John Scifres just through me for a loop. I have been thinking... and it makes sense to me, that the stiffer limb should be the upper.... and i have built my bows with that thought in mind. he says the stiffer should be the lower, and while i do not doubt his wisdom one iota, i need it explained. most or all of us pull from above the actual center of the string right? so wouldn't that cause more of the force to be exerted on the upper limb, requiring it to be stiffer. whenever i try to think about things that have relatively small effects, like arrow spine or positive tiller, i just think about it in a very extreme case, in this case, if i was pulling a bow from a foot above center, or around where my upper silencer is, the upper limb would flex alot and the lower would flex a little... right? so if i wanted my bow to shoot while being drawn in such a fashion... i would want my upper limb to be a good deal stiffer... right? or no? I figure i must be wrong in my thinking... i just need to understand it so i can begin tillering properly and move on with my life :biglaugh: :dunno:
Wrong. If you move your hand toward the top limb, it automatically ACTS stiffer. It will tip in the hand with the top limb coming toward you. Try it with any one of your bows. Simply slide your string hand up 3 or 4 inches, just begin to draw it, and see/feel what happens.
In order to maintain limb timing/equal relative limb strength in this scenerio, the top limb would have to be made weaker, so it 'gives', instead of tips in the hand toward the shooter.
That said, I see no sense in tillering a bow to specific predetermined brace height measurements or profiles(positive, equal, or negative). Rather, I tiller the limbs so that they're syncronized, and let the measurements be what they will be.
Particularly in the realm of wooden bows, since one limb often has a different unstrung profile than the other, tillering all bows to measure the same at brace means that many of them could be tillered/timed considerably better.
You want to tiller your bows properly/optimally? Syncronize their limbs early and maintain it as you tiller them all the way to full draw, THEN take your brace height measurements. The only reason I take those measurements at all is so I can keep tabs on the bow as it's being shot in. But to be honest, if a bow's limbs are dynamically balanced, they generally don't suffer from shifts in tiller.
Besides, we can't say that your bows should be tillered negative or positive... since there are other factors at play of which we have no clue... like whether the bow is designed symmetrically, or asymmetrically... and whether you shoot split-fingered or three under, etc, etc. These things all factor GREATLY into a bow's dynamic balance and how the braced profile will ultimately reveal itself.
For my 55 plus years of shooting bows we always had the stronger limb on the bottom. Usually the tiller would be 1/8 inch or more less on the bottom limb.
Then the compound nd release aids came into play. On a compound which was adjustable if you shot fingers we set it up the same as the recurves. With a release the tiller was set even.
So the answer could be that's the way it's always been done.
I know that isn't much of an answer. I've always thought the more finger below the arrow the more it pulled against the
Lower limb.
I take the bow down from the rope and pulley. Then I have someone snap a digi to check the tiller. Nothing really approximates how you hold the bow. I like the bottom 1/4 stiffer at full draw.
I like bows with same sized limbs and the arrow pass is about 1.25 in above center. Pretty close to pulling from center with split finger draw.
Jawge
I final tiller by feel and tuning vs. measurements. But, more often than not, after all is said and done, tiller ends up being positive. In other words, there is more distance between the string and the bow on the top limb than on the bottom limb. But measuring tiller at brace is just a rough judge as all the variables that Jeff, Ron and George allude to are more important to making a good shooting bow.
Dean Torges wrote an compelling article years back that helped me understand some of these things. Read it here: http://bowyersedge.com/organic.html
yeah i went and tried it on a bow... yep... i was wrong in my thinking. its not that i set out to make any certain amount of positive tiller, but if i had one limb that wanted to be stiffer, i have gone ahead and made that the top limb, even though my bows have been pretty much even tiller, cause i have supported the handle at center and pulled the string at center on the tree. i guess somewhere along the line i missed or forgot this little nugget of bowyer wisdom. thanks for setting me straight guys. you know... just when you think you understand the basics.... :knothead: I blame Roy. he must have taught me wrong cause he was afraid i was gonna make better bows than him. :laughing:
I'm in agreeance with Dean's logic on tillering and utilize some of his methods and practices and devised some of my own to make bows that are dynamically balanced at full draw. There is no guesswork. There's no need to avoid the tree in the end because I can't trust what it's telling me. There's no need to run back and forth taking pictures to help with assessment. When it comes off the tree for the last time at full draw, it's done, kaput.. And I KNOW it will balance perfectly in my hands from brace to full draw, shoot sweet and treat the arrow well. Final assessment is done by drawing and shooting it of course, but if I did my job on the tree, all I'm gonna have to do after drawing it by hand and watching arrows fly is smile :)
I tiller them all by the same ways and means, whether symmetrical or top limb longer, whether three under or split finger, whether identical limb profile or quite different.
If a bow has reflex in one limb and deflex in the other, what predetermined profile or measurement would folks shoot for on that one? It wouldn't slow me down for a second or change what I use for assessment. I'd have those limbs syncronized for my holds on bow and string before she reached brace height.
I never pull a bow from the center of the handle. If it will never be drawn that way after it's complete, why would I draw it that way to assess limb bend, action, relative limb strength/timing, exercise and train the limbs in accordance to it, etc? But that's just me.
I don't want folks to do it my way, per se, but rather, be critical and objective of their methods and goals as I am of my own... I'm continually looking for the most versatile yet direct route to the best bows I'm capable of. I'm a little slow, so it's a work in progress :)
Well, I'm off to the shop. All this tillering talk gave me an idea.
Ya, your a little slow alright... :laughing:
Dean sure uses a lot of words.
Yeah, and he hides stuff in them too.
Guru talk.
Dean is as much a craftsman with words as he is with bows. And it takes a while to get the depth of his writing...as much time as it takes to get the depth of tillering.
You can follow a simple board bow tutorial and make a bow. And I highly encourage all to do so. But to become a craftsman, you have to go a lot deeper.
If you have ever done a good Bible study, the concept is similar. You can read John 3:16 all by itself and get it on one level. Read the whole Gospel and you get a deeper understanding. Read all the Gospels and yet more meaning comes to it. Go so far as to read the New Testament and then read John 3:16 again and it will mean something even deeper. Put it in place in the entire Bible and something more shows itself. Then go back to the actual context in history and you really start to get what is happening. Then discuss it with your Brothers and Sisters and you get even more. Then read it every year and each time, something more will pop out.
I once told Dean it took me 3 times of reading that article to understand what he was saying. I think it surprised him because he takes such care with his words. But I was reading it from my perspective which is vastly different from his. And I read it today from an even different place.
See I warned you it gets pretty deep Eric :)
I think I've finally got my mind wrapped around some of this, so I'll share my take for what it's worth (I'm still just a newbie.)
As to why the bottom limb needs to be stiffer if you're pulling closer to the top, it's about moment/torque arm. The lower limb ends up being effectively longer as measured from the center of pressure on the handle and the arrow and hand placement on the string. If both limbs were the same stiffness, the bigger moment arm on the bottom limb will cause it to deflect further, bringing the tips out of synch as you draw.
In glass bows, you have consistent material properties and shapes, so measuring tiller at the fades for repeats of a certain design is a good way to get close. Final adjustments by feel and shooting are still the best way though. Wood bows and especially self bows will not have identical upper and lower limb shapes and stiffness, so measuring positive/negative tiller isn't that valuable. Bottom limb will likely still need to be stiffer, but by how much at brace is different for every piece of wood. Bowjunkie's description is good I think.
Proper tiller that brings the limbs into dynamic synch (positive, negative, or neutral) for a bow leads to no hand shock at the end of the shot which results in more energy being passed to the arrow. Bow is quieter, has a little better cast, and is just nicer to shoot. I feel like I can now tell when one of my bows is synched, I just can't always tell how to get it there if it isn't.
Now to read Dean's article (thanks for posting) and see how far off the mark I am.
I've read Dean's article, and now my mind is once again unwrapped. Uhg. I think I'm going to go home and play with a strip of fiberglass and a string and map some of this out.
I'm still a newbie with only 3 or 4 under my belt, but the last couple I've tillered out I have been using the same concept as Jeff described and it is working well for me. I center the bow on the tree where I grip the bow and pull from the point on the string I intend to shoot the bow from (ie split finger or three under). I then continue to tiller it out making sure the limbs are "timed" as Jeff says. The last couple have ended up even tiller and a hair positive on the top limb, repectfully and shoot hard and straight with good balance. I like this kiss method. :thumbsup:
I wish Dean would have written it so a redneck like myself could have understood it:) LOL
John, I was the same way with Dean's writing. With HOB and especially the organic bow tillering article. Each time I read that article I had more experience and was able to understand it better and see more truths revealed. Read, absorb, apply. Repeat.
I too told Dean that I had to read it repeatedly, some paragraphs, even picking sentences apart, over and over, until it sunk in... same thing.... he gave me 'the look' over top of his glasses. Then he said, 'You think that's bad, reading you OWN words over and over and over to ensure you're getting your thoughts out to folks proper is absolute TORTURE.'
Canopyboy, I've done that very thing to learn about limb length, handle position, balance... and used flat pieces of oak trim to quickly learn about the proper way to remove twist from limbs, etc. Even made tiny bows of various materials, 4" long to bring reality into the light for me when I've been confused.
Folks have good intentions I'm sure, but I've found some bowmaking advice fatally flawed in theory and practice, even defying the laws of physics.
I'll tell ya what Dean told me...Try to be careful who you listen to, and question everything. Do your own testing.
I'm another one of those that has to read and reread Dean's writings. Probably because I don't prescribe to Dean's method of tillering. There's one thing I don't understand, period.
Jeff, since you seem to have a better understanding of Dean's writing than most perhaps you can straighten me out.
Dean stated in 'who's on first, what's on second' in his article " Tillering the Organic Bow" that on same-limb bows that the lower limb worked 4" further from the dynamic fulcrum than the upper limb. That would place the dynamic fulcrum at the top of a 4" handle or arrow pass, right? Gezzzzz, that would rattle some teeth!
Perhaps Dean's describing how things would work on his 'second generation tillering tree'. Drawing by hand, and on the same type of bow, I feel little if any dynamic shifting going on. Your thoughts please..........Art B
been away from this thread for a couple days, man, you guys have put some deep thinkin out there for me! I am going to start rereading the book and the article today. Dean certainly is a master wordsmith. Art, can you explain that dynamic fulcrum thing? i know what a fulcrum is... and what dynamic means.... but its the first time i have heard that term in regards to bowyering. and what's the "second generation tillering tree"? is that an artical of his that i have missed?
OH BOY----Ya went and done it now, Art.
Stand by for a 3,000 word essay from Jeff... But he will explain it very well in words we can understand...
Echatham, yeah, read Dean's article again. Save me some typing, LOL!
His 'second generation tillering tree has a radius base instead of the standard cradle type to support and approximate his preferred grip. All this is in his article" Tillering the Organic Bow"............Art B
I've been thinking of making a new tillering tree bow holder for my tree. Instead of the solid 1" wide bracket I use now and place in the center of the handle. Been kicking around the idea of a 4" wide nylon strap that would float on a centered pivot point on the tree and span the 4" width of the handle area to more replicate the bow hand grip.
Roy I like that idea.... been thinking along the same lines myself.... the two different cradles i have used didn't seem to be the best way.
Rusty Craine used to have a strap to hold his bow for tillering. His contention was that it showed imbalance better by swinging. This was before youtube so I never saw it in action but it made sense. Not enough that I changed my setup though :) I miss Rusty.
wow... guess i hadn't read tillering the organic bow yet after all... i thought i had... but this is all new to me.
ok, i have only read as far as this... and may yet answer my own confusion... but here he says a same limb bow will balance with the upper being stiffer.... did i read that right?
"Upon realizing this, my second generation tillering tree replaced the cradle with a radiused shoulder. It requires positioning the bow's handle on one contact point, specifically upon that contact point which most closely resembles your own handhold. Such a point would represent the dynamic fulcrum. For me, since I grip the bow by the side of the handle, that contact point is inside the thumb joint, about 5/8" below the arrow rest. By placing the bow on its dynamic fulcrum and then pulling it to full draw from the position of the middle finger on the bowstring, regardless of your finger style, you will learn what you need to know about balance and whether or not your bow achieves it. (You will better learn something of its stability, too, as rocking and twisting during the draw will reveal itself more readily with this set-up, especially from an end view.)
If you do this with a same-limb bow, you will discover that the bow only balances when the upper limb is a bit stronger than the lower limb, not weaker. How much stronger (negative tiller) depends upon the wood of the bow and the discrepancies in length between the upper and lower limb designed into the handle."
you cant read something that Dean wrote without feeling smarter at the end of it.
I just sent Dean an email, inviting him to join in here. Hope he does:)
So, based on a conversation with Nate Steen (Sunset Hill Bows), I changed my cradle to a leather strap awhile ago. I started with one as wide as my hand, but since it didn't pivot well, I've cut it back to about 1.25" wide. I try to center where I think the bow is meant to be gripped. For me, that means about 1" below the arrow shelf. If you then pull at the correct part on the string (I use another strap of leather to approximate the pull of three fingers instead of a single hook point), you can see the bow swing as you first draw but come into balance as you get closer to full draw. Makes sense, as you'll always be pulling on the arrow slightly above your grip center of pressure if you're shooting split. (More in line with 3 under tillering though.)
QuoteOriginally posted by Echatham:
you cant read something that Dean wrote without feeling smarter at the end of it.
Actually, I usually feel smarter before I read something he wrote...
:biglaugh:
(Afterwards, I'm left feeling a bit overwhelmed by what I don't know.)
Art, yes, the dynamic fulcrum on a symmetrical bow is round-about the top of the 4" handle, or just very slightly below it. The reason is mostly due to geometry and leverage, and it can vary slightly depending on some things, including how we tiller/time the bow, but, that is roughly where it will be. This is assuming a 3/8-1/2" high nock point and split finger grip. When I set my tree up to replicate this, as I just did again 10 minutes ago to verify, and began to draw the bow, it practically teetered on the top edge of the grip. (This is with the pull rope on the string in such a place as to replicate my middle finger's position with the 3/8" high nock point)
Now, with the symmetrical bow braced but no pull on the string, its 'static' balance point is center of the bow/center of the handle, right? But as soon as the draw is begun, the 'dynamic' part of the balance comes into play, AND since we're pulling the string about 2" above the bow/handle center, the bow's balance makes the shift from the static to the dynamic. I can feel this as plain as day the instant I begin to draw the bow... and this is what Canopyboy sees on his tree.
Additionally, as the balance point shifts to the dynamic, almost 2" higher, the bottom limb effectively becomes graced with 4" more leverage than the top. (the bottom limb gains 2", and the top loses 2") Or as Dean put it, "...the lower limb works almost 4" farther from the dynamic fulcrum than the top limb."
So, in the drawn symmetrical/same limb bow, the bottom limb has almost a 4" inherent, dynamic leverage advantage... AND folks frequently tiller this bow with the bottom limb stronger. So that it's stronger AND has a 4" leverage advantage?
Countering the bottom limb's 4" advantage and establishing synchronization is a simple matter... the top limb should be STRONGER, relative to the bottom, not weaker as is commonly proposed.
Ever notice how many guys' bow's top limbs are tilted forward in their full draw pics?
The path to resolve is a tillering tree setup that mimics the archer's holds on bow and string and allows the bow to show you its relative limb strength.
John, I miss Rusty too. Quite the character.
So then, by comparison... DIFFERENT length limb/asymmetrical bows...
Their 'static' balance/geographic center is generally positioned 3/4-1" above handle center... close to and between the bow hand and string hand fulcrums, which tends to keep the dynamic center of balance right there among them as well. In fact, since they're all close together, unlike the symmetrical bow, it allows virtually equal leverage to each limb, and an indiscernible amount of shift to achieve dynamic balance.
Unless these are odd-shaped bows, they often reveal a neutral tiller at brace for me once they've been synchronized to full draw.
Hey Roy, Dean's to smart for that, LOL!
Thanks for the reply Jeff.
As Dean mentioned, there's more that one way to tiller bows. True enough, but with same-limb design, he missed the mark here. When it comes to Dean's explanation of same length limb bows he seems rather confused about it's applied positive tiller. He himself said it 'makes no sense'.
Well, I suppose it doesn't if you believe the bow's dynamic fulcrum is 2" above center or under it's arrow rest. I would draw the same conclusions about a stronger upper limb also if I believed that. Not accounting for the heel pressure of one's grip to cancel out the heavier boy on the upper limb (laughing, sorry) is his fatal flaw.
So in reality, a same limb bow's dynamic fulcrum strays very little from center. Maybe a smudge below center if anything. That's why a positive tiller or weaker upper limb works here. Limbs are always the same length, so no 4" advantage here. Longer upper limb is nothing more than the handle shifted down to accommodate one's preferred grip.
A lot of what I see of full drawn bows is that the bow hand is not accounted for on the tillering tree. Lower limb, right outside the lower fade takes on a greater bend when it goes to the hand. And limbs tilted forward as you describes is the result of the archer not applying the correct amount of heel pressure to the bow's handle. But then again you see all kinds of things in drawn bows Jeff. Like a full grip on a asymmetrical limb bow, or a straight wrist grip on a symmetrical limb bow. Few bowyers understand the relationship design, proper grip per design, and their required tillers.
So be honest here Jeff, only you, Dean, and perhaps one our two other bowyers that I've conversed with over the years have like minds on this subject. Are so few right and so many wrong? Art B
ok, i realize that Art and Bowjunkie have differing views on this... and im really hoping i can get something useful out of the debate. i just want to make sure im understanding what you are both saying. Jeff and dean both say you need a STRONGER upper limb on a symetrical bow... and Art says that thinking is flawed, the upper limb needs to be WEAKER.... do I have that right? haha once i know i understand the two opinions... i can start trying to decipher the theories and physics of "why". :campfire:
and Thank you to all of you putting your thoughts out there. It may be a little over my head yet.... but i feel like Im about to grasp some important concepts here.
Dean and Jeff's arguments make a lot of sense, I can't figure out how to refute them based purely on physics.
But I have bows with positive, negative, and neutral tiller. The only ones that really give me a thumpin' and/or create a lot of noise are the negative ones (stronger top limb). And I have some samples (made by myself and others) with both high wrist grips and straight handles. Heck, I even have them in glass and wood.
The problem is that I don't like anecdotals if I can't back them up with a good physics based logic behind them.
Since I haven't completely figured it out, I start with neutral, and then slowly add a little positive tiller until the bow turns sweet. Last bow I made was the sweetest one I've ever shot, let alone made. Straight grip glass hill-style longbow, a little under 1/8" positive tiller.
So, I'm trying to reconcile this. Luckily, Mr. Beam is helping me out. (For you other engineers, we had a great Beam Theory T-shirt in college with a twist of Jim, wish I still had one.)
I'm playing in the bow shop right now, covered in Osage dust. Beer is cold, AC is running. Just glued on a Bocote riser on my third tri lam. Don't have to work in the morning either. I love retirement an making bows. And this is a very informative thread. I sure hope Dean surfaces.
sounds like a lovely evening Roy.
Dean declined my invite and I understand why.
In Dean's Tillering the Organic Bow article, he mentions that he grips the bow by the side of the handle, which means the most pressure (dynamic fulcrum) is right below the arrow rest. That is quite a bit higher than it would be for someone using heel pressure - probably a couple of inches. Hmmm...
so what it all comes down to.... if i understand this right.... is that the tree needs to hold the bow and pull the string the same way that you will. and then the tips need to move together to full draw... synced or timed or whatever you want to call it. correct? so if my bow is braced and on the tree.... supported (and allowed to pivot) at the point on the handle where my bow hand will be.... and the string is pulled from where my string hand will be. and just say i can draw a perfectly horizontal line from one nock to another.... at any point of the draw i can still draw a perfect level line from one nock to the other... and the handle does not pivot on its cradle. would that be "perfect" tiller.... regardless of limb length?
A balanced draw is nice, but what I look and feel for is a balanced release. No matter how you hold it draw it there is only one purpose, get the arrow down range. After all that is what a bow is designed to do since its inception.
Eric, you're on the right track by setting the tree up to hold the bow like the archer will hold it... and there's often even more than one way to do that correctly. But forget about the tips creating a level line between them. If the limbs aren't exactly the same profile, starting the same distance from the handle, of exact internal strengths, etc.. then tillering to achieve and maintain a level line is not only an unreliable indicator of limb timing, referencing it could easily be as counterproductive as predetermined braced profilles.
This is probably the best thread on tillering to have shown up on this forum. I usually pass by the thread when the question is asked but this one is great and needs to be stuck at the top.
Very well explained.
I like what you said Jeff, "He hides things in them". I have read Deans writings and talk with him many times. Great bowyer/writer/person. I miss seeing him at the shows.
CTT
When I tiller bows for myself, I have my tillering tree set up to hold my bow with the pressure distributed fairly evenly across my hand, and I hook on the string where the string hand fulcrum will be with a 3/8" nock point heighth... then I adjust relative limb strength so the string hand fulcrum pulls straight down the vertical line I have drawn to mimic its travel perpendicular to the handle. If for instance it pulls to the left of the line, the left limb is too strong, and it's adjusted as needed until it pulls neither left or right.
I made inserts that drop right into the cradle of the tree that are various shapes to mimic different bow hand holds/pressure high or low, and/or allow the bow to pivot and reveal limb balance and point of dynamic balance.
I've also got 4 pulleys on a shaft down by the floor that are used for split finger or three under holds with the top limb facing either left or right. They are also easily moved by loosening a set screw if a different string hold needs replicated.
I set it up to be as versatile and revealing as possible, and while it works, I don't declare it to be the only right way to tiller a bow... and in fact, I expect my methods to continue to evolve and refine.
makes sense, but wouldn't that require that the tips at least maintain their relative position on the y axis while on the tree...errr.. so if not level, say one tip half an inch higher...wouldnt it remain half an inch higher throughout the draw? so if at brace, the tips were level... or close to it, and then we started drawing, but the left limb is weak... or the tip falls behind the other, our drawing hand fulcrum would stray from the vertical line right? wouldn't the vertical line tell you the same thing as tip location?
Told you Ol' Dean was smarter than the rest of us Roy. :readit:
I think Canopyboy has the right idea. Build even tillered bows and adjust from there. And if every bow after that requires a positive tiller then you might as well go ahead and say Dean's notion of a stronger upper limb is incorrect for YOU. But if YOU require a stronger upper limb then stick with his version. Simply as that. It's all about making the best shooting bow for yourself. Absolutely noting wrong with that and I can't condemn anyone for that. If it works, it works.
What works for me is to keep the static and dynamic fulcrum as close as possible. As we all should (Jeff does exactly the same thing I'm guessing). That's the best and I reckon you could say, the most direct route to achieve best balance/timing. Diverge these two very much and it's a rocky road ahead. Dean's assertion that the two fulcrums diverge by as much as two inches is totally incorrect. This is where he tries to fit a square peg into a round hole to make it fit.
Most of us know from experience that we can build a smooth shooting well balanced/timed same-limb bow. But if you take Dean at his own words, this can't happen. But we know better.........Art B
Holy Cow, your up early ole boy, what's up wif dat? :)
I used to make my bows with a +1/4 tiller. Then some ole coot from WV said try making them with a +1/8th tiller. So I tried that and my bows began shooting and feeling even better.
It's all fun an I just love building them...
QuoteOriginally posted by Echatham:
makes sense, but wouldn't that require that the tips at least maintain their relative position on the y axis while on the tree...errr.. so if not level, say one tip half an inch higher...wouldnt it remain half an inch higher throughout the draw? so if at brace, the tips were level... or close to it, and then we started drawing, but the left limb is weak... or the tip falls behind the other, our drawing hand fulcrum would stray from the vertical line right? wouldn't the vertical line tell you the same thing as tip location?
If the bow is held vertical (measured by the string), you are pulling on the string at a point centered above where you are pushing with the center of your hand pressure. So that force vector is just a line between those two points and cannot be perpendicular to the string (unless you're shooting through your bow hand.) If you put the bow on the tree and pull straight down with a pulley system, use a pivoting cradle of some sort, and hold the bow and string as you would shoot it, you will find the bow will immediately tilt upper limb down until those two points are in line with the pull vector to the floor. As I increase tension, the bow (especially one that shoots smooth and sweet) seems to start to tilt back a little, but the upper limb will always be a little lower than the lower limb measured against a horizontal.
I need to play with this idea a bit more, but I think the fact that you're not really pulling straight back perpendicular to the string but slightly up and back is why Dean's theory for the upper limb isn't always borne out by the way most bowyers have found a slightly stronger lower limb to work better. As you essentially pull up and back on the string relative to a vertical bow, you are pulling harder against the lower limb as the draw progresses, offsetting or completely reversing the extra force on the upper limb that would be a result of pulling higher on the string than the center point.
Does that make sense to anyone else? I want to try to put it into a diagram, but will have to wait until later. Gotta get to getting to get paid right now.
-Dave
(Even if I'm way off course, this has been one of the most thought provoking threads I've read, let alone participated in for awhile....)
It's hard to keep a good man down Roy!
This has got to be the most frustrating subject to discuss and convey. I reckon that's why it's not talked about in-depth in articles or books that much. Dean gave it a shot but I feel his judgment was clouded for whatever reason.
Let's do a comparison of what I've been saying vs Dean's description using his see-saw method. I maintain static and dynamic fulcrum diverges very little (below center if anything) and on a same-limb bow and Dean states a lot (as much as two inches above center).
OK, now for my version: Keeping the static and dynamic fulcrum dead center (for best balance/timing), and placing a heavier boy (stronger lower limb) on the lower (limb) plank, how do we go about maintaining balance? Well, here's what's been missing. You simply use a brace (heel of the bow hand) from the fulcrum (center of bow/hand) to the lower plank (limb). Now the see-saw is balanced using a heavier boy on the lower plank and a lighter boy on the upper.
But Dean mistakenly diverges the dynamic fulcrum (best balance/timing is lost here) from the static fulcrum and has to compensate by using a heavier boy on the upper (limb plank). Thus his reasoning for a stronger upper limb/negative tiller.
So judge for yourself folks, and see which bowyer reveals himself........Art B
Dave, we're saying exactly the same thing here. Heel pressure of the bow hand is the equalizer here and what makes this design (symmetrical) work. Not a stronger upper limb. So for this design, I'd say let the shooter have the final say and not the tillering tree. Cause we all know, archers shoots bows, tillering trees don't :biglaugh: .....Art
Art are you saying that holding the bow with the heel of the hand.... or lower on the grip is what maintains balance? What does Dean do that causes Static and dynamic fulcrums to diverge?
Art, Dean's not saying symmetrical bows can't be synchronized. To the contrary, he's saying they should be.
Canopyboy, I dont want to have to pull up and back, heal the grip, etc... my goal is to have a bow that i can pull straight back, perpendicular, against the handle with equal strain on the limbs throughout the entire draw. No detectable shift of dynamic balance, tipping, etc.
As soon as I can make time, I will try to do a better job of explaining with pictures... a couple of tiller-alongs perhaps.
Echatham, you're not holding the bow with the heel of the bow hand, the handle kinda settles there during the draw. To make it clear we're discussing a bow of same length limbs, 4" handle dead center. This requires a low wrist grip. Dynamic fulcrum settles below center of the handle for best limb balance/timing.
"What does Dean do that causes Static and dynamic fulcrums to diverge?"
Only way you can get that much divergence (2") is by gripping this design inappropriate and tillering from there. That's trying to fit a square peg into a round hole again.
Jeff, I agree with you. I'm saying he missed the mark when it came to him trying to describe why everybody thinking was wrong but his. But then again, Dean's a caggy Ol' fellow, and it may have been his intention all along to get folks thinking. Who knows, but I have nothing but great respect for his knowledge and admiration for his ability........Art B
so say i got a bow with same length limbs and im gonna grip it from dead center. lets pretend im going to shoot with a d loop and mechanical release... from dead center of the string...yes im shooting through my hand i just want to get the theory. if both limbs are same strength.... that bow would have dynamic and static fulcrums in exactly the same spot... and would be balanced. right? so say i take this same bow and i pull the string from a more realistic 2" above center..... and that would make my "even" tillered bow tip toward me in the hand ( top limb towards me) .... right so far? so to counteract that.... i need to make one limb longer or one limb stronger (which limb.... im not sure yet).... so that the dynamic fulcrum stays under my hand while i pull the string. am i cooking with peanut oil yet or am i still missing something
Bowjunkie - I'm not saying that you try to pull up and back when you shoot. But unless you grip the bow tightly with your lower fingers induce a resisting torque (top to bottom), you can only pull in a line that is drawn from the center of pressure in your bow hand (don't care if the heel of your hand is involved or not) and the center of your grip on the string. This line of pull basically intersects at the nock for a split shooter and slightly under the shelf for a high grip or up to 2" under the shelf for someone who really gets their heel into the bow. If your arrow is perpendicular to the string, this line of pull/push is not, it aims slightly down. "In Effect" you are pulling up on the string relative to string perpendicular and the arrow whether you are trying to or not. A three under shooter brings his string hand lower, making the angle of the push/pull line I described closer to parallel with the arrow and perpendicular to the string; reducing the secondary force vector putting additional strain on the lower limb. That is why a bow tillered for 3 under is likely to be neutral or even negative tiller and comes closer to Dean's theory.
I don't think Dean is wrong, I think he just left out this part. If you do pull perfectly parallel to the arrow by either holding the bow both above and below the shelf such that the center of pressure (push) is at the arrow or if you lower your string hand until your center of pull is directly across from your center of push, I think you will find that you need a stronger upper limb for the bow limbs to be balanced and synchronized.
Art, I'm not sure we're saying the same thing. What I'm saying is that the grip doesn't change the underlying physics. And if anything, getting the heel of your hand into the grip will lower the center of pressure on the bow, increasing the push/pull line's angle relative to string perpendicular and necessitating an even stronger lower limb for the same string grip.
Eric, I'll just make ya a damn bow and send it to ya, son.. LOL
First thing you need to learn is how to grip the bow Echatham. Properly gripped, the bow won't tilt in your hand to begin with. And if you have a tendency to favor the lower limb to achieve that, then a little stronger lower limb is required.......Art B
Everybody gets a bow but me, huh! :mad: I see where I stand now! Bottom of your xxxx list :biglaugh: ..........Art B
Roy that will work lol! Art, actually i haven't experienced a bow tilting in my hand, so maybe i am gripping the bow right haha who knows! what im really trying to say i guess is that the bow would want to tilt, and if supported by a radiused or single point cradle on the tree, actually would tilt. would the rest of my assumptions about that hypothetical bow be somewhat correct?
Roy make it 66" ntn and 55#@28 and tillered for 3 under. one of them fancy tri-lams will do just fine. and cut me a shelf in there would ya... you know you got to be centershot to shoot good. :laughing:
Bull crap on center shot to shoot good, all ya gotta know is how to tune arrows to your bow. Now ya whizzed me off so I hain't gonna make ya a bow.
Give me time ole boy, give me time:)
Make sure you tiller it right :)
If you're asking if drawing dead center of both the bow and string keeps the static and dynamic fulcrum the same, then yes. Trying to mimic the dynamics of what happens in the hand to the tillering tree/board isn't going to happen with this design. Not to say you can't tiller out a bow for this design on a tree but you have to be remindful of tiller requirements as you proceed.
"Art, I'm not sure we're saying the same thing. What I'm saying is that the grip doesn't change the underlying physics. And if anything, getting the heel of your hand into the grip will lower the center of pressure on the bow, increasing the push/pull line's angle relative to string perpendicular and necessitating an even stronger lower limb for the same string grip"
Yep, same thing Dave. Take for example you use an elevated rest and the hold on the string raises also. What happens? More heel of the hand is required and a stronger lower limb to maintain balance. Shooting upright vs canting, same requirements. Do you disagree with that? .....Art B
geeez roy, just ribbing ya about the centershot, you ought to know ya done schooled me right on that. so... Im sorry i said that... can you still make the bow? :laughing:
NO.
so pulling from a higher point on the string does what to the dynamic fulcrum? moves it down? let me put that another way... pulling from a higher point on the string puts a heavier boy on the lower limb?... which makes the dynamic fulcrum lower? meaning that the higher up the string you are pulling from, the stiffer you need the lower limb? assume im gripping from geographic center of the bow. i don't know if i am building same length limbs on my next bow or not.. but i really want to understand this before i do anything.
:bigsmyl: :wavey:
QuoteOriginally posted by Roy from Pa:
NO.
:laughing:
Jim Fetrow used to recommend weighing each limbs draw weight separately. Thoughts?
Perfect tiller, 1/8th negative, low wrist grip.
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/29a.jpg) (http://s47.photobucket.com/user/ROY-CHRIS/media/29a.jpg.html)
Even better perfect tiller 1/8th positive higher grip, and sweet form:)
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/IMG_7444.jpg) (http://s47.photobucket.com/user/ROY-CHRIS/media/IMG_7444.jpg.html)
So it all depends on the archer and how they grip the bow as to how you tiller them. But limb sync is everything:)
QuoteOriginally posted by Roy from Pa:
So it all depends on the archer and how they grip the bow as to how you tiller them. But limb sync is everything:)
so how did you determine the amount of positive/negative tiller to be optimum for each of you? and what method do you use to ensure limb sync?
guys i really do apologize if my questions are dumb. I feel like you guys are talking about calculus and im bugging you about multiplication tables. I just really really want to understand! :pray:
Hey Roy..
On that one in the pic you did the "follow the line" trick on the tiller tree.
Would you say that's the ticket?
Thanks :thumbsup:
Echatham, heavier boy, yes.
Your ticket for the sweetest shooting bow, IMHO, would be where the static/dynamic fulcrum is the closest to center. That would be a straight wrist/low contact design like Dean and Jeff makes. Upper limb appears longer (it's not really, handle is lower to accept grip) Tiller/search for even limb strain as you shoot your bow in. After a couple of bows of this type tiller requirement will reveal itself.
That's all I got to say on this subject......Art B
Thanks Art. would any one care to talk about timing/sync?
NO.
My head hurts enough now.
I'm going to the bow shop and make a bow.
Might even put wheels on it, then I kin adjust the wheels for equal timing:) :)
Your nutten but trouble, Eric...
:laughing:
QuoteOriginally posted by Art B:
Yep, same thing Dave. Take for example you use an elevated rest and the hold on the string raises also. What happens? More heel of the hand is required and a stronger lower limb to maintain balance. Shooting upright vs canting, same requirements. Do you disagree with that? .....Art B
Not sure, we might be saying the same thing, but not sure for the same reasons. Then again, I've never been that good at explaining myself, so maybe.
What I'm saying is that as this virtual push/pull line between the center of your bowhand pressure and center of your string hand pressure takes a larger angle to the arrow, you need a stronger lower limb. If the angle is zero and you are pushing and pulling in the middle of the bow and the middle of the string, both limbs should be balanced. If the angle is zero (parallel to arrow) and you are pushing pulling above the center of the bow, you will need a stronger top limb per Dean. But if this line starts to angle down from the arrow, you will need more and more of a stronger lower limb.
So, I agree that elevated rest does the same thing as low grip by increasing the angle of the push/pull line relative to arrow. Do not agree that an elevated rest means you need more heel (in fact I think less would be better.) Do agree that more heel AND an elevated rest lowers the center of pressure on the bow while rasing the center of pressure on the string and increases this angle even more. So therefore I do agree that an elevated rest will need a stronger lower limb for the same grip. Do not agree that canting the bow versus straight up and down will change the limb dynamics unless the shooter changes his/her grip as a result (although this is often the case.)
Here is the problem (I think):
"What does Dean do that causes Static and dynamic fulcrums to diverge?"
"Only way you can get that much divergence (2") is by gripping this design inappropriate and tillering from there. That's trying to fit a square peg into a round hole again."
and...
"First thing you need to learn is how to grip the bow"
I also like to shoot with my palm and heel off to the arrow side, and use my thumb for a fulcrum, when shooting my Torges-style selfbow. It shoots the best that way, and I don't have to worry about bending my bow elbow. I don't care for the suitcase style, heel down grip. That doesn't mean it's incorrect (although it might be for a Hill-style straight grip).
Will also mention again that I'm a relative newcomer to the bowyer thing, and my few years are nothing compared to a lot of y'all's....
I'm just working on it from a fundamental physics perspective as an engineer that can't let things like this rest until they make sense to me. Not saying I know what I'm talking about there either though....
This has been a great thread and I've really enjoyed working through this. Hopefully some of what I said made sense. If not, hopefully it didn't bore or irritate too badly.
When we talk about dynamic function we often ignore the balancing the limb's masses. So to use less hand pressure on an elevate rest, would, imo, ignore the latter. But that's just my opinion.
You're right of course, I do modify my grip somewhat when shooting this type bow. But that's more of a natural response rather than a planned event for me.......Art B
didn't realize it but this thread has been done before here: http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=125;t=006299;p=1
i found some more nuggets in there that helped clear it up for me. its making some sense now. I really needed the physic's teacher explanation on the force and leverage applied to the limbs.
Eric,
I've spent the last 15 years on one forum or another hashing this out. This thread has been done many times before. It almost always fun to do it again though. Honestly, I still don't understand it but I keep trying.
The more I know; the more I know I don't know.
John thats the best post yet. you knew exactly what you were getting me into when you suggested i start this thread didn't you?!
Hey Roy, although I would love to have one of your bows, no way would I accept yours without building you one in turn. But at my age, everything I touch turns to you know what. So I guess we're both out of luck, LOL! Art B
QuoteOriginally posted by John Scifres:
The more I know; the more I know I don't know.
And unfortunately, even that I'm unsure of at times...
:campfire:
so i think we can just all agree that this is all way over any of our heads, and continue to make shavings. if we haven't mastered it after thousands of years of archery, then in my book that makes it a true art and not a science.... and there is no perfect. but i bet my next bow is better than the last one... hope so anyway.
Ok Art, I was gonna give ya the next one, but be that way ya old coot:)
I think it's a lot more confusing in theory than it is in practice.
If the tillering tree is set up to mimic our preferred grips on bow and string, and the bow is tillered so the string hand fulcrum and arrow come straight back, perpendicular to the handle, without tipping, the bow will be tillered to send the arrow perfectly straight away from the predestined nock point, will require no torquing of the grip, and limbs will be sync'd.
Art, I'm curious, do you prefer to heal your grip, or do it out of necessity? If I had to do it out of necessity to keep the bow from tipping, I'd weaken the bottom limb until I didn't have to. Perhaps you and I would simply shoot the same bow tillered quite differently due to personal preference.
IMO, if the bow asks me to heal the grip, the bottom limb is too strong. Such bows feel a tad wild and uncontrolled at the shot and tend cause the top limb to jump upon release... perhaps because it's returning to brace a split second later?
I saw this dramatically displayed recently on youtube as I was watching some folks shoot Yumis with bottom limbs that were obviously too stiff. These bows tilted forward on the top limb at full draw. Perhaps the archers weren't applying enough heal pressure... or perhaps the bottom limb was so much stronger they COULDN'T heal it enough. Maybe their bow hand wasnt positioned correctly which caused the stronger bottom limb... dont know. That Yumi is a strange animal, but it intrigues me in regard to this tillering stuff.
The Yumis whose limbs I assumed were matched in relative strength, stood straight and square in the hand at full draw and were still at the shot.
I don't want Roy to make me a bow either. He'd have to screw two of those girly bows together... and that would just look silly :rolleyes:
I use a medium grip Jeff. Like you would use on a Hill style bow. Arrow pass 1 1/2" above center. For an even tillered bow I apply equal hand pressure per limb. But since I shoot split-finger, and dynamic fulcrum is slightly below string pressure, lower limb receives extra strain requiring it to be a little stronger for long term tiller health.
I can shoot an even tillered bow and maintain good tiller health too, but arrow trajectory is lower then I like.......Art B.
When you said you place the arrow pass 1 1/2" above center, is this on a same limb bow?... everything built symmetrical, with a 4" handle that is slid down the midsection 1/2"?
If so then it was my mistake assuming 'same limb' and 'symmetrical' to mean the same thing. When I reference symmetrical bows, I have in mind those when divided in half would show two identical pieces. Center of 4" handle on bow center, arrow pass 2" above.
No Jeff, that's my preferred layout. Sorry for the confusion.
We were discussing same-limb bows as you described. For that type layout I would use a full hand/low wrist grip w/slightly more positive tiller.
I think a lot of misunderstandings may stem from the type handles we like to use. I dislike a bulbous handle which may favor the decisions you make. Likewise here......Art B
to the top.... cause i just read it all again to refresh myself... and maybe somebody's new and interested, or missed out on this thread. lots of good stuff in here.
Thanks Eric, now I'm gonna have bad dreams again.. :)
:laughing:
Haha Roy, I'm with you there. This thread was confusing as heck when I first read it and that hasn't changed much rereading it. It raises as many new questions as it answers and that frustrated me to begin with, but I see that as a good thing now. What I've taken from it and use when I tiller now is a combination of Jeff and Art's p.o.v.'s; position of the handle on the tree plus the handle's shape and where my thumb and forefinger and heel will rest on it. But I've tillered all of a dozen bows at this point, still have much to learn and enjoy trying to tweak the next one. Keep bringing this topic back up again Eric. Maybe I'll get it by the tenth time. :)
I just feel like this is extremely important to making the best bows... And i think maybe alot of people ignore it cause its a difficult topic. this is one of the things that keeps me up at night. Wish i had a high speed camera i would do some real testing. I wonder if "perfectly timed as we draw the bow" translates exactly to "perfectly timed as the bow recoils and launches the arrow" particularly with a three under draw where the point of pulling on the string is not the same point of pushing on the arrow
Eric none of the above works for three under... :)
E., depend on your senses to tell you if the bow is tillered well, when you draw and release the arrow. We've got 5 senses and some of us use only sight to tiller.
Perhaps using all our senses would be better. I use sight, hearing and touch. The use of smell and taste in bow making have eluded me
I made my living teaching kids science/chemistry...but i did not teach physics and have little training in it so I stay out of these discussions.
I've chosen to keep science out of my bowyering except for this comment.
Question: how do some see a bow as a first class lever or seesaw?
Those who do please explain.
My understanding is a seesaw (first class lever) where the effort and resistance go in opposite directions...one up and the other down. Obviously, both are in the same direction in a bow (towards the archer).
Please explain. I'm not too old to learn. :)
I don't see a bow as any type of simple machine.
Anyway, try making bows with different sized limbs and same limbs and see how they shoot.
After all these years of making bows I haven't seen much difference but I haven't made many with shorter lower limbs. I like symmetry.
Jawge
First time bow maker here. I started on my first bow two months ago and now it is complete. I'm still learning about arrow tuning so judging sweetness of my tiller is difficult at the moment because I am using plastic vanes and they tend to hit the arrow shelf and do a little bit of bounce off of the shelf (I have to get feathers)
But that said, I am happy with the tiller. while making the bow I landed upon the confusion that is discussed here and it would be nice to get Torges opinion of it. Torges' Organic Tiller article discussing dynamic centre made sense to me, as he was the only writer in forums and websites and how to vids on youtube to start to offer what seem to be sufficient enough explanation so I could understand. But on second guessing the article, i read it again, then it kept me up so I had to hash it out with my own logic.
Here's why I think torges is right..... I don't offer a proof, I think we would need a hadron scientist to explain all of the complexities in finite detail and come to a full answer of the question....
but my best working choice at how to proceed.... (because I like to get things right, and don't have infinite time to theorize and had very little experience) was through reference to fred bear's video about the history of bow making. I had a light-bulb moment when he referenced the japanese bows made of saplings the 7 to 8 foot tall ones. Such an unusual design, in cross examination to torge's article shed a little light for me on the subject. The bows they were using had a short and powerful lower limb (the bottom of the sapling was much thicker naturally, and the handle portion was therefore located only a 1/3 way up the limb)so handle, the shelf and the draw line come from very far below the actual measured centre of the bow. This required a long upper limb to compensate for the short and strong lower limb, to equal forces (as is related to gravity of the large child vs the gravity of the small child) The smaller child, or the weaker limb (less force) would require that it be further from the dynamic centre of the bow. so the shorter limb should always be stronger is where I decided to proceed from.
...when I began making the bow, I just started hacking at a piece of wood, and bravely pressed onward. I didn't yet have the foresight to make my the portion where the heel of my hand would be a little below centre, because I didnt then realize I like to grip more between index and thumb. Also, I cut my arrow shelf high. my arrow sits about three inches above centre, so I went with a raised fulcrum on my tillering tree and made the top limb a bit stiffer. It turned out great. Ii got my dad to draw it and the limbs draw out evenly, despite the high hand hold (and split finger shooting)
I cant wait to see how it shoots with feathered arrows so that I can feel that the tillering method was correct.
It seems like a huge difference whether or not torges is correct or not if I understood correctly that the top limb should be stiffer if shooting from above centre.. Am I right here?? there seems to be disagreement but that people rather than trying to figure this out are avoiding getting deep into it to prove one way over the other using vector physics. THe second post at the beginning of the discussion threw me.... so I thought I did things all wrong... but again the pendulum swung... yet I see most bowyer's masters and all making the top lim just a bit weaker???
what do you guys think??
echatham .... thanks for pushing your confusion.. because like you I have not found an explanation I am satisfied with.... but thanks to you all... this has been the best yet
Oh geeze, he we go again :)
I'm going to try to wait until I can get to my computer, before I get too crazy with this stuff. It's easier than typing on this stupid smart phone :)
George, I use everything I can to make the best bows I'm capable of... including my senses. I would not call a bow well-tillered if it didn't feel perfectly balanced in my hands during the draw and at anchor. I also use pictures at times to verify everything is as it should be, but consistant success breeds trust and confidence in one's methods and tools, so I've learned to trust my tillering tree setup and what It reveals to me.
Your advice is sound, and is what I tell folks if they haven't gone to great lengths to ensure their tillering setups very closely mimic their own actual shooting peculiarities... and/or haven't yet established adequate trust in it.
Stay dusty my friends...
:wavey: :thumbsup: :dunno:
These type threads are always fun..
QuoteOriginally posted by Bowjunkie:
Stay dusty my friends...
love it!
lol :biglaugh:
ok im gonna stir this pot a little ;) I read somewhere, and it may have been Dean himself, but im not going to research to make sure at the moment, but its been said that an asymmetrical design would be even more advantageous for a bow tillered for 3 under... but im having a hard time putting that together in my mind. it seems to me, that if my string hand is closer to the geographic center of the string, the more symmetrical the bow ought to be. thoughts?
It's not about the geographic center of the string. It's about the static and dynamic center of the bow. And tillering for three under moves your drawing hand closer to the dynamic center than if you were tillering for split finger. But Bowjunkie can explain all this better than I. :)
Bowjinkie, I love digi tillering though my wife gets sick of taking pictures of me drawing a bow. LOL. Mirrors and windows at night work well also.
My neighbors think I'm weird anyway. :)
Jawge
QuoteOriginally posted by Roy from Pa:
It's not about the geographic center of the string. It's about the static and dynamic center of the bow. And tillering for three under moves your drawing hand closer to the dynamic center than if you were tillering for split finger. But Bowjunkie can explain all this better than I. :)
Right so wouldnt that mean the bow would be better off more symmetrical?
I'm not an expert on this theory yet myself.. :)
But with a symmetrical bow with handle center at the center of the bow, the static balance would be the center of the handle or very close to it, depending on the mass of the limbs. If you take that symmetrical bow and cut 1 inch off the bottom limb, that moves the static balance up 1 inch towards the top of the handle. Or in other words, closer to the arrow shelf.. But this theory all depends on how one grips the bow, that's the sticker point..
I told ya not to bring this thread back up, now look what ya went and done? :) Shouldn't you be working on a Submarine or something? :) LOL
Roy, cutting 1" off the bottom limb would move the center/static balance point up 1/2". Jes sayin'.
Ya that's right.. I had the up right.. :)
"...its been said that an asymmetrical design would be even more advantageous for a bow tillered for 3 under... but im having a hard time putting that together in my mind. it seems to me, that if my string hand is closer to the geographic center of the string, the more symmetrical the bow ought to be. thoughts?"
Eric, it's true that an asymmetrical design is better suited to the three under string hold than the symmetrical design... if keeping static balance (usually synonomous with geographic center) and dynamic balance in the closest possible proximity are valued. With three under, the asymmetrical design can put the static balance point, string hand fulcrum, and dynamic balance point all in practically the exact same spot. This may well produce the sweetest drawing and shooting bow possible.
In comparison, using a symmetrical design with a three under string hold would move the static balance point down to the center of the handle... which moves it away from the string hand fulcrum a little bit. Not a big deal, it just requires that a slight shift be made during the draw from static to dynamic balance points.
Coincidentally, shooting a symmetrical bow three under offsets the string hand fulcrum from the bow center the same distance as shooting an asymmetrical bow split fingered.
If I HAD to make a bow symmetrical, I would try to make it for a three under shooter... because symmetrical and split moves things too far apart for my liking.... but if I didn't HAVE to, I would elect to use asymmetrical bows for both three under and split holds.
thank you. that makes perfect sense now. :notworthy:
By how much????On symmetrical vs asymmetrical 1/2"-2" depending on the grip Style and 3 under vs split :dunno:
This is gonna take some graph paper and some deep thinkin. I gotta get to work on a hunting bow for this season. Ive decided i dont like the way straight standing bows stack at my draw length so im gonna build me another recurve.