Can MDF Board Be Used For Pneumatic Limb Form Jigs?

[Erwincm]

Has anyone out there attempted to make a pneumatic limb form tool with MDF board (not OSB)? It's economical, very easy to work with, and a highly dimensionally stable "wood" but I'm not sure if it would be strong enough to handle the 60psi imparted by the inflated fire hose. Btw, I'm using a Bingham Projects limb form tool design.

Thanks,
Charles
Madison, AL

[cbatzi01]

I have read that it doesn't stand up to repeated heating very well.  KennyM actually posted something about a form failing on his site look at the (bottom for the note):

 http://www.kennyscustomarchery.com/Bow_forms.html

I used plywood for my two forms, using the Bingham's plans, and had no problems.  

Good luck!
Chris

[delongbows]

I built a takedown limb form out of mdf a few years ago. The form looked great, but twisted and took a set after the third time in the hot box. I remade the form out of sandwiched plywood, and it has been fine ever since. I'm not sure if the failure was due to the pressure, heat, etc., but I would recommend against mdf just to be safe.
Dave

[jess stuart]

I have several forms made from MDF and have made many sets of limbs without issue.  I did put a 3/8" plywood skin on the outside of the form.  I do live in a very dry climate which helps MDF and moisture do not go well together.

[kennym]

The pics I've seen of breakage were all with a bow and happened in the hot box. Bummer!!

I have a couple , one has 6" square plywood at all bolt holes with glue and many screws on each.

The other , I lined like Jess, but with 1/2" ply(what I had), it is a bit heavy to suit me but have had no probs yet with either one...

[ChekDE]

They do not hold up to repeated heating.  Actually, they don't hold up to heating...  Period.

I've had two fail on me.  The first had the glue up in it.  What a mess.  The second was me testing to see if the first was a fluke.  It wasn't and the form failed again.  Stick with 3/4" plywood.  I also screw a piece of heavy angle iron on the bottom to ensure the form doesn't warp.

[Erwincm]

I live in the humid Southeast (Alabama) so I don't think I'll take any chances with MDF based on your responses. It would break my heart and I might have to give up this hobby if my hard work was destroyed in the oven! Btw, ChekDE brings up an interesting point. Has anyone else had issues with form warpage? The thought never even occured to me but I can see how that could happen with all that pressure. I suppose it wouldn't be too difficult to screw a piece of angle iron to the bottom of the form for security sake. Thanks for the great input guys!

[Rigs]

My forms are MDF but I use a different clamping system that the wood fits in that makes it a non-issue...

Happy hunting,
Jason

[Matt Moline]

My forms are ply and MDF and they work great.  Here are a few photos.


 

 

[Bowjunkie]

Yes Matt, but you have plywood inside, right?

I made a one piece recurve press with MDF, it broke the first time I used it. The whole end broke off in the area of the recurve. It was glued and screwed together. I never used it again. I'm not big on wasting time, effort, and material. Now I use plywood or LVL.