Speculation please

[SLIMBOB]

Very counter intuitive.  I'm interested in what the mechanics or geometry or vodoo witchcraft behind this is.  Is string angle a player?  String length?  The string isn't feeling tension in just one spot, it feels it along the string.  If you measured it in different spots on the string does it change?  If you measured it in 2 spots at the same time are they the same reading?  Lot's of questions....

[simk]

 

[bradsmith2010]

it makes since to me,, that if the brace is higher, its like drawing the bow,, so the string tension would be lower,,and I hate to say this,, but maybe shoot slower,,

[SLIMBOB]

Yeah but shooting slower with a higher brace is a different matter in my mind.  That can be explained by the distance the string travels before the arrow leaves the string.  That makes sense.,,,to me....this doesn't.  Not saying it's not accurate, just that it defies logic, or the logic I bring to the table, which is very non-mathmatical.

[DC]

I greased up the turnbuckle so I could move it under tension. I can watch the string tension go up as I lower the BH until it hits about 5 1/4" and then it goes down. This is just about the time that the string starts laying on the belly so I think that's the culprit. Shorter string or maybe the string angle goes up about then.
The tension is going to be the same all along the string and I don't have two scales anyway.
The string angle changing kind of explains it for me unless someone can explain why a shorter string(shorter bow) would drop the tension. I'll do some more testing when I get a jig that works better. The turnbuckle I have isn't long enough and a longer one would get more cumbersome to use. It's a real PITA the get this braced with all the gear attached.

[DC]

Yeah but shooting slower with a higher brace is a different matter in my mind.  That can be explained by the distance the string travels before the arrow leaves the string.  That makes sense.,,,to me....this doesn't.  Not saying it's not accurate, just that it defies logic, or the logic I bring to the table, which is very non-mathmatical.

Maybe the brace height/performance thing just didn't explain it well. Maybe the real reason the you get more speed with a lower brace height is because of the increased string tension, not extra travel. Or maybe both or maybe it's the same thing just looked at sideways sorta.

[DC]

The test will be to do this on a straight bow. I'd bet a nickle that the ST (string tension) would keep going up.

[SLIMBOB]

Maybe it is string tension, so why is string tension higher on a bow string at brace height than full draw when the draw weight is  under10lbs at 6 inches and 50lbs at 26 inches?  That's...baffling.

[SLIMBOB]

So if it is string length (lift off) then the longer the recurves (more contact) the higher the tension,?  So we need to be making the recurves as long as possible to capitalize on that?  Has to be some other factor that mitigates that...I think.

[DC]

We're still not positive that higher ST improves performance, at least I'm not, yet . I don't think ST and draw weight are really dependent on each other althought it is hard to separate them in your head.

[SLIMBOB]

I’m not a scientist lord knows,but there is a relationship between stored energy, and kinetic energy. Seems reasonable that string tension would fit in there under stored energy.

[PatM]

I think it's definitely the higher string tension that's making the difference.

[DC]

Would you venture a guess as to whether it's actually the higher ST or is the high ST just an indicator that you got something else right? It just seems to me that the ST is kind of tied up with itself and I'm not sure that it could affect anything else. Just thinking outloud

[bradsmith2010]

ok its over my head now,, but a very interesting way to look at it,,

[sleek]

The string tension is higher at brace because you have a very low string angle. As the string angle increases, leverage increases against the tip. As leverage increases, the required force to do work decreases, which is why the string tension drops. Its literally stacking in reverse.