I have made some longbows with a Bingham Projects air hose form. I have had problems with air bubbles where the riser curves steeply. It just doesn't get good pressure with the airhose there i guess. Part of it might be that the form is for 18"risers risers and i am building 14-15" risers.
To make Hill style/ short riser (12-14") bows should I:
1) make a new form for shorter risers and an airhose
Or
2) get a clamp system.
Any ideas or opinions would be appreciated.
Eric.
New airhose form, thats just me tho! :D
If you shortened the riser and didn't modify your form ,there is your air bubble prob, I like to maintain about 1.25" all along the form , including up and over the riser.
I have done both and I always prefer and airhose form.
If you already have a form that just wont give you good results, Try gluing the riser cut-out back in the top of your form, and then re-cut it to the size you need.
Also, try using thin lams on those short, steep ramped up risers. The air bubled are coming from not getting good and even pressure and it is a lot easier to bend in a thin lam than a lam .100 thick on those steep riser ramps. Try a dry run at 35 PSI...if it doesnt comform correctly at that pressure something needs to be fit better.
I had that problem on one bow when I changed from an 18'' riser form and made up a 16'' Hill type but forgot to modify form. Ended up making a form for the 16'' and no more problems.Cutting curves to suit the shorter riser as bjansen suggests and adding to the upper form would probably work if careful.
I usually put the riser behind the stack with just glass or veneer and glass behind it.
I guess i will plan on trying to build some new airhose forms. The current form is straight and I want a reflexed form and a reversed handle reflexed form.
Thanks guys,
Eric
I would still try modifing the hill form you have ....I have stuck short sections of dowel rods in the fade area (in between the top side of the form and the air hose) to get more pressure where needed on that fade. Just would hate to see you go through all the trouble to make another form if you already have one that will work...
Or just make a new top section of the form you already have?
Here's a pic of my form that I modified from the 18" Bingham riser design to a 16" riser design. I just cut out the old riser section of the top part of the form and glued in a new one.
(http://i954.photobucket.com/albums/ae23/jsweka/BowBuild/CAM_1730.jpg)
Bjansen,
The form i've been using belongs to our school's shop program so i wouldn't be able to modify it as you suggest. I may put temporary shims in there though if i decide to make another straight limbed bow.
You could also go with a rubber band (inner tube) pressure system. That way you would be able to change riser shape and length at will on any future build.
In the past when I'd make a bow with a shorter riser, I'd just cut a spacer out of a chunk of 2x4 or something to fill the void. Then you can use it or not use it depending on which length handle you're using.
I guess my biggest concern is if an airhose form can work for the steep curves of a short risered longbow.
Any idea if HHA, Northern Mist, etc...use airhose or clamps??
Eric
It will work, but it is essential that you have a proper fitting top side to the form.
It's harder to get good pressure on the shaper fades of a short riser with clamps. Air hose all the way. Shims should still work fine with the old top section if you decide to still use that form