Bow form plywood

[Treespain]

I was wondering how you ensure that the plywood for the bow form is completely straight and doesn't have a crook? Is there a way of straightening them that people aren't posting or does it come out pretty straight when the two pieces are screwed together? I got a real nice piece of plywood $50 But its not completely straight along the length of it. Is regular flooring board good enough so long as its not particle or do I need to have the cabinet grade sanded ply?
Thanks

PS. The flooring boards seemed to be the full 3/4' whereas the sanded cabinet grad is about 1/32 to 1/16 shy of 3/4". If i used the sanded how do i make up for the lost width?

[Sam Harper]

If it's warped, you can rip it lengthwise and glue the other piece on it so they two pieces warp in opposite directions.  That'll take most or all of the warp out of it.  Then you can attach an angle iron to the bottom part of it to get it completely straight.

[Sam Harper]

Actually, I think I"d attach the angle iron while gluing and screwing them together.

[bigbob2]

x2 what Sam says

[Treespain]

So screw them together through a piece of angle iron first, and then set all of the other screws? What kind ply did y'all use to get a perfect 1.5"?

[Sam Harper]

3/4" + 3/4" = 6/4" = 1.5"

I'm not sure how I'd do it.  I'd probably lay one down so that the edges bowed up (assuming it's warped).  Put glue all over it.  Then lay the other one down on top of it with the edges bowed down, stand on it, and put the screws in.

Or maybe I'd put it on a table so part of it hangs off the edges, and put c-clamps on it so I can tweak it, getting the edges lined up.  Before putting screws in it, I'd clamp the angle iron along one edge, then put screws in it near that edges.  Then clamp the angle iron to the opposite edge and put screws along that edge, too.  Then I'd put screws in the middle, and check again to make sure it's not warped.  If it's still warped, I might just screw the angle iron on to it.

Or maybe I'd clamp an angle iron along both edges from the get-go.  I just don't know.  I'd figure something out, though.

[Trux Turning]

You are right- getting a 1.5" form with plywood takes some doing. On my current form my 3/4"x3/4" plywood is 1/8" shy of 1.5" so I add another piece of 1/4". This gives me a form that is a little oversized- I'll take a straight cutting router bit to the bottom part of the form and take off that excess to get my 1.5" width- I don't worry about reducing the upper part of the form. As for putting them together I glue and screw all pieces together and then bolt on a piece of angle iron to the bottom part. The angle iron adds a bit of weight, but the form is straight and doesn't warp.

[Troy D. Breeding]

I built several forms out of plywood years back. When the manufactures started reducing the true thickness of the plywood I was always having to build the forms wider and then run thru my sander until it was the right thickness. After trying my first LVL beam I no longer use plywood.

[Treespain]

Where do you get an lvl beam at? I'm open to better suggestions hah. I have a planer so I guess if I counter sank the screws I could do 3/4 +3/4 +1/4 and trim down to size.

[Sam Harper]

I got a big ole LVL beam at McCoy's, but it was warped.  I sent one through a planer and got it straightened out with 1.5" thickness left.  The other one, I wanted 1.75" to do a recurve form, but it's still a little bit warped.

[Sam Harper]

LVL at McCoy's:

 https://www.mccoys.com/search/apachesolr_search/lvl?bundle=product-catalog&keys=lvl

[Mad Max]

I think you can order at lowes or home depot (CONTRACTOR COUNTER)

I drive two small nails in my plywood form as locators (before i put glue on) to keep them from sliding around during glue up

[Crooked Stic]

3/4 1/2 and 3/8 will get you just a smig wider than 1 1/2. then run it thru the drum sander.

[Troy D. Breeding]

I get my LVL beams at Menards. I haven't bought any in awhile, but the last one was 2"x 12"x10' and cost approx. $35.00

[rockkiller]

I use LVL also.Its comes a little thick and I run it through the planet to get it to 1.5.You can get it at any local lumber yard.

[Treespain]

Nice! Thanks for all of the help guys I'm going to go and grab one of those!

[savage1]

I been using menards yellow pine lvl and they work great. Easy to cut, shape and sand.
In making my latest form I got smart and purchased
a pc. of doug fir lvl for the mother of all forms.
Sanded it to thickness, cut limb shape
and left it on the bench for the next day.
I come back and find it has warped at the
butt end. Never had that happen with cheap pine.
I have decided to stick to what works. Whatever the lamination process is or glue on the pine
it has always been good. The doug fir is pretty
but watch out it might come back to haunt you.

Lou

[Pheonixarcher]

I used 1/2" ply, with a piece of roofing paper in between the three layers. Glued and screwd together, makes a perfect 1.5"!
Worked great. I've only ran it through the oven four times now, so I'm not sure of the longevity without the angle iron, but so far so good. I may add some before the next batch of limbs just in case.