lets talk positive vs negative tiller

[John Scifres]

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.

[John Scifres]

The more I know; the more I know I don't know.

[Echatham]

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?!

[Art B]

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

[canopyboy]

Originally 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...

   

[Echatham]

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.

[Roy from Pa]

Ok Art, I was gonna give ya the next one, but be that way ya old coot:)

[Bowjunkie]

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:

[Art B]

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.

[Bowjunkie]

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.

[Art B]

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

[Echatham]

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.

[Roy from Pa]

Thanks Eric, now I'm gonna have bad dreams again..  

[Echatham]

[takefive]

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.    

[Echatham]

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

[Roy from Pa]

Eric none of the above works for three under...  

[George Tsoukalas]

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

[smokey1983]

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.

[smokey1983]

...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