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Heavy bow strings

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Yeomanbowman:

--- Quote from: markinengland on May 31, 2007, 06:10:40 am ---
I think I owe you a pint by the way. If my slightly bleery memory is correct I knocked one out of your hand while waving my hands around while we chatted about this subject! I hope you had a good time at the Batsford field shoot. I chickened out!


--- End quote ---
Hello Mark,
Don't worry, any beer stains were washed out during the field shoot :D.  I must give the timber hitch another go.
Cheers,
Jeremy
     

Garry:
Interesting thread,
I was forced into using FF-Plus on my 125# warbow due to the stretch on D50. It is quite difficult to string a 100# plus bow when the string stretches so much.
It seems to me that FF is the material of choice (when quality linen cannot be sourced) because it has about the same stretch as linen.
Weight of the string does not make bugger all difference when you are loosing a 1000 plus gn arrow. (my opinion)
Just for interest I use the 10 times at 15" calculation (tested it on the "Old Oak 110#er" first tho!) FF-Plus weighed in at 53# per strand, 10 strands = 530#, about right. I added a few more totalling 12 strands (yew is very expensive in Aussie). This works just fine.

Marc St Louis:
I used D-75 for the 2 heavy ELB flight bows I built Marlon last year and I think I used 12 strands on the BBB. It pulled about 170# and the 12 strands worked just fine

markinengland:
Garry,
From what I have read FF is meant to have about 100lbs per strand. Why 53? Is this tested breaking strength?
I copy this from a flight forum where I asked this same basic question. These guys are good so know whatthey are talking about from formulas through to actually setting records!
"At around 200 fps, the energy lost to the string is about equal to as much as 45% of the string weight getting shot with the arrow.  If your string has a mass of 100 grains, and arrow has a mass of 500 grains, then the bow will feel like it's shooting a total of about 545 grains.  At 200 fps, 45 grains is equal to about 4 ft-lb which is pretty significant.  The 500 grain arrow traveling 200 fps has about 44.5 ft-lb of kinetic energy so right away, nearly 10% just went to propelling the string.  Of course, heavy serving makes it worse since it is moving at the same speed as the arrow."
From my understand an efficient heavy warbow is a fast bow. It needs to be to get the distances being acheived. Though the arrow being shot is heavy at double 500 grains or more, then the string is also probably at least double in mass and things may equal out. This still points to the basic idea that reducing string mass within sensble limits will no doubt increase arrow speed and distance.
I wonder what difference you would notice between a 10 strand string and 20 strands?
Mark

duffontap:
I've been reading this with great interest.  A couple things I'm wondering:

Not only is FF super strong, durable, and less streachy, it's lighter.  This allows for lighter, faster strings of the same size as Dacron.  Take into consideration that a 16-strand FF string will be much smaller than it's B-50 counterpart and you've gained significant performance advantages by only changing the material.  Beyond this point, how much can you gain I wonder?  If it's only a difference of 20 grains or so, I think I'd rather use a normal-sized string with heavy bow.  There are practical limits to these kinds of things.  Beyond pure fligh shooting, isn't there an obvious impracticality to such skinny strings (not fitting nocks, cutting the fingers, etc.)?

I'll have to go weigh the FF string on my warbow.  Great thread.

Another thing, the published strength of currently-availible linen thread is adequate to build a 1/8" safe string for about a 150# warbow--using the draweight at ten inches (or fifteen, I can't remember either) formula.  I haven't tested this yet, but I don't see what the big deal is with everyone (perhaps Pip started this theory?) saying it's impossible.  I think you could go do it right now with linen bought off the internet.  Before long I'll put my money where my mouth is. 

            J. D. Duff

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