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Selfbows, Longbows, Recurves, Hybrids
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Abshunts
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Question

Post by Abshunts » Sat Jan 02, 2010 6:59 pm

All else being equal, in a perfect world, hypothetically speaking, and all that stuff:
You have two bows both drawing #50 at 28". One shoots 160fps, and the other 185fps, with the same weight arrow. To get perfect arrow flight, will the faster bow require a stiffer spined arrow? It seems to me it would. You would certainly have different amounts of force being delivered to the different arrows even though the bows are the same draw weight starting out

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Rick P
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Re: Question

Post by Rick P » Sat Jan 02, 2010 11:11 pm

Same amount of force just more speed, both bows are still pushing 50#.
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Okie
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Re: Question

Post by Okie » Sat Jan 02, 2010 11:35 pm

I think you've answered your own question. I'd say a heavier spine for the faster bow. Because...the faster bows limbs are returning to original shape faster for some reason, being design or materials, causing more energy to be applied to the arrow.
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Rick P
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Re: Question

Post by Rick P » Sun Jan 03, 2010 12:07 am

You guys are confusing down range force with initial accelerating force. Yes the more efficient bow, the faster one, will deliver a higher percentage of the bows total load to the arrow. However that difference in percentage of total loading force is so small we are in effect talking about maybe half a pound. If you can spine for half a pound difference your the best arrow smith in history. They are for all practical purposes identical.


However the faster arrow will penetrate more and deliver a higher percentage of initial load to the target. Force is a product of speed and arrow mass on the down range end.
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Hooked
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Re: Question

Post by Hooked » Sun Jan 03, 2010 12:31 am

I think the best way to answer your question would be to take each bow and tune them separately. See if you come out needing the same arrow.

I am not a bowyer or an arrowsmith, but don't understand Rick's reasoning. Seems to me that if an arrow is coming out of one bow faster, then that bow is delivering more energy to the arrow thus you would need a stiffer arrow. Doesn't matter if the bows are the same poundage or not, if one bow is more efficient and delivering more energy then it might need a stiffer arrow if the difference is big enough.

Not saying Rick is wrong, just that his reasoning doesn't make sense to me!

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Rick P
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Re: Question

Post by Rick P » Sun Jan 03, 2010 12:55 am

OK again yes the faster bow is delivering more of the initial 50 pounds of the bows load but at such a small amount more it is barely measurable. A arrow will loose 5-7fps if its 40 degrees colder outside. Changing fletchings can effect the arrows speed even more than temp(sorry I can't give you a range of loss at the moment). I would be stuned if we are talking about half a pound....arrows are spined in 10 pound increments!

Theoretically one bow should be spined for around 49# the other 49.5 at the most and the real numbers are probably more like 49 and 49.05 If arrows were spined that way you would have to change arrows as you shot more because your arm is getting tiered and your drawing 1/8 of an inch shorter.


So in theory, ya the original post is right, in practice it is impossible to spine an arrow accurately enough to compensate for the difference.

Hope that is clearer, with draw weight and arrow spine 50# is 50#.
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Rick P
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Re: Question

Post by Rick P » Sun Jan 03, 2010 1:15 am

Here is another wrinkle to consider. Higher draw weight doesn't always mean faster. Longer limbs are slower than short, wide slower than thin, strait slower than curved.


This will really muddy stuff up but lets put names to these theoretical bows and say the slower is a self bow with a center cut shelf and a actual measured draw weight of 51 pounds and the faster a Kodiak magnum with a measured draw weight of 49. The Mag is more efficient might even have a higher actual initial force........should we spine for calculated force based on draw weight and limb efficiency?


Yup 50# is still 50#


PS I edited this post due to the omission of "with a center cut shelf". Normally a self bow is spined differently to aid the archers paradox......can't remember for sure but I think they are spined lighter?
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Re: Question

Post by Hooked » Sun Jan 03, 2010 4:03 am

Rick,
One thing you have mentioned that I don't understand is if I am shooting the same arrow with two different bows, forget about poundage, and one bow is faster than the other. If the arrow leaves the bow faster, then at 20 yards it is still going to be traveling faster. Maybe I just don't understand physics enough, but the reason the faster arrow would penetrate more (as you said) is because it is still going faster when it hits the target. The force or momentum of the arrow is a factor of its' weight and speed.

Just trying to understand what you are saying!

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Re: Question

Post by Greywolf » Sun Jan 03, 2010 7:21 pm

If the two bows were described. NTN length, limb width, design of the bow, cut of center and #50@28 inch each.
#50@28 inch is the only thing in common between the two bows. With all being equal....that's the problem it's not. or they would be shooting the same FPS.

A reflexed handle will change the speed, as many other things differences.


It's one of those "Just is" things.
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Rick P
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Re: Question

Post by Rick P » Mon Jan 04, 2010 3:40 pm

Good post Graywolf you right "it just is"

Hooked

There are 2 ways to make the same arrow penetrate more. Increase arrow speed or increase arrow weight. Theoretically you could drive a 100 grn arrow as deeply as a 700 grn arrow if it was traveling fast enough, you'd need a rocket booster on the lighter arrow but in theory it could happen. Thing is in the practical world we run up against the law of diminishing returns, eventually the arrow will be too heavy to fly well, or too light to hold up to the forces involved in being shot from a bow.



PS Bows of the same efficiency can also have different speeds. Lets take the Kodiak Mag and this time compare it with a TarTar. The mag in theory is no more efficient but it will still be faster.....why? Because the limbs of the Tartar are so long it takes them more time to travel through the firing cycle. They simply have further to go. But all this is just mental masturbation what it still boils down to is recurve to recurve 50# is 50# and longbow to longbow 50# is 50#.
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Apex Predator
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Re: Question

Post by Apex Predator » Wed Jan 06, 2010 5:26 pm

I promise you the faster bow will require quite a bit more spine in the arrow.

Rick P, I love your passion!
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Re: Question

Post by xring » Wed Jan 06, 2010 5:38 pm

Ok, now you got me thinking. How much difference is there in speed between 60" and 62" limbs on the same bow? I ask this because I've got a 62" bow headed this way.
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Re: Question

Post by Sparta-T » Wed Jan 06, 2010 5:58 pm

OL Adcock of ACS limb fame contends that the advantage of a higher efficiency bow is that you can shoot a heavier hunting arrow with the same speed. He is a believer in heavier vs lighter hunting arrows for maximum penetration and suggests that rather than utilize the added limb efficiency in more FPS, it is better invested in propelling a heavier mass arrow with authority.

From personal experience after 30+ years of trad shooting and bowhunting, I attest that not every bow of a specific poundage will shoot the same spined arrow. Some of that is due to factors such as the amount of center shot, but limb design and efficiency are not always an apples-to-apples comparison. I briefly owned a recurve bow with static limb design was was indeed faster and required more arrow spine at the identical poundage to the BW MAIII I also owned. The "lightening fast" BW limbs were no match in speed or required spine, but they certainly shot more stable and consistent. That is why the static tip recurve only lived in my home a short while..............

TL

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Rick P
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Re: Question

Post by Rick P » Thu Jan 07, 2010 7:10 pm

Predator

Thanks! I hope it reflects in my hunts and the bows I biuld as well.

Sparta

Agreed total arrow weight and % foc are the most easily manipulated factors in arrow penetration and in practical terms were more focus should lay.

Also after muddling this around in my head I'm convinced there are too many variables to the original question and it is basically flawed. So many things can effect both speed, archers paradox and limb efficiency. I feel a bit like a fish but I've come to believe 50# isn't necessarily 50#.
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Rick P
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Re: Question

Post by Rick P » Thu Jan 07, 2010 7:16 pm

xring wrote:Ok, now you got me thinking. How much difference is there in speed between 60" and 62" limbs on the same bow? I ask this because I've got a 62" bow headed this way.

Doubt it is noticeable but wouldn't ya love to get your hands on a high speed camera and find out! :D
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Re: Question

Post by quiet man » Thu Jan 07, 2010 11:34 pm

How close are the bows on being cut to center? That changes the paradox alot.

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