Trying to decide between width and length

[DC]

My last couple bows have taken a little set so for the next one I'm thinking I'll make it a little wider or longer or both. How do I decide? The set was acceptable to my eyes but the bows started out shooting in the low 190's, high 180's which I was very, very happy with but within 100 or so arrows had dropped 10 or so fps. Still fast but I'm wondering if just a little more bow might stop that.

PS My last bows were in the 1 1/8 - 1 1/4" wide.

[bradsmith2010]

just try it and see,, but really if you make it wider and longer it may not have the initial cast,, but probaly wont drop as much,,

[DC]

Is there an advantage of length over width or vice versa? Does a thinner, wider bow take less set?

[bradsmith2010]

I think that is going to depend on the kind of wood,,, and the overall mass of the bow,, both will work given its not taking set and the mass is reasonable,, I know thats not so clear,, both will work,, like osage and yew will make a narrow long bow with not much set and not too much mass,, you can make a wider version, but it would have to  be shorter,,,,, I really dont know which one would be best,,ok how bout ,,, just a little longer ,, and a little wider best of both,,

[Halfbow]

DC, are these longbows or recurves or what? (I'm tempted to ask if they have persistent reflex, as I talked about in the design thread. I'm immediately finding this term very useful. :p)

I don't know the answer to your question and I'm also interested to know more about this subject. But here are my thoughts on the matter.

Assuming you're going for the same draw weight as before, both options will increase the mass of the limbs. But my instinct is that widening will increase it less. Because you wouldn't just be making limbs wider, you'd also be making them thinner. You're increasing one dimension while shrinking another. Conversely, because lengthening limbs will make draw weight go down, you wouldn't just be making the limbs longer, but also thicker. Increasing in 2 dimensions.

So widening seems likely to win in mass, but lengthening gets you another benefit. A more efficient string angle/longer lever length. This is important and helps to store more energy.

I'm really not sure how all this balances out, and I'm not claiming to. So take this with a grain of salt. But my instincts say... longer for longbows, and wider for bows with persistent reflex. Because limbs that maintain reflex at brace will have a more efficient string angle anyway, and the tips will draw a more ideal line when drawn (as in your test in the design thread).

[DC]

It's an R/D. Probably Bamboo backed Yew. I'm trying to fine tune the design that's worked well for me. (Thanks Marc) I have to differ with you on mass. Narrow thicker limbs have less mass than wide thin ones. Double the width doubles the draw weight but double the thickness increases the draw weigh by eight times.

[Halfbow]

No, I’m aware of that. But you forgot a dimension. You’re playing with all 3 here. Are narrow thicker longer limbs lighter than wide thin shorter limbs. Lengthening adds mass.

[DC]

Not necessarily changing the length.

[Halfbow]

I’m not sure what you mean. To start making bows narrower and thicker without making them longer would cause them to take more set, which is what you’re trying to avoid. I thought the original question was you trying to decide between making them wider or longer or both.

In my last post when I said “shorter” I just meant shorter in relation to the lengthening option. Not in relation to the last couple bows you’ve made.

[Selfbowman]

Osage?   If so if the bow is shorter than 67". I would first add length assuming you are building for say 28" draw. This is also considering you have a 10" or so stiff handle. Adding length to the bow on the inner limbs does not hurt cast that much. Helps on set fades to mid limb. This can be in width or thickness. Keep the ends light as possible. At the end of the day it's going to get back to tiller. When it comes to set. DC I still fight the set battle with nearly every bow. But when you get one that takes near no set. It sure puts a smile on ones face.  Arvin

[DC]

I thought the original question was you trying to decide between making them wider or longer or both.

Yup not narrower. Don't want to go there.

[DC]

Osage?   

Bamboo/Yew about 66". I know I'm going to have set. I'm trying to minimise the loss of speed between 1 and 500 arrows. Probably as improbable as a no set bow but maybe I can reduce it.

[Halfbow]

Right. I feel like I'm being misunderstood.

I have to differ with you on mass. Narrow thicker limbs have less mass than wide thin ones. Double the width doubles the draw weight but double the thickness increases the draw weigh by eight times.

Yes, narrower thicker limbs will have less mass than wide thin ones, all else being equal. What I said originally didn't contradict that. Because between the two options you're weighing, all else is not equal. Length isn't equal.

The two options you laid out, wider or longer, can be stated more completely as: 'wider and thinner', or 'longer and thicker'. Or, of course, some blend of those things. Do you agree with that phrasing?

[DC]

No. I could make it longer and wider. Anyway you're getting to picky for me. Sorry.

[Halfbow]

As I said, "or a blend of those things". But alright, was just trying to be helpful. I won't go on about it.