Author Topic: Bending wood stock  (Read 431 times)

Offline Stormin'n

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Bending wood stock
« on: March 28, 2011, 11:58:00 AM »
My son wanted a new bow, since he outgrew his el cheepo compound.  He built a very primitive stick bow from a pine branch, but was somewhat disappointed in the performance. :)

We decided to try building one with hickory.  I cut down a straight grained board (yeah, not totally traditional, but this is a rough first attempt.)  I would like to reflex the tips, but have a few questions.  I have never steam bent wood, much less dried wood. The ends of the limbs are about 3/8 thick and taper from about 1 1/4 to 1/2".  I was thinking about making a plywood form and clamping to the form after steaming, but would appreciate any advice. Any plans or specs for a steam box?

I would also like to back the bow with fiberglass or other material.  Any advice/suggestions?
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Offline Loren Holland

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Re: Bending wood stock
« Reply #1 on: March 28, 2011, 03:42:00 PM »
Hickory shouldn't need a backing, but if you do just use more hickory. resaw a 1/8th inch strip to back, flip the grain the other way and glue up. that way you can glue in the reflex you are looking for without messing with the moisture content (hickory is notorious)...do not put glass over the hickory. hickory is a great backing or self bow, but in compression strength vs the tension strength of glass it will crush.  if you don't back and glue in Perry Reflex, you can put in on a caul (form) and dry heat also. You could even back after inducing reflex, you just can't glue a backing and then use heat, so plan your steps accordingly

Offline Stormin'n

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Re: Bending wood stock
« Reply #2 on: March 28, 2011, 06:37:00 PM »
Was thinking of using a piece of silk in epoxy for a backing.  The bow will be way too stiff if I use hickory (i think). Backing is mainly for safety (if it breaks, i don't want my kid digging splinters out of his eyes.)  I do like the idea of just laminating the curve in.  Might try that.  Can I adjust the tiller after that by taking stock off the belly?

Are you saying don't use steam? just dry heat, like with a heat gun and a form/caul?
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Offline eflanders

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Re: Bending wood stock
« Reply #3 on: March 28, 2011, 08:43:00 PM »
To answer your questions:

Considering that you are using a hickory board and that you are in CO. I would suggest that you use dry heat to form your reflex.  Hickory is moisture sensitive and there is an old wood working term that says that you should use dry heat with dry wood to form it.  Depending on the thickness you are working with and how straight the grain is will really determine your success in forming.  I would use a metal strip to use as a backer to the wood as you bend it.  Allow the wood to rehydrate for several days before flexing it.  In my opinion only, it might be better to use several laminations as was suggested earlier.  The glue adds strength and you cabn then glue in the reflex desired.

Offline Stormin'n

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Re: Bending wood stock
« Reply #4 on: March 28, 2011, 11:46:00 PM »
So, i used a heat gun and a caul I made from a 2x10, over exagerating the bends because I expected the wood to spring back a bit.  Worked great up until my son noticed that one tip had a crack where it was forced to bend too much.  It did not break through, but has an slight angle.  Anyway, Dry heat worked well!  I decided to go ahead and laminate another thin strip of hickory to back what we had and to help make up for the crack.  This is going to be a lightweight (30#) bow, so if it is not over drawn (Sam pulls about 22" now, more later) should (might)be ok till we get more built.  So, epoxy drying, and now we will see what pops off the form tommorrow.
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Offline Stormin'n

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Re: Bending wood stock
« Reply #5 on: March 28, 2011, 11:47:00 PM »
Next time, several thin laminations, for sure.  Much easieer to bend and glue than heating and bending.
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Offline Loren Holland

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Re: Bending wood stock
« Reply #6 on: March 29, 2011, 11:53:00 PM »
did you bend it all at once?or over several sessions? use the metal backer like eflanders said to keep from lifting a splinter during bending. let it cool then come back and bend some more.  how aggressive of a reflex are you putting in to break hickory? is it almost a recurve?
earlier you mentioned that the backing would make it too heavy... you will still tiller it after backing. in fact the best way (IMO) is to floor tiller, then glue in Perry reflex, that you will actually reduce stress on the wood while storing more energy. this is also a good way to get good performance from a light bow like for your son.
don't give  up on the dry heat. it is good to learn for shaping staves. also you can use that heat gun to heat treat your white woods (just do't do it on something your glued up)...if you had floor tillered the board, heat treated the belly, then glued up reflex, then scraped off the char as you tillered, that would be combining the best aspects of all those options...i don't know what your MC is like in CO, but do't forget to let your whitewoods adjust MC after you heat treat...good luck

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