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Offline Aries

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bow death diagnosis
« on: August 11, 2009, 08:37:19 pm »
Can you guys please help me diagnose the cause of this bows explosion?  I had just completed floor tillering this bbo stave and had been flexing it up to about ten in...  when i attempted to string it with a short string it  exploded at one of the nodes of the bamboo outside of the handle.  The grain of the osage slates was fairly straight but my bamboo was relatively thin at the area of the explosion.   

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Offline Dano

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Re: bow death diagnosis
« Reply #1 on: August 11, 2009, 08:47:21 pm »
Hinge, To me it looks like you got the fade area a little too thin.
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Nevada

Offline Aries

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Re: bow death diagnosis
« Reply #2 on: August 11, 2009, 09:06:21 pm »
ugh that sucks, i didn't even notice it bending much through that region i was focused more on the outer limbs than the inside. So what do you think should be different next time?  Do you think making my handle riser longer would help? this one was 12"
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Offline Dano

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Re: bow death diagnosis
« Reply #3 on: August 11, 2009, 09:26:37 pm »
A 12" handle is a little long if you don't have a power lam between the bamboo and the belly. It depends on the length of the bow of course, but 6 - 8" is fine for the handle and the power lam should extend at least 2" beyond the handle at each fade.
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Nevada

Offline Aries

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Re: bow death diagnosis
« Reply #4 on: August 11, 2009, 09:41:27 pm »
can you please explain the concept of a power lam to me for future reference.   This bow was a RD and i just traced the curve of the bow onto a 12" piece of wood and cut and paste. If i was to do the power lam would i just need to clamp it between the bow and handle when i glued up the handle. 

Im really wanting to make one of these bows This is my second failed attempt. but Im learning tremendous amounts about them each time I make one, Im hoping to have my first lam bow soon still.. I've already started cutting up wood for my next attempt  ;D
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Offline Jesse

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Re: bow death diagnosis
« Reply #5 on: August 11, 2009, 10:18:29 pm »
too bad :( Keep at it though.
the power lam goes between the bamboo and the osage. you dont need one if you have enough belly wood to work with just make it ramp up  in the fades before your glued on riser.
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Offline Jesse

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Re: bow death diagnosis
« Reply #6 on: August 11, 2009, 10:22:00 pm »
This bow has 2 power lams between the bamboo and the ipe.
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Offline mullet

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Re: bow death diagnosis
« Reply #7 on: August 11, 2009, 10:24:52 pm »
 I have to agree with Dano. I try to take more wood off the side instead of the belly , tillering boo backed bows.
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Offline Marc St Louis

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Re: bow death diagnosis
« Reply #8 on: August 11, 2009, 10:57:45 pm »
Interesting break.  Can't say I've ever seen Bamboo break like that.  Personally I don't think a hinge would do that.  Hard to tell but you may have worked the the node down too much.
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Offline Pat B

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Re: bow death diagnosis
« Reply #9 on: August 11, 2009, 11:05:23 pm »
There is a lot of stress in that portion of each limb. Maybe the node should be placed so it doesn't lay right at the limb/fade transition area.  Just a guess.
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Offline Timo

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Re: bow death diagnosis
« Reply #10 on: August 11, 2009, 11:19:15 pm »
 Pat summed it up to my thoughts exactally.
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Offline Dano

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Re: bow death diagnosis
« Reply #11 on: August 11, 2009, 11:24:01 pm »
Normally a node will create a stiff spot, so it's a good idea to place them evenly. The node doesn't look like it's been worked down too far. Who knows.  ???
Maybe if we could see a picture of the handle and the limb that didn't break we could make a better assumption.
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Nevada

Offline Pat B

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Re: bow death diagnosis
« Reply #12 on: August 11, 2009, 11:46:14 pm »
Did the glue line fail or did the boo fail? What glue did you use?
   A bit of glue and a wrap will have you shooting again by the weekend! ;D
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Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline bcbull

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Re: bow death diagnosis
« Reply #13 on: August 12, 2009, 12:22:53 am »
take a real close look at the nodes  i can see where it s been filed down  or sanded or somthing  looks like the node was weakend and thats right where i see the clean break where it snapped in the pic  my 2 cents  brock
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Offline Aries

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Re: bow death diagnosis
« Reply #14 on: August 12, 2009, 12:50:49 am »
I hadn't worked the nodes down any at the point the boo gave.  My glue bond held strong it would seem because torn osage fibers line the inside of the boo. It just looks like the boo snapped clean off at the space on the node.  Here are some pics of the other side of the handle.   I didnt have my nodes evenly spaced on this attempt, mainly because i was just using what material i had available, and i couldnt space it properly with this piece of boo ::)         pat) I used urac 185 to glue this up.       And what kind of thickness do you guys think i should start with on my osage boards if i was looking for a bow of  same style with a finish weight of around 60-65 lbs on a 64" ntn bow?

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« Last Edit: August 12, 2009, 12:56:18 am by Aries »
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"If the only tool you have is a hammer,
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                               ~Abraham Maslow
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