Plywood for Forms

[White Oak]

Guys, I'm having trouble finding 3/4" plywood to build my forms. Most common stuff is nominal. I have even looked at cabinet grade material  and it is about 1/32 under. 2pcs. laminated together= 1/16 under. The lams and glass that I have measure 1.525. I am most concerned about the eccentric washers binding the material if the form is undersize. MDF is the only thing I have found that is full size. Kennym has pretty much proven that that aint the way to go.Am I being too particular or how have you gotten around this?

Thanks,
       Ed

[broketooth]

go to a lumber supply that builds trusses for homes they have what they call lvl ( laminated veneir lumber). its a full 1 3/4 wide. even if you are building a glass longbow 1 1/2 wide you can still trim the excess

[White Oak]

Thanks broketooth. That is definately a good option. We have 2 places here that build trusses.
I just got back from a building supply store that had full 3/4" CDX one side sanded but only in 4x4 sheets. So there is 3/4" stuff out there I just aint found it yet. I have a couple of places to try tommorrow night and one has lvl. If they don't have 3/4 I'll go that route.
Thanks,
       Ed

[PM_Mining]

Do you have a Home Depot or Lowe's in town?  Both sell 3/4 CDX in full sheets.

[Hojo]

Ed --
If you go to one of those truss manufacturers, ask if they have any old /weathered LVL.  With the slower economy, they probably do and will sell it at a very reasonable price.  If you are buying it at normal prices, it can be a little salty (but then again, so is CDX...).  
Howard

[Glenn Newell]

I would go for the LVL as well, if you have to buy a thicker piece than you require you can have it gorund to you exact dimensions by someone with a wide drum smander. I wouldn't muck around with plywood as I have found the LVL to do a much better job...Glenn...

[White Oak]

Thanks guys.PM we have both Home Depot and Lowes in the area. I was in both today and also Menards. Have also checked Builders Supply earlier in the week. Everything everyone had in stock was atleast 1/32 under. They were labeled 3/4" but that isn't what they measure.
I have 2 other sources to check tomorrow.
Thanks all for the tips.
Take care,
         Ed

[OH Longbow]

I bought a sheet of 1/2" and used 3 layers.  It measures 1 1/2".  It might be just a fuzz under but, nothing significant.  I will say though, my next form will be made from a piece of LVL.

john

[Glenn Newell]

I wouldn't be too bothered with it being 1/32" under size as you could and is not a bad idea to face the form with a thin lamination or two of the correct width anyway once the form is shaped up. I always do that to my forms anyway...Glenn...

[BMN]

I haven't tried it yet but was told you can glue together a piece of 3/4, 1/2, and 3/8 plywood and obtain a true 1-1/2 inch thick form. I think some also use two pieces of 3/4 with a thin piece of masonite sandwiched between to make up the difference.

[ghost rob]

How about putting spacers under your washers to build them out? Chances are when you sand the sides of your limbs you'll do away with anything that didn't glue up square. Just a thought.

[TNstickn]

I glue up what ever scraps I have, lay out the bow on the plywood. cut it out and rout the profile of the finished form same as Kenny. After I get the two halves done I run'em through a 12" ryobi (cheap) benchtop planer. I run each piece then adjust. Lots of shavings removing 3/16-1/4" but I dont have to worry about any material/form issues, and it seems to take out any minor flaws concernning straightness of the wood. Have done the same with the lvls as well.

[White Oak]

I did manage to find some full 3/4" ply this afternoon. The stuff is called Form Ply and is used for concrete forms. Both sides sanded and flatter and straighter than any CDX I found. It is suppose to be available at lumber yards that cater to concrete contracters. The only negative I can see is that it is formaldehyde (sp) reg. exempt. Can't see that as a problem for what I am using it for. Cost $34.00 a sheet delivered.
Take care,
Ed

[kennym]

Check to see if it is oiled so the concrete(or glue to put form together )won't stick.....

[wihill]

I've often wondered if you couldn't just use two pieces of hardwood for a form (oak, birch, etc).  Menard's here has regular sales on 6' pieces of red oak that "say" they're 3/4" thick, but I didn't take the time to measure them...  

now you've got me wondering what the real thickness is on some of these boards.

[monterey]

I built a 1.5" form from 3/4" OSB from Home Depot.  It measured a true 3/4"!  It was T&G.  Have not seen any lately but it apparently is out there.

[White Oak]

You are right Kenny. They tell me this stuff comes both ways. This is not supposed to be oiled. A very good point for anyone who is looking.
Ed

[kennym]

Good deal, I know the stuff lasts really good for forms,and if I remember,doesn't warp too bad!

Let us know how it works if you go that direction.

LVL isn't availabe locally here.

[White Oak]

I tried to go LVL. Not only was the price prohibitive, for me atleast, I couldn't find anyone to bring it down to 1 1/2. I don't know anyone with a drum sander and the guy who was selling it said he would not run it through his planer. That told me that I might not want to put it through mine. Otherwise I sure would have liked to have tried it.
Ed

[Pennsyltuckey pete]

I have to say that I use the 3/4 cdx with the masonite sandwich.  I also use a Formica spacer under the eccentric washers on one side.  I always take a tape measure when looking for form wood.  Many times I have seen 3/4 stamped on the wood only to find it thinner.

pete