Until I’m able to score an FRP daggerboard, Has anyone had success making one? I know pine is maybe not the first choice but I found these stair riser blanks that are cheap and just about the right size to cut a pattern from. They even have a rounded edge. I’m looking to paint with several coats of oil based white. Crazy?
Yep, they have the oak stair treads as well. I'll start there then. The first issue I'm seeing though, is that these stair treads are exactly 1 inch thick. So the boards will need to be planed down to below the 27/32" max to fit into the DB trunk. I don't have a planer so that may be an issue. I'll need to check around and see if someone has one I can use. I do have a belt sander. It should make quick work of the initial shape knockdown."Soft wood" (like pine) tend to warp or "cup" when wet.
If you're going to the trouble of making a board for temporary use, to sell afterwards—or keep as a spare, why not spend the extra few bucks for mahogany or oak hardwoods? A warped board or those with a cup may not retract from the daggerboard trunk!
A belt-sander will make short work making rounded edges.
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This time however I put a 4" strip of fiberglass on the leading edge and sealed the board with two coats of epoxy.
I'm curious to see the results.I made a new daggerboard and rudder for my vintage Sunfish last summer from laminated birch plywood, the material used for furniture. I shaped them as good as possible compared to the standard drawings one finds. I gave them 5-6 coats of spar varnish - but this did not prevent their delamination by the end of the first season on the lake behind my house. I bought an FRP daggerboard but made a second rudder this spring from the same quality plywood. This time however I put a 4" strip of fiberglass on the leading edge and sealed the board with two coats of epoxy. I sail every day, sometimes twice, when the wind is good. The rudder still looks like new. West Systems epoxy is the way to go.
The standard daggerboard and rudder shapes are pretty basic. My engineering background is in fluid mechanics including aerodynamics and hydrodynamics. I am designing new shapes for both based on low-drag hydrofoils and then will make these 'wings' from foam and carbon fiber to reduce their weight, which right now is quite high. I will report on the results after testing.
Looks great. You did a daggerboard too?
Yes, last year. It vibrated a lot though and eventually delaminated. Water got into the plies and weakened it. It snapped at the bottom of the truck when I flipped the boat in high winds and was righting it. After that I decided this was too critical of a part and I bought an FRP board from SFD. The first rudder also delaminated, and snapped partly during high winds, which made it nearly impossible to steer. I had only used spar varnish on these two. The new rudder has several coats of epoxy and is working great.
For airplanes we tend mostly to use spruce for spars, birch and poplar for plywood. These have the highest strength to weight ratios.
Good point. We have squirrely winds on our lake, surrounded by tall pine trees. I have climbed up the daggerboard a few times after getting a dunking. I figure, if Boeing can make the B787 from carbon, a daggerboard ought to be strong enough if designed correctly. I have a new FRP board and it is nice, but the thing is heavy and the hydrofoils are not the best. But good enough for most people sure. I used to design airfoils and wings for a living so it is more of an engineering challenge to see if I can improve things. The big problem will be testing to be able to compare apples to apples. Fortunately I have some good prediction software that should enable this.
Nice to have such input in these forums... Nevil Shute was an aeronautical engineer, excellent small craft sailor & best-selling author circa WWII and post-war years, his novels still enlighten and entertain readers to this day. Good to have a site member with similar perspectives toward sailing & flying, two pursuits which share many common factors. CHEERS!!!
Thank you for the encouragement. I am impressed be the One Design racers, but do not want to be limited by those rules. Pratt in Hartford, CT was a client of mine in my previous aerospace career and they have some terrific engineers. What in your mind constitutes better performance though? Speed? Stability? We get a lot of powerboat-induced waves on our lake that reflect off the seawall surrounding the shoreline. Leaving the board fully inserted helps keep the boat moving when cutting through these waves, I have noticed. It would be fun to try a winged board, but tricky to insert and remove. Or one with a flap that could be deflected while sailing to increase or decrease camber on an otherwise symmetric foil. The key will be to make it effective and practical. A fun winter project. My guess is that many of these ideas have been explored and I am a newcomer to sailboat work. I did a few minor things for the 1987 Stars & Stripes, which was an exciting time for the America's Cup, especially when we won.
I did a few minor things for the 1987 Stars & Stripes, which was an exciting time for the America's Cup, especially when we won.