Artificial sinew bowstring and thumb slap

[Vespusius]

I made a Flemish bowstring with artificial sinew for a 40# 68" selfbow. The string looks great, but slaps my thumb when I release the string. I adjusted the string so there is about a 71/2 inch standoff from the belly of the bow, and now it doesn't slap, but I wonder if that is the best way of dealing with the problem. Is artificial sinew not a good material to use for bowstring on a traditional longbow style bow?

[aaron]

some artificial sinew is quite stretchy, depending on what it's made of. Stretchy is bad. A high brace will strain the bow more than a lower one.

[JackCrafty]

Artificial sinew comes in different grades.  The nylon based art-sinew is very stretchy and not good for bow strings.  There is a variety that doesn't stretch very much... about the same a B50.  B50 is used by the vast majority of bowyers.

My Favorite for artificial strings these days is Dyneema or Spectra.  No stretch and very strong.  Fast Flight is made from it.

The traditional material for the old longbows is linen (flax) strings or hemp strings.

[Vespusius]

By different grades of artificial sinew, do you mean Dyneema or Spectra? I do want to avoid the high brace.  I have heard that a bow must be certified to use Fast Flight, and I suppose a hickory selfbow would not be a good match?

[Grasshopper Mouse]

Artificial sinew comes in either polyester or nylon. Those are the two grades.
Nylon will make a stretchy, performance robbing, string. Polyester will make one that will work well.
But if you want the look of an art. sinew string I suggest getting actual bowstring material in a suitable color. B-50, B-500, B-55, or one of the FastFlite-type strings will serve you a lot better than artificial sinew.
As for putting a high performance string on a self bow... lots of guys do it and are pleased with the results. Be sure to pad the eyes out so the string diameter is fatter and don't be tempted to go the "skinny string" route and use something silly like six strands in the bowstring.

Guy

[Vespusius]

Thanks on the info about nylon and polyester artificial sinew. I have several different types, none of them identify what they are made of, which makes it hard to know whether they would be good bowstring material or not. I wonder if there is a stretch test that would help separate the wheat from the chaff. I have ordered some B50, different colors.

I have just got to know what "pad the eyes out" means.

[aaron]

Pad the eyes out:
if you use spectra/dynema/fast flight, your string will need less strands and therefore be thinner. Thin strings dig into bow tips, causing breakage. padding the loops means adding extra strands in the loops to thicken these parts.

[Grasshopper Mouse]

Yup, aaron got the padding right.
Even if you use more stands making a high performance string the strands are thinner and the finished string is thin enough to warrant padding the eyes. A lot of string makers use B-50 or equivalent for the padding material.

As for telling the difference between nylon and polyester artificial sinew, you can do a burn test. The two materials smell different when they are burned. Of course, you'll need to have a control material that you know is nylon or polyester in order to tell what it smells like.

Guy