Tiller Question

[NOMADIC PIRATE]

I might have made same length limbs bows in the past but I can't remember.

On my usual longer upper limb bows I go for a positive tiller,...... do you do positive tiller on equal length limbs bows too ?

My new Guava is almost ready to tiller and has equal limbs

thanks in advance.

[wizardgoat]

I've done a positive tiller on a bow with limbs equal length and had a hard time balancing it. It felt best when I moved the arrow pass down making the top limb longer anyway.
I'm a big fan of 2" longer top limb with about 1/4" positive tiller, and it's what I do on most my bows

[PEARL DRUMS]

Mine always have a slight positive, I never measured so I have no idea how much. My tillering eyes can see it. That doesn't mean all equal length limb bows should. Depending on how you grip the bow, that can change. I shoot a low wrist, so naturally when my limbs are balanced my top will pull back slightly, that's when I sand the bottom limb until it balances like a dream. That same scenario with a higher wrist may balance right off with an equal tiller.

[Hamish]

Tiller the bow so it looks good on the tree, has relatively even set when unstrung(maybe a tad more in the upper limb, max 1/4" difference, so it indicates the lower limb isn't being strained more).
It shouldn't matter what limb design you use, if you follow those directions,you will end up with a correctly tillered bow.
When I use same length limbs and the above approach the result is usually negative tillered, ie the lower limb is slightly more than the top. Conversely if I use a top limb longer design, it usually ends up positive tillered. Its really only useful if the stave is extremely straight and even, or it is a laminated or board bow, otherwise character can easily make the measurements  at brace height useless.

[PlanB]

Sorry to ask a very basic question.....does positive tiller mean the upper limb tip bends past a line parallel with the handle section even with the lower tip? Or a different curve in the upper than the lower.....or something else?

[George Tsoukalas]

I like the lower limb slightly stiffer or even at full draw.
What counts for me is how the bow feels in the hand as I draw it.
Is the handle pressure even or tippy.
Jawge

[Hamish]

PlanB, Positive tiller is when the distance between the belly and the string of a braced bow is more on the top limb, than it is on the lower limb(measured at the same point down each limb).

It historically has been used to check to make sure that the lower limb is slightly stronger than the upper, to take into account the uneven application of force from a three fingered draw. This came into being when virtually all bows being made had a longer upper limb.

These days bows are just as likely to be made with even length limbs. Even limbs are a bit easier in my opinion for a beginner, both in layout, and in judging the tiller on the tree. I also find it trickier to get a bow with a shorter lower limb to brace height, in the early stages of tillering, slightly harder to judge.
 

[Dances with squirrels]

I find symmetrically designed bows more difficult to tiller because since we pull the string farther from center on them, they stubbornly tip in the hand during the early draw. This is assuming we pull the string on the tree from the spot we'll pull it while actually shooting it... which I think is imperative.

They too can be dynamically balanced at full draw, with a tillering tree that reveals such balance, or imbalance, but such bows require a greater shift between static(where it balances prior to pulling on the string) and dynamic balance to be made when they're drawn. Personally, I don't like the feel of that in my hand while I'm drawing the bow. The farther from center we draw a bow, the greater the shift that must be acounted for. That's as much about geometry as it is physics.

Asymmetrical bows on the other hand, can be made to put the bow's center closer to the string hand fulcrum, and in fact, in some instances, we can design the bow so that it's drawn exactly from its center, requiring NO shift whatsoever between static and dynamic balance. These are the easiest and most predictable bows to tiller and the sweetest to draw and shoot.

When folks ask about, or offer advice about, predetermined tiller measurements they're usually making inherently wrongful guesses and assumptions about one of the most important aspects of bowmaking, imo... limb harmony, timing, equal limb strain, balance... whatever you want to call it. Sure, it's easier to offer and take such generic advice... 'tiller them equal at brace', or 'tiller them 1/8" positive'... but is it RIGHT? For him? For that bow? We honestly have no way of knowing. We haven't seen the stave, and don't even know if he shoots split finger or three under... prefers pressure at the heel of the grip or the throat...

I use no such measurements as beacons during tillering. I design them relative to my holds on bow and string so there is a minimal shift, allowing me to balance the limb's strengths relative to those things early in the tillering process, and continue tillering them with that balance as my guide as to which limb is acting stronger or weaker, making adjustments as needed. When I'm done and it comes off the tree, I  know it's balanced. I know how it wants held. I know how it will look and feel throughout the draw and at full draw in my hands. I know how it will act toward me and the arrow before I draw it the first time. I know exactly where to put the nock point for good arrow flight. These things are really quite predictable. What I DON'T know is what the exact tiller measurements are. They're irrelevent. In the end, the side profile, or 'tiller difference between top and bottom limbs' is whatever it is... always a RESULT of my efforts, never a guide or stencil.

We're making wooden bows, with countless irregularities, visible and invisible differences between the limbs that can be quite considerable. Common sense should tell us not to expect a single, predetermined tiller measurement to best suit them. And then to offer that advice to someone else, with shooting idioms different than our own? I don't even know how my own bows are going to end up, how could I possibly begin tell you how yours will?

I know... not the answer you're looking for, right?   

That being said, this is not bad advice from Hamish, "When I use same length limbs and the above approach the result is usually negative tillered, ie the lower limb is slightly more than the top. Conversely if I use a top limb longer design, it usually ends up positive tillered. Its really only useful if the stave is extremely straight and even, or it is a laminated or board bow, otherwise character can easily make the measurements at brace height useless."

[NOMADIC PIRATE]

Well, I never tiller on a tree, I don't even know what tippy means or feels, nor limb timing,

Guess I'm just an instinctive wanna be bowyer  ,
the negative tiller makes sense but that would look funky at brace I might just chop the lower limb than,......what was the formula for the distance of the center of the bow from the center of the handle again ?

[Pat B]

I never measure for positive or negative tiller. I just look at the drawn bow and want to see the lower limb slightly stiffer.  I don't think you can get an accurate measurement on a stave selfbow because of the irregularity of the stave. Also, positive tiller is only appropriate on a fully drawn bow. IMO.

[Dances with squirrels]

That's usually how I balance mine, Pat, so that the bottom limb is just a wee bit stronger at full draw. Of course, how it acts at full draw doesn't usually parallel how it looks at brace because there are so many factors involved. When tillered so the bottom limb is a tiny bit stronger than the top at full draw in my hands, my particular asymmetrical layout will usually show something close to even tiller(in a bow without much contradicting 'character'), sometimes even slightly negative tiller at brace. If I made them exactly the same strength at full draw, i.e. perfectly balanced, I would see a very slightly negative tiller the majority of the time... instead of ocassionally.

Nomadic Pirate, if you give us more info on your stave and your shooting style particulars, we may be able to give you a ballpark idea regarding how it should look at brace, but it will be no more than that.

As Hamish mentioned, in a symmetrically designed bow which shows both tips even with the handle for instance(neither net reflex or deflex), and shooting split finger with a 3/8" high nock point, and even pressure across the length of the handle, most properly balanced bows will show a negative tiller profile.(bottom limb weaker at brace). I understand the mental hurdle this requires since we've been programmed to make positively tillered bows without question.

On average length bows, I usually offset the handle and bow center by 3/4 - 7/8". That is, the bow center is 3/4 - 7/8 above handle center. This balances it perfectly in my hand to carry, while minimizing the 'shift' between static and dynamic balance to a manageable degree.

Hope this helps.