questions

[stuckinthemud]

OK, so here is a little bow I am about half way through tillering.  It has about 20 degrees of prop twist at the moment. It also is a little stiffer in the centre of the right hand limb ( I think, could be wrong about that though).  Anyway, first question, at what point should you heat out any twist, I was going to go with last step and combine it with a good heat treatment but I'd be glad of your comments.  Second question, self-bows often (usually?) have natural positive tiller as the growth rings tighten and reduce in number the further up the stem you go (a bold statement and if I am wrong, please chime in).  So, do you remove that positive tiller, and if you do, what's the best way - by width or by thickness, or a little of both?

[Del the cat]

 I think your assertion about natural positive tiller as you go up the tree has nothing to substantiate it AFIK
Del

[bownarra]

I think your assertion about natural positive tiller as you go up the tree has nothing to substantiate it AFIK
Del

[stuckinthemud]

Its just that a few bows I made recently I mirrored exactly the measurements of one limb onto the other around the centre point and found one limb was always stronger than the other. I checked the measurements with calipers but I only use saplings and no doubt that skews my findings

[dylanholderman]

The way I see positive tiller is just that tiller, growth rings on the belly are a indicator or guideline not something to judge tiller with.

Your plan to take the twist out when you heat treat I think is fine but if I’m able to tiller a bow out all the way I don’t normally bother taking twist.
 

[willie]

Its just that a few bows I made recently I mirrored exactly the measurements of one limb onto the other around the centre point and found one limb was always stronger than the other. I checked the measurements with calipers but I only use saplings and no doubt that skews my findings

there are differences in wood properties in a tree as you go from butt to crown, and it may be the historical reason some bows have a stiffer lower limb. Others keep the lower limb stiffer by design or tiller. Some bowyers always keep the top and bottom limb in the same orientation as the tree grew.  Possibly to avoid making the bow upside down?