New string and brace height mystery

[huntin_sparty]

I just purchased a new string for my Great Northern Fireball.  Old string I measured 59 1/4 the BH was 6 3/4 with a 5/8 nock point.  Other than the arrow thwacking the target silence.  I bought it used and the string was begining to fray so I ordered a new string at 59 1/4 put it on the bow and the BH is 8 1/4 so I think they were made wrong take it off and measure 59 1/4!  Lay it next the the old string same length!  I untwisted until I was concerned about untwisting the string and got it to 7 1/4 but some twang versus silent like before.  
How can the same length of string produce such a difference in brace height?
Thanks,
Andrew

[straitera]

B-50 vs FF maybe?

[Jeff Strubberg]

Same material?  Sounds like stretch is the differrence.

[huntin_sparty]

Both are fast flight.

[metsastaja]

try measuring both strings under tension. one way would be to string the bow and measure tip to tip along the string. this will give a rough idea.

I use 2 bench dogs with nails inserted and vice on my workbench. gently crank the vice out and measure.
This is also the way I take stretch out of new strings.

I think you will find the old string "stretches" more then the new thus giving you lower Brace height.

[Night Wing]

Fast flight strings stretch.

At 4pm one afternoon, I put a 62" D97 flemish style bowstring on my 66",  37# recurve. I set the brace height at 8 1/2". Twenty four hours later at 4pm the next day, The brace height was sitting at 8 1/4". I waited another twenty four hours and at 4pm on the second day, the brace height was at 8 1/8".

I then decided to shoot the bow with the new string. I shot about 150 arrows over the course of 2 hours time. I then checked the brace height and it was 8".

The next morning, I checked the brace height again and it was down to 7 15/16". Since that time, it hasn't stretched at all. With no more stretching, I fine tuned the 2212 arrow for the brace height it likes and it likes a 7 3/4" brace height. This brace height hasn't moved in probably over 750 shots so my D97 fast flight string is "shot in".

[dragonheart]

Originally posted by Night Wing:
Fast flight strings stretch.

At 4pm one afternoon, I put a 62" D97 flemish style bowstring on my 66",  37# recurve. I set the brace height at 8 1/2". Twenty four hours later at 4pm the next day, The brace height was sitting at 8 1/4". I waited another twenty four hours and at 4pm on the second day, the brace height was at 8 1/8".

I then decided to shoot the bow with the new string. I shot about 150 arrows over the course of 2 hours time. I then checked the brace height and it was 8".

The next morning, I checked the brace height again and it was down to 7 15/16". Since that time, it hasn't stretched at all. With no more stretching, I fine tuned the 2212 arrow for the brace height it likes and it likes a 7 3/4" brace height. This brace height hasn't moved in probably over 750 shots so my D97 fast flight string is "shot in".

Takes a little time for all strings to settle in.  If you want ot speed the process, cut the serving off and let set 48 hrs then reserve.

[Roadkill]

Count strands
Wax it rub in to generate heat to season it