Plywood for form?

[Don Armstrong]

I can't find any 3/4" plywood except birch and blondwood for about 45.00 a sheet. Would sheeting grade work for a form or do I need the good stuff. Also, what glue do you use to laminate the 3/4" together to make a 1 1/2" form. I will use drywall screws but do you use glue to. Thanks, Don

[Trux Turning]

I use the less expensive plywood for my forms, just get a straight sheet. Plain old wood glue and screws to put it together. If there are voids in the surface of the finished form-  Fill them with bondo.

[kennym]

You might check on the LVL stuff used for headers and such. It comes all glued up in exact widths.I haven't found it locally here, but this is a smaaaall town!

[jess stuart]

You can get to exactly 1.5" with the correct thickness.  I think the plywood are about 1/16" less than full thickness.  If you use two 5/8" and one 3/8" it comes out to 1.5"  I just take a tape with me and measure and select in the store.  I have used MDF on my last forms, I know some people have had them fail but so far so good.  I do like Trux and use the cheaper stuff.

[Badwithabow]

I use Melamine boards from home depot. for my form they are laminated mdf boards. so the only edge not laminated is the edge the bow is on but i screwed in a strip of metal. no problems so far.

[Don Armstrong]

Thanks guys, the LVL is not available here either. That was going to be my first choice. I have a formica strip coming from Binghams to glue to the form. I'm going to Lowers and Home Depot tomorrow to see what I can come up with. Don

[Robertfishes]

I have bought the good 3/4" birch cabinet grade plywood directly from my local cabinet shop, it was stored perfectly flat and was under $35 per sheet. I have been using Tite bond II glue and over a pound of dry wall screws, I understand tite bond lets loose at 150 degrees so the screws are really important.  1 1/4" screws are on both sides of the 1 1/2" form. I have been using 040 black glass on my forms instead of the thin formica strips. The spray adhesive that I use to hold down the fiberglass on top of the form is called "High Strength 90"  

[Don Armstrong]

Robertfishes, Thanks for the info. Where do you get the " High Strength 90". I guess a piece of .040 glass will need to be ordered from Kenny. That is a nice looking form. Thanks again, Don

[Robertfishes]

My first material order was from Binghams and they sent 040 glass in place of the formica strip so i just always use glass now.. The HS 90 came from Lowes, they also sell the 77 spray adhesive but the 90 is high temp rated.. the 90 is expensive but I knew I would be building several forms..

[Don Armstrong]

Thanks, I'm going to Lowes today. Don

[**DONOTDELETE**]

You might want to consider adding hardwood edge banding or flat steel to the edges of your plywood forms to help keep them straight. especially if you are using a hot box.

Using heat strips is a LOT easier on forms and you can adjust the form straightness if need be prior to turning them on.... food for thought... Kirk

[monterey]

I used 3/4 OSB for one form and had no problems.  Strange thing was that I found OSB at HD that was true dimension and two pieces gave a true 1.5"  Shoulda bought more cause I've never come across it again.

I have some roofing felt in the shed and plan to use it to build the additional thickness with the next form build.  Feel free to talk me out of the roofing felt though!!!

[Bob Sarrels]

I use the lvl strictly on my forms. I am in a big city so I just drive over to McCoys and order it just the length I need.  No waste.  I do have to run it thru my surface planer for 1.5.  It comes 1.75 which is just right for the recurves. I use the strips on all my forms so I have not suffered any movement.  I do have 1 form that was cnc,d out of aliminum cause this is a 1.5" recurve form and the wood one just gave me grief.  It cost about $1000 but it is true, true, true.  Only problem is the aliminum sucks the heat out of my lower strip so I added a 1 1/8th strip of hard rubber to it and it stopped the problem.

[Shaun]

Check the bargain bin at your larger home lumber yards. You can often find damaged sheets of high end 3/4 ply for a fraction of the cost. Most of the damaged sheets just have a crushed corner or surface scratch.

[Don Armstrong]

Shawn, I tried that about an hour ago. Guy at store said to check at Habitat for humanity store. Having a hard time spending 44.00 a sheet   :(   . Don

[D]

Don't blame you on the not wanting to spend the 44 on a sheet but I've got a question.  Is it a bad idea to use a regular 2 by 10 or 2 by 12??  They are and 1.5 inch in width.  I made my form out of a 2 by 10 with a pieces of alluminum as the pressure strips.  I've got six pieces of steel on each side that bolt it together.  Is this a bad idea?? I've only glued one bow up in and the glue lines all came out fine.  I can see where plywood would be a better surface but it was a cheep way to go.

[Don Armstrong]

You risk them twisting and ruining a bow. The laminated feature of plywood helps to keep the form straight. If the steel keeps it straight, your home free. Don

[Sixby]

72 in by 12 in Versa rim in 1 3/4 width costs me 34.00 No gluing needed just cut out and sand and build bows. I'll never use anything else unless I absolutely have too. I have forms over 5 years old that are still absolutely straight and turn out a good bow/ the nice thing is that they are exactly 1 3/4 wide and the glue is a waterproof glue . These things really hold up. I have not had any voids at all in mine. I do smooth on a piece of glass and put the airhose on it and let it set over night. I guess i could use heatstrips. I wonder why I didn't think of that LOL.
God bless you all , Steve