After listening to the latest mothcast I decided to check my main foil angle of attack. I made a template of the foil section and drew the chord line and lines at 1.5, 2.5, and 3.5 degrees. It slips over the tip of the foil. I added some thickness to the trailing edge and did a really quick and dirty job of fairing the thickness into the flap. I've got it in pdf and dwg formats, so if anyone wants it I'm happy to email it to them. It plots on a letter sized sheet. I used a laser level to get the boat level and then shot it on the template. Wow, my foil was at not much more than 1/4 of a degree! That explains a little why I had to hike off the back of the wingbar and was sailing around in full flap down mode. I guess I was a little less than accurate in drilling the hole for my main foil and/or set it up at the wrong angle. I thought I was doing the right thing by putting the daggerboard at 7 degrees of forward rake, but apparently not. Needless to say, the boat sails a lot better now.
I didn't realize people would be so interested in the photo of Karl's boat. My attitude is that the more people that see your stuff the better, and I hope that everyone takes another look at the bowsprit concept. It's definitely on my list of stuff to do once I figure out how to keep the boat upright. The funny thing is that the bowsprit is possibly the least radical part of Karl's setup.
I don't use any more than 0.5 degrees (to the waterline) and foil generally before anyone else... I think a lot of this depends on how parralel the rocker line is to the waterline where the daggerboard leaves the hull.
ReplyDeleteCookie it also depends upon the zero lift AOA of your mainfoil section.
ReplyDeleteNat - don't you need to cross reference the mainfoil to the rudder foil also? For takeoff the hull is certainly important but once flying the relative angle to the rudder seems the critical bit. I suppose it is really two things - angles of lifting foils relative to each other and to the hull.
You're right, you need a reference point to measure this stuff from. I made some marks on the boat at the design waterline and have been referencing that plane. The boat most likely doesn't sail at that angle, but its what I picked.
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