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PSE Decree HD
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Discussion Starter #1
Just getting into string building, and I've built a few recurve strings using Brownell B50 material. I'm building for a 60" bow, so I'm trying to get a 56" string.

I built my first one using 14 strands and starting at 56". I served the ends using the B50 material, put in 15 twists and then stretched the string at 100 lbs overnight. The next day I added the center serving and measured. The string measured 56 5/8. I removed the string, and let it relax for about 15 minutes and mesured again. It's measuring 56 3/8.


I built my next one again using 14 strands but this time started at 55 5/8, allowing for 3/8" of stretch. This time I served the ends using the Brownell #4. I again put in 15 twists and then stretched the string at 120 lbs overnight. The next day I added the center serving and measured. The string measured 56 3/4. I removed the string, and let it relax for about 15 minutes and mesured again. It's measuring 56 5/8. So this string stretched even more.

Should I not twist before stretching? Should I not stretch B50? Any info would be helpful.
 

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Caution! Sardonicism!
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B50 will never cease stretching over the life of the string, IIRC.
 

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A.K.A Osage Outlaw
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If its for a modern bow I would use a string material with less stretch. I made a simple stretching jig that stretches the string way tighter than when it's on a bow. I leave it stretched over night and the next day I can see excess wax that has been squeezed out of the string. I'm making a B-55 string tomorrow for a 1962 Bear Kodiak. I would much rather use Fast Flight or similar material but I've been told it's not safe for the old bows.
 

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Dacron is great for vintage bows and kid/class bows. It is inexpensive, durable, and stable once it's done stretching. I have never pre-scretched - just leave it on the bow and shoot it, monitoring the brace height and adding string twists when necessary. I also follow the general pattern of making actual length and then taking up the stretch with twists. That usually ends up with a reasonable twist count.

It great to learn string making with Dacron and dealing with the stretch, but when you switch to modern no-stretch materials it is like a dream. I use D97 for my recurves and it stays put!
 

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Lowered expectations
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Dacron has both "stretch" and "creep". Stretch is like a rubber band - it lengthens under tension and contracts when slack. Creep is a permanent elongation under tension.

The key to making a good dacron string is to start at the correct length for the posts. In your case for an end 56" string, I'd suggest 55 1/4". It's important to keep even tension on all the strands when winding, because if you gave some strands tighter than others, they stretch first under tension and the string does lengthen more than you want or expect.

Put only about 5 or 6 twists to start. String the bow, check the BH, then put the bow riser down on a padded surface, like a chair, and push down hard on the limbs. You will noticeably feel the string stretching. Check the BH again, then twist to get it about 1/4" higher than you want. Serve the center and go shoot. It should come down that 1/4" within a few dozen shots.

Check the BH again every few dozen shots and twist as necessary.
 

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PSE Decree HD
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Discussion Starter #9
I'm building a string for a newer bow, so I could go with FF or something similar. I'm just building these B50 strings to get a feel for things since this is all new to me and the material was cheap.
 

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(aka lug nut)
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I'm building a string for a newer bow, so I could go with FF or something similar. I'm just building these B50 strings to get a feel for things since this is all new to me and the material was cheap.
Do NOT stretch a B50 bowstring overnight. B50 never ever stops permanently stretching. You will FOREVER measure the brace height, when you string your bow, and then, you will discover the brace height is longer than you want. So, you unstring the bow and add more twists, and check the brace height. Back and forth and back and forth, measure brace height, unstring bow, add more twists, and re-string the bow, and check brace height. So, the more you shoot with your dacron string, the more it stretches. So, there is ZERO point to stretch a B50 string overnight.

If you want a FINAL length of 56-inches of bowstring, for a 60-inch recurve bow, set the posts SHORTER than what you want. If you think 55.25-inches distance between the posts is too short, then, try 55.5-inches distance between the posts on your string jig. 1 twist per 1.5-inches of length, I would add 35-37 twists. BUT BUT BUT, the string is too short. Not really. Go shoot 100 shots and the B50 string will have stretched longer. Bottom line. Recurve B50 string, you must forever measure brace height, EVERY time you string your bow, and FOREVER add more twists, due to the inevitable B50 string stretch, which never stops.
 

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(aka lug nut)
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I'm building a string for a newer bow, so I could go with FF or something similar. I'm just building these B50 strings to get a feel for things since this is all new to me and the material was cheap.
BCY 8190 is nice. BCY 8125 is nice. Some like to use D97. I use a spring scale to measure the stretching tension, and then, I can come back in 30 minutes and read the scale to see if the stretching tension has stabilized or not. NO need to stretch over-nite. If you do a quality job laying out the strings around the string jig post, the scale will show you that stretching at 300 lbs+, will hold that stretching tension exactly, when stretching is complete. I use a boat winch to STRETCH a bowstring, and set the scale reading at 325 lbs, cuz that is the max my scale will read. After 10 minutes, scale reads 320 lbs. So, crank the boat winch another click or two, and scale reads 325 lbs again. 100 lbs stretching is only for measuring string length. STRETCHING a bowstring to break it in, and kill any initial stretching is at 300+ lbs. So, after 30 minutes, maybe my scale now reads 322 lbs of tension. So, I turn the turnbuckle and get the stretching tension back to 325 lbs. After another 30 minutes, the scale reads EXACTLY 325 lbs. STRETCHING is complete. No guessing. No over-nite stretching.
 

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Lowered expectations
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Did you mean to say start at 56 1/4? Am I starting 1/4" longer and taking that in with twists? Or am I starting 3/4" shorter and expecting it to stretch?
Yes, I meant 55 1/4" - that's 3/4" short, and the string will stretch.

Read my post again and what nuts&bolts posted. He has considerable stringmaking experience and I wouldn't discount anything he says on the subject, but be aware that when he uses the word "stretch" in his posts he's actually referring to "creep". Read this for a more detailed explanation: http://www.bcyfibers.com/FAQs.php

String stretchers are for compounds where it's a major pain to twist the strings after they're installed, and definitely not for dacron/polyester (Brownell B50 or BCY B55) string materials.

Non - stretch materials literally have no "stretch" (the elasticity type) but do exhibit some creep, but to a tiny degree compared to dacron/polyester. Read the manufacturers' or other comments on each material - some will say things like "zero creep" or "low creep", but most of them don't have any "stretch", so once they are fully stretched out on a stretcher and the creep is taken out at tensions far higher than you get when installed on a bow, they will stay perfectly stable.

Bottom line, though, save yourself a lot of hassle and go to 8125 or some other modern synthetic unless your bow absolutely requires dacron, or you're on a really tight budget.
 
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