How many strands of

[monterey]

fast flight for a 110# bow?

[frank bullitt]

I built several thousand of the original Fast Flight for Ken, Black Widow, in 1990 and 1991.
Don't remember making any larger than 20 strand.

[McDave]

You should be able to find out the breaking strength of a strand of the type of bow string you're using from the manufacturer.  Or, if you already have some of it, you can just pull a strand with a bow scale until it breaks and find out for yourself.  The string should have a breaking strength at least 4X the maximum weight of the bow.

For example, a 100# bow should have a string with a breaking strength of at least 400 pounds.  If a strand has a breaking strength of 50#, then you would need at least 8 strands, or 2 bundles of 4 strands each to get a bow string with a breaking strength of 400 pounds.  Probably you would add a few more strands to each bundle just to have an extra margin and to give a good nock fit.  If you made a 14 strand string with 2 bundles of 7 strands each, it would have a breaking strength of 700 pounds. 

If you decide to make a string with more than 7 strands per bundle, I recommend making 3 bundles with less than 7 strands each instead.  A 3 bundle string with 6 strands per bundle is stronger than a 2 bundle string with 9 strands per bundle.  The 3 bundle string will also look better and have a rounder shape.