Author Topic: Hollow Back Bow no.4  (Read 11533 times)

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Offline willie

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Re: Hollow Back Bow no.4
« Reply #45 on: January 31, 2018, 06:08:56 pm »
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With hollow back this bow draws 7 kg when the string is pulled 21 cm.
When turned around (hollow belly) it dropped to 6 kg.......My conclusion was that a hollow back can take more draw weight per bow-mass.
+1
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The broader (and lighter) tip will be less prone to torsion or sideway bending.
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In a bow with strong recurve and short working parts, it might certainly becomes another game...

or possibly a long working recurve?     http://www.primitivearcher.com/smf/index.php/topic,5717.0.html

Offline simson

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Re: Hollow Back Bow no.4
« Reply #46 on: January 31, 2018, 10:06:32 pm »

....
Simon, thank you for your thoughts. I must admit that I doubted for some time whether I should respond. That you do not agree, okay. But the tone of your posts in particular surprised me. But maybe, because I am a little sensitive on this subject,  I'm mistaken. So, I will try to explain properly why I can not agree with some of your thoughts. It is also a good opportunity to sharpen my thoughts and exchange more information.
I am afraid it became quite a story....
....


Jan, it wasn't my intention to affect you, or anybody else here.
After rereading my post (reply 40), I personally cannot see any harsh words.
Sorry you understood it so, perhaps my bad English.
All the best and good luck on your projects!
Simon
Bavaria, Germany

Offline Jan de Bogenman

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Re: Hollow Back Bow no.4
« Reply #47 on: February 01, 2018, 05:18:59 am »
Thanks for your reaction Simon. Plain text is always a little tricky when emotions come in.  Also takes some time to understand each other. Hope to hear from you again.

Offline Jan de Bogenman

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Re: Hollow Back Bow no.4
« Reply #48 on: February 01, 2018, 05:29:45 am »
or possibly a long working recurve?     http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
[/quote]

Willie, I think that should work!  Such limbs are somewhat wide for stability. Seems perfect for hollowing out. And on a spot to be pefered most, the outer limb.
Oh man, so many ideas, so little time.
But a glue up can be done relatively easy? And one can save on materials too.

Offline Philipp A

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Re: Hollow Back Bow no.4
« Reply #49 on: February 01, 2018, 05:33:52 am »
Hi Jan and Willie, when looking at the feather profile it is actually recurved for the full length. With a deflex handle one could definitely get close to that design. I think it is a good idea. A glue up would definitely be faster for a proof of concept than to carve this thing out of a stave.

Offline Springbuck

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Re: Hollow Back Bow no.4
« Reply #50 on: February 01, 2018, 06:03:48 am »
  OK, here I go again, lots of talking and not as much doing........sorry.

But, I have several designs in mind I have never seen or tried to make a super lightweight but stable recurve.  They mostly involve the wood or bamboo of the recurve being very thin back to front, maybe even thinner than the rest of the limb at any point.  Maybe even a shallower "C" shaped bamboo limb up to the recurve.  The recurve itself is FLAT, not "C' shaped, and holds it's recurve with a cable. 

Several small sections of bamboo or rattan could be used as bridges to allow binding of the cable to the limb while keeping the main of the cable raised.  The recurve portion of the limb is thus maybe 60% air.  The bridges can be held in place basically by the wraps that bind down the main cable, and by use of some thoughtful zig-zag wrappings the lateral or torsional stability of the recurve can be mproved.

The other type I have seen attempted here before is a recurve that is actually thickened with a wedge under the backing or belly overlays until it becomes NON-bending, and then has material removed down the middle to reduce mass.

Offline Springbuck

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Re: Hollow Back Bow no.4
« Reply #51 on: February 01, 2018, 06:11:35 am »
Also, I do have a lot of luck with crowned or trapped bows, but in my own experience, simply due to the reduction of width toward the tips, the bow becomes less "trapped" by default.  I believe a lighter overall limb is beneficial, but I also believe that the most benefit is derived from reducing the tip weight, say the outer 1/3 of the limb length.

I could be wrong.  But Baker's design in the TBB's where he uses flax fiber to prevent lateral flex on a bow with a very narrow outer limb half still has me thinking a lot.

One thing I would like to try is making a backed bow with a belly slat that originates as two narrower slats which warp symmetrically away from each other just a bit.  During glue-up, the two halves could be drawn together at the tip of each limb, creating an effect similar to Perry reflex, but laterally, and then the backing applied in side profile.  I expect that would create a very stable outer limb, regardless of design.  Possibly most beneficial in a R/D with skinny tips.

And I want to see what you do with that bamboo, next.

Offline Jan de Bogenman

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Re: Hollow Back Bow no.4
« Reply #52 on: February 03, 2018, 05:41:34 am »
Interesting thoughts and ideas Springbuck. I am afraid one lifetime will not be long enough to make them all come alive!
But let's do our best.

Offline Del the cat

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Re: Hollow Back Bow no.4
« Reply #53 on: February 03, 2018, 01:03:31 pm »
Wow, lovely bow, interesting engineering.
I need to study this thread in some detail.
I shall refrain from comment, because one of my key skills is recognising when I don't know what I'm talking about  ;D
Del
Health warning, these posts may contain traces of nut.

Offline DC

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Re: Hollow Back Bow no.4
« Reply #54 on: February 03, 2018, 01:08:51 pm »
That's a really good skill to have :D