Author Topic: Juniper bow problem  (Read 2423 times)

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Offline RandyN

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Juniper bow problem
« on: October 23, 2019, 04:08:45 pm »
Determined to get a Juniper bow shooting. Short history on this bow. I cut the limb from an old Juniper tree in my front yard. Let it sit with the bark on it until this summer. Not a perfect stave but a good one to learn on. The profile is crazy, half moon design from tip to tip. I tried steaming it first to get it straight. Didn't work. Then dry heat. Worked a little. Decide to keep working it and got it tillered evenly to 18". Then decided to back with sinew. I now have 4.5" of reflex. Struggled to get a string back on it. I have it braced at 6.5". This area lifted on the belly side of the bow about 3" down from the tip. It has not changed even though I pulled the bow a few times. What do you think is going on? I've never seen this before.


Offline TimBo

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Re: Juniper bow problem
« Reply #1 on: October 23, 2019, 04:12:59 pm »
It looks like the heartwood is delaminating from the sapwood.  Do you have enough weight/thickness for an all-sapwood bow?  I have never seen anything quite like that either. 

Offline Hamish

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Re: Juniper bow problem
« Reply #2 on: October 23, 2019, 05:22:17 pm »
Slap some glue in there whilst its strung. Unstring it, then wrap the area tightly with rubber strips from an inner tube.

Use a good glue like a proper bowmakers epoxy, or urea formaldehyde. Let it cure properly before continuing tillering.

Offline Ryan Jacob

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Re: Juniper bow problem
« Reply #3 on: October 23, 2019, 10:13:12 pm »
I’ve had that same issue before. Don’t stress the bow anymore, glue it down first. The damage runs deeper than you might expect.

Offline bassman

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Re: Juniper bow problem
« Reply #4 on: October 23, 2019, 10:30:13 pm »
I would make the repair , and  drop the brace height to 5 inches for now , and continue tillering by trapping the back little by little. The wood didn't do that before sinew backing, so it may be  over powering the belly. JMO ,so take it with a grain of salt.Others on here may have a better way.

bownarra

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Re: Juniper bow problem
« Reply #5 on: October 24, 2019, 02:12:14 am »
 Sinew cannot overpower the bellywood - it has low stretch resistance. However adding a bunch of reflex will increase the strain.
There is a thing called laminar separation, where the wood split between growth rings. You have something along those lines happening.
6!/2 inches is a high brace height.

Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Juniper bow problem
« Reply #6 on: October 24, 2019, 03:55:33 am »
I think it's just a weak growth ring (wind shake/disease etc) giving up and letting the wood buckle. I had that on some Elm recently.
Get some low viscosity CA in there when it's open like in the pic, the unstring it and clamp it up between some soft jaws (with paper round it to stop it gluing to the jaws  ::) )
You can add a fine binding for security too, if you want.
Del
Health warning, these posts may contain traces of nut.

Offline RandyN

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Re: Juniper bow problem
« Reply #7 on: October 24, 2019, 12:07:21 pm »
Thank you all for the advise. I was thinking along the lines of a growth ring separation. I have the high brace height because the bow would twist and reverse the string to the back. Because of the high reflex after putting the sinew on. It reflexed that amount on its own while the sinew dried. I will put some CA glue into the area while its open (strung) and then unstring it and clamp it. Then a sinew wrap should fix the problem. Thanks again for the advise.