Tillering question

[DC]

In the drawing I'm showing a small cross section of the limb. This does't represent the whole limb but just a small section, maybe 3-12", whatever. I'm looking at the belly and it's relationship with the back. "A" is the ideal but if you have a short section that twists and then twists back I'm assuming you should shape the belly like "C" rather than "B". With a twisty stave this could go from side to side down the limb. My question is what will be the effect of ignoring the twist and just having a flat belly? I'm assuming you get the thickness right so you have a nice bend.

[Badger]

I know what you are talking about, sometimes I get a surprise where the limb twists too much. I have the best over all luck trying to keep them flat and even for the most part.

[bradsmith2010]

if you shape it like B,, its gonna twist more one way or the other,, than C... B,,, one side is gonna be way strong,,

[DC]

But if you have a little one way and a little the other won't the twist kind of cancel out? I've wondered about a limb like "C", wouldn't it have a tendency to bend off to one side. Kind of wanting to bend a 90° to the belly?

[bradsmith2010]

I think the C has a tendency to straighten out at full draw,, that being said,, either would probably shoot good if bending evenly,,,but I have never done one like b,,,, so just spit balling,, but c will probably straighent at full draw and B will probably twist,,

[upstatenybowyer]

I try not to mess with (or over-predict) what the wood wants to do naturally. That is to say, I go with "A" throughout the length of the limb, regardless of twists and turns.

[leonwood]

Personally I always use c. Actually I am working on a horrible piece of apple which has this on both limbs going everywhere. The belly has not a single flat spot on it...

[Del the cat]

A... C... A as it runs through the twist.
Bottom line... it doesn't matter as long as it draws straight.
A good trick is to tape a couple of thin spills of wood to the back or side of the bow. Line 'em up so that viewed from the side they are parallel. Get someone to pull on the tiller rope while you stand to the side and watch the spills... that should stay parallel if the limb is coming back nice and straight. While you are there you can also look out for any sideways bend.
This post from my blog shows what I mean:-
https://bowyersdiary.blogspot.com/2011/03/twisting-bow.html
Del

[Eric Krewson]

Limb layout is very important to eliminate the possibility of twist. There is no reason to have any side thinner than the other unless you freehand the shaping and get off track.

Lay out very precise side taper lines and don't violate your lines, make your belly slightly rounded to start with and tiller the center.

If you do get limb twist with everything even take it out with heat. I have found taking out twist by drastically reducing the strong side of a limb to be counterproductive and you end up with a wonky looking bow and most of the time you still have some degree of twist.

Take the natural twist out of a stave while it is a bow blank, lay it out precisely, constantly trying to correct for limb twist won't be a problem.



 

[Pat B]

You can reduce twist by tillering it out. By reducing the strong side the twist can be straightened as the bow is drawn. Ideally you want to start with even limbs whenever it's possible or straighten out the twist with heat but you can also reduce twist in the tillering process.
Also, a little twist isn't so bad in a selfbow.

[Eric Krewson]

A little twist will usually pull out of a limb after you shoot it a while

[bradsmith2010]

I have experienced that as well,, sometimes I cut the string nocks to accomodate a little twist,, after shootin a bit,, the limb has ,, straightend a bit, and I have to re do the nocks so the string is where I want it

[Selfbowman]

I have done all the above in bows. The more twist the more shock. So I try to get them straight as possible with heat. But that's just me!  Arvin

[George Tsoukalas]

I don't bother with twist unless it is excessive. If excessive i will heat it out.

If I caused the twist by uneven wood removal then I fix it with even wood removal.

Jawge