I am following with great interest. I am working on my second hollow. The first one is too heavy.
I like the way you have those long strips running over the carbon fiber posts that transfer the deck pressure to the bottom. How thin are you going with the deck?
My 1/8" deck collapsed in the vac bag. I think I will add more support where my feet will be and lower pressure for the glue up.
It looks like an excellent airplane. I would be concerned regarding strength for a surfboard. I sure HOPE it works, though.
What kind of skin are you planning?
It would be nice to see more of your pictures. Try not putting so many in one post, see if that helps.
Here is the layout for the skin.
the bottom. (layers from inside out)
2 oz fiberglass cloth weave at 45 degrees
veneer grain going rail to rail
loose weave of carbon tow wrapped around the whole board at 45 degrees
veneer and carbon cloth grain going front to back
2 oz fiberglass cloth weave at 45 degrees
the top. Identical to the bottom, except where my feet are there will be an extra 2 ply veneer with many lightening holes. The grains will run at 45 degrees
i think it sounds like an incredible project, you are obviously very capable, it looks great.
i too am worried about strength under t he feet and the fins, but you are the only one who can actually feel the structure in your hands and know how stiff it is and all that good stuff.
i cant wait to see the end result…GREAT work!
“i cant wait to see the end result…GREAT work!”
yep !
I like the look of this …
…I, too , eagerly await the finished product , and a report on how it surfs , and holds up !
cheers !
ben
Today I put a block of bead board foam on the ground and put the surfboard’s frame on top of the foam. Then I put another piece of bead board foam on top of the board so the board was sandwiched together with foam. I then stood on top of the sandwich (170 lbs). NOTHING HAPPENDED!!! thats a good sign. The basic frame can hold my weight. (even though the weight was somewhat distributed by the foam) Im guessing that the load will be more distributed in the water, except on that big bottom turn or the hard lip smack. My theory is that the arch structure of the ribs will translate a tensional force on the ribs from rail to rail and send the stresses directly to the rails and the stringer. Thats where all the strength lies. Im debating whether or not to add more carbon truss members to the frame. I have so much extra 1/8" carbon tube, I dont know what to do with it!
That board is a superior piece of workmanship, and I love the modelling workshop. I grew up wanting to make planes like those but got into boards instead!
Just one thing:- Try not to read the thread about broken Salomon S-cores!!!
Speedneedle
I attatched some new pics. I added the top and bottom sections to the ribs so each rib makes an I beam. I laminated the top of the stringer with carbon. I added a balsa triangular section to the top of the stringer. This will lower the shear stress on the skin because the carbon makes a very sharp edge. The balsa will give a little so the skin will not be subjected to shear stress, instead it will be stretched in each hollow bay, like a drum. Check out the pic of the leash cup. It is integrated into the stringer. NOTE: I HAVE LOTS OF SANDING TO DO IN OREDER TO MAKE THE TOP DECK LEVEL!!! thats why it looks a little rough
after getting some feedback, I agree that the structure might not be strong enough to prevent crushing. This morning, I had a Eureka moment. In each empty rib bay I am planing to take two carbon tubes and cris cross them from corner to corner and bend them to make an arch (kind of like the supports in a modern tent) The apex of the arch will be directly under the sub stringer which is supported be single vertical carbon tube in the middle of each hollow section of the rib. The apex of this arch will fall in between each rib. Its hard to describe. Im planing on building a few tommorow and I will have pics.
PLEASE GIVE ME FEEDBACK!!! IM LOOKING FOR ANY IDEAS TO IMPROVE THE DESIGN Thanks!!
This should give you the idea…
that’s looking and sounding much better. The extra support trusses should help keep the deck up.
Now, add a couple of SuperTigers, pressurized fuel tanks and 100% nitro… (just kidding)
Wow, really nice craftsmanship, but it seems to me like it’s getting unnecessarily complicated.
To figure out if the deck is going to be strong enough make a test section of 2 or 3 ribs and put a panel of whatever it is you are going to use for the deck on it. Jump up and down on it, test it to failure and see if you are happy with the results. If not, make another test panel and test other methods before you blindly do the whole board without knowing the results. It will hopefully save you some time in the long-run and some headache if whatever you choose isn’t strong enough.
Take a cue from the sandwich knowledge being posted and glass under and over the deck skin for added strength.
Keep posting pics, this is a great thread!
This board is certainly unlike anything else I’ve seen on here 
I’m utterly fascinated by the addition of the dozens (hundreds?) of little bits inside. You could post 10x as many photos as you have, I’d still be drawn to them…and I still wouldn’t feel qualified to give you any feedback! I have no idea how a structure like this will hold up. Of course, I’ve never let that stop me before…
On first flush - from a non-engineer - I’d imagine that, at rest, this might be the strongest, lightest surfboard ever, for static loads. I would worry a little about it when it started to be surfed, just because of the flexing & probable twisting that you’ll exert on so many lightweight pieces & small glued areas. But I’m really hoping I’m wrong, just because this is so cool I want to see more like it built. I guess wings are subjected to dynamic loading by air, but it isn’t often that King Kong is jumping up & down on the top of a wing at the same time wind shear is pushing up on the bottom.
I agree with the suggestion of a layer of glass both inside & outside the skins.
Please finish this up so we can hear how it surfs!
here are some updated pics. I added the arched carbon like I was talking about in my last post. Also is a shot of the veneer I bought yesterday.
I forgot to add that the total weight of the frame pictured above is just under 2 pounds. I am able to lay the frame on hard ground and walk on it with bare feet. It’s very rigid with the addition of the new carbon supports.
wow …it’s really coming along quickly “lp” , good stuff …
cheers mate !
ben
Here are new pics. I built a small carbon truss on each rib because I thought there might be a possibility for collapse at the lightening holes in the ribs. That brings the frame’s weight to exactly 2 pounds. I also made the 2 layers of veneer for the sub deck. I will laminate them with grain at 90 degrees to each other and 45 degrees to the stringer. I am considering putting a grid of carbon tow in between the two sheets of wood for extra support. I will significantly lighten this deck with my hole saw. The sub deck will be where my feet are and it will give the skin extra thickness to avoid collapse.
Hey LP,
You better run out of that CF rod soon, otherwise the whole board will be made from it. ;-))
Little bit here, little bit there, oooh there’s some more bits, wonder where I can put them…
Great thread, can’t wait for the next episode…
So all your little carbon rods are…what? Solid? Hollow? Carbon string with epoxy resin already hardened? Soft strings?
How do you attach them? 5 Minute epoxy would be my guess…but I can’t tell from the pics.
This thing is a trip.
Those carbon arch springs are brilliant.
This is a great board. I was thinking along the same lines, except foam ribs with glass reinforcement but had nowhere near as developed idea as that. My thought was if I made it look like airplane wing parts I could get away with using my schools cnc hotwire cutters and routers, since I’m an aerospace engineer. I think I’d be limited to a kneeboard for that so they don’'t start asking questions.
Jeff Sharp
