Trad Gang
Main Boards => PowWow => Topic started by: Hogdgz on September 25, 2009, 08:13:00 AM
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I always thought that raising the brace height (ie- from 8 - 8 3/4) would stiffen the spine b/c it caused shorter length of travel for the string, and that lowering the brace height would increase arrow speed and therefore weaken the spine.
Am I correct on all this?
Thanks
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I don't know. I just get shafting about the right spine and shoot 'em. This whole math thing is too much.
:knothead:
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Hog, you are correct from what I've read.
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Think opposite. I'm not smart enough to explain it, but lowering the b.h. will actually make your arrow shoot stiffer, and raising it will make it weaker.
I learned this from Ken Beck in one of the Black Widow tuning videos. It has held true to all of my bows. Some seem to react to it more than others.
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raising the braceheight will weaken the arrow
lowering creates stiffer arrow
there is a valid reason..but im not smart enough to explain it.
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Lower brace heights shoot faster, so go from there. It's like adding draw weight. How can that make your arrow act stiffer?
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With a lower brace height the draw weight actually drops so the arrow is now stiffer than it should be; i.e. - if your arrow worked fine when the bow had a 50# draw weight and the bow now has (with a lower brace height) a 45# draw weight then the arrow is effectively stiffer than it should be.
One of the reasons that lower brace height adds speed is that the power stroke is longer (the string is pushing the arrow for more time so it is absorbing more energy). You are not getting higher draw weight.
One of the problems with understanding how a bow works is that there are many factors and most folks just look at some of them. Hope this helps.
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..... remember guys...the arrow spine will stay the same... the change is in the bow braceheight..which will make the arrow "act" weaker or stiffer...
I stole this from oldyork on a previous post..hope this helps...
Short version -
Arrow shows too stiff, raise BH.
Arrows shows too weak, lower BH.
Long version -
Easton Tuning Guide, 2nd edition
Brace Height
For recurve bows, another way of altering arrow spine is
with the brace height. By increasing or decreasing the
distance from the bowstring to the pivot point of the grip,
the dynamic spine of the arrow can be made slightly
weaker or stiffer. Increasing brace height will make the
arrow shoot weaker, and decreasing brace height will
make the arrow shoot stiffer.
Brace height affects arrow spine by increasing or
decreasing the amount of energy delivered to the arrow
at the moment of release. Raising the brace height
(shortening the bowstring) compresses the limbs,
increasing stress (prestress or preload) in the limb material.
The more preloading of the limbs, the greater the
actual bow poundage at full draw. The reverse is true
when lowering brace height. A lower brace height
(lengthening the bowstring) reduces the prestress in the
limbs and reduces bow weight at full draw.
However , raising brace height produces some small loss
in arrow velocity as the slight increase in draw weight
does not equally compensate for the reduction in the
bow's "power stroke". When the power stroke is reduced,
the amount of time the arrow stays on the bowstring is
also reduced, in turn, decreasing the length of time the
arrow has to absorb the bow's energy.
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Thats pretty interesting Larry,
I would not of thought that shortening
the BH would actually give you more speed.
You would think a heavier draw would.
Interesting.
I learned something today.
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With a lower brace height the draw weight actually drops
Exactly what I was about to say.
**Sorry, Jacobsladder. You posted while I was typing.** I didnt mean to repeat your info.
Super low brace heights will result is lower lbs at the same draw but raising the brace height dramatically INCREASES the draw weight.
With an already further back starting point, the limbs react the same to as they would to a longer draw (but will have a shorter power stroke).
Find the balance of quiet (higher brace height)and speed (lower brace height) and, at least IMHO, you've found the best brace height for most preferences.
I prefer quiet over everything else and set my brace heights accordingly if I have to choose between the two.
This isn't a guess on the weight thing, I've put several on mine on my scale and it holds true.
The change is not DRASTIC but 10 percent of the bow's labeled poundage is about how much mine will change in poundage from pretty high to pretty low brace heights.
Im sure the limb design, material, age, length etc all come into play when considering such on any particular bow so this is only a "rule of thumb" that has worked for me and is not carved in stone.
I can change my brace height on my "43lb" Super K and get 41 lbs and 46 lbs at both extremes of brace height (at 28 inches of draw on the scale)which is a bit OVER 10 percent of the draw weight, in difference.
Picking the right arrow for your desired brace height would seem, to me, to be the right choice but other methods will work with changes in speed or noise resulting that may not be what you find to be what you want.
A couple pounds either way isnt much to give you much of anything by draw weight ALONE, but does exist.
God Bless
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slowbowke...no problem bud.... i was just trying to help folks make sense of this...it is fairly confusing....
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I approach this with a fundamental outlook; I could give a rat's patoot about any such information, other than to refer to it when I'm old and need some nonsense to blather about in the old folks home.
:rolleyes:
It's amazing how we can delve into the intellectual side of physics, biomechanics, and other such stuff, and then can't hit a target at 17.3 yards on a regular basis.
Now, of course I'm old and particularly stodgy about my sport of simple archery. I like the fact that I don't have to think much any more and still get perfect flight from any bow I own without using quantum physics, or even elementary math.
:knothead:
Now....what was the question again????
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I'm glad I read this post. Don't know where I got the info, but I've been doing things backwards, i.e., trying to stiffen spine by raising the brace height, lowering to weaken it. No wonder I wrestle so much with my tuning!
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Oh....just one more thing, if an inch of brace height, either way, sends your arrow tuning into oblivion, you are dancing on the line of dimishing returns with the spine of that arrow.
A well tuned arrow should tolerate a lot of dynamics from the bow without being unduly affected.
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What George said,,, and said well..I think!!!!
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What George said. Both times. Things like this are one of the reasons I got rid of my compound. Doesn't matter how it works. Just so it works. That's supposed to be the fun part of shooting a bow. MAN, I'm cranky today!
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Thanks guys for all the comments but i was just really confused b/c i have heard so many different things about brace hieght and was wondering what everyone elses thoughts were on this. I guess it can get as complicated as you let it get. Thanks again b/c there is some good info going here.
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George has spoken. If you are trying to correct an arrows spine and have to revert to twisting or untwisting your string do get there, you are way off base. Buy new arrows.
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raising bh will make your arrows show weaker dynamic spine.
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I take issue with what George has said. I may be a johnny-come-lately at age 35, but some things need to be put into perspective. I seriously doubt I'll change anyone's mind, but I'll try.
About 150 or more years ago, someone decided to not just perform a trial-and-error approach but thought about things and broke them down into their respective components. It was a time when archery was emerging from lore and people had lost much of the practical knowledge gained from 400 years earlier.
Horace Ford took a scientific approach to nearly all aspects of archery. What happened is he laid the foundation for much of what we use in modern archery. He used this approach to dominate archery competitions until his competitors caught on to what he was doing.
I understand that we want to have mindless escapades, but don't give people a hard time for giving things some thought. They might give us some insight into some knowledge that we never had or had lost hundreds of years ago. I doubt we know all we could know about archery. Some are happy with a very basic understanding of archery, others want to know more, let's be tolerant of both.
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Well said Jason.
There are people that want to know "why" and people that don't. One of those groups is wrong? Really?
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I'm with Jason on this...I think George should try lowering or raising his braceheight to do a little fine tuning.
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jacobsladder, my brace height is fine son...thank you though 8^).
Jason, I've read Horace Ford, have you? Have you read Klopsteg?
Thomas Forbes? Walter Perry? And lastly, go back and read my post...particularly the very last line. The whole post was tongue-in-cheek, and I'm sorry you couldn't see that. Perhaps that's another aspect of us old archers that's not much understood....we have a sense of humor and don't take life so seriously.
I don't really care about such drivel, but I think it's good for folks to know such things. Things, by the way, which were discussed by my generation back forty years ago or more. So please excuse my levity if it offends you in any manner. It's a cross I must bear.
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anytime George.... :biglaugh:
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Originally posted by George D. Stout:
Oh....just one more thing, if an inch of brace height, either way, sends your arrow tuning into oblivion, you are dancing on the line of dimishing returns with the spine of that arrow.
A well tuned arrow should tolerate a lot of dynamics from the bow without being unduly affected.
I agree with George here. I am shooting exactly the same arrow setup from both my 46# Kanati and my 53# Kota, so I don't see how an inch of brace height is going to make that much difference. BTW - I get great arrow flight from both.
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I would be willing to bet that Mr. Stout has forgotten more about archery than some of us know and I Kinda like to see just what he's gonna say next. Seems like a guy I could hang out with and gain some wisdom. I know he always make me laugh...
:biglaugh:
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For folks who need to make a set of arrows they have work and can't afford or are to frugal to buy a new dozen, understanding how the mechanics work can make a marginal arrow flight(read wounded as opposed to dead game)into acceptable arrow flight. One needs never apologize for questing for knowledge and understanding in this pursuit of our's.
George one can only read the typed word, inflection is easily lost on the WWW. ;)
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George, I've read Horace Ford (loved it), haven't most of the others you mentioned, but will at some point. I only have so much time chasing 3 kids around.
If most of your posts are intended as tongue-in-cheek, fair enough. I'll remember that from now on. I've just been picking up on many of your posts (and a fair number of others) a fairly negative attitude on those interested in analyzing things. It's very hard to pick up on tone in emails and on the web. I usually pick up the phone after a couple of electronic exchanges to figure out what's going on, unfortunately we don't have the luxury of that here. I rarely get offended so no worries.
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George, one of my bosses in a past life was fond of the phrase, "Reinventing the wheel". It's taken me a few years to get to the point where he was at the time, but now I understand more fully. I think you do, too. Don't worry, these young whippersnappers will get there, eventually. They might even develop a little more tolerance and sense of humor along the way.
The "old" literature reveals much... and I don't mean the TradGang archives.
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Originally posted by Hogdgz:
I always thought that raising the brace height (ie- from 8 - 8 3/4) would stiffen the spine b/c it caused shorter length of travel for the string, and that lowering the brace height would increase arrow speed and therefore weaken the spine.
Am I correct on all this?
Thanks
Above is the original post. All we're doing is answering his question and trying to explain our answers so this man can get a better understanding of how things work. And, to defend our answers as there are differences in what some of us believe to be true. So all we're really trying to do is to separate fact from fiction. One way is correct and the other is not, period. It's not a matter of opinion but a matter of finding out the only correct answer so that someone can save time through trial and error. Isn't that what we're here for? To help our brother find the best way to gain knowledge so he can enjoy this wonderful journey we call traditional archery? So, this is why we explain what we believe to be true, so people can gain a better understanding of the science of a simple, yet sometimes complex, machine we call a stick and a string.
By the way, jacobsladder's second post contains the correct answer and explanation.
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The knowledge and understanding of "properly" tuning archery equipment is helpful to most people. If you understand how something works, it makes it easier to diagnose problems and find solutions. Through minor adjustments such as brace height and point weight, I have been able to use arrows when a lot of people would be buying more AND they fly great...Great question Chase, good luck with your shooting...
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the world according to george is a very scary place. we live in an information packed time. the thirst for knowledge and greater understanding of our simple passion is important! i hope we all continue to ask why in an effort to better our shooting.
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Wow! So many words in response to a simple question!
Jacobsladder answered it with both a short and long version. Take your pick.
I'm now realising that my tuning process has been a bit out of order, and I shouldn't be messing with the BH at all after finding the point where my bows shoot the quietest. After going through this batch of arrows that are now a tad too short due to my lack trad gear tuning knowledgge, I will start tuning the arrow to the bow. In the mean time, I need to adj. the BH to get the arrows I have flying correctly without changing the point weight.