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Author Topic: belly lam  (Read 6711 times)

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Offline jayman448

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belly lam
« on: March 01, 2015, 11:38:52 pm »
So i was thinking (never a good thing xD) birch has a tendency to get compression fractures. If a guy was to tiller up a bow and it developed compression fractures, would laminating a 3mm thick strip of say, maple save the bow from Belly compressions and ultimate failure?
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Offline Pat B

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Re: belly lam
« Reply #1 on: March 02, 2015, 12:10:02 am »
I've used osage and ipe as add on belly lams with good results.  If your bow is birch, maple might be a good option but that is just a guess.
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blackhawk

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Re: belly lam
« Reply #2 on: March 02, 2015, 06:54:20 am »
Maybe and maybe not pending on how deep they go...I've seen them go all the way to the backing strip before
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Offline PEARL DRUMS

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Re: belly lam
« Reply #3 on: March 02, 2015, 12:04:03 pm »
Even the name brand Band-Aids loose their adhesion after a while!
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Offline adb

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Re: belly lam
« Reply #4 on: March 02, 2015, 12:13:02 pm »
Quote from: jayman448 on March 01, 2015, 11:38:52 pm
So i was thinking (never a good thing xD) birch has a tendency to get compression fractures. If a guy was to tiller up a bow and it developed compression fractures, would laminating a 3mm thick strip of say, maple save the bow from Belly compressions and ultimate failure?

So... have you tillered up a birch bow which developed compression fractures?

Maple is another tension strong wood, and excels more as a backing wood. My favourite, actually. Try using a more compression strong wood on the belly. Any of the standards... ipe, osage, yew heartwood, etc.

All you're really doing is trying to patch a critical mistake. Birch will make a bow if you design and tiller it carefully. If you don't, learn from your mistake and endeavour to not repeat it. I've learned far more from mistakes than successes.
« Last Edit: March 02, 2015, 12:31:12 pm by adb »
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Offline arachnid

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Re: belly lam
« Reply #5 on: March 02, 2015, 12:25:41 pm »
A friend of mine sucsessfuly patched a chrysaled bow limb. The chrysals where in one week spot. He sanded thay spot and glued on a thin lamination and once the glue dried he sanded it smooth and adjusted the tiller. I never tried it but he ssid it hold.

I wonder what the experts here have to say about this fix....
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Offline PEARL DRUMS

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Re: belly lam
« Reply #6 on: March 02, 2015, 12:36:05 pm »
It will hold, but for how long? The truth of the matter is underneath that ultra thin laminate is a hornets nest held together by glue. Eventually after repeated shots that chrysal will expand to the back causing an explosion. It doesn't matter that the tiller is corrected after the lam is added. That limb is like a spring and after repeated bending back and forth those chrysals will grow, they have to.
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Only when the last tree has died and the last river has been poisoned and the last fish has been caught will we realize we cannot eat money.

Offline jayman448

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Re: belly lam
« Reply #7 on: March 02, 2015, 02:11:22 pm »
Quote from: arachnid on March 02, 2015, 12:25:41 pm
A friend of mine sucsessfuly patched a chrysaled bow limb. The chrysals where in one week spot. He sanded thay spot and glued on a thin lamination and once the glue dried he sanded it smooth and adjusted the tiller. I never tried it but he ssid it hold.

I wonder what the experts here have to say about this fix....

well yes.. very shallow in one concentrated spot. ( this bow is still the one i spoke of a while ago that was given up on by a guy i know. ive been trying to save it XD. also at very worst i figure its a good learning experience eh?)
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Offline jayman448

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Re: belly lam
« Reply #8 on: March 02, 2015, 02:17:04 pm »
Quote from: arachnid on March 02, 2015, 12:25:41 pm
A friend of mine sucsessfuly patched a chrysaled bow limb. The chrysals where in one week spot. He sanded thay spot and glued on a thin lamination and once the glue dried he sanded it smooth and adjusted the tiller. I never tried it but he ssid it hold.

I wonder what the experts here have to say about this fix....

i dont have access to any of those woods. (im quite north of your uppermost boarder) what about something like hickory or walnut?
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Offline adb

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Re: belly lam
« Reply #9 on: March 02, 2015, 02:59:39 pm »
Quote from: PEARL DRUMS on March 02, 2015, 12:36:05 pm
It will hold, but for how long? The truth of the matter is underneath that ultra thin laminate is a hornets nest held together by glue. Eventually after repeated shots that chrysal will expand to the back causing an explosion. It doesn't matter that the tiller is corrected after the lam is added. That limb is like a spring and after repeated bending back and forth those chrysals will grow, they have to.

+1
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Offline Marc St Louis

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Re: belly lam
« Reply #10 on: March 02, 2015, 04:39:41 pm »
Quote from: PEARL DRUMS on March 02, 2015, 12:36:05 pm
It will hold, but for how long? The truth of the matter is underneath that ultra thin laminate is a hornets nest held together by glue. Eventually after repeated shots that chrysal will expand to the back causing an explosion. It doesn't matter that the tiller is corrected after the lam is added. That limb is like a spring and after repeated bending back and forth those chrysals will grow, they have to.

If you thin the Birch so that the remaining wood, and chrysals, are near the neutral plane then you should be ok.

I made a sinew backed BC recurve many years ago that developed horrid chrysals.  I worked the Cherry down and glued a 1/4" thick strip of Osage on the bow, it's still holding.   In fact it's more than just holding, it's a power house of energy.
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Offline Springbuck

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Re: belly lam
« Reply #11 on: March 03, 2015, 08:52:17 pm »
  3mm isn't nothing on the thickness, though  That is going to really raise the draw weight.

If I were you, I would definitely work down below the chryshal, and then add the belly (and hard maple is fine belly wood, but not super belly wood) and really do your best with the glue joints.
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Offline jayman448

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Re: belly lam
« Reply #12 on: March 04, 2015, 12:46:38 am »
Quote from: Springbuck on March 03, 2015, 08:52:17 pm
  3mm isn't nothing on the thickness, though  That is going to really raise the draw weight.

If I were you, I would definitely work down below the chryshal, and then add the belly (and hard maple is fine belly wood, but not super belly wood) and really do your best with the glue joints.

would something like hickory or walnut be better as a belly?
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Offline PEARL DRUMS

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Re: belly lam
« Reply #13 on: March 04, 2015, 10:08:18 am »
If those two are all you have, Id choose the hickory.
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Only when the last tree has died and the last river has been poisoned and the last fish has been caught will we realize we cannot eat money.

Offline Zradix

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Re: belly lam
« Reply #14 on: March 04, 2015, 03:05:05 pm »
Hickory x2
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