Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on November 10, 2018, 11:58:26 am
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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.
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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,, (SH)
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Is there an advantage of length over width or vice versa? Does a thinner, wider bow take less set?
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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,,
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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).
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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.
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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.
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Not necessarily changing the length.
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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.
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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
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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.
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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.
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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?
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No. I could make it longer and wider. Anyway you're getting to picky for me. Sorry.
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As I said, "or a blend of those things". But alright, was just trying to be helpful. I won't go on about it.
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This is how I do it. My length is determined by how much working limb I want. If I feel my working limb was sufficient and I got set on a bow, then I will make the next one wider, not longer.
In your case DC, I would make your bow wider, maybe .25”. I like to go a little wider than I need anyway, as you can always side tiller if you aren’t getting set. It’s a little harder to reduce length.
I think your bows have sufficient working limb for your draw and draw weight. I would make them wider. Just how I would do it. Obviously more length could do it too.
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Bayou that sounds like a good plan,, could I add,,
shoot the bow at the over built width,, through chrono,, you can see its a bit slow cause the speed,,,
now leave the bow braced for four hours at a time,, so it settles in,, without shooting it much,, a gentle approach to getting the wood to stablize,,you will see the tiller change when you unstring, and can adjust accordingly,,,if it starts to take set,, you need more bow,,
side tiller the bow down a bit and shoot it through the chrono,,till you start to get the speed you think it should do,,
at that point,, you know about how wide to make to bow and how much mass that bow has,,( hopefully leaving it braced will have made the bow stable and it wont loose much when shooting,,)
if for some reason,, after the side tillering its still slow,, then it is probaby a bit to long,,
there will be a point of diminishing return,, where when you side tiller the speed wont increase,, you know you are past your sweet spot for that design,, (-P
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shoot the bow at the over built width,, through chrono
Should it be a little over target weight here? If I have to side tiller it's going to lose some.
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yes,, but I didnt know you had a target weight,,,but I think that is a good idea,,cause then you would have to do some fixing if you go under too much, ,,,,mabe if you had some flexibility,, on the target weight,you could dial it in closer on the next bow,,
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for example,, you shoot it at 50#,, its shooting 160 fps with 500 grain arrow,,
you side tiller to 45# now its shooting 450 grain 165
now you side tiller to 40# and its shooting 170 plus,,with 400 grain arrow,,
you go to 35# and still 170 plus with 350 grain arrow,,
the best mass for the poundage was about 40#,,,on your next bow you could design for a heavier bow,,
or as suggested you could start a bit high of a target weight,,
the closer you start to the sweet spot ,,, I think the less set the bow will take,, I have heard different thoughts on this,, but after shooting it at the 50# weight, if may have taken a bit of 50# set,, and starting closer 40 # with that design would stress the wood less,,,????
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I can't pull much more than 40# so when I started this speed quest I made that my goal.
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I worked on some ash bows. And tried different cross sections. I found out that this influence the amount of set too! T he one with the narrow back and wide belly, took less set.
But I guess this is very wood specific
Bttw