I talked to a good bowyer this morning and he got me thinking....
So tonite I cut some .060 parallel lams exactly the same length, checking thickness on each one and adjusting as needed to get as close to .060 as possible. Also cut all to 1.5" width with table saw set for all so as close as possible to exact.
The deflection was checked by hanging over end of bench 6" and clamping it and a straight board down to bench. Then measuring deflection to straight board, and flipping over to check and average result. I used a 2" spring clamp square on the lam end 1/8" onto the end of lam , was gonna weigh it but didn't yet.
Here are the results so far, most of these would be core woods, and are edge grain.
Wood -- weight in grains -- deflection in "
R. elm ------- 32.4 -------- 1 1/16
A-wood ------- 44.2 -------- 7/8
Amber boo ---- 37.4 -------- 1 1/4
Nat boo ------ 41.0 -------- 1 3/16
Ash ---------- 34.8 -------- 1 5/16
Walnut ------- 32.4 -------- 1
H locust ----- 39.5 -------- 1 3/8
Hickory ------ 39.6 -------- 7/8+
Osage -------- 49.1 -------- 7/8+
Maple -------- 41.1 -------- 7/8-
See why a lot of old bows were maple core? LOL
Hope these numbers can help you decide on cores, but the numbers are pretty much controlled by the individual tree they came from. YMMV
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The yardstick I was using was in 1/16" inc. so I added a plus or minus if above or below the 1/16" measure. So the maple bent less and the hickory was lighter . Maybe it should have been -7/8".
Or maybe should have done in 1/1000 " I have a dial indicator but it is an inch job.
Seems to be a correlation in weight vs stiffness of lams in general but some just seem to fail in both and need to be veneers.....
Should have done a bocote lam and some glass for fun...