once they were ironed out, we had a couple great sails. The winds were light (probably around 5-7) but the boat moved nicely. There wasn't too much motor boat traffic considering the holdiday weekend. All in all, a great first outing. I still have some work to do taming the wishbone sprits, but nothing major.

Here are a few pics and a link to a short video.

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http://goodfootsaili...st-weekend.html

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Congrats, Pete! Looks very nice. I'll be interested to hear your thoughts on the wishbone sprits once you've had a chance to sail with them for awhile. I've heard others debate their merits, and although I've always been happy with basic sprits, I'm curious to know what you think. I would think having the wishbone to keep the sail captive (plus some lazy jacks, perhaps) would be very convenient.

Enjoy the boat!

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Thanks everyone! As fun as the build has been, it is nice to be done...mostly. I guess there will always be little tweaks and other boat-related projects, but being able to actually go sailing is a nice change. Wes, so far I love the sprits. The main sprit is currently a bit too long and will need to be shortened by about 6 inches. As for performance, I know most people feel the the straight sprits do not really hurt. However, coming from a racing background where I spend so much time tweaking sail shape, I just knew that the crease from the straight sprit would drive me crazy. With the wishbones, you get to see the designed shapoe of the sail all the time, which makes me happy. Speaking of the sails, mine were made from a Sailrite kit. Jeff Frank at Sailrite desgined the kit from information provided by Graham. There is some roach added to the basic sail design and three battens per sail, none full length. I am VERY pleased with the shape and would definitely recommend the kit to anyone considering making their own sail.

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I'll get some measurements on the wishbones next time I'm at the boat. If I had to guess, I would say 30 inches or so. plenty of clearance on the sails. they could be narrower without any problems I'd guess. One issue is how they can rotate about their longitudinal axis. This is especially true when a motor boat wake comes along and gets the hull rocking. I worry about the sprits putting a ding in the mast if they get enough power behind them. I'm trying to figure out the best way to put some kind of stabilizing lines on them to tame this motion. I'd love to hear any thoughts anyone might have on this.

Pete

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One issue is how they can rotate about their longitudinal axis

I'm trying to figure out the best way to put some kind of stabilizing lines on them to tame this motion. I'd love to hear any thoughts anyone might have on this.

I have some experience on a larger scale- a 10 metre tri. The average sailing induced twists along the long axis are reasonably controlled with lines from a point higher on the mast to each arm of the wishbone which at least prevented the arms from dropping and so limited the movement. They didn't work so well in stronger breezes when there is a lot of torque and when the torque changes suddenly in manoeuvres like a gybe. We bent the aluminium wishbone in a corkscrew fashion twice...each time gybing in strong conditions (40 knots plus).

Here's a photo.

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Cheers

Peter HK

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The photo of Peter's boat shows a slightly different wishbone geometry than the large, sweeping curved sprits Pete created. The thing I noticed from Pete's video was what appeared to be a lot of flexing of his wishbone sprits. Look at most commercial bones (Presto 30 comes to mind) and the sprit arms are more or less straight, with very little curve to them. To achieve that, there is a wide connecting crossbar at the head end.

From my understanding of this, having the bones flex is not good. In building wind or a gust, when you want the foot of the sail to stay taught so the top of the mast curves to flatten the sail and depower it, the flexing bone allows the foot to actually induce more curve and draft, powering it up. Something to be aware of and watch for.

Have studied several bones and have noticed a lot of different solutions to stabilizing it around the mast. Seems to be a recurring theme.

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Adding more bits that need assembly or fiddling with makes wishbooms even less attractive. On Lapwing, I have not noticed any flopping of the booms like described. I do notice that the pull of the sheets do put a droop in the booms on the leeward side though. That may be mostly due to the torque from my sheets and the method used to attach them. Will try another attachment method like a small loop of line from the clew. My booms are not nearly as open and clear of the sail as yours so some touching of the sail is seen. My booms are quite stiff and I've seen no appreciable bending that would cause the sail to get fuller in a gust. Haven't sailed with wishbooms in big wind yet though.

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This was my first stab at making wishbones and I agree that there is probably too much camber in them. Mostly this was just to start getting an idea how they would work out and what issues I would face rigging and sailing with them. I think my winter project might be carbon sprits.

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