Help with a laminated bow

[Bighornangler]

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.

[LittleBen]

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)

[Bighornangler]

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.

[Bighornangler]

Lets try this again. [/IMG]

[JkChenault]

try  reducing the width and trapping it i was able to lose 15 lbs on a glass bow that way

[LittleBen]

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.

[Bighornangler]

[/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.