just curios how many layers/weight of kevlar used on your rails. As an ex R/C’er i can really aprecciate your work!
2 layers of 5 oz
1st layer @ 90 degrees
2nd layer @ 45 degrees
here is the setup for the second hollow kevlar rail.
first I tacked the mold to the board with a layer of wax paper in between (note the small holes cut in the wax paper for a dot of C.A. glue). Then I slaped on some mold release wax on the mold. I wetted up the cloth and then pinned it down on each side with 1/4" square balsa sticks. After I pop the rail out of the mold, it leaves me with a nice 90 degree flange to glue against the board. The balsa also doubles as a guide to cut off the excess cloth (A jigsaw slices through kevlar like butter as long as it is supported by balsa) and the balsa will also support the cloth when I sand it flush with the deck.
I know kevlar is a bitch to work with, but I’ve got the procedure down so It cuts easily. To cut the raw cloth, I first draw a line with a water based marker. Then I run a bead of thin C.A. glue along the line. The C.A. causes the cloth to become very brittle. I can easily cut along the line with regular scissors because the fibers are held together by the C.A. glue.
wow im impressed
I started installing the ribs in the hollow kevlar rails. The ribs stiffen the rails alot. Each rib is cut from a balsa/carbon plate.
The plate has 5 layers
1: 3/4 oz glass cloth
2: 1/2 oz carbon mat
3: 1/32" balsa sheet
4: 1/2 oz carbon mat
5: 3/4 oz glass cloth
The plate is super stiff and only about 1/20" thick
you can see the plate in pic surf 77
In order to get the shape for each rib, I made a tool which consists of about 40 thin strips of wood which are sandwiched in a sleeve. The strips can slide in and out of the sleeve. I push the strips into the hollow portion of the rail at the rib location. The strips mimic the size of the inside of the rail. I can trace the strips on the carbon plate. I drilled a hole in each rib for ventalation.
here are the ribs installed in the rail
does this construction look familiar… check out the leading edge of the wing
brilliant.
I especially like the tool you made for measuring the inside concave of the rails.
I’ve got nowhere near the R/C plane experience that you do, but appreciate the application from one discipline to another.
pat.
I cut out some to the pieces for the final skin. You might get some idea of what the finished product might look like. The final finish will match the fins.
To attach the rails, I made a few balsa guides which will be glued to the board. Each rail will slide over the guides when I glue it to the board. This will keep it in perfect allignment with the board.
I glued the balsa guides to the board. Then I placed the rail on the guides. I used epoxy in a syringe to glue the two parts together. The internal wood is waterproofed with thinned epoxy. There are ventalation holes in all the ribs and a ventalation hole to the inside of the board at the front of the rail.
I glued the other rail on.
I’ve been kind of haphazardly following this thread. You mention a few times that you want feedback- positive or negative. First of all let me say you’re nuts. Then again so was Howard Hughes, right? Like everyone else I’m dying to know how the thing eventually holds up and how well it works.
A couple of questions- I was looking at the pics of the curved carbon rods under the deck meant to take some of the deck loading, but it looks to me like they end on balsa. How is the balsa supposed to take a big load focused on the little tiny point of the rod? Or, more likely, is there some kind of (kevlar?) patch where they end that I just couldn’t see in the photos?
Also, did you try yanking back and forth on the fins? The box supports look so light. If you turn as hard as I do… LOL… you’re gonna put a lot of lateral load on those.
Finally one critique- and this is just me and my boat building experience, but the outline looks kind of sequential. That is- it’s curvy in the nose, then goes kind of straight through the middle, and then is curvy in the tail. It might be just an aesthetic question of taste, but I always look for a really smooth continuous curve. In boatbuilding we’d call it a “fair” shape- no bumps or bends. It’s also one of the reasons so many longboards look funky to me- they get that really straight, parallel thing going on “amidships.” Of course, the stealth bomber’s not very “fair” and it flies, so what do I know?
Anyways, my compliments for an absolutely fascinating project.
First of all let me say you’re nuts.
I take that as a compliment. Thanks
I was looking at the pics of the curved carbon rods under the deck meant to take some of the deck loading, but it looks to me like they end on balsa. How is the balsa supposed to take a big load focused on the little tiny point of the rod? Or, more likely, is there some kind of (kevlar?) patch where they end that I just couldn’t see in the photos?
If you go to the beginning of the thread, look at the internal truss of the main stringer and the kevlar/balsa rail when the board was first framed. There are 1/4" carbon tubes on each edge of the rib location. That is where one end of the arched rod butts against. If you notice the rail has an internal layer of kevlar tape between 2 plys of balsa. That is where the other end butts against. My Idea behind the board is that the general design of the internals is a balsa frame in the rough shape of a surfboard. This frame is designed to act as a jig to hold carbon and kevlar parts which would otherwise be VERY hard to assemble on there own. Most of the balsa won’t see much stress because the carbon and kevlar parts are so stiff that they will reach their yeild before the balsa encounters any stress. If you study the design, you will notice that all carbon and kevlar parts are in contact with each other and the balsa is like a fillet in between the joints. Its is really easy to put together because the carbon punches a clean hole through the balsa when installed and CA glue whicks into the whole joint to make a rock solid bond.
Also, did you try yanking back and forth on the fins? The box supports look so light. If you turn as hard as I do… LOL… you’re gonna put a lot of lateral load on those.
I use a structure that is MUCH LESS sturdy on my airplane tails. Some of the tail sections are made of only a thin balsa truss and superthin mylar covering. Check out the tail section on the attached pic. I can put this plane in full throttle spins strait down for hundreds of feet and probably doing over 50 mph. All of the GIANT control surfaces are deflected at least 45 degrees in this manuver. They have over twice the surface area of a surf board fin, and are still holding up fine after getting some crazy bending sresses. Remember that the fin box is interlocked into the rear rib and the rail. It also is anchored into the top and bottom skin.
Finally one critique- and this is just me and my boat building experience, but the outline looks kind of sequential. That is- it’s curvy in the nose, then goes kind of straight through the middle, and then is curvy in the tail. It might be just an aesthetic question of taste, but I always look for a really smooth continuous curve. In boatbuilding we’d call it a “fair” shape- no bumps or bends. It’s also one of the reasons so many longboards look funky to me- they get that really straight, parallel thing going on “amidships.” Of course, the stealth bomber’s not very “fair” and it flies, so what do I know?
I don’t credit myself as being a good surfboard shaper at all (however I do consider myself a good wing shaper but thats where my strait lines come from). This is only my 6th surfboard. I know it looks a little flat around the center. I was waiting for someone to call me out on that. Congradulations!! But there’s nothing I can do about it now so the hell with it. I think the shape twards the tail is a little out of symetry too but its hard to tell because the strips of carbon across the board aren’t quite strait either. Im hoping that the curved shape of the final layer of skin will distract from any aesthetic imperfections in the shape.
I ran a criss cross of carbon tow across the deck and bottom. Each strand is anchored to the flange on the rails.
Im laying the final skin on the deck.
ooooohhhhh
me likey , me rikey a rot !
when is honolable raunching day , oh sensei "lpc etc ?
ben
a long an interesting journey nears completion …you must be STOKED , mate ! [I AM , just WATCHING it through the screen , for all this time …EXXXXCELLLLLENTTTTTTT !! Well done ! …in the absence of young Josh …I’LL give you a big “YEWWWWWWWW !!!”]
now it’s REALLY looking like a surfboard to fly on the WATER…can’t wait for the launching photos ! [hint hint ]
now it’s REALLY looking like a surfboard to fly on the WATER
You just gave me an idea. Would it be possible to create some kind of board that could glide for short periods, not just get air but glide, ala flying fish? Some kind of Crazy hollow carbon balsa kevlar composite flying fish? I’ve seen flying fish on the way to catalina. They sort of glide right in front of the wave occassionally using their tail to get more speed.
I don’t know if you have see WIGs (wing in ground-effect) but you actually get more lift near the ground with a wing beacuse of the compression of the air between the wing and the ground causing higher pressure.
… have you been working on too many hover crafts lately buddykai ?!
ben
What are you using for a vent plug?
Jeff
Some kind of Crazy hollow carbon balsa kevlar composite flying fish?
you’ve got me baffled now!!! I have no idea
What are you using for a vent plug?
Jeff
I have 3/16" hole through the nose of the board and the whole interior is waterproofed and vented to the nose. But I havn’t shopped around for a vent plug yet. There’s a place near me that does windsurfing. They might have something I can use. Last resort: brass insert, and a screw + o-ring
