In my photo there is a James Parker Bamboo Back/Bamboo Belly bow (the bow on the bottom) I got as a blank and finished myself. It came out 48# @ 25". I took measurments of all of his lams with a dial caliber and attempted to come up with my own bow hoping to come out with about the same poundage (bow on top in photo). The boo is flattened from 1/8" to about 1/16. I have osage lams directly below the boo on the back & directly above the boo on the belly .095 tapered .002 per inch purchased from Kenny M. In the middle of these I have a piece of IPE .156 center of risor, midlimb .095, and about .045 at tips. This piece of IPE I tapered myself the best I could by hand without any tapering machine. I know that leaves a lot of room for error, but I did do another bow the same way and it came out great. I did add a tapered tip wedge 12" long starting at .070 (no wedges on Parker bow). I took thickness measurements of both bows at the fade outs, midlimb, & the tips. Except for the tips, they are about the same ( my tips are a little wider because of the wedges). I should mention also that the Parker bow has the same wood combinations as mine. Having said all this, I am at a loss of why my bow shows about 55-59 lbs at only 3 inches or so of brace height which would make it over 100 lbs @ 25". Does the fact that my bow has a lot more reflex have anything to do with this? The added tip wedges? Any help would be appreciated.
Alot more reflex .... in short absolutely.
The wedges, almot definately.
Are you saying it has 55-60# @25" when braced to only 3"?
That should bring you closer to 70# @ 25" than 100# when you brace higher.
Also very little change in thickness makes a lot of change in draw weight. For example. a 25% change in thickness makes a 100% increase in stiffness (i.e. draw weight)
A 12% increase in thickness (i.e. .56" vs .5") will make a 40% increase in draw weight (i.e. 67lbs vs 48lbs)
Thanks LittleBen. What you said about the difference in reflex plus the added tip wedges was what I was thinking, but wasn't sure. I know I can only trap the boo (I've already done quite a bit) and reduce the sides some to lower the weight, but in any event it's going to be heavy. So it looks like if I want to use the same form, I will have to reduce my core lams a a bit. Maybe more that a bit. I'm thinking of taking off the belly boo & the lower osage tapered lam and reducing the IPE a little more. Than I will put on a new belly lam boo (without the osage lam) and re-glue. What do you think? I have given up on the photo.
Lets try this again. (//%5BIMG%5Dhttp://i1201.photobucket.com/albums/bb357/bighornangler/001-1_zpsa2045e29.jpg)[/IMG]
try reducing the width and trapping it i was able to lose 15 lbs on a glass bow that way
Give us the total stack thickness. I'd reduce it by about 10%-15% to get to the weight you're looking for. Or like you said reduce the reflex and no tip wedges.
Very interetested to see pics.
I would just glue up a new one instead of grinding off half the bow. I'd reduce the weight as much as you can and give it away to someone who's abnormally short and strong haha. I only qualify for the first half of that.
(//%5BIMG%5Dhttp://i1201.photobucket.com/albums/bb357/bighornangler/001-1_zpsa2045e29.jpg) (http://i1201.photobucket.com/albums/bb357/bighornangler/001-1_zpsa2045e29.jpg)[/IMG] The photo isn't that great, but you can see the difference in profile of the two bows. My bow at fades measures .053 R. Limb .056 L. Limb- J. Parker .053 R.L. .054 L.L./ My bow 15" from center of risor .043 R.L. .045 L.L. - J.Parker .045R.L. .046 L.L./ My bow 25" from center is.041 R.L. .041 L.L. - J.P. is .038 R.L. .038 L.L./ Tips my bow (excluding tip overlays) is .031 &.031 - J.P. is .030 & .030. It looks like J.P. left the tip portion of both boo pieces thicker to come up with that thickness, whereas I added a tip wedge of .070 12" long.