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Main Boards => The Bowyer's Bench => Topic started by: Steve Kendrot on September 03, 2008, 10:29:00 PM
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I've been doing a lot of reading and video watching over the last couple years and just finished my first hunting wieight BBO using Dean Torges design from Hunting the BBO and the Dryad tillering method. Dean paints a compelling picture of why a bow with a longer upper limb will result in a sweeter shooting bow in his essay Tillering the Organic Bow. I just got TBB4 and was reading Tim Bakers chapter on design and performance and he seems to favor a symetrical design with even limbs. Which do most people here prefer? I've never made a symetrical bow. Are there real differences and why are such renowned and experienced bowyers so ardently arguing different designs??? Does it really make that much of a difference?
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Steve, I used to build bows with the handle offset...1 1/4" above center and 2 3/4" below. That's the way all the books taught it when I was learning. Now I prefer a symmetrical bow for ease of seeing proper tiller. Comparing the bend of 2 limbs of the same length is easier for me than comparing the bend of 2 different length limbs...the bend is different. With the bulbous handle like Dean teaches my bows are well balanced in my hand. Pat
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I like to offset mine. Up to 2" for longer bows and as little as 1" on a short design. Each bowyer has his own idea of what is a perfect bow, draw weight, length, fine or heavy built, feel when shot, etc. That's why there are so many different bows out there and why we keep experimenting and looking for what feels best to each of us.
Search for your own perfect bow Grasshopper.
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I think the offset handle with a longer top limb is a better bow because the static and dynamic balance points are closer together. If you do make an equal length bow then the tiller will differ from the offset handle bow. Most of the fibreglass bows I make are equal length bows but I do make most of my selfbows these days with an offset handle...Glenn...
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I don't think it makes a bit of difference on bows over 64". I think it makes some difference on bows 60-64". I think it makes a lot of difference on bows shorter than 60". Don't ask me why. Blame it on Dean :)
I'm pretty much a stream-of-consciousness bowyer though. The older and more experienced I get, the less I seem to know. By the time I'm Dean's age, I'll have to start all over again. Probably every day. I'm sorry, what were we talking about.
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I blame a lot of things on Deano, just can't remember why. :D
This is why I like bendy handled "D" bows, just give em circular tiller and bend em in the middle.
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I find the off set bows balance much better in the hand when carried, and that is a good thing. As far as performance differences, well experts never agree-or they aren't an expert!
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I can blame a lot of things on Dean as well, everytime I hear the name Candy I duck for cover...Glenn...
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Dean who? :) Jawge
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May be if we talk about him behind his back he'll come out of hiding once in awhile. :) Jawge
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Just mention Candy and my name, that will draw him out...Glenn...
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I start out a bow of equal length limits. I can flip them if the string doesn't line up on just right with the handle, I can pike the lower limb if it gets weak(it's always the lower limb) and still have a nicely balanced bow. Bottom line, I have more options during the bow making process if things don't go as planned.
If I remember correctly, when I stated my bow making process in a previous thread, Dean said I was a disgrace to the true art of bow making.
My goal in life as a bow maker is to make the bow making process an easily understood, simple procedure for everyone regardless of their wood working skills. No mumbo jumbo, lofty artistic pursuit or elevating the process beyond the reach of the average traditional archer.
That is why I use and teach Eric's goof proof method of making bows.
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Dean holds to a higher standard than most, I guess that's just one of the traits of his profession. All his "mumbo jumbo" has raised the bar for a lot of us. I don't believe he's elevated any thing out of our reach. My goal in life is to learn and understand as much about this great hobbie as I can.
http://www.bowyersedge.com/
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Without Dean's teaching I wouldn't be be the bow maker I am today. His book and video are the ones I recommend to osage bow newbies above all else.
We all have different skill levels and understanding. I have always been a crafty guy, working with wood in one way or another. Lots of folk aren't and I try to make things very basic and achievable.
I have held several bow bees and was surprised how many people let fear of failure prevent them from even attempting to make a bow in the first place.
I am simple minded and come up with simple ideas to do things. My Tillering Gizmo is an example.
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I like the Gizmo, I use one all the time. Sure helps ya spot those flat spots. :thumbsup:
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I started using the gizmo a few months ago and find it a very useful gizmo! Pat
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Dean has been a huge help to people all around the world to advance and refine their bow building skills. Seeing how the limbs bend when you draw the bow has been a huge help to me, even when making fibregalss bows. I like Paul Comstocks book as well. I met Paul at Deans house in 2000 and couldnt get over what a good bloke and how humble Paul was...Glenn...
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I have a friend that owns 2 of Deans bows.I think I DO pretty good work,but compared to Deans finish work I AM JUST A HACK.
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My bows are symmetrical. Both limbs are the same size even with an off set handle. I adjust riser lengths in that case. Al Herrin's Cherokee Bows and Arrows is a gem of a book and in it he talks about that handle design. Jawge
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Jawge, I was wondering when someone would mention the offset handle with symmetrical limbs.
All of my custom glass longbows were made that way and it works great on a selfbow.
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I lay my bows out symmetrically with both limbs even I mark the center of the bow and grab it with the center line in the middle of my hand. Then put a mark right above my hand for the arrow pass. This usually gives me an offset handle. For me the balance is perfect with the bottom limb slightly heavier for quick shooting. Pat
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Jeremy, I meant to say that I adjust fade out lengths. The book Cherokee Bows and Arrows is a great book and where I got that design from. I don't believe I've seen any pictures of Native American bows with different sized limbs. Jawge
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Jawge, I haven't read Al Herrin's book, but I did steal that design from you a number of years ago :) It's easy to get the limbs balanced and bending correctly... you just have to get used to the look of the different fade out lengths.
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I make mine with equal limbs and make the handle 5 to 5-1/2 inches long. My grip is the lower 4 inches and the arrow passes at the top of my hand--no shelf.
I got the principal from "Archery the Technical Side," first published in the 1930s. Can't remember whether it was Hickman, Klopsteag or Nagler who first made a bow with the handle area twice as long as usual, limbs equal and arrow passing at center.
There are few new ideas after millenia of archery design.
I like the compromise of the 5-1/2 inch long handle and equal limbs.
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Dean's article "Tillering the Organic Bow" set me upon a quest to revisit what I thought I knew about bow mechanics. The negative tiller aspect in particular directly contradicted what I'd read and the whole basic premise behind the positive tiller paradigm. I resolved the issue eventually by assuming Dean simply used the negative tiller aspect as a literary device. Specifically, IF we choose to build a bow essentally upside down, what is called a "symetrical bow," which is in effect a bow with a shorter upper limb, THEN negative tiller would be the only way to balance the forces at work equally between the upper and lower limbs. He made a perfectly valid point, but used a method I could not initially accept. This is different in my view than advocating the "symetrical" design AND negative tiller. Rather, I think it exposes the so called "symetrical" design as being doubly wrong, at least in the sense that the upper limb gets a free ride at the expense of the lower, both in terms of the geometry and physics.
My view is that no bow can be made perfectly symetrical, as we must grasp the bow string at a point above the fulcrum of the bow hand. One simply can't shoot an arrow thru his bow hand. This is why bows have always been made with positive tiller, it offsets this inherent asymetry. One could just as easily make the lower limb a little bit shorter, putting the arrow pass nearer the dimensional center and perhaps more importantly the nock point of the arrow at or nearly at the center of the bow string. This would mitigate the need for positive tiller. If you go the other way, by putting the arrow pass say 2" above center in the so called symetrical bow, then you need MORE positive tiller to compensate. That's why a three under shooter can use a bow with less positive, or even tiller. He grasps the string lower on the bow, closer to center dimensionally, closer to the fulcum of the bow hand. In effect, he shortens the lower limb. So, shorter lower limb needs less positive tiller.
For glass bows, or longer bows where we have plenty of extra work capacity in the material it's not really as important. But for really short bows where we tax the material nearly to it's limits, it can make a difference. That is where I think or assume Dean focuses most of his efforts, at perfecting the design of short, heavy weight hunting bows. In the so called symetrical scenario, by having the upper limb be shorter (by grasping the string necessarily above the fulcrum) AND weaker (positive tiller) we stress it more than the lower. The lower gets a free ride, benefitting from the extra lenght in the handle, below the arrow pass.
It's a simple matter to see the asymetry in the so called symetrical bow. Just look at where the nock point is on the string, and compare that to a bow where the arrow pass is closer to dimensional center.
I've made a butt load of bows, and I honestly cannot say just how much offset, from none to 2" is "best," or that it really makes a heck of a lot of difference. But the science, and our experience from antiquity, sides with using a little geometry AND a little positive tiller. That's why most of the bows you see are made with the arrow pass at 1" or 1 1/2" above center, and relatively few where the arrow pass is 2" above which would be the truly symetrical 1/2 the 4" handle. It doesn't sound like much, but remember it is doubled, putting the arrow pass 1" to 2" closer to dimensional center, respectively, than the truly symetrical design.
I regret that internet discussions have left folks feeling as they do, that others have assumed some guru status and look down upon them, condemn them as being a disgrace or whatever. Knowing what I do, and who I do, I honestly don't think that was the intention, and no ill will was intended. I know I get pretty rough with my language in some of these discussions, and sincerely regret it later.
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DCM, it is good that you are thinking more about this topic. Let me see if I can get this straight. Symmetrical bows are inherently asymmetrical so let's make bows more asymmetrical by making the lower limb shorter. I'm a bit tired now to rewrap my mind around this topic again. I guess retirement is tough work. I'll leave you with this since Dean used levers (seesaw-lst class lever) in his article and you used the term fulcrum in your last post. I am having a real problem seeing the bow as a lever. Seems to me you don't want a fulcrum in the handle because then the bow is tipping on you. I see it as more of a spring. Either way I'm still going hunting 9/15 with a symmetrical hickory bow. Hope all is well. God bless. You've got mail. Jawge
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No of this is very complicated. If you make a symmetrical bow and you shoot the arrow 1.25" above centre the string length to the top limb is 2.5" shorter to the top limb than to the bottom limb, anyone can measure that and see for themselves. This places more pressure on the top limb. Positive tiller does not and never has suited all bows. Bows have to be tillered and balanced according the hand placement on the bow and where the string is drawn from. Anyone can do this, when you make your next symmetrical bow laminated or selfbow, just shoot the bow from the positive position and then turn it around and shoot it from the negative position and see which way shoots the smoothest and in the case of selfbows see which way takes the least amount of set also. A symmetrical self bow will take more set on the top limb when made with positive tiller. How can a bow with more set to one limb be in time with the other or even be balanced. These bows are always rough to shoot, just my experience...Glenn...
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Thanks for your mail George. Responded earlier this morning.
You may be uniquely suited to having this discussion with me, and I'd be delighted to entertain it if you'd like. But it will require a bit of an investment on your part, in order that we might achieve a common foundation, or understanding and set of common language from which to start. I've based my argument largely upon the information published by Tapley, which is based upon the experiments and papers published by Kooi. You can find these at this link:
http://www.goarchers.org.uk/mechanics/#
Use the [Bow Mechanics], then [Tiller] menu to access the page "Tiller," "Introduction" as well as the submenu to access the page "Static v. Dynamic." While interesting and relevant in some context, thst static versus dynamic aspects aren't as important for our discussion in my view. Rather what I'm interested in is the discussion of is these fundamental concepts:
a) Regarding arrow rotation in the verticle plane "The aim is to have the total accumulated angular momentum equal to zero when the arrow leaves the string."
b) Regarding the difference in stiffness between the upper and lower limb "The nocking point may move up and down as the arrow moves forward as the relative spring strengths' vary."
c) Regarding this nock point travel "You can offset this effect by making the lower limb stiffer than the top limb so it doesn't move as much."
Before we start I want to make it plain I don't care how we all make our bows. JD Jones for example seems to favor a good bit more offset (1 1/2") than Dean (0"). I can't make a bow that even approaches the quality of either of these gents. And one can find variations from antiquity that demonstrate darn near any concievable combination of design and materials can be made to work admirably. Rather, I simply want for the conversation about our choices as bowyers to be based upon a sound understanding of the underlying science, rather than some kind of conclusion of "right or wrong," "better or worse" based upon antecdote and conjecture, or by popular vote. IMHO, in that direction madness lies, and it ain't how we managed to land men upon the moon and return them safely to earth.
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Glenn you make some good points, some for the wrong reasons imo and some I don't agree with but I wanted to acknowledge your contribution and apologise for our last conversation. I made some absolute comments about negative tiller which while admittedly inaccurate, still aren't really relevant. More specifically, that a bow with negative tiller can be tuned to shoot well is not really all that important in my estimation. But take that for what it's worth, and intended, it's only my opinion.
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One of the questions, and there are still many, I haven't resolved completely for myself is this:
Does a bow with positive tiller have nock travel above or below the vertical plane on the power, or return, stroke?
What about a bow with negative tiller?
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When I hear some "absolute" rule of bow making I always thing of that scene in Butch Cassidy and the Sundance Kid where Butch is about to fight that monster of a man and tells him they need to discuss the rules of the fight first. Butch eases up to the guy like he wants to talk, kicks him in the nads and says "by the way there ain't no rules".
Bow making is much the same way to me, no rules apply. Make a bow any way you want to. If it shoots an arrow well enough to suit you, you are a successful bow maker, no excuses necessary.
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All of this makes my head hurt. I try not to think too deeply about any of this...mainly because of my shallow brain.
I build symmetrical bows(center of bow in center of handle) because it is easier for me to see proper tiller while building. I have built asymmetrical bows. That is what I learned on from all the older wood bow building books. Either style shot well for me but like I said, symmetrical is easier for me to see tiller while building. I never measure positive or negative tiller when building but go by the look of the bow unbraced, braced and at full draw to tell how well, or not, it is tillered. Pat
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DCM, you take care and I will check out the site you gave me again. We can discuss. Glenn and DCM, I have to admit from the outset that the bows I take into the woods have to be similar to bows that were made by the Native Americans. I don't make many bows these days so experimentation is not going to happen. I made one for myself and helped 3 others make 4 bows. This is my hobby, except for the occasional mag article, so I don't turn out a high volume of bows. Ole Jawge is slowing down a bit anyway. DCM, stay in touch please. Be back later. Going for a bike ride. Jawge
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I think in the case of both bows, we want the same tiller (talking arc here) at full draw, and to have both limbs recover equally, right? I guess I just don't see why it really needs to be debated. I use the same tillering process,(tillering gizmo type device) no matter whether the limbs are the same length or not. I think the different limb length has more to do with balance and feel than anything. Maybe one design will outlast the other, should you own both kinds, and shoot the same number of arrows through them, under the same conditions, throughout their life. Maybe one will hold tiller longer. Who knows? (Oh crap, I'm thinking and debating!) What I'm getting at, is pick they way you want to do it, and tiller it the best you can, and go have fun! Don't forget to trace your "footprint" and check tiller after shooting that baby for awhile. Wood tends to change ya know.
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Now see, this is why I'm starting to like "D" bows or bendy handled bows, heck just give em circular tiller and don't worry too much about negative or positive and enjoy em. Like DCM pointed out to me they shoot real good knocking them close to the center of the bow. I can see now why Jawge likes this design.
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I would have though the whole thing of achieving tiller and a balanced bow is fairly simple. If the bow is placed on the tiller board where you would hold it and it is drawn from where you would nock the arrow, what else do you need to know. Seeing limbs bend from this position is what is needed. I don't see the point of placing a bow on a tiller board and then tillering it when being drawn from the centre of the bow, it's just a waste of time, the first thing the bow will do when you start shooting it is take uneven set and go out of tiller because of the different dynamics placed on the limbs when being drawn. If you have a selfbow that has taken uneven set it is already out of tiller. Change your hand position and you have to start again. There is no such thing as a bow must have positive tiller...Glenn...