Parabolic Tiller?

flint kemper · September 26, 2009, 10:01:00 PM

Can anyone tell me about parabolic limb tiller? I know that this is how Howard Hill and John Schulz tillered their limbs to this profile and it is a ever curving bend. Thanks Flint

Shaun · October 03, 2009, 12:17:00 AM

It bends more towards the tips compared to an arc of the circle tiller. Imagine one quarter of an ellipse vs one quarter of a circle.

George Tsoukalas · October 03, 2009, 11:06:00 AM

I've never heard it put that way but if you want that type of tiller do make the bow longer or she'll stack on you. Jawge

ChristopherO · October 03, 2009, 05:16:00 PM

Shaun, are you refering to an elliptical tiller? Are Parabolic and elliptical one in the same?

Dano · October 03, 2009, 07:00:00 PM

Isn't the term "whip tillered" ?

Pennsyltuckey pete · October 03, 2009, 08:31:00 PM

Not being the sharpest tool in the shed what I am saying is to be taken with a large grain of salt.

A parabola is a shape obtained by dissecting a cone with a plane. 1/2 of a parabola is a decreasing radius curve.

A parabola will have a very long radius curve starting at the one end, and then decrease the radius (Tighten the curve, or make it sharper to the point where the ray of the curve is at 90 degrees to the original ray. At that point the radius of the curve begins increasing in exactly the same proportions as before.

Looking at it this way it tells me that a bow that is tillered in this fashion barely use the working part of the limb and puts most of the flex in the limb tip. This is something that I shy away from.

I am basing this on my understanding of the shape of a parabola. Is parabolic tiller a totally different shape than what I am imagining? Please help me understand.

Dano · October 03, 2009, 08:39:00 PM

Well that makes sense Pete, but in the ten years of building selfbows I've never heard of "parabolic tiller", but that don't mean much. Flint Kemper, please clear this up.

Pennsyltuckey pete · October 03, 2009, 10:35:00 PM

I have never heard of it either. I agree with the term whip tillered but I am wondering if there is something I am missing.

flint kemper · October 04, 2009, 02:06:00 AM

Dano, I am not sure either. That is why I asked. I may have the term messed up as well. Thanks FLint

George Tsoukalas · October 06, 2009, 10:04:00 PM

Never heard of it either. But I understand that you mean whip tillered which is not good unless left longer. Jawge