Speculation please

[DC]

Here is a FDC of my newest Boo Yew(pencil) and my old stand by (red). They weigh 453 grams and 461 grams respectively. The new one has a bulkier handle so I'm assuming the new one has lighter limbs. The new one is 50#@28", the old is 40@28. The new one shoots 10 gpp@ 183fps, the old one shoots 10gpp@191fps. I tried to arrange the beginning of the chart so things made sense. The only thing that makes this make any sense to me is the old ones FDC is slightly humped compared with the new one. Is that little hump enough "early draw weight" to make the difference. I shot a 300 grain arrow with both bows and the new one was 217fps and the old was 211fps but I think that's to be expected with 10# more draw weight. I can probably take some weight off the tips of the new bow so there may be some improvement possible. The draw length and draw weight are written in 5 # and " increments. Each graph line is 1 # or "

[bradsmith2010]

Maybe its more about the qualities of the wood,.not so much the fdc,,I am just guessing,..a bit like the stave u are working on now,,,that seems to have different qualities in resisting bend.

[DC]

They are both edge grain yew possibly from the same stave. When I first got a bunch of yew it was in big staves that I split up and just stacked in the corner. The color and grain are very similar.

[bradsmith2010]

Are they holding same reflex,,.the fdc seems to reflect the conference

[DC]

Ah, good point, that's probably it. The new one has less reflex even though it has bigger hooks. 1 3/4" versus 3/4". I'm having trouble guesstimating limb thickness before glue up. If the limb is thicker the pucker factor enters into it and it's harder to glue in more reflex. The new one started with 1 3/8" reflex and ended with 3/4" so it lost 5/8", I can live with that.
I'm sure happy with the old one. I've shot at least a thousand arrows and the speed dropped 3fps from 193 when very fresh to 191 now. i sure wish I could duplicate(and improve on) that.

[bradsmith2010]

Seems like putting a bit more reflex,,,should help...it seems to me,,,the heavier the draw,,,the more difficult to get fps,,.?..maybe it just takes more skill,..like a 70# bow shooting a 700 grain arrow 190 fps,,,whew,..I am sure I read somewhere that as bows become heavier in draw they become less efficient...may not be true,..but I have read after 70# it is more noticeable..I think its in volume 1...I will look today

[DC]

Back to the original question, sorta. Is it the extra reflex that causes the "hump" in the FDC?

[bradsmith2010]

im guessing yes,, once you get above 190 fps, the speculations seems to drop off dramaticly,,im sure Badger will chime in,,

[Marc St Louis]

I know the one has a heavier draw weight but taking that into account would you say that the lighter bow has more string tension at brace?

[DC]

I've been meaning to make a jig to make measuring string tension easier. Maybe that's a job for today.

[bradsmith2010]

cool

[DC]

That was easy, a length of chain and a turnbuckle makes it infinitely adjustable.
OK this is interesting. The 50# bow has 76# of string tension. The 40# bow has 96#. Now if I could just figure out why. I made the test "string" the same length as the bows normal string. Brace heights are with an eighth inch of each other.

[Badger]

The string tension might be a reflection of how little or how much set the bow took. I have seen bows with a lot of refex and really not that much string tension

[DC]

Do we know for sure that more string tension is better?

[DC]

I measured another 40# bow that shoots about 185 and it only has 70# of string tension.