Side/belly tillering

[DC]

If you have a stave that needs to be reduced, how do you decide whether to take wood off the belly or the sides?

[PatM]

 Based on wood type, length of stave, projected draw weight and draw length.

[DC]

Oh, you broke 3000 Pat.

So pretty much everything goes into the decision. Correct me if I'm wrong

Wood type- higher compression woods can be narrower?

Length of stave- longer bows can be narrower?

Draw weight- lighter can be narrower?

Draw length - shorter can be narrower?

I'm seeing a pattern here- the lower the strain the narrower the bow can be?

[Pat B]

...but with some woods there is a minimum width.

[wizardgoat]

You reducing a stave or roughing out a bow?
If I reduce my staves I usually make them about 2" wide and 2" thick.
I leave them full length.
If your roughing out a bow you need to figure out what design your going for first.

[Badger]

   If you think about it in terms of creating radiuses it becomes a little more clear. A bow with a short bending area will have a much smaller radius than a bow bending through the handle for instance. The inside radius needs to stay within 1% or less of the outside radius. So anything you do to shorten or lengthen the radius you need to increase or decrease the width and increase or decrease the thicknes accordingly. That is what the mass principe is based on.

[DC]

I'm attempting another boo backed yew. I've spliced the billets and glued on the boo. Now I'm trying to decide on how much to take off where. My last one was about 35# and was an inch wide at the fades. It was a really nice bow but I've toughened up a bit so I want this one to be low 40's. At the moment it's 1 1/4" at the fades and 5/8" at the tips. It's even taper. Appearance wise, I'm happy with the 1 1/4". The tips I want to narrow to 3/8", approx. I'm sure I could just hack away at  and it will shoot fine but I took the time to do the Perry Reflex thing and I thought I should try to get the best out of it.

[DC]

   If you think about it in terms of creating radiuses it becomes a little more clear. A bow with a short bending area will have a much smaller radius than a bow bending through the handle for instance. The inside radius needs to stay within 1% or less of the outside radius. So anything you do to shorten or lengthen the radius you need to increase or decrease the width and increase or decrease the thicknes accordingly. That is what the mass principe is based on.

This sounds good. I'll break out the TBB and read your chapter, Again. Do you just use an average limb thickness to determine the different radii ( I don't think I've ever typed that word before )

[Del the cat]

Width can be adjusted late in tillering process for fine tuning as it doesn't make as much difference to stiffness.
Thickness is what makes the most difference.
Stiffness is proportional to width, but proportional to thickness cubed.
So if you half the width, you half the stiffness... but if you half the thickness you reduce the stiffness to 1/8 of what it was.
That's why you can have paddle bows, parallel bows, bows with scallops out of the edges.
Front profile has very little to do with tiller unless the bow is of constant thickness, see the miniature bow at the foot of this post on my blog, which illustrates the point:- http://bowyersdiary.blogspot.co.uk/2014/04/ashbow-re-try.html
Del

[George Tsoukalas]

On my selfbows, if I feel that the bow is not really responding to belly wood removal, then I begin to narrow it slowly while checking tiller constantly.

Width measurements get  me close.

Jawge

[Pappy]

What Jawges said.
 Pappy

[PatM]

Why would a bow not respond to belly wood removal?

[George Tsoukalas]

Too wide for the  lower target weight wanted, PatM.  Jawge

[PatM]

Ah. "Not responding" made it sound like you scrape and it doesn't change the bend.

[George Tsoukalas]

...and not wanting to get the limb too thin. Jawge