Hey guys, so I have always heard the rule of thumb to be about 3" shorter than bow length for longbows and 4" for recurves.

Just curious is this before string stretch or after?

Also about how much will a string stretch in total??

No short answer here.

First, the "rule of thumb" is hit or miss.  AMO states 3" shorter, recurve or longbow, but that's also hit or miss.

I've seen recurves that got a string anywhere from 2.5" shorter to 6" shorter than the bow length;  longbows from 1.5" to 4" shorter.

This is after the string has stretched/been shot in.

How much total stretch/creep you get depends on several variables:

What material you are using--

polyester ("Dacron") stretches the most, Dyneema/Vectran blends stretch the least.  
How many strands you are using

The draw weight of the bow--

Low strand count strings stretch more than higher strand counts, all else being equal.


How the string is made--

Flemish generally settles in more than endless if neither is pre-stretched.  A poorly made string will settle more than a well made string, all else being equal.

Whether it was pre-stretched or not

With many materials, the temperature also makes a difference--some materials stretch more in higher temps.  This will also vary depending on the other factors listed above.

The AMO explanation is here:

http://texasarchery.org/Documents/AMO/AMOStandards.pdf

It's under "AMO Conventional Bow Length Standard", (page 3)

Thanks LBR. Thinking about this more, if I planned on running a flemish twist anyway, I suppose I could always shorten it easily.

Is there any limit to twisting the string (after it's made) to shorten the string and increase the brace height?

There is a limit, but I'm not good at explaining it.  I just look and I know when there's more twist than I'm comfortable with.  Too much twist will affect the performance and cause the string to wear prematurely.  The number of twists can vary--i.e. you can put more twists in a longer string vs. a short one.