I put a form together today (glued and screwed), but as the exterior grade plywood had a slight bend in it from being stacked during shipping, the form now has a slight 1/4" bend or warp. Anyone else have this happen? If so, how did your bow turn out?
  I put it on a workbench for the night, with a 100# dumbell on each end, in hopes of flattening it out.

It may not flatten now that it's glued and screwed.  Would like to hear how it comes out.

I used a piece of wood like that once and defeated the warp by glueing and screwing with the wood laid out and pressed flat on the patio.  It stayed straight.  

I know, kinda late for that advice!

If you are talking about bending or warping on the length of the form, take a piece of angle iron and screw it to one or both sides of the form to bring it in straight.

QuoteOriginally posted by stringstretcher:
If you are talking about bending or warping on the length of the form, take a piece of angle iron and screw it to one or both sides of the form to bring it in straight.

stringstretcher is on track--check the iron before you buy and use 2 pieces-then thru bolt them
-------------------mike

Thanks for the angle iron suggestion. If my dumbells don't cure the warp, that will be my next step.

I use LVL from Menards it is laminated beam material. It comes in long lengths and is 1.75 thick. Works great no glue and no screws.

You can help yourself out sometimes by gluing/screwing the pieces together with the warps countering each other. I think it is important to ALWAYS use some means to make the form straight while it is glueing a bow up. The angle iron works good for that purpose. The wood can and will move during the heat-up/cool-down cycle.It is best to keep it under control,with steel.

Chuck

One thing I did with a form made from a 2X8 was to spray down the inside of the warp with a spray bottle of water.  A liberal dousing and the expansion of the wood on that side of the form pushed it straight.  Only temporary though.

I think Two Tracks is on the right track.  Something to keep it from bending such as the metal.

If you had reversed the bends in the plywood and clamped it down straignt until the glue set it probably would have corrected itself and stayed straight. Trial and error, the fun of bow building.

sand it flat/straight.. Do you have access to a wide belt thickness sander? Then add another piece to bring back the width.. Consider making a new one,  this one could cost you a bows worth of materials.

Even angle iron can bend a little. Channel iron would be even stronger. By the time it gets repaired, you could have gotten a piece of LVL. Just stuff you learn I guess. Cost and time spent vs a re-do. If you're turning lemons into lemonade however, the iron would give you something to clamp to!

All the lvl around my area is stored outside and is worthless as bow form material. Lvl's are not weather impervious. 11 ply cabinet grade plywood stored properly for me. A perfectly flat work surface is a must.

like TN said 11 ply cabinet grade birch works nicely, 2 years ago I got lucky and was able to buy 3 sheets of 3/4" and some thinner stuff to make 1.75" from a local cabinet shop for a very good price. they even cut it to size for me..I got it home and glued and screwed it into three 1.75 inch bow form blanks.. used one right away, still have two 18" x 70" blanks for future use and they are still straight since they are stored flat.. try to find a cabinet shop near you, they might have some good ply there