It has to do with the cross section of the limb.

If the sides are perpendicular to the back and belly, then you would call it a rectangular cross section. This is the usual cross section.

If the back of the bow is more narrow than the belly, then the sides of the limb are not parallel to each other. The cross section is now a trapezoid.

Here’s a picture : __
/__

Pretty sweet graphics eh?

I know that Shrew “traps” their longbow limbs as a way to do fine-tune tillering. The design may have other advantages I’m unaware of, but it’s done for practical rather than aesthetical reasons, though I like the way it looks. I’ll invite Gregg Coffey, who builds Shrew bows, to come on here and explain further. Patrick, you never seem to run out of excellent questions: a Zen archer’s “beginner’s mind.” 8)

Steve explained the cross section pretty well. Many bowyers make their limbs with a trapezoidal cross section. Most of them make the back narrower.

As Dave stated, I trap the limbs on Shrews for two reasons. the first is to bring the bow to correct draw weight and fine tiller the limbs.

The 2nd reason is to remove limb mass, especially in the outer portions of the limb. This helps some with arrow speed and softness of the bow as the arrow is released.

Gregg

Thanks, Gregg. Always good to get info from the experienced horses’ mouth. As a shade tree bowyer you’d think the advantages of weight reduction toward limb tips would have occurred to me. A signal it’s been too long since I built one. Dave

Patrick

That was a “Shrewed” question you asked.:lol:

I’m sorry, I could not help myself. Please forgive me Patrick. My children say when I resort to corny jokes they label it “Pop Corn”. Honestly I did not know the information either. I always learn from listening on these posts.

Tom

very on top of your game… there tom
thats funny ,when I resort to cornisums,my wife calls me a corn ball:shock::lol:
deaddrift

My wife just rolls her eyes and doesn’t bother with an intelligent response…lol…but hey, the only jokes I can remember are the corney ones.

Michael

I think reducing limb mass is the key word here. In selfbows a trapziodal cross section is a good way to reduce mass, and it plays on the fact that most woods are stronger in tension than compression.
So a trapped back can take the tension while the increased area of the belly means reduced kompression.

Thats how I see it anyway.

Cheers
Please stop reminding me of Shrew bows…I want one so bad it hurts:-(

There’s a good explination an pic’s of trapped limbs on the Tomahawk web site.

John.