String length

[DC]

You will get some initial "stretch" as the twists pull tight and the wax squeezes around. If you measure the diameter of a freshly twisted string and then measure it again after it's been tensioned you will see that the diameter has reduced. This reduced diameter becomes length.
You said over in your "Hazel Longbow" thread that the stretching had stopped. Has it started again?

[PatM]

This spectra power pro fishing braid has been marketed as near zero stretch and creep. It shouldn't stretch at all.

 If made correctly your power pro string should be  as near zero stretch as the material can be. Let's see it and your loops.

[FilipT]

Yeah, maybe I wrote the post too late. Stretching stopped around the time I tillered to brace height, but still I find it interesting that it stretched for me before that. I suspect it had to do with twists.

[DC]

The number of twists seem to make it stretch more. When I started making strings they would seem to stretch, I thought the twists were slipping so I made the twisted portion longer, up to ten inches long. The problem got worse. People told me that 4" of tail was plenty. Finally I gave in and tried it. It worked. They "stretched" for about 15 minutes after the first brace and then they were solid. I use double loop Flemish twist. PITA to get the length right but I got tired of fighting with the timber hitch(bowyers knot), they do slip on FF IMO even with the double loop and extra wraps.

[bradsmith2010]

DC,, if you put a knot behind the timber hitch,, it will stop, even on a small diameter string,,

[FilipT]

DC, what is the part of string you call tail? Immediately behind loop?

[gfugal]

Just enough twists to hold the loops from slipping is ideal. Beyond that you start turning the string into a spring.

Agree

[gfugal]

DC,, if you put a knot behind the timber hitch,, it will stop, even on a small diameter string,,

Do you have a picture? I'm having a hard time imagining it

[DC]

DC, what is the part of string you call tail? Immediately behind loop?

Yes, but to be more specific, when you are making the string and are just starting to form the loop, the ends that stick out I call the tails. Boy, this is tough and English is my first and only language

[FilipT]

I will put a picture tomorrow of my string.

[FilipT]

Here is my string. This part behind the loop is probably too long and caused stretching.

[WillS]

No, you've just made it badly

The section after your loop is cabling around the main body of the string, which is never good.  Also, considering the weight you're trying to achieve with your current bow, the loop itself is way, way too thin.

[jeffp51]

That fishing line is good stuff, but it is harder to work with than dacron-and I wouldn't say the string is too thin, but the stuff is slick right out of the box and needs lots of wax. I bet most of the stretch is coming from that loose loop.

[PatM]

That's a messy unevenly tensioned string.  Even no stretch stuff HAS to have stretch. When your strands are unevenly tensioned when laid up the string balances itself to the longest strand length.   So all your errors are accumulating and manifesting as increased length.

[FilipT]

Sorry but I don't understand you guys. I could make a new one, but what does mean "cabling around", how is that uneven and too thin? Yes, its ridiculously slick, I rubbed a lot of pure beeswax onto it to make strands stick to each other and it still didn't get cohesion as I have with strings I bought for particular lengths.

P.S.
Forgot to mention, this is 20 strand string, with each having 80# breaking strength.