Author Topic: Very short bow help please  (Read 625 times)

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Offline stuckinthemud

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Very short bow help please
« on: October 10, 2018, 09:38:21 am »
If an admin wants to move this post then that's fine with me.

Here is my yew and sinew crossbow prod on my 'Heath Robinson' windlass with some cheap braided nylon rope.  I have shown fully unwound and fully drawn, I have to get it to draw to 9" but it's so strong it's stretching the rope rather than drawing any further . I am re-lacing the windlass in heavy duty paracord tomorrow. I have rasped 2mm off the belly and have reached the edge of the sinew; there is now a sharp edge where the belly meets the sinew as it wraps over the sides, is it ok to round this edge over as this will start to cut into the sinew ? Any and all tillering advice is most welcome.





I realise there's very little to go on, I'll post more as I go on
 
« Last Edit: October 10, 2018, 09:53:02 am by stuckinthemud »

Offline Bayou Ben

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Re: Very short bow help please
« Reply #1 on: October 10, 2018, 09:54:06 am »
Lol...Sorry I don't have anything to add I just wanted to laugh at your title.

Offline stuckinthemud

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Re: Very short bow help please
« Reply #2 on: October 10, 2018, 09:58:17 am »
yeh, made me smile too, figured a short bow might get more views than an angry bow

Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Very short bow help please
« Reply #3 on: October 10, 2018, 09:56:37 pm »
I've just been through this with the Xbow I've built... nightmare to string. The bracing/stringer/cocking string needs to be made of some decent non stretch material. I used an old crossbow string in the end.
Paracord is stretchy isn't it? (as it's designed to absorb shock). I'd look for some decent hemp cord/rope, I've used that for warbow stringers, a bit of initial stretch then it settles down.
Del
PS, I just looked at cheaprope.co.uk they have some interesting looking sash cord, unfortunately, no breaking strain figures  >:( ::)
Toolstation do 10m of sash cord for less than 4 quid, and as it's made to run over a pulley it should be good.
« Last Edit: October 10, 2018, 10:12:43 pm by Del the cat »
Health warning, these posts may contain traces of nut.

Offline stuckinthemud

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Re: Very short bow help please
« Reply #4 on: October 11, 2018, 12:05:45 am »
Hi Del, I've been following your crossbow adventure with much interest.  Got to agree, its all a huge learning curve; I've already destroyed an old linen stringer - 14 strands of 18/4 managed to bend it a 1/2".  I'm hoping the paracord will stretch initially and then stabilise but if it doesn't I will have to source something with a bit more oomph.  The differential windlass has been a revelation though - one hand to wind back a bow that powerful with zero effort!

Offline stuckinthemud

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Re: Very short bow help please
« Reply #5 on: October 11, 2018, 02:58:01 am »
Paracord is working ok at the moment. Strikes me the left limb is a tad stiffer than the right. Right limb might have a hinge developing?


Offline Hrothgar

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Re: Very short bow help please
« Reply #6 on: October 11, 2018, 03:09:41 am »
Hi, interesting post going here. I'm not into crossbows, but was wondering. Could you use plastic coated braided wire for tillering?
Vive la liberte!

Offline stuckinthemud

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Re: Very short bow help please
« Reply #7 on: October 11, 2018, 03:30:36 am »
Would have thought that as long as it could travel through the pulley and wrap around the winch it would be fine.

Offline Hawkdancer

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Re: Very short bow help please
« Reply #8 on: October 11, 2018, 07:18:16 am »
If I remember correctly, paracord stays stretchy for quite a while.  Don't remember the mil specs, but the 'chutes had a set number of jumps before the gore (shroud) lines were replaced.  Maybe a big bunch of strands of B50 or fast flight would work, like 50 or so!  But I don't know anything about crossbow technology, haven't even shot one!
Hawkdancer
Life is far too serious to be taken that way!
Jerry

Offline Stick Bender

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Re: Very short bow help please
« Reply #9 on: October 12, 2018, 01:32:43 pm »
Just a thought but if you could get a hold of some mule tape electricians use it to pull wires long distances the stuff is like cloth cable you could tow with it, its brutally strong and no stretch ,I use it for fire house forms , the size in the pic is 5/8 but they make it down to 1/8 its tuff tuff stuff that doesent stretch or break ! It would easely string any bow.
If you fear failure you will never Try !

Offline stuckinthemud

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Re: Very short bow help please
« Reply #10 on: October 13, 2018, 06:42:41 am »
I'l keep an eye out for it, one of my friends works as a power-cable design engineer, he might know someone who knows someone.... My next angry bow is a full repro of a medieval gothic composite bow, should be 500# or so, and I will definitely be needing heavy duty winding eqt. for that one, tho its currently little more than a plastic bag full of small pieces of horn - shaping the horn, grooving and gluing it together is my project for this winter.  >:D

Offline Stick Bender

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Re: Very short bow help please
« Reply #11 on: October 13, 2018, 08:17:52 am »
This stuff will be your ticket it holds that pressure form under full pressure it broke the 3/4 hard wood dowels replacing with metal great for pulling dear out to it's amazing stuff !
If you fear failure you will never Try !

Offline stuckinthemud

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Re: Very short bow help please
« Reply #12 on: October 13, 2018, 11:04:40 am »
Biggest problem I'm now finding is that as the cord travels across the drum it pulls the centre of effort sideways.  Still, any comments as to the tiller?


Offline Morgan

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Re: Very short bow help please
« Reply #13 on: October 13, 2018, 05:30:50 pm »
You can get the mule tape on amazon.

Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Very short bow help please
« Reply #14 on: October 13, 2018, 10:36:14 pm »
Can't really see enough bend to comment on tiller... there's nothing obviously wrong tho'.
maybe a more conventional single roller windlass with a spreader bar so it's pulling the rope back from 2 points , say 6" apart?
Dunno if you can see what I mean below, the \\\/// is how the rope is on the roller.  ___ is the spreader bar
     ___
     |   |
\\\\     /////

Del
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