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Author Topic: Diagnostic issue w/ pics  (Read 5725 times)

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Offline PEARL DRUMS

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Re: Diagnostic issue w/ pics
« Reply #15 on: July 23, 2018, 08:42:02 am »
I don't believe the breaks would be so consistently placed if it were a backing quality issue. You'll note the breaks all happened where all the reflex was introduced. Too early and too abrupt in my non-professional opinion. If you start the reflex that early then it needs to carry out to the tips evenly and bend accordingly.
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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #16 on: July 23, 2018, 08:47:37 am »
One of the things I can't figure out is that the limbs appeared to be bending pretty evenly prior to the bows breaking. It felt like the backing just couldn't handle the stress. That's why I suspected grain runoff.

It's hard to tell from the pics cause they're after the breaks, but I put a lot of thought into reflexing evenly across the limbs, but maybe not enough. I think you're probably right pearly. Your explanation makes the most sense.

This is driving me crazy!


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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #17 on: July 23, 2018, 08:49:18 am »
Quote from: bushboy on July 23, 2018, 08:39:45 am
My best guess is a combo of what was stated and to much pressure at glue causing a staved joint.oh my I have broken so many backed bows!

I did put a lot of pressure on them during the glue-ups. What's a staved joint?
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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline bushboy

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Re: Diagnostic issue w/ pics
« Reply #18 on: July 23, 2018, 08:53:25 am »
Sorry I meant starved joint,meaning squeezing out all the glue.
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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #19 on: July 23, 2018, 08:54:41 am »
Got it bush. Thanks  :)

I'm adding the reflex w/ dry heat on a caul designed to make the reflex even across the whole limb. Then putting the spliced bow's tips on blocks and pushing the center down and clamping to glue in more reflex. Should there be support under the entire limbs when I glue in the reflex?
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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline Pat B

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Re: Diagnostic issue w/ pics
« Reply #20 on: July 23, 2018, 08:57:19 am »
A starved joint is where you squeeze the glue out of the joint with too much pressure.
 Have you built straight limbed backed bows successfully? Can you show up a pic of a bow that you have glued up and before it breaks.
 By adding reflex you add more stress to the limb. If that stress is concentrated in one area it can cause a break.
 Are you pre-tillering the belly before glue up? are you allowing the heated areas to cool completely? Are you heat treating the backing?
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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #21 on: July 23, 2018, 08:57:31 am »
Here's a pic of what I use to glue in the reflex...
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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline Pat B

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Re: Diagnostic issue w/ pics
« Reply #22 on: July 23, 2018, 08:58:34 am »
That's similar to what I use. I doubt that's the problem.
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Offline DC

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Re: Diagnostic issue w/ pics
« Reply #23 on: July 23, 2018, 09:00:03 am »
Are they straight sided pyramids? I just looked a a few of mine and it looks like I left them a little wider mid limb. Still tapering all the way. It's strange because I never put a lot of thought into it. The wider mid limb was to minimise twist. It's hard to tell after the fact but they really don't look like too much reflex. My money is with bad backing but I won't argue with Pearly's ideas. :)
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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #24 on: July 23, 2018, 09:03:58 am »
It's highly possible that it's one of the things you mentioned Pat. I've build a backed bow successfully with not nearly as much glued in reflex. I have been allowing it to cool. I haven't been pre-tillering the belly cause I'm afraid it will break without the backing. Maybe I should splice and pre-tiller before heating in the reflex?
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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline DC

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Re: Diagnostic issue w/ pics
« Reply #25 on: July 23, 2018, 09:07:13 am »
Here's mine. It looks like your's has more bend on the inner limb. Maybe where they're breaking.
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Offline upstatenybowyer

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Re: Diagnostic issue w/ pics
« Reply #26 on: July 23, 2018, 09:07:43 am »
Quote from: DC on July 23, 2018, 09:00:03 am
Are they straight sided pyramids? I just looked a a few of mine and it looks like I left them a little wider mid limb. Still tapering all the way. It's strange because I never put a lot of thought into it. The wider mid limb was to minimise twist. It's hard to tell after the fact but they really don't look like too much reflex. My money is with bad backing but I won't argue with Pearly's ideas. :)

Yes DC, and they do taper pretty narrow. I start at 1.5" down to 3/8. Maybe a more gradual taper till close to the tips, then more abrupt right at the end.
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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline bushboy

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Re: Diagnostic issue w/ pics
« Reply #27 on: July 23, 2018, 09:13:21 am »
Agreed,maybe Marc will chime in as he is the resident expert on this style of bow!
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Offline PEARL DRUMS

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Re: Diagnostic issue w/ pics
« Reply #28 on: July 23, 2018, 09:49:26 am »
This hand sketch better explains my thoughts on your issues. Just my thoughts is all.
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Offline DC

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Re: Diagnostic issue w/ pics
« Reply #29 on: July 23, 2018, 09:54:54 am »
If you hold the broken bows up to the caul maybe the break will point to the problem.
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