lets talk positive vs negative tiller

[Echatham]

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        

[Bowjunkie]

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.

[macbow]

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.

[George Tsoukalas]

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

[John Scifres]

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

[Echatham]

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....         I blame Roy.  he must have taught me wrong cause he was afraid i was gonna make better bows than him.    

[Bowjunkie]

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.

[Roy from Pa]

Ya, your a little slow alright...  

[Onehair]

Dean sure uses a lot of words.

[Bowjunkie]

Yeah, and he hides stuff in them too.

[John Scifres]

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  

[canopyboy]

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.

[canopyboy]

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.

[Fritz]

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.  

[Roy from Pa]

I wish Dean would have written it so a redneck like myself could have understood it:) LOL

[Bowjunkie]

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.

[Art B]

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

[Echatham]

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?

[Roy from Pa]

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...

[Art B]

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