Reducing bow weight

[LESKEN2011]

I need some advice on the best way to take off some weight on a bow that turned out heavier than I hoped. The glue up turned out great. No bubbles in the glass and tiller is pretty close to perfect at 28". Unfortunately I miscalculated the thickness of my veneers when converting from mm to inches. The bow turned out about 70 lbs at 28". For all-wood bows, no problem, but with glass...? I have read about trapping the limbs and I have even sanded the glass on the first bow I made. I would like to get it down to around 55# at 28, if that is possible. I used .040 glass on the back and belly, so I don't have a lot to sand. What kind of angle should the trap be? I have trapped wood bows, but really don't want to screw this one up. If you think it is likely to result in failure, I can just finish it out and trade it to someone that wants a heavy bow. I am sure this has been covered before, so if someone could direct me to a prior post, I would appreciate it.

[typical2]

If you decide you want to trap it you'll find you will remove the most draw weight by trapping to the back.  I put a 10° trap on my longbows (but to the belly). It seems like quite a bit though.  Might start a but less.

[macbow]

How is the overall width?  If there is some room you might start with some reduction in width before trapping since that is a lot of weight to loose.

I did take a 68 pound longbow down to 55 with reducing width a little then trapping to the inside.

[LESKEN2011]

It is 1.25" wide at the fades with a pyramid taper to the tips. Not much left for a width taper. I may just finish her up and trade her for some more materials. It has been a great learning experience.

[BigJim]

You can reduce the thickness of the belly glass...this will give you the most profound weight reduction. just do it evenly and you will be ok.

Trapping should take off a few pounds too.

BigJIm

[chackworth3]

You might could take it down to 1 1/8" and lose some weight too.

[BigJim]

Be careful of reducing the width of limbs. It doesn't take much and you will have a crappy bow. Plus reducing weight by narrowing limbs is like hunting dinosaurs....lots of work for very little results.

BIgJIm

[LESKEN2011]

I let it sit for a couple of days while I thought on the best way to approach it. I decided I am going to smooth everything out, do a mild trapping of the limbs belly and back and see where I am. My Wally World luggage scale shows 73# @ 28", but I think it shows about 5# heavier than reality based on using the same scale on other bows I have purchased. If it is really 68#, maybe I can lose about 10# and get it down to a manageable weight. Thanks for the advice, guys.

[jhk1]

Kenny,

In your last post above you said "do a mild trapping of the limbs belly and back"-- did you mean reduce the thickness of the glass on the back and belly?  You can't trap back and belly-- it's one or the other.  "Trapping" is narrowing either the back or belly of the limbs so that the cross-section is trapezoid shaped.

I'm not sure whether trapping to the back (narrowing the back) or trapping to the belly (narrowing the belly) yields a greater weight reduction.  I'm assuming that BigJim is correct above ("You can reduce the thickness of the belly glass...this will give you the most profound weight reduction"), since he's an expert bowyer; if reducing the belly glass thickness gives the biggest weight reduction, I would think that trapping to the belly would yield a greater weight reduction than trapping to the back (you're removing glass from the belly instead of the back).  But what do I know?

[LESKEN2011]

I don't mean to trap in the normal sense. More of a thinning of the outer edges of the limbs on the belly and back as well as rounding the edges a good bit. If I decide to take any off the middle, it will be on the belly just a tad. Maybe I can get down under 60#. 55# would be great.