the mass principle in one sentence

[Badger]

   Zen, heat treating does slightly reduce the optimum mass. Backing a bow via the perry reflex method also reduces the mass by about 10%.

One more stab at one sentence: Optimum mass for any particular wood bow design is predictable and attainable. 

Steve

[zenmonkeyman]

Thanks, Steve!

I'd like to volunteer to do that mass principle buildalong with you if scp declines.  I have to wait at least another week for my sapling stave (already roughed out) to mature.

[Badger]

Anytime Zen, it would be a pleasure. You just decide the design you want and we go from there. Steve

[zenmonkeyman]

Awesome!  I'll be in touch.

[Tractor]

I for one would very much enjoy seeing it as a thread.  May not comprehend it all but would enjoy the brain calisthenics.  So please when you two run your experiment please post it to the board.

Thank you,
Mike

[gutpile]

all mass is used with nothing to waste and nothing too stressed...gut

[Badger]

Gut, i like that one!
I just built a 40#@16"X40" long stiff handled bow, I didn't build it by the mass principle but used the tecnique that developed the principle, I just now weghed it and it was 7.7 oz, mass principle called for 7.5 oz. Close enough. I am going to use it for a crow killer with 200 grain arrows, Steve

[dragonman]

the lighter the limbs the faster they move, so I would say it just means make the limbs as light as possible , getting rid of all surplus wood that doesnt do anything ( thats a bit more than 1 sentence)

[scp]

One more stab at one sentence: Optimum mass for any particular wood bow design is predictable and attainable. 

Let me be a little more constructive.

IMHO the mass principle say that, if we assume that for bow making purposes all wood is pretty much equal, the optimal total mass of a bow is predictable and attainable through the use of the table obtained through the experience of many good bowyers. Of course, it also matters a lot how we distribute the mass. There we should use the sound bow design principles, especially concerning the proper tillering for a specific profile. We also need to know how to adjust the figure in the table according to the length of the nonworking grip, the unbending tips, and etc. How to do this is in the directions after the table.

[Here we need to put the table and the directions.]

This principle is a work in progress. The proper issue is not whether it works or not, but how we can make it work and refine it to make its application easier. I still don't know how to use the total weight in figuring out the proper distribution of the mass. Is there any way we can refine the principle to tell us how to do it, other than invoking the sound bow design principles? I guess the mass principle is a part of the design principles. If so, what does it say about the proper distribution of the mass by itself?

[Badger]

Scp, it is becomming more and more obvious that you either did not read the chapter of did not comprehend it. All the things you mentioned are well covered in the chapter. The distribution of the mass is determined by width only, the depth is what you use to control your bending. Mass logic simply means that the full drawn side profile of a bow should agree with the front view of a bow. You make up a design and I will give you the mass and the tiller shape in about 3 seconds. Steve

[Badger]

Better yet, let me e email you a calculator, you feed in the handle size, the length, draw length, and draw weight, it will give you back the mass needed, you control the mass by controlling the width. Now to use the calculator you have to know how to manipulate the stiff handle area number to accomadate your tiller shape, and the draw length to accomadate stiff tips. Steve

[scp]

the lighter the limbs the faster the move, so I would say it just means make the limbs as light as possible , getting rid of all surplus wood that doesnt do anything ( thats a bit more than 1 sentence)

Thanks. That must be a major part of the mass principle. If so, it might also mean that the tips need to be as light as possible. Does the mass principle say anything about the proper length of the unbending tips? All other things equal, is it correct that the unbending tips should be as long as the optimal table allows? How do we know when to scrape the side of the working part of the rims instead of lightening the tips? Can the mass principle be rephrased to help us in answering the question?

[zenmonkeyman]

Steve, I am following this closely, and it occurs to me that the principle can be espressed (perhaps more simply), through specific gravity and surface area.

That is, since unbending handle is just a complication to the mass principle, can we not eliminate it all together?  Would the surface area of the belly of the working limb be a good predictor of optimal design if the specific gravity of the wood is known?  I suppose calculation of the surface area could be as complicated as accounting for handles anyways...

[scp]

The distribution of the mass is determined by width only, the depth is what you use to control your bending. Mass logic simply means that the full drawn side profile of a bow should agree with the front view of a bow.

I don't think the first sentence above is correct. The relative distribution of the mass can be measured by using the width and the depth of sections.

As for the second sentence, it appear that the total mass would be optimal if "the full drawn side profile of a bow should agree with the front view of a bow." Does that mean the mass principle is a way to tell whether the profile agree with front view?

[scp]

Better yet, let me e email you a calculator, you feed in the handle size, the length, draw length, and draw weight, it will give you back the mass needed, you control the mass by controlling the width. Now to use the calculator you have to know how to manipulate the stiff handle area number to accomadate your tiller shape, and the draw length to accomadate stiff tips. Steve

I'm afraid we can control the mass by controlling either the width or the depth or both. I agree that given the profile/style and "the handle size, the length, draw length, and draw weight," we can probably figure out the optimal mass of the bow. That means, as you have written in the book, the mass principle can tell us when to stop tillering and even when to start scraping the side instead of the belly, as doing so would change the mass much more without affecting the draw weight too much. But it probably cannot tell us whether we need to lighten the unbending tips instead of scraping the side of the working part of the limbs. Can it? Better yet, can we refine the principle to do so?