This is a topic of repeat but anyway.  What is best to round off more so the back or the belly on Laminate bows, self bows or board bows....?

Depends on the wood used. Some benefit from trapping the back and some benefit by putting a radius on the belly.

I'm thinking about the benefit of tillering if that makes sense. Or I guess trapping either side.  Maple or yew or cherry or BW.

Yew obviously works great with a rounded belly, ELBs have proven that a few times over. Maple and BW would be best left flat back and belly. You could probably trap the maple some as its quite elastic compared to BW. But its not needed. This in regard to self bows only.

Mathematically, a perfectly flat back and belly are superior on a wood bow. That's not to say that trapping is a bad idea, probably nearly every common and reasonable wood or wood combination would benefit from trapping, but even if you trap, the back is best left flat.

Obviously you should always round the corners on the back to prevent splintering, and on the belly to prevent fretting at the limb edges.

There seems to be many bamboo backed bows that are crowned somewhat.

They all are in my shop. Otherwise Kaboom...

You should clarify... by "round off" do you mean 'round off' as in to create a rounded/radiused surface, or do you mean to 'narrow' as in... 'when creating a trapezoid cross section in a limb, is it better to narrow the belly or the back?'

I radius the bellies of ALL my wooden bows and most of their backs are naturally radiused. I vary the degree of radius on the belly depending on the wood's properties... but even something like a cherry bow has a full radius without a single flat spot to be found anywhere.

Aestetics aside, there are several construction, tillering, and durability benefits to be realized in radiused bellies on wooden bows.

When it comes to a trapezoidal cross section, I narrow the back on wooden bows, since as was mentioned, virtually all woods are stronger in tension resistance than they are in compression resistance.

On glass bows, I've done it both ways and haven't noticed a difference... though common sense tries to tell me it should be the opposite... that is, narrow the belly... since any glass I've seen fail has failed on the bow's back, I'm inclined to deduce that the glass is stronger in compression resistance/fatigue than tension... but I wouldn't swear to it.

Thanks Junkie on your insightful knowledge.

The way something bends involves a concept called 'moment of inertia'.

It leads down a road of horrible math, but if you are mathematically inclined, it could help answer your question.

I've only ever done the math for steel I-beams, way back, but the principle applies.

Failing math, give it a go and see what happens.

Some of the greatest discoveries have come from experimentation.

So if the tips are bending more than enough I would round off the belly side more....?

The roundness of the back is determined by the back ring on a self bow.
I round off all 4 corners and leave the belly flat.
Jawge

QuoteOriginally posted by George Tsoukalas:
The roundness of the back is determined by the back ring on a self bow.
I round off all 4 corners and leave the belly flat.
Jawge

How about on a laminate bow having all hardwood no Boo..?

Round all the corners but trap to the back for best stability. Trapping to the belly can cause limb twist very quickly with minor differences in material removal, or even material in general. It can be done successfully but it's trickier.

Thanks Over,  makes sense.  Like I stated previously I read about this subject before, but its getting to that point of forgetting more than I know.  

I trap the back pretty good then round over all the other edges.