taper

[jayman448]

While reading bowiers bible i came across a section that basically said design a tapers x, design b tapers y, qnd design c tapers z, in order to achieve proper tiller. Have any of you found this to be so cut and dried true? Logically without much working knowledge i would think the major fight is to make it uniform the whole way rather than continuing to taper it the whole way. Perhaps ive read it incorrectly tho?

[J05H]

I believe the part your referring to is basically saying that the belly taper (and therefore tiller shape) is dependent on the front profile. So a pyramid bow should have very little belly taper and a circular tiller, and a flat bow that is full width until the last six inches should have a steady belly taper and an elliptical tiller. If you focus on getting the limbs bending evenly and getting the tiller shape right, then the belly taper will take care of its self. That's all just my opinion. I'm sure you'll get many more.

[Jim Davis]

JO5H, that's not JUST your opinion about the tapers. That's fact. You have it exactly right.

And, the only reason to taper the belly of a pyramid bow at all is that we can't make the nocks a dimensionless point.

Jim Davis

[mikekeswick]

The key fact is that as wood gets thinner it can bend further without excess damage to the woods fibers (set).
So elliptical/circular tillers are dictated by what width taper you use.
A bow with no width taper (until close to the end) HAS to taper somewhere so it tapers in thickness. Thicker wood near the handle can't bend as far as the thinner wood near the outer limbs. Therefore an even taper produces an elliptical tiller.
If you watch set as you progress the wood will tell you all this (and more!).

[Dances with squirrels]

Folks also sometimes end up with thickness taper on a pyramid bow if it wasn't designed wide enough at the flares.

[George Tsoukalas]

Josh, good post. The thicker the wood the  more work it should do to cut down on set. Therefore, a pyramid bow, which has thicker near handle wood should bend more there resulting in a circular tiller.

Also, as mikekeswick said, bows with parallel limb profile out to just before the tips should show an elliptical tiller and somewhat stiff the last 6-8 inches.

As DWS pointed out, sometimes you have to remove wood from the belly in a pyramid bow.
Jawge