Stretching a String

PLEASE HELP TO FUND ARCHERY INTERCHANGE

carl7

New member
Brownell recommends a pressure of 300 lbs. to stretch a string. Just to be absolutely clear, is this measured with one string end fixed and a scale pulling to 300 lb. on the other end?

Or, how about a 300 lb. weight hung on the end of a vertically suspended string?

How long do you leave the string under the 300 lb tension?

Thanks,
Carl
 

geoffretired

Supporter
Supporter
I never bothered to stretch my strings until recently. I had other ways to even out the tensions.
I experimented with a stretching frame, so I can twist the string while stretching it.
I have bolts at opposite ends of the frame that have hooks to take the string loop. I fix one hook with nuts inside the frame and outside. The other hook can be turned to twist the string and during the turning it screws through the outside nut, stretching the string.
I used a fisherman;s scale to see what stretch 60lb made. Then I counted the turns to get that amount of stretch. If I wanted 300lbs, I would turn 5 times as many twists.
 

carl7

New member
Thanks Geoff, this stuff is really getting the old brain to become active, perhaps it will delay the onset of Alzheimer's...haha!

I've been thinking of a idea where I can use a torque wrench to apply the needed tension with a ratchet device. I might as well use one of the winches I have.

I have a long ladder hanging in the basement, perhaps using the ladder to hook one string end and the winch on the other seems would be a simple ready made way to do it.

Either that or, a gear and bearing puller, one has a heavy hook attachment. Just mount that on a suitable main beam.

Carl
 

geoffretired

Supporter
Supporter
A ladder might be a good idea, along with the ratchet.Might be worth planning some way to twist the string under tension and then fix it so it can't untwist while stretched.If it's an extension ladder, the hooks at the end of one part could be used to hold a beam across so it can be drilled to take a hook on a threaded rod.You don't want to use the rungs as they would be weakened if drilled.
 

EVC

New member
Carl, AFAICT stretching compound strings increase the chances you do not have to redo serving and adjusts to the bow.

For recurve just leave the bow stringed overnight (or even better two full days). Overnight the string will nearly settle to its final length. You still may need to add a few twists to it after 100-200 shots as it may creep a little. That has been my experience with 8125.

HTH

Elder.
 

Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
If you are making recurve strings it doesn't matter how much (or for long) you stretch them they will still stretch a little more when on the bow and shot. I reckon I need 40 shots at correct BH (ie the right number of twists) to get it to settle, and my stringmaker is extremely expert, experienced, and stretches it hanging with a huge bar bell weight and a screwdriver.
There is nothing like the forces exerted by the functioning machine itself to get a new string into shape.
 

Alun

New member
If you are making recurve strings it doesn't matter how much (or for long) you stretch them they will still stretch a little more when on the bow and shot.
Yes, my experience, too. It may be 40lb (say) at full draw, but there is something about going from 150 mph to 0 in a zillionth of a second at the end of the power stroke that seems to encourage strings to stretch that little bit more.
 

albatross

Supporter
Supporter
It may be the 'shock wave' going through the string fibres on release that encourages that 'extra bit of give'.

Dennis
 

carl7

New member
Thank you guys, all valuable tips to understand the nature of strings and their materials. As soon as I clear enough space in the basement to have elbow room, I'll start assembling the string jig and some kind of stretching device.

Carl
 
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