Form gap

[buckeyebowhunter]

What is the gap between your forms top and bottom and how much psi are you running in your air hose? Let's just say in the working portion of the limb area on your form. Asking for a friend.. thanks fellas

[JGR1269]

How wide is your form? I build off 1 3/4” forms and I like a small gap. A bigger gap will allow your hose to inflate and be too round putting more pressure in the center. A smaller gap keeps it flatter with more evenly distributed pressure. Usually 1 1/4” or less gap is sufficient.

[kennym]

I use 1.25 on longer bows with thicker limbs and 1.125 on the 58".  Not sure on recurves because I don't do em...

Been using 70 psi for a long time, but I noticed when using ziptys and airing to 10 psi and pulling the tys out , very little glue comes out after the 10 lbs.

So been cutting back to 60 psi lately

[Mad Max]

1" for a recurve form
On a dry run if the gaps will close up at 45# I put 55#

[Longcruise]

I used to go to 80 but now go with 60

[buckeyebowhunter]

Thanks fellas. I posted awhile back about getting the tiniest hairline cracks in my back glass, and got another one on my last glue up. I'm still scratching my head on it. I backed off my pressure to 55psi on the last several runs and thought i had it figured out and then got another one. I think I might try 50psi on the next one. I just can't figure this out and it's so random and frustrating lol

[Crooked Stic]

Ideally when your hose is inflated in a form looking at the end should be dog bone shaped. My space is about 1.25.
Seems topless forms are getting popular and they are strapping down with mule tape .don't know how much pressure they run.

[Longcruise]

Ideally when your hose is inflated in a form looking at the end should be dog bone shaped. My space is about 1.25.
Seems topless forms are getting popular and they are strapping down with mule tape .don't know how much pressure they run.

I do topless and run at 60#.  Could probably use less.  My widest form is 1.75".  With topless it's important to completely deflate the hose before strapping it down.  Also it must be centered down the lay up with equal measurement of hose one each side and the strap material must be pulled very tight with every wrap.  Pressure strips are .130 thick.

[onetone]

Which brings up a question or two. Buckeye are you using a pressure strip between the hose and the bow? Are you careful to all the residual epoxy of it before use?

I have always pressured up to 45/50 psi. Works fine for me and I have switched over to topless forms.

[buckeyebowhunter]

Onetone,  yessir I use a pressure strip. It's a fairly new pressure strip so there's not much gunk on it maybe just a little residual goo from the strapping tape on it. I do my best to keep everything clean but maybe I need to do better, hard to stay perfect when building is such a messy endeavor.
It's been such an inconsistent occurrence that it makes it hard to pinpoint.

I am going to try less pressure on this next set, but I have a rough time believing 55 is too much when ppl say they use 70+

Thanks to all for trying to help me solve this issue.

[Kirkll]

With 1.5" wide forms and glass you can go a bit wider gap between the top and bottom forms, but its best if the shape of the top form follows the same taper rate of the wedge and limb assembly. So on a limb form the actual gap is about 3/8" wider at the butt than the tip. I make mine about an inch or so gap.

I want the gap set so when i put the top form on, the hose is deflated completely, and  giving it the "Dog bone" shape..... Doing this requires much less air pressure....But it's even pressure.

90% of the bowyers using an air hose system use WAY more pressure than needed.  I've laid up limbs with 25# pressure before with no issues at all. Anything over 50# is over kill, and can in fact cause problems if you go higher than 55-60#

I have a few RC forms where i got a bit too far apart at the curl, and i use wedges on top of the hose to flatten it out... with lower air pressure you can adjust the wedges to get the lams settled in tight to the form, then add a few more pounds....    Hope this is helpful....   Kirk


Btw..... This is using a 2" air hose....   

[Mad Max]

I don't cut the gap until all the clamping hardware is installed and then I mark it and cut it back.