Trapping

[PEARL DRUMS]

Yup. That's why most of us temper locust, elm and hickory.

[Stick Bender]

Ok just a thought trapping can be done prior to tillering the bow leaving the belly less strained as where belly tempering is usually done at some point with tillering already under way would there be any advantage of doing both on the above mentioned woods ?

[bradsmith2010]

for example is someone said,, I had a bow not trapped,,it shot 150fps,,10gpp
I trapped the bow ,, now it shoots 10 gpp 157 fps,, I would start to be more interested,,,
I have not heard Badger say much about trapping, he is my voice of reason most the time,,,,
Pearl seems to be right on,, as well,,
I am still listening for the "benefits",,,always willing to learn ,, just not easily convinced at this point,,

[DC]

I think it just helps prevent chrysals. I don't see how there would be much performance gain, if any.

[GlisGlis]

for example is someone said,, I had a bow not trapped,,it shot 150fps,,10gpp
I trapped the bow ,, now it shoots 10 gpp 157 fps,, I would start to be more interested,,,

I think trapping could only decrease actual bow poundage and speed (you're taking away a consistent part of the bow) but you'll end up with a more balanced bow.
A less stressed design for those woods that are more strong in tension than in compression.
After a decent number of shots your trapped bow may actually shoot better than your stressed untrapped design

[Stick Bender]

If you where splitting hairs on a more stressed design bow one trapped the other not  and both bows same draw weight  the trapped one would be less mass , it's like any thing with this bow designs I'm going to have to try one with hickory  to find out  keep us posted on yours there DC. Interesting topic !

[loon]

it prevents chrysals but is a narrower back more prone to splintering/breaking in tension? i think trapping would move the neutral line further from the back, so it stresses the back more..?

[PEARL DRUMS]

It doesn't prevent frets from happening.  A solid design and tiller job does that.

It doesn't stress the back more, it wakes its lazy butt up and tells it to work equally with the belly. Proper tempering does the exact same thing.

[steve b.]

If tempering equaled trapping I'd much rather trap because its much simpler and less ambiguous.

Brad--Its not that you trap an efficient bow and it suddenly becomes more efficient.  Instead, you take an otherwise inefficient design and make it more efficient.  Its no less theoretical than tempering where we find the constant questions about which wood should be heat treated how much or maybe it broke because of the tempering. 
We already know for sure that alot of wood types are tension strong relative to the compression side so we know that making the tension side more narrow balances the two out so that you get to remove mass from the bow in order to achieve a better balance. 
If you took an otherwise efficient bow and then tempered the belly the only way that improves it is if you have now raised the draw weight so that you get to remove mass in order to bring it back to weight.  Its the same principle, as far as I understand it.  But my experience is that tempering is more subjective.

[bradsmith2010]

I guess since I work mainly with osage,, trapping has not been needed much, if there are other woods that benefit,I just dont have experience with it,, it sounds interesting,,

[BowEd]

The gray area where the 2 methods overlap in benefiting bows is that number 1 in trapping you relieve the belly from compressing while tillering taking the back down to the bellys' compression level.Number 2 heat treating the belly makes it denser or harder to with stand the compression better to balance it with the back.A flip flop version of getting a balancing act of the 2 forces.Although a person has to remember heat treating does not make the wood more elastic.In fact less.Keeping a wood elastic is good.Trapping will still keep the woods elastic qualities.Both will make the limbs lighter but I would say heat treating and retillering does a better job of that in the performance arena because of the limb mass lost if the design is not too extreme or to the edge to risk tension failure.Good osage does not benefit as much as it is just plain too dense already.
That's my take on it as I rarely trap any wood,but do heat treat a variety of white woods.

[mikekeswick]

The key to effectively using both of these techniques is to first understand the properties of the particular wood you are working. You just can't generalise here.
As mentioned both trapping and heat treating are methods used to help 'even out' the forces in tension strong / compression so so woods. Trapping takes 10 mins and is easy to be precise. Heat treating is as mentioned above a bit more subjective and takes longer (not that time taken bothers me!).
The bend test mentioned in TBB is a great starting point to determine how your wood behaves when bent. As are half size/ scaled small bows.
As for not being able to test the effectiveness of trapping or heat treating.....take two slats of your chosen wood one heated or trapped and one not....bend them and look at results.

[shofu]

great topic - learned lots already, hoping for more.
Cheers,
George

[Wooden Spring]

define benefit,,,,,I dont disagree,, just dont understand

The neutral axis of a bow limb does zero work (imagine a line drawn through the center of mass of a cross section of bow limb), so the idea is to get as many fibers as possible away from the neutral axis where they do not work, but instead sheer... This sheering of the neutral axis combined with the compression of belly fibers and stretching of the back is what contributes to string follow.

One way to reduce the neutral axis is to hollow out the sides of the bow limbs somewhat by shaping them into a heavy "I-Beam" cross section. However, given the difficulties in the construction of a bow limb of this shape, the same result can be had by giving the bow a trapezoidal cross section.

In doing this, the stronger back of the bow is reduced, evening out the forces between back and belly, and reducing overall fiber stress of the bow limb.

[Wooden Spring]

Ok just a thought trapping can be done prior to tillering the bow leaving the belly less strained as where belly tempering is usually done at some point with tillering already under way would there be any advantage of doing both on the above mentioned woods ?

Trapping a bow should always be done before tillering! If not, then excessive fiber stress has already occurred, and the neutral axis has already taken excessive shearing forces. Doing both? I don't know, try it and let us know!