lets talk positive vs negative tiller

[scars]

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.

[Bowjunkie]

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.

[2treks]

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

[Bowjunkie]

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.

[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?

[Art B]

Told you Ol' Dean was smarter than the rest of us Roy.    

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

[Roy from Pa]

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...

[canopyboy]

Originally 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....)

[Art B]

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

[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    .....Art

[Echatham]

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?

[Bowjunkie]

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.

[Art B]

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

[Echatham]

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

[canopyboy]

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.

[Roy from Pa]

Eric, I'll just make ya a damn bow and send it to ya, son.. LOL

[Art B]

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

[Art B]

Everybody gets a bow but me, huh!  :mad:   I see where I stand now! Bottom of your xxxx list     ..........Art B

[Echatham]

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?

[Echatham]

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.