DIY daggerboard options

Thread starter #1
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?
 

Attachments

L&VW

Well-Known Member
#3
"Soft wood" (like pine) tend to warp or "cup" when wet. :oops:

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! :confused:

A belt-sander will make short work making rounded edges. :cool:

.
 
#4
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?
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.
 
Thread starter #5
"Soft wood" (like pine) tend to warp or "cup" when wet. :oops:

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! :confused:

A belt-sander will make short work making rounded edges. :cool:

.
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.
 
Thread starter #6
This time however I put a 4" strip of fiberglass on the leading edge and sealed the board with two coats of epoxy.
I was wondering how to keep the knife edge from being prone to chips and dings. So a single layer thin fiberglass wrap over the wood should be sufficient to help with that? If you have time, it would be great to see pics of your board.
 
#7
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.
I'm curious to see the results.
 
#8
Here are pictures of the plywood I used. The original rudder I made from 19mm (.75") birch, the lighter-colored wood. The second I made from Lauan, 18mm. Since it only has to last one season until I make the carbon fiber parts, all I wanted was something smooth. The thickness of these boards (from Lowes) was perfect for the existing hardware, purchased through SunfishDirect. Coating it with epoxy makes it nearly as good as a heavier FRP rudder. You can not see it, but there is a strip of fiberglass cloth covering both sides of the thin trailing edge of the rudder, shaped (crudely) on my belt sander after cutting the blank with my band saw. Considering the entire effort took maybe an hour + time to cure the epoxy and reinstall the parts, I am happy with the results. Plus wood just looks nice when epoxied.
 

Attachments

#11
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 SFDirect. 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.
 

beldar boathead

Well-Known Member
#12
Older posts on here strongly recommend white oak vs red oak. You should be able to search for those posts.

The foil shape of current Sunfish boards results in vastly better sailing than the old slab-side boards.
 
Thread starter #13
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.
It would seem that solid plank blanks should fare better than laminate? I'm guessing even better when wrapped in a layer or two of fiberglass.
 
#15
Solid might indeed be better. You could probably wrap cardboard in epoxy and this too would work, but maybe put a spar in their as on a wing. In my case I just wanted something quick for a season as I intend to do it 'right' with carbon fiber. I am sure others here know what wood would be best - I am thinking something like a butcher board made of thick laminates. This is what is used for instance for plugs used in metal spinning. Maple is typically used. It machines almost like metal and is hard and strong. But probably heavy. For airplanes we tend mostly to use spruce for spars, birch and poplar for plywood. These have the highest strength to weight ratios.
 
#17
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.
 
#18
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!!! :cool:
 
#19
Thanks Coastal Redneck from Central Carolina Redneck, and proud of it! War Eagle!

Especially sailplane pilots are often sailboat enthusiasts. Self included. The reasons are the same - it's just me, my craft and nature / my Maker. My grad school adviser, an old-school German\ aerodynamicist, split his free time between soaring and sailing. He never married, no surprise. The more we understand about the science behind flying and sailing, the more we want to learn. Air and water are still very unpredictable, which makes it all the more fun. I would trade though all my fancy books for the experience of a sailor from years past.
 

beldar boathead

Well-Known Member
#20
It would be interesting to see if you can make a board the same length as the current frp one that performs noticeably better. Racers won’t be interested in it due to the class rules, but it’s an interesting challenge.

I think the lead designer of the frp board was an engineer at Pratt and Whitney.
 
#21
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. I want to see what I can get out of the board. It would be great to have access to a tow tank, but I might be able to set up something similar on the quiet inlet off our lake where we live. I have a long dock the length of the property that might allow some kind of a towing apparatus with force measurement. It might be possible to go with a shorter board if I can find the right combination of hydrofoils and planform; that is my hope at least. 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.
 

beldar boathead

Well-Known Member
#22
I think the definition of better is ability to improve VMG vs the current board. What other measure is there? It is unlikely a Sunfish board could improve stability - and that assumes a Sunfish is unstable at some point of sail when the board is normally down, and I’d disagree that a Sunfish is unstable in a way that hurts performance (and again performance is defined as VMG.)

The ability to angle the board so the leading edge is further to windward is the one performance option I can think of. A trailing edge flap would theoretically have the same effect, but be harder to engineer and use than a board that could be angled within the trunk.
 

L&VW

Well-Known Member
#23
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!!! :cool:
Since I sail on a lake with many large powerboats, I would add: SURFING! :eek:

.
 

L&VW

Well-Known Member
#24
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.
There's a member here you ought to meet... ;)
 

mixmkr

Well-Known Member
#25
Would not 20lbs of lead on the lower end increase stability? Would be fairly easy to do. My extended daggerboard[experiment], slightly foil shaped, just made me find the bottom easier and was another topic pulling it up and out.
A wing could be accomplished and pulled up flush into/against the hull (initially inserted from the bottom side and a stopper/preventer then inserted on the top side). But unless correctly designed. I would suspect it would just create more wetted surface and drag ...even upwind instead of lift.
Now a canted blade would be a design challenge, as would strenghtening the boat for a foil! If a Laser can be adapted...I guess the hard chine Sunfish is just best the way it is and foiling is the wrong mindset for the given sailplan and hull shape.
 

mixmkr

Well-Known Member
#30
dang...and I was hoping to get a source for rivlets…. you know...that shark skin stuff. Upper foils on my gaff just looked stupid ! ;-D
But ya know...having the white deck color, curve around over the edges and slightly down the hull side, over the light blue, has to be one of the coolest paint jobs.
 
#31
Sorry, I am out of riblet tape! 3M worked on this stuff but as I recall there never was a clear indication of it working. Her is an old article on the work: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020087761.pdf
The riblet pattern needed to be aligned with the flow direction, or something like that, which is pretty hard to keep constant. Plus they tended to foul with the usual underwater goop. I have no idea if 3M pursued this - I don't see the stuff on the rack of tape at my local Ace. The sharkskin suits on swimmers supposedly work. In the early 70s when I swam some of the guys would shave their legs for the same reason, until Mark Spitz with his cool mustache and longer hair won 7 gold medals at the '72 Munich Olympics. The human still has a lot of influence over the outcome.
 
#33
You are probably correct. I do not follow these things. They were one of many new ideas tried by the S&S team in 1987. The cats have pretty much changed everything and they are quite amazing.
 

mixmkr

Well-Known Member
#34
Yes ...you don't want a MOB in front of one of those Cat foils. I've had catamaran racing friends, that called their smaller cats...(aka Nacra, Prindles, etc) "Human Cheese Slicers"... when you're out on a trapeze and it pitch poles, throwing you into the standing rigging...
I'm wondering what will trickle down into the "consumer" market, originating from these new AC boats. I guess we're seeing the "fat-head" mains...and although also not all that new...the foils of course. My guess is most recreational sailors on their Hunters and Beneteaus don't realize their wing keels came from AC boats.
 
#35
The foils appear too much of a Rube Goldberg yet, keeping them stable without some kind of electrically-actuated autopilot seems to be a real challenge. I am more interested in minimalist, KISS-based, fail-safe stuff. The airplane guy in me says try a wing instead of sailcloth. The first big AC wings came from Burt Rutan I believe, an icon in aircraft design. The lateen rig on a Sunfish is pretty hard to beat though in terms of practicality, cost and fun factor. Maybe a 50% larger sail for less windy days? Something that could be attached to the standard sail and removed as desired? How about a bolt-on Trimaran conversion so a guy could take his gal and a Yeti along?
 
#36
I like the way you think, LOL. And that's DC's pic for the "Connor" avatar... hey, Kmisegades, didja ever meet a sailor named Bill Bennett? Billy Bones, I called him, but many others called him "Baby Dennis" because he looked somewhat like DC himself. Bad@$$ sailor, a real hand to have aboard during a race... sadly, I read somewhere that he passed away, I mentioned him in my "Laser Island Voyages" thread (first page, I think) because he was a cool hand and a heller good sailor, aye? Seems like we're losing the wrong ones in this crazy world... and I get your earlier statement about being close to nature, that's what my island voyages were all about, the islands are designated wildlife sanctuaries and they are chockablock with critters, from colonies of sea birds to colonies of seals & sea lions, and everything else thrown into the mix, including 2-ton Great Whites, LOL. Those pinniped colonies are like buffet tables for sharks, you understand... I always hunkered down in the cockpit of my Laser whenever I approached the islands, didn't want some cruising shark to make a meal out of me. I venture into the wilderness to have fun and get closer to nature, not to f#%ng DIE, LOL. :eek:
 
Top