Bow form question

[kristalik]

Hi guys,
I want to build kennyM bow form, but I cant find 3/4" plywood localy. My guestion is would 3/4" OSB or mdf board sandwiched between 3/8" plywood work. I will be using firehose. Thanks you

[fujimo]

no on the osb, but i have heard of quite a few folks using mdf with success.
i use a few layers of plywood glued and screwed together to get my thickness.
all plywood is under the designated size anyway- so i glue up a bit oversize- and then run it through the drum sander, or if you can find a 1/4 ply for in the middle somewhere- you can get it pretty close to size.
do you have laminated plywood beams over there- over here there is a product called L.V.L.- and those seem to be really goood.
 cheers
wayne

[jess stuart]

I have several MDF forms that have an outside skin (plywood) that have held up well.  They are takedown limb forms never built a full length one of MDF. It would be pretty heavy, you need to be careful to keep MDF away from moisture, it is also easily dented.  It does grind nice, much more so than plywood.  
The LVL is probably the best overall form material.  Like fujimo said you can get very close using three pieces of plywood, take a tape measure with you and pick out the best combination for your purpose.  I think I used to pieces of 3/4" and one of 5/8" to get to 1 3/4" total thickness sorry can't remember for sure.

[Robertfishes]

I built my kennym form 5 years ago. I can't remember exactly what I used..but I know I used birch "cabinet grade" plywood with a "filler" piece to make it 1.51" wide. The filler piece looked like brown peg board without the holes, I put it towards the middle of the stack.. I used three pieces of the 1/2" birch and one piece of the "filler". I used titebond 2 glue and a bunch of 1.25" drywall screws. I hand picked the plywood making sure it was straight, my form is still straight after 12 trips to the oven at 160 degrees. I took a set of micrometers into the store to figure out what combination I needed to get the right width.

[Krasus]

I use mdf. Also since your in a metric country look for 18.5mm ply.  Or use lvl (laminated veneer lumber) like Wayne was suggesting.

[monterey]

When you are right down to that last little smidgen needed to get the exact thickness desired, roofing felt layered up helps.

[monterey]

OSB   :mad:    :mad:    :mad:    

Don't do it!

I have two 1.5" forms that were originally made to build the Bingham 1.5" longbows.  Both swelled from moisture and are no longer useful for full width bows.  They are fine for Hill width design, however.  The Problem is the squirm factor.  .

I like the full 1.5 Bingham bows and plan to make several new forms in 1.75" for that purpose.

[Scott F]

I have used 3 pieces of 1/2" plywood with good results in the past.  I dont make many bows so maybe the form would degrade over time, but for only a couple of bows it should work fine.

[kristalik]

Hi guys,
I bought some 3/4" plywood, but with two sheets it is only 1.46" thick instead of 1.5". Do you think it will work ok? Or do I have to build it up to 1.5" any sugestions?

[Crittergetter]

I have a couple of forms from 3/4" ply. I glued a strip of 1.5" black glass on the form and haven't had any issues. I just be sure to not tighten my guides on the side very much so it doesn't pinch the stack when I pressure my hose.
Someone with more experience may have better ideas. Good luck and pics are a must!

[Beau J]

I also made my form with 3/4" plywood and it turned out a smidge under 1 1/2". All I did was shim the guides out to 1 1/2" and so far it has been fine...BeauJ