Tillering question

[DC]

When I draw this bow for the first 12" the spot marked with the arrow goes up, not much, maybe 1/8-1/4". The same spot on the other limb goes down. So it kind of teeter-totters. What is it trying to tell me? It's at full brace. It's an older bow that I'm reducing the weight on.

[Del the cat]

It's telling you that it's exactly what happens when you hold a bow in your hand and first start pulling the string... Try it.
You hold at centre and pull above centre, the bow will rock.
Look at the video here, you'll see it happens on my bows too.
http://bowyersdiary.blogspot.co.uk/2015/06/spliced-yew-bending-nicely.html
If you support the bow dead centre and pull the string dead centre, you can tiller it so it won't rock, BUT the tiller will be out when you draw it in your hand!

Also if the lower limb (I'm guessing left in your pic) is a tad stiffer (which is usually the case) it will pull the other limb up a bit.
It can get V confusing. The way I look at it is to imagine what happens if one limb was completely rigid, the tip would pull down still and the limb would have to stay straight (if its' rigid) so the other limb would come up at the fade and the grip would rock.

I compromise slightly when pulling a bow on the tiller. I support it at the top end of the grip and draw from where my fingers would pull. I even use a double hook which I made to simulate my fingers. You can see it if you click on the full draw pic in that blog entry to enlarge it.
Del

[bushboy]

It's stiff,over powering the other side. Imho

[DC]

It's supported and pulling on the center. So bottom limb (left) is a bit stiff. That's a good thing, right?

[Dances with squirrels]

It's telling you that you're not pulling it from the same place on the string that your string hand will pull it  from ... actually, that's more what it's telling ME, because when someone says a bow is rocking in the tree, before I respond, or judge the bow, I immediately look for... How/where is it being held? and how/where is it being drawn? and it appears that you're holding it and pulling it from its center.

If you pulled it from the 'correct' place on the string, it would act differently... in fact, it would almost have to tilt the OTHER way, as that particular bow should early in the draw... because.....

The second thing I check is whether the bow is designed with equal length limbs. It appears yours is. Such a bow, in the early draw, held and drawn as the archer will, will usually try to tilt the opposite way until it makes the shift from static balance to dynamic... assuming it IS dynamically balanced.(balanced for equal limb strain, relative to the archer's holds at his full draw)

My advice would be to set the bow in the cradle to reflect your BOW hand fulcrum point, pull it from the place on the string that best reflects your STRING hand fulcrum point, and THEN judge it. Until you do, judging it, and correcting it, is a guessing game at best.

To answer your question as it stands(because I can make a good point with it)... With the grip center as the bow fulcrum AND string fulcrum(which is how yours appears to be set up)... what the tilting is telling you is... the limb on the left is stronger(relative to those holds) than the limb on the right, because if a bow is allowed to rock or rotate in the cradle, as it's drawn the relatively stronger limb will be pulled down and the weaker limb will lift up... like Del described.

"It's supported and pulling on the center. So bottom limb (left) is a bit stiff. That's a good thing, right?"

No. Not necessarily. With all-wooden bows, predetermined braced profiles... i.e. 'tiller measurements', such as 1/8" positive tiller... "the bottom limb should be stronger", etc... are just guesses... at the very best. I don't know how to stress that strongly enough without cussing   

Instead, hold them how you'll hold them, draw them how you'll draw them, and seek relative limb balance throughout their construction.

Achieving good relative limb balance can either be detected by using 'true holds' while allowing a bow to rock freely in the cradle, and then adjusting limb strength so that it doesn't...

OR, by holding it firm in the cradle, and adjusting relative limb strength so that the 'true' string fulcrum isn't pulled at all toward one limb or the other at full draw. With the grip held as such, if one limb is stronger than the other, the string fulcrum will always be pulled toward the relatively stronger limb.

[DC]

OK, I tried. I put the bow on the tree where I hold it. The base of my thumb basically. I hooked the scale just below where the arrow would sit. I get this. But when I hold and draw the bow in my hands it sits vertical, like a bow should. What's up?

[bubby]

you don't draw the bow with one finger do you?

[Del the cat]

OK, I tried. I put the bow on the tree where I hold it. The base of my thumb basically. I hooked the scale just below where the arrow would sit. I get this. But when I hold and draw the bow in my hands it sits vertical, like a bow should. What's up?

No it doesn't!
You are not looking! Well you are looking but you are not seeing .
When you first put an arrow on the string and start pulling, the bow does tilt like that... you just don't see it because you are looking from an odd angle, sort of down the upper limb towards the grip. The effect is also masked because you are holding bow, not just supporting it., and the draw force tilting it is very low in the early draw.
If you hold the bow up in front of you like you have it on the the tiller (without gripping it) you will see it is tilted.
In that picture, we can now see which is the lower limb (left), and to me it looks weak.

It's up to you... support the bow on the tiller like it is in your hand, or support it dead center, or clamp it rigidly either on the centre or as it is gripped.
I know which gives the most realistic result for me. You have to make your own mind up...
Del

[DC]

Del-I went and stood in front of a mirror and held the bow up with no strain and then started pulling to full draw. The bow stayed plumb the whole time. I'm missing something. Here's a full draw in hand. It doesn't deal with what we're talking about but maybe it will help

Bubby- no I don't, but I shoot Med style and I figured most of the load would be on my middle finger which is right below the nock.

[Del the cat]

Ok, maybe you hold it more firmly than I do, so maybe you want a tiller tree with a flatter support for the bow...
I dunno, you just gotta figure out what works for you.
I'd just add, you are not doing it the same as you are on the tiller.
Hold it horizontally just resting on your thumb, not gripping it (in front of the mirror).
It simply must behave the same as it does on the tiller if you support it and draw it the same.
You have to compare like with like else it's not a valid experiment.
Del

[DC]

I agree with you. If I was holding it the same as it is on the tree it would behave the same. I'm looking at my full draw picture and if you were to draw a line down my arm it would go to the center of the handle. But the arrow rest is 2" up from there. I suppose if I'm pulling mostly with my ring finger then things would line up better. Like you said it doesn't take much to skew things one way or the other. I'll keep poking around and see what I can come up with.

[Dances with squirrels]

In your picture of the bow on the tree, it did as expected. It did what it HAD to do because there, it's being both held and pulled above center. Its sharp leaning tells us that it will need to make a big shift in order to be balanced at full draw, and the bottom limb will either need to be weakened or the bow hand fulcrum will need to be lowered as it's drawn.

In your pic, it does look balanced pretty well.... at full draw... following the shift... but I think your bow hand fulcrum is lower than it was on the tree.

To take this deeper in that direction... how a bow is designed... more specifically, how its geographical longitudinal center(static balance point) is oriented in relation to the string fulcrum will determine not only IF it tilts, but also how harshly. In other words, it's design can greatly influence the 'relativity' in "relative limb strength".

A symmetrically designed bow, shot split-fingered will tilt more than most any other popular combination early in the draw... and so requires navigating a wider shift from static to dynamic balance. Even when this shift is navigated to our best ability, these bows aren't as dead in the hand to draw or shoot and are harder to tune arrows to... because for every action there is an equal and opposite one... i.e. it must 'shift' its way back to brace in the bow hand upon release... and this can be felt and affect arrow flight.

On the other hand, many asymmetrical/split finger configurations are better at this, with a smaller shift needing navigated than the symm/split because the bow's center is closer to the string hand fulcrum from the onset... just a fraction of an inch apart. Less shift... less effects.

The easiest to navigate, and likely the most balanced-drawing and sweetest shooting bow is the asymmetrical/three under combo because the static balance point and the string hand fulcrum is virtually the same spot... i.e. virtually no shift.

[bow101]

I think sometimes you over rationalize things, the tiller looks great from here.  I go so far on the tiller stick then I go into the house and do the mirror shot.   Thats real time holding it in your hand.

[DC]

Oh, I'm the poster boy for overthinking. I just gotta know

[bradsmith2010]

how does the bow shoot,, that tells you more than the way it looks,, or validates what the tiller may be telling you,, in my mind,, if the bow shoots great,, I usually dont adjust the tiller,,,even if the target weight is off a bit,,, the tiller tree and pulley is just a rough idea of what the bow is doing in your hand,, not the final step in tiller,, how it shoots in your hand is the final step,,,, not how it" looks" in your hand,,