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Author Topic: Postmortem request  (Read 4318 times)

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Offline sieddy

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Postmortem request
« on: September 14, 2015, 05:10:31 am »
Hi guys.
Sadly the bow I thought of as my most successful to date- blew on me the other day. I am a bit gutted as I thought it was solid and would be shooting for years. Maybe I overdraw it slightly, but it can't have Been by much as my max draw is pretty short.
The bow was 69" and pulled 45@27". I did violate the hell out of the sapwood but it was sanded down pretty smooth. I think it was the knot in the wood that did for this bow but I would appreciate your thoughts. Cheers Simon.
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Offline Del the cat

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Re: Postmortem request
« Reply #1 on: September 14, 2015, 05:25:13 am »
Upper limb looks stiff in the outer 1/3 when I hold a CD up to it. The implication of that, is that there is excess strain at the top of the inner 1/3 ... which is where the break is...
Could be coincidence, but we work on such small margins.
Bow I've just finished chrysalled in exactly the area where yours broke due to the same problem... I ended up patching and re-tillering, a good save, but I was damn annoyed to have missed the slightly stiff area. http://bowyersdiary.blogspot.co.uk/2015/09/you-snooze-you-loose.html
Del
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Offline bubbles

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Re: Postmortem request
« Reply #2 on: September 14, 2015, 07:47:08 am »
How close to the bows death was that pic taken? What looks like a insignificant flaw right after the bow is built can get a lot worse after 1000 arrows.
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Offline sieddy

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Re: Postmortem request
« Reply #3 on: September 14, 2015, 07:52:50 am »
Cheers guys. I never would have thought that a stiff spot would have had such a devastating effect. But you live n learn.
I had shot a couple of hundred arrows through it so I guess the stress was just building. Also there were quite a few little holes in the wood around the knot. Maybe this was bug damage and contributed to the Bows demise?
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Offline Marc St Louis

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Re: Postmortem request
« Reply #4 on: September 14, 2015, 09:52:01 am »
Quote from: sieddy on September 14, 2015, 05:10:31 am
Hi guys.
I did violate the hell out of the sapwood but it was sanded down pretty smooth. Cheers Simon.

I have a friend I tried to teach how to build bows about 15 years ago.  He was a furniture builder and thought the rough back needed sanding, even though I had told him many times to leave the back alone, so he sanded it..........Boom.  That was it for him.  He never tried again
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Offline Knoll

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Re: Postmortem request
« Reply #5 on: September 14, 2015, 09:58:13 am »
Yeah, I'm a sander also.   :-\
But I don't give up!   ;)
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Offline PatM

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Re: Postmortem request
« Reply #6 on: September 14, 2015, 10:15:12 am »
I wonder who told  you it was OK  to violate the hell out of the sapwood? Actually I don't.   ;)
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Offline Jim Davis

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Re: Postmortem request
« Reply #7 on: September 14, 2015, 10:26:07 am »
Quote from: PatM on September 14, 2015, 10:15:12 am
I wonder who told  you it was OK  to violate the hell out of the sapwood? Actually I don't.   ;)

+1 Bows with unviolated back rings don't break at a stiff spot. In that case, stiff spots make the bow break somewhere else.
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Offline WillS

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Re: Postmortem request
« Reply #8 on: September 14, 2015, 10:47:30 am »
Did it break where that patch of greenery is behind the fence?

Every Yew bow I've ever made with violated rings has survived - even the ones well over 100#.  I would say it was the knot if anything or plain bad luck.  I've had bows with sapwood so funky that the heartwood was showing through the back that didn't break.  Yew rings just don't matter. 
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Offline sieddy

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Re: Postmortem request
« Reply #9 on: September 14, 2015, 11:07:51 am »
Hi all thanks for the input. Actually a number of people on here (including some who are very experienced with Yew) told me it was ok to violate the sapwood on a Yew stave! However I did cut right through the knot that ran thru the the spot where it blew- so maybe this was my problem!  :o
Hi Will-  yes the area you pointed out on the before picture seems to be where it went.
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Offline wizardgoat

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Re: Postmortem request
« Reply #10 on: September 14, 2015, 11:39:33 am »
Bummer
I'm no yew expert, but I have made over 20 yew bows, have violated the rings on about half, and haven't blown a yew bow yet. A stiff spot with a violated knot could of been the problem.
I really don't think it has to do with your ring violations.
Could of just been the wood too. Save the bottom limb! You could splice a new top limb someday
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Offline sieddy

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Re: Postmortem request
« Reply #11 on: September 14, 2015, 11:47:38 am »
Cheers for the tip Wiz- i would love to have a takedown! :-)
Also I have two more staves from the same log. It'll be interesting to see how I get on with them!  ;)
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Offline TimBo

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Re: Postmortem request
« Reply #12 on: September 14, 2015, 11:57:13 am »
It would be good if you could post a closeup photo of the little holes around the knot - that does sound like bug damage.  Although the cut-through knot may certainly have caused your blowup, bug damage wouldn't help either...and I wouldn't reuse buggy wood.
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Offline WillS

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Re: Postmortem request
« Reply #13 on: September 14, 2015, 12:27:03 pm »
Yeah - violate the sapwood as much as you need to, but don't cut through a knot! Ideally leave an island around it about 2 or 3 rings thick and you should be fine.

Sometimes though they just go pop.  Its often nicer to have one blow up at a knot or dodgy area and it to make some kind of logic, than to have a perfectly sound bow with no ring violations, knots, rot, bug damage etc go bang.
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mikekeswick

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Re: Postmortem request
« Reply #14 on: September 14, 2015, 02:40:29 pm »
When you cut through a knot you are also violating the rings. Ipso facso don't violate rings.
I don't see the point other than to make it look 'pretty and straight'.
If a tree didn't need unviolated grain to stand up then they wouldn't grow that way in the first place....Nature knows best  ;)
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