Author Topic: A theory  (Read 15411 times)

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DCM

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Re: A theory
« Reply #30 on: January 11, 2008, 05:43:50 pm »
Steve, I'd either allocate that to extra mass (crushed wood) or hysteresis ("rubbing" wood).  But I agree.  I still think simple Newton physics accounts for most of the "lost" energy, that is KE left in, invested in depending upon the exact point in time, the bow, string and archer after the arrow leaves the string.  In a way this could be called "hysteresis," because it is not retained as either PE or KE.

Offline tom sawyer

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Re: A theory
« Reply #31 on: January 11, 2008, 05:51:38 pm »
Didn't know you were quoting Baker, I'd have been more reverent.  I haven't been to play on the other site lately, not enough time or interest.  It'll be an interesting new volume I'm sure.

Steve, your idea that wood is best prior to being over-stressed goes right along with hysteresis.  One way to get hysteresis is to overstress something.  On the pull, you change the material so that it isn't the same on the loose.  If its not terribly overstressed it can fully recover, just not in the space of time of the loose.  I'd agree that wood that hasn't been damaged by training, certainly performs best.  I understand you flight shoot people don't bother breaking your bows in prior to competition for this reason.  I do think there's competing factors though.  If you make a bow that shows no set after shooting in, it is likely overbuilt and underperforms even though it has undisturbed wood.  and if a bow takes an inordinate amount of set (>2") then you probably lose what you gained in efficiency, by reducing the performance of the wood (per unit mass).  A little mashing of the spring wood to the point it has a similar density to summer wood, is all you probably want.

It'd be interesting to be able to look at the effects on a piece of wood in training to be a bow, at a cellular level.  I just don't know how you'd prep the sample without altering it.


Lennie
Hannibal, MO

Offline Kegan

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Re: A theory
« Reply #32 on: January 11, 2008, 07:17:30 pm »
So far, most of my questions have been anwsered here's what I got:

1. Big tips, wouldn't help enough to make them worth it.

2. The Cherokee Warbows efficiency is explained by Steve- not abusing the wood as much. Seems they found the best balance for their needs.

3. Theories hurt the head alot more than those extra few yards/fps are worth ;).

But I'm still unclear on the strike plate. I've seen alot of harder amterial strike plates. But in order to get away without a strike plate you need perfect arrows. I'm still need some more help here :-\.

Glenn R.

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Re: A theory
« Reply #33 on: January 11, 2008, 10:04:35 pm »
What noise? Oh you mean the kawomp! when the arrow hits the target and you say "tat the spot" :o  Sorry, I couldn't resist. :)

Offline Justin Snyder

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Re: A theory
« Reply #34 on: January 11, 2008, 10:57:50 pm »
But I'm still unclear on the strike plate. I've seen alot of harder amterial strike plates. But in order to get away without a strike plate you need perfect arrows. I'm still need some more help here :-\.
Most bows arent hunting bows so the little bit of noise dont matter.  If you are making a hunting bow I suggest a soft strike plate.  Justin
Everything happens for a reason, sometimes the reason is you made a bad decision.


SW Utah

duffontap

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Re: A theory
« Reply #35 on: January 12, 2008, 01:23:29 am »
If your arrows are perfect, Perfect, PERFECT in spine they will barely touch the bow as they clear the strike plate.

        J. D.
That statement is about as true as any, but under hunting conditions barely touching or barely making noise can be to much.  Even if it don't make noise when released, the arrow makes noise when being drawn since it has to slide about 20" across the arrow rest.  Use a soft strike plate.  Justin

Agreed Justin.  It is important to note, however, that well-matched hunting arrows will not smack the bow as it clears the strike plate thus will be quieter regardless of the material used at the pass.  In fact, the arrow wont touch the bow at all after it begins to paradox.  This is yet another desirable characteristic of a matched set of arrows. 

          J. D.

duffontap

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Re: A theory
« Reply #36 on: January 12, 2008, 01:27:16 am »
True JD, but you could not possibly move the freight train the same distance as the golf club with the same expenditure of energy.

Oh I know Gordon.  I'm just silly enough to point out extreme at which the analogy breaks down.   ;D  Most of us aren't going to be shooting 2,000 lb. arrows.  We'll give Mark Stretton a couple more years to prove us wrong.   ;D

           J. D.

duffontap

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Re: A theory
« Reply #37 on: January 12, 2008, 01:37:30 am »
But I'm still unclear on the strike plate. I've seen alot of harder amterial strike plates. But in order to get away without a strike plate you need perfect arrows. I'm still need some more help here :-\.
Most bows arent hunting bows so the little bit of noise dont matter.  If you are making a hunting bow I suggest a soft strike plate.  Justin

Justin's got the answer to your question.  Keep them as quite as possible.  You'll dampen almost all of your noise with a good, soft strike plate.  Tune your bow's brace height and spine your arrows carefully for silent death.   :)

       J. D.

Offline Kegan

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Re: A theory
« Reply #38 on: January 12, 2008, 04:54:37 pm »
Ahh, now I get it ;D!

Thanks everyone- you've all been a ton of help :)!

Offline Shooter

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Re: A theory
« Reply #39 on: January 12, 2008, 05:42:42 pm »
Interesting discussion. Well worth remembering who said what.

I put big/long tips on my rigid recurves so I can get more string. Also, laminates can be worked in different ways to achieve different characteristics. And relatively speaking, the shorter the working limb, the faster the recovery.

Offline jpitts

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Re: A theory
« Reply #40 on: January 13, 2008, 01:42:28 am »
Ok.....
What about harmonics? Limb balance. Could not one limb recover differently than the other? Would that not be a source of vibration upon shooting?

Just a thought.....
Jimmy / Dallas, Georgia

Offline Badger

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Re: A theory
« Reply #41 on: January 13, 2008, 02:44:16 am »
Pitts, as per some discussion about just what you are mentioning I did some experiments a few years back. I spliced a broken but fast recurve to a slow straight bow limbs and handle. No particular extra vibration. I even built a bow about 9 feet long with one limb about 2 1/2 feet long and the other limb about 6 ft long, didnt seem to make much difference. Biggest cause of vibration I have seen and I almost hate to say it is overbuilt limbs. Another thing about vibration I have noticed is that many times perfectly tillered bows bending evenly throughout the entire limb will sometimes be the worst tooth jarring bows around. I think the perfect tillers would often have allowed the bows to be much narrower and lighter thn they actually are and it will often creat a "soft" bow that shocks hard when it hits home. Steve

duffontap

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Re: A theory
« Reply #42 on: January 13, 2008, 03:06:52 am »
Pitts, as per some discussion about just what you are mentioning I did some experiments a few years back. I spliced a broken but fast recurve to a slow straight bow limbs and handle. No particular extra vibration. I even built a bow about 9 feet long with one limb about 2 1/2 feet long and the other limb about 6 ft long, didnt seem to make much difference. Biggest cause of vibration I have seen and I almost hate to say it is overbuilt limbs. Another thing about vibration I have noticed is that many times perfectly tillered bows bending evenly throughout the entire limb will sometimes be the worst tooth jarring bows around. I think the perfect tillers would often have allowed the bows to be much narrower and lighter thn they actually are and it will often creat a "soft" bow that shocks hard when it hits home. Steve

Wow Steve, that's a lot of bow building wisdom packed into one paragraph.  Brilliant experiments, too. 

I have often wondered (casually) about harmonics.  I have an acquaintance who is a gifted, hobbyist luthier.  He told me once that every piece of wood that he puts on his guitars is individually tuned to a perfect 'G' note.  Thus the entire structure of the instrument is designed to resonate in perfect harmonic balance.  The result of perfect, harmonic balance?--Louder guitar!  I'm thinking, the principle is essentially the same in both disciplines.  We are both trying to store and release energy as efficiently as possible.  The principle that makes a wooden instrument louder may make a bow more efficient.  Not that I could begin to prove it. 

        J. D.

Offline jpitts

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Re: A theory
« Reply #43 on: January 15, 2008, 12:49:05 am »
Badger,
Thats some interesting experiments....
I wonder then if maybe it's not the limbs shape (in relation to each other) per se......but more it's tillered balance.
Interesting thoughts  J.D.
I have wondered myself if there was a way to tiller the limbs in such a way that the negative harmonics of the limbs slamming back to their homes, would be absorbed or turned to a positive harmonic outcome.......maybe the weight of the handle plays a part.....wish there was a computer graphics program we could plug these forces into to see what a simulation might bring to light...

See what enginering school will do to you.....
Jimmy / Dallas, Georgia

Offline Badger

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Re: A theory
« Reply #44 on: January 15, 2008, 01:33:41 am »
pitts, there is a program online you cna download by Allen Case, who is also a friend of mine. The program is called super tiller. Allen is also somewhat of a musician and has similar theories about harmonics in a bows limbs. I think I do to but don't know enough about harmonics to really discuss it LOL. I can tell you one thing interesting, a good flight bow will never have any perceptable handshock even shooting arrows as low as 3 grains per pound, even dryfiring the bow for that matter. Normaly weight is added to a bow to absorb the shock but flight bows are feather light in the hand to start with. Steve