Pyramid Bow Questions

[mmattockx]

My next project is going to be a red oak board pyramid bow. I am thinking 66"-68" NTN, 35lb draw @ 28". From reading TBB V.1, I understand that 2" wide at the fades would be lots for my length and target weight.

1) Is 2" tapering to 1/2" at the nock going to be enough taper to tiller as pyramid bows usually do? Do I just work the limb thickness as required to get the circular bend that pyramid bows are supposed to have, regardless of the taper?

2) Will the limb actually stay at a fairly constant thickness with such a minimal taper?


Thanks,
Mark

[bownarra]

A true pyramid would go to needle tips and that width taper would give you a true circular tiller.
The 'extra' width at your tips means that you will end up with a slight thickness taper, with the bend increasing as you progress along the limb (just a bit).

[mmattockx]

A true pyramid would go to needle tips and that width taper would give you a true circular tiller.
The 'extra' width at your tips means that you will end up with a slight thickness taper, with the bend increasing as you progress along the limb (just a bit).

Well, I can live with that.


Thanks for the reply,
Mark

[willie]

I understand that 2" wide at the fades would be lots for my length and target weight.

could be if you have a straight grained dense boarded. TBB4 P115 has info for density vs width in that length and a simple method to determine density. making a few tests beforehand helps, or you could switch to side tillering some excess width if you see your limbs getting too thin.

[Allyn T]

I imagine wider at the fades would work with a shorter bow for draw weight?

[bassman]

What bownarra said.

[Selfbowman]

I make my pyramid Osage  bows wide as the staves allow . Inter limb mass is not as critical as otter limb mass. Most are 67-69" long . The bowyers bible calls for 1-5/16" in width on the density chart I think. The extra with seems to help me in tillering low set bows. So 2-1/2 inches won't hurt you. Use 1" of limb for every inch of draw. It's a good recipe. Arvin

[airkah]

I've made quite a few red oak pyramid board bows, and I like them. 2in wide tapering to .5in should work out pretty well. Just make sure its an actual 2in wide, and not the measurement listed  on the board at the big box store, those are only 1.5in. Those still work, but I prefer a bit more width than that.

[willie]

you will end up with a slight thickness taper, with the bend increasing as you progress along the limb (just a bit).

so for a circular tiller you would need no taper or a slight reverse taper?

[mmattockx]

So 2-1/2 inches won't hurt you. Use 1" of limb for every inch of draw. It's a good recipe. Arvin

You don't think I would end up with really thin limbs that way for a 35lb draw weight? The 30lb maple mollegabet bow I am finishing is only 1.5" wide and the working limbs are around 1/4" thick up near the levers. They look scary thin to me.

I've made quite a few red oak pyramid board bows, and I like them. 2in wide tapering to .5in should work out pretty well. Just make sure its an actual 2in wide, and not the measurement listed  on the board at the big box store, those are only 1.5in. Those still work, but I prefer a bit more width than that.

It is a nominal 1x3, so is 0.75"x2.5" in reality. Maybe I will go with 2.25" near the handle just to be sure. The grain is not quite dead straight on this board and I plan to skew the centerline of the bow to better match the grain, so 2.25" is probably as wide as I can go anyway.

so for a circular tiller you would need no taper or a slight reverse taper?

If I understand him correctly it is the other way and it needs a bit thinner tips than at the base of the limb. Because the tip doesn't go to a point there is extra material out there and that makes it a bit stiffer than a theoretically perfect triangular limb profile.


Mark

[Del the cat]

This post answers the questions about thickness taper
https://bowyersdiary.blogspot.com/2014/12/pyramid-taper-test.html
Del

[airkah]

I've made quite a few red oak pyramid board bows, and I like them. 2in wide tapering to .5in should work out pretty well. Just make sure its an actual 2in wide, and not the measurement listed  on the board at the big box store, those are only 1.5in. Those still work, but I prefer a bit more width than that.

It is a nominal 1x3, so is 0.75"x2.5" in reality. Maybe I will go with 2.25" near the handle just to be sure. The grain is not quite dead straight on this board and I plan to skew the centerline of the bow to better match the grain, so 2.25" is probably as wide as I can go anyway.

I like your idea, I don't think you'd need to go wider than 2.25 anyways. I think you are setting yourseld up for success.

[Allyn T]

Del that answers all the main question for sure

[mmattockx]

This post answers the questions about thickness taper
https://bowyersdiary.blogspot.com/2014/12/pyramid-taper-test.html
Del

Thanks for that, it is very helpful.

Del that answers all the main question for sure

It sure does, that clears the question up very well. I find it pretty surprising that it tillers semi-circular no matter the taper ratio or thickness as long as the taper is to a point and the thickness is constant. Math and mother nature are sometimes amazing that way.

I like your idea, I don't think you'd need to go wider than 2.25 anyways. I think you are setting yourself up for success.

I like to hear that, thanks.


Mark

[Jim Davis]

This post answers the questions about thickness taper
https://bowyersdiary.blogspot.com/2014/12/pyramid-taper-test.html
Del

Thanks for that, it is very helpful.

Del that answers all the main question for sure

It sure does, that clears the question up very well. I find it pretty surprising that it tillers semi-circular no matter the taper ratio or thickness as long as the taper is to a point and the thickness is constant. Math and mother nature are sometimes amazing that way.

This is  why I say that  once you make a pyramid bow, you may see little reason to ever make  anything else. I  have seldom made another style in at least 20 years.