Can anyone give me a reliable b-55 strand-count guideline for heavier bows? Safety is a HUGE CONCERN for me. I don't want to get injured or injure someone else.
Speaking of that, are all spools of b-55 standardized? Meaning, is a given strand-count the same no matter the brand of b-55 I choose?
The breaking strength of a strand of B-50 is about 35#. The rule of thumb is that breaking strength of a bow string should be a minimum of 4X the maximum draw weight of the bow, so for a 75# bow, the breaking strength of the bow string should be at least 300 pounds. This would require at least 9 strands of B-50, or 2 bundles of 5 strands each. This math was done to show you that the breaking strength of the bow string is not really the key factor in designing the number of strands in the bow string for bows in the poundage range we normally shoot. Unless a person is interested in skinny strings to keep the weight down, the key factor is usually how well a string fits a nock. That is the main reason you see a lot of 16 strand bowstrings (2 bundles of 8 strands each).
I don't particularly like 16 strand bowstrings, because 7 strands in a bundle is the ideal number in order to have equal force on each strand. Tests have shown that when the strand count exceeds 7 strands in a bundle, the 8th strand is not really pulling its weight; it's just along for the ride. If I need a thicker string to fit my nocks, I just use a thicker serving material on my 14 strand strings.
I don't know how this varies among string manufacturers, but as you can see, 14 strands is so far above the minimum required breaking strength that I doubt it is something you need to worry about.
What you do need to worry about is any cuts or abrasions the string may get after you make it, which will substantially weaken any string.
(Edit: I don't know what the breaking strength of B-55 is, but since it is a newer material than B-50, I would assume it is at least 35#, if not more)