Author Topic: Positive tiller..why is it required? How does it vary with shooting style?  (Read 48236 times)

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DCM

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #30 on: September 27, 2008, 04:46:59 pm »
Did not see any deer George.  Had a great morning though.  Got my food plot cut up, trails cleared to my stands and the tractor home.  Ready for the rest of the season now.

Sorry Red Dwarf, I did not read the 3 under part.  It is said that 3 under shooters do better with zero, or even tiller.  I know when I shoot 3 under on a bow with positive tiller that it's louder and more hand shock than when I use my conventional split finger.  And it follows, the farther from center you draw the bow, the more tiller you need, or to more center the less.

I always wondered about that, why a 3 under shooter needed less tiller.  Wondered why you always need some rule of thumb positive tiller.  Assumed it had to do the nock point but was not real sure how exactly.

A bowyer buddy of mine from Indiana first introduced me to the nock travel phenomenon.  He saw it on his tiller tree and asked about it.  He had rigged up a model on his CAD or whatever, was an engineer for a GM I think.  I had never heard of it, and honestly haven't tried to replicate it.

It wasn't until years later when Dean published the negative tiller stuff that I went back and read about nock travel, spring rates and the purpose of tiller.  Then it all made sense to me.

Compound boys are all into it as well, single cams being the rage because it cuts out the nock travel nearly completely as I understand it.  Don't play in that game, just saw references to it on the web.

Offline Red Dwarf

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #31 on: September 27, 2008, 05:09:03 pm »
DCM et al

Thanks for taking the time to try & straighten things out for me but..surely, with a split finger style you are pulling from above the dimensional centre of the string, thereby putting more pressure on the upper limb which should then be stiffer to deal with the extra load (negative tiller..?)

Red Dwarf

Offline Skeaterbait

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #32 on: September 28, 2008, 10:14:19 am »
Do you suppose tribal elders sat around having discussions like this?  ;D

My head doesn't work like ya'lls, way to technical (your heads, not mine). I make the limbs bend as even as I can, or to match a picture that caught my eye, and if the bows shoots good, Ta-Daa. I am done.

Offline George Tsoukalas

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #33 on: September 28, 2008, 10:30:29 am »
Nock travel is an interesting concept, DCM. I try to tiller my bows so that the lower nock travels a little less by about a 1/4 inch than the upper nock. This stuff is really complex. Jawge
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DCM

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #34 on: September 28, 2008, 11:43:51 am »
George I don't get what you are saying about nock travel.  I assume your are talking about string grooves.  Somehow I get the impression you didn't read the reference I cited.

"When you shoot an arrow the nock end moves forward, from side to side (Archers Paradox) and up and down. Tiller relates to the up and down movement of the nock. One aim of the bow setup is to get the arrows leaving the bow without any rotation in the vertical plane. If the arrow leaves the bow with say the arrow rotating in the pile upwards direction then drag forces will push the arrow upwards and vice versa if the pile is rotating downwards. If during the shot the string force runs above or below the arrow centre of mass then a torque is generated producing rotation of the arrow shaft in the vertical plane. As the nock of the arrow during the shot moves up and down relative to the arrow centre of mass both the magnitude and the direction of the vertical torque on the arrow will vary."

It's only an interesting concept when you actually make an effort to examine it.  Given your background I'm kinda surprised honestly that the pubished science, such as it is, is not interesting to you.

In our culture, I would consider Kooi and Tapley tribal elders, in a sense.

Offline Marc St Louis

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #35 on: September 28, 2008, 12:06:31 pm »

"When you shoot an arrow the nock end moves forward, from side to side (Archers Paradox) and up and down. Tiller relates to the up and down movement of the nock. One aim of the bow setup is to get the arrows leaving the bow without any rotation in the vertical plane. If the arrow leaves the bow with say the arrow rotating in the pile upwards direction then drag forces will push the arrow upwards and vice versa if the pile is rotating downwards. If during the shot the string force runs above or below the arrow centre of mass then a torque is generated producing rotation of the arrow shaft in the vertical plane. As the nock of the arrow during the shot moves up and down relative to the arrow centre of mass both the magnitude and the direction of the vertical torque on the arrow will vary."


Sorry David but that just doesn't make sense to me.  Udjusting where you nock the arrow would cure the problem you describe and not positive or negative tiller
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Offline George Tsoukalas

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #36 on: September 28, 2008, 11:04:18 pm »
I have read Taipley but  not recently. I bookmarked the url you gave up to for some futured reading.  I got confused. I was referring to something else. jawge
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DCM

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #37 on: September 29, 2008, 08:37:51 am »
Marc,

I don't see it as a problem, simply an opportunity to understand the underlying mechanics.  We have long since solved the problem by trial and error.  I see benefit in understanding the mechanics, even if I don't have a specific problem to solve.  And that we can tune a bow to shoot well by raising the nock point doesn't necessarily mean we could not have used geometry in combination, by positioning the arrow pass slightly differently, to minimize the need for positive tiller and/or higher nock point.

It's just a topic I've become fascinated by, like low stretch strings, because I questioned the choices I make with an open mind and went looking for the reasons.  To be honest, I thought I understood the mechanics and really didn't put too much significance on the reasons until Dean suggested negative tiller.  This was so counter to the dogma I knew it could not be so simple as it seemed in his article.  If so, why had not negative tiller been employed more universally throughout history.  It was in this way that I found what I consider to be the benefit of positioning the arrow pass nearer to center, which ironically re-enforced the theme of Dean's article but for different reasons than he used.  An inane topic perhaps, but for me as much a part, perhaps as essential a part of bowyery as any other. 

I just don't understand why others aren't similarly inclined.  But I can see I should probably back off my online rhetoric a few clicks.  People are intimitaded enough by the topic itself, and most already so much set in their ways that something as simple as suggesting alternatives somehow puts them on the defensive.  But absent the discussion, not being able to bring others into the specifics, I don't have an opportunity cement my own understanding.
« Last Edit: September 29, 2008, 06:51:59 pm by DCM »

Offline Postman

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #38 on: September 29, 2008, 10:15:00 am »
Great thread  - thanks adb for that link to Torges' "update" on his HOB book's tiller method. had my tiller tree actually set up like he now advocates, using a quick-clamp instead of the cradle for pressure. (blind hog finding acorn ;D)  hate to add anther variable to the fray, but to those who build the shorter/stronger limbs, do you find a slightly higher knock (so the arrow is pointing slightly downward) at release shoots better, and if so, do you feel  it is because of one limb tip is travelling faster or more forcefully at release? I've built three selfbows in the Torges method, and find a tiny bit (on two ) above and even (on one) to be the best, but feel I have yet to "nail" a tiller perfectly.
Thanks,
Postman
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Offline JackCrafty

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #39 on: September 29, 2008, 11:23:18 am »
It's funny, but I think that this is a subject that both engineers and artisans can agree....if it's insignificant, it can be ignored.  If it's not constant over time, it cannot be easily quantified.

Within primitive archery, there are many shooters who adjust their shooting style to fit their equipment.  With wood, the properties of the bow in the beginning of its life are not equal to the properties after long term use.

Interesting subject though. ;)  (translation...my head hurts)
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Offline Marc St Louis

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #40 on: September 29, 2008, 06:06:04 pm »
David
I don't see it as a problem either, I just don't agree with it.  When I tiller a bow I go by how it feels in my hand as I draw it back.  Most of the time a positive tiller produces a clean feel with no pivot in my hand.  This can run from 1/8" to 1/4" positive tiller.  Occasionally I do have a bow that needs a negative tiller for it to feel right in my hand but that is rare.  So far as I know Dean is the only bowyer expounding negative tiller, all other bowyers of note go with a positive tiller.  Also a symetrical bow that is tillered with a negative tiller will quite often take more set on the bottom limb.
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DCM

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #41 on: September 29, 2008, 07:11:41 pm »
Marc,

I can see how you may have gotten the impression I advocate negative tiller from my typo.  But I don't.  I'm sure exactly what you disagree with.  Sorry, it's been a few days.  How would you answer these questions?

Why is positive tiller required?

How does it vary with shooting style?

Offline Marc St Louis

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #42 on: September 30, 2008, 10:22:04 am »
David
It is required when I make a bow.

As too shooting styles, I can't really say because my style is always the same.  I can say this though.  The people that I have made bows for come back and tell me that my bows are the finest shooting bows they have ever used.  Must mean something  :)
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DCM

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #43 on: September 30, 2008, 11:48:06 am »
I'm not a bit surprised Marc.  What you get away with using natural materials is a wonder to me, and I ain't exactly a raw rookie myself.

Offline Red Dwarf

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Re: Positive tiller..why is it required? How does it vary with shooting style?
« Reply #44 on: September 30, 2008, 02:01:44 pm »
DCM/Mark etc.

At the risk of sounding pushy......Can anyone tell me why positive tiller is required and how the amount might vary with split finger, 3 under etc.?

Red Dwarf