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 Post subject: Concave bottom on a composite wood board
PostPosted: Tue Feb 22, 2005 3:50 pm 
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Joined: Tue Dec 23, 2003 6:30 pm
Posts: 832
Location: Traverse City, MI usa
Seems like 50% of all new boards have the diminsions of 138x39cm, and half of those boards have a concave bottom for edging and to help with going up wind. If that diminsion is the one that works, I guess I mite make a wood board for 20$.
You ask, what is a composite wood board?
Well Its two pieces of luan ply with .25x1.5in spuce stringers x3 in between those 2 pieces of ply, also there is some pink PVC foam and some extra ply between. Plus some epoxy glue to hold this mess together.
Ok, how do you get a concave bottom?
Make a jig, I took a big piece of heavy ply put some .75in thin boards at the ends and took a .75in stinger board through the middle, Then I took some Laun and bent it over this jig and screwed it down on the ends and middle. Valla concave and rocker jig.
Every piece of wood will be screwed to this jig at some time.
First screw your bottom piece of laun down, then make you diminsions, bottom, top, ect.
To get your rails screw your spuce stringer in the middle and one end, then carefully bend the stringer to the mark on the opposite end, ad screw, Valla a nice curve. After all this work take the stinger off then, put it back on with epoxy glue. Screw it done good.
Then put epoxy some luan pieces at the ends of the board for strength at the ends.
Now your half way done.
Note all those holes will be filled with,( wood dust, or flour) epoxy paste, yes I use epoxy and flour sometimes, If you what to be high tech, epoxy and Microballons.

Discussion:
The board will be 3/4 in thick and nicely tapered at the edges, going with this thickness easied the construction and it should look more like a production board. I plan to paint it.

The weight should also be decrease compared to my previous woody, due to decrease in thickness, tapering, and use of light wide spruce stringers. and less epoxy.

Concave bottom should also increase stiffness, since the board is laid up bent it will stay bent, in the vertical, Z, and horizontal axis.

Rails are also going to be reinforced with a little glass and epoxy, because I like to surf up onto the beach and with a concave bottom the edges are going to take a beating, I have a new innovative method for doing this, 3in wide fiberglass drywall tape. the tape is sticky on one side. Stick and then paint with thick"ind (epoxy and flour)......

Ok I half way there, here is what I've done so far.
Here are some PIX.
http://myweb.core.com/photos/bsurfer@fr ... surfboard/

Note the concave
Note the rocker
Now I'm getting ready for layup of inside PVC foam and Instert Strip.
Epoxying the parts in.

The Instert strip is screwed and I use a method I've have used before on past project to press things down, Duct tape.

The duct tape applies pressure to the pink foam as the expoxy glue cures.
Screws hold the center wood strip with T bolts as that cures. This lay up was for the inside of the board.
Duct tape works great, because it has lots of spring to it, Cheap and does not leave or damages the foam, which is light, and easily bent. But with the wood strips you need a lot more force.

Next layup will be the wood/top/cap, Note the pieces of board on the ends, had to Scarf peices in, I was to lazy to get more ply, Plus the scraf will end up stiffin the ends and act as a stinger accros the board, after this shaping will be done with a jigsaw and plane.

http://myweb.core.com/photos/bsurfer@fr ... oardshape/

About 9lb I'll shave off some more shaping, so not to increase the wieght when expoxing and reinforcing. Maybe even decrease the wt.
more pix to follow


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 Post subject:
PostPosted: Sun Mar 20, 2005 10:02 pm 
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Joined: Tue Dec 23, 2003 6:30 pm
Posts: 832
Location: Traverse City, MI usa
Ok I guess I spent 30$ on the board itself, instead of 20$, the insterts cost alot. Plus the expoxy is expensive, But I think it was smart to beef up the edges of the board and to finish the board with 2 coats of expoxy.

Made the Pads, but the rest of the assesorys I bought.
Here are the finale PIXs.

http://myweb.core.com/photos/bsurfer@fr ... Finishing/


[img]http://my.freeway.net/~bsurfer/finished2[1].jpg[/img]


Last edited by bay surfer on Fri Jul 22, 2005 2:45 am, edited 14 times in total.

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 Post subject:
PostPosted: Thu Mar 31, 2005 11:59 pm 
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Joined: Tue Jan 06, 2004 3:14 am
Posts: 3
Location: Ontario Canada
Hi I used to build a ply board with a cheap foam core, you are right they are cheap to build but alot of time to complete, now I use corecell I worried It would be a waste when I didn't know what I was doing and plywood was greato learn on consider I used to spend as much as 25 hours on a board now it is more like 12 hours the results are great, now its time to make a next step try a structural foam core board and you won't go back to wood and when you work out the $'s You'll see its very close in comparison.

Cheers
Jim


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