trapping limbs

[walkabout]

so i was pondering designs for my other hickory stave today, although it will be some time before i can work on it. i was thinking something in the range of 65", 55#@28', but was contemplating a narrower limb profile than say a flalbow with 1 3/4" limbs, maybe something like 1 1/2" wide or 1 1/4". this brings me to the dilemma of having enough wood to be able to keep my weight up, and from what i know hickory isnt well suited for thicker applications such as an elb design. would trapping the limbs toward the back help to alleviate the stress of a thicker limb?ive read that in theory it would help minimize the area of stress along a thinner section, thus allowing the thinner/thicker limb with weak compression wood. any feedback would be greatly appreciated, im not yet sure what im going to do with this stave so really im just throwing out ideas and taking advice into consideration.

[Pat B]

Hickory is a good candidate for trapping. It is very strong in tension but not so much in compression so trapping in favor of the belly should work well for it. I think 1 1/2" would be wide enough and especially if you trap the limbs.

[walkabout]

yea ive read 1 1/2" is wide enough to get 50# or so, im hoping to get 55 at least out of it if not 60#. ive been reading alot on trapping and havent really gotten any specifics as to methods, aside from dividing the limbs into facets and doing it that way, which seems easy enough. also i see alot of posts about trapping the belly rather than the back because the wood is generally tension strong, thereby needing less on the back, and leaving more on the belly to be able to handle compression.from what i know though this seems a bit off.the elb design wouldnt be good for hickory because hickory isnt great in compression strength, but great in tension. taking away the tensile strength and leaving more wood getting compressed seems like it would just cause failure to me.

[Pat B]

Woods for an ELB has to be very strong in compression. All of the compression stress is down the center of the rounded belly. On a flatbow the compression stress is equally distributed along the entire working portion of the limb. Hickory is strong enough to handle the extra compression of the trapped limb.
   I think you are trying to put too much engineering into your bows. Wood bow building can be an engineered project but for me I want to see what the wood wants to be(in the case of a stave) first then work with it to achieve a well tillered bow. If I have to trap the limbs because of a problem I take my rasp and reduce from the side of the limb with the rasp at an angle. In most wood bows trapping generally gives you a wider belly than back; alleviating the compression stresses by reducing the tension strength.
  We all have our ways of doing things. For me I want to see how simple I can make it. That doesn't always work for everyone but I think some folks try to "over think" the bow building process.

[tishtail]

i hate to sound supid without looking up what your both talking about i guess i don't read enough just try and follow whats seam as productive making a bow just a thing that came from a piece of wood came alive from it and nothing more not questioning any question but i'm looking for help on this delemia i'm lost please help thanks LjT

[walkabout]

i probably am overthinking it to tell you the truth, i should just wait and see what comes out of the stave good or bad. really i just want to get something of a decent draw weight, while maintaining a thinner limb as far as width is concerned. tishtail trapping is when you make the limbs of a bow a trapezoid shape, making the back more narrow than the belly(or vice versa) it basically allows the limbs to have more material to handle the compression on the back. compression is more or less what causes set in bows, as the wood fibers crush on the belly of the bow.

[tishtail]

thanks for reply it helps me not over think whats being discussed now i understand thanks LjT

[walkabout]

no problem