Trapping Hickory

[psychmonky]

So I've started my first hickory self bow, and I've heard/read that hickory should be trapped (Back narrower than belly) because it's so good in tension but not as good in compression.

The bow is 60" tip to tip. 4" handle, 2" fades. It's 1 5/8" wide for 10" before tapering to 1/2" tips. I plan on heating some mild reflex into it, but i'm not sure if it'll be the whole limb or just the tips.

My question is this: When trapping the limbs, should the whole cross section of the limb be trapezoidal as in "A", or just the corners as in "B?" Any info you guys can give would be greatly appreciated.


 

[Steve B.]

I've trapped a hickory and oak bow now.  I trapped the whole profile, vs just the corners.  You just have to remember to make the belly width the intended width of your bow, at least.
So don't cut a 2" wide stave and then trap it because you'll end up with a bow that is less than 2".....by the time you round the corners.  And its impossible to trap the sides of the bow without reducing width of back and belly.  So start out with a stave wider than you want and work it down with trapping.

I did the same thing with a ipe bow but it cracked due to grain runout so I don't count it.  I will always trap the high tension woods and I like the looks.
I'll send you pics if you want..........

[SportHunter]

You don't have to trap hickory. I built a pignut hickory board bow this year that had 1 9/16" wide limbs at their widest point and it worked out very nice. The limb profile was rectangular with slightly rounded corners.

[4est trekker]

I prefer to trap hickory, as it is very strong in compression but quite weak in compression.  Trapping helps to create a balance.  I prefer to trap similar to diagram A, as it removes "dead mass" on most bow designs.  However, I leave an 1/8"-3/16" of the edge untouched where it meets the belly so that when I round the corner over, I don't eat into my belly wood.  That is, it helps retain the full width of the belly after rounding the corners.  

Further, because it's terribly humid in the warm months where I live, I like to temper the belly in addition to trapping when using hickory.  This serves the same purpose, and is considered by some to be "heat trapping."  Hope that helps!  

Regards,

[Bowjunkie]

My 'trapped' cross section looks a little more like this... at mid-limb.

 

As it nears the dips and tips, I put less and less angle on the facets, and as a result, it leans more toward an oval shape.

The way I trap it, it doesn't narrow the limb any more than I had it layed out for. In other words, I don't work the vertical sides while trapping. If I want the limb 1 1/4" wide, that's how I rough it out to the line, and that's how wide it'll be when it's done.

Upon being roughed out, the limb is rectangular... like most bows. The cross section might look similar to this at midlimb(showing the finished limb cross section inside).

   

I get to it by adding belly facets, and the trap facets... leaving a small vertical flat on the side(which maintains my layout width). Here it is with the facets added.

 

The facets may round over some as I tiller, but I try to maintain proportions as long as possible(which lends to accurate tillering), and then once the bow is tillered 3/4 of the way or farther, I start rounding stuff over with more facets and blending it all together.

[psychmonky]

Now that's an in depth explanation!  Thanks to everyone who replied.

Bowjunkie, do you make all your bows with a rounded belly like that? I had planned to make this one with a flatter belly. Or do you just make the facets shallower to make the belly flatter?

[Bowjunkie]

I make all of my bows with a radiused belly, but they're not all trapped. The amount of radius depends on things like which wood I'm using, the width, and other design criteria. None of my wooden bows have flat bellies. I like em curvy  

Yes, by changing the angle and width of your facets and how they relate to each other, you can make anything from a very thin and wide bow, like I did with a hickory-backed cherry bow I made, or as deep and round as an English Longbow, and the tillering process is all basically the same.

[Cataska Mtn]

Never heard of "trapping", but I guess I've been doing it all along.....