Thoughts on stability

[Jerry Tee]

I pick up another compound last week at a shop and of course it had no stabs on. It had a really thin grip on it and I drew it. I did not draw the bow well, I moved my hand around to find a reference and as a result I noticed that the bow was wobbling left and right in my hand.Later I repeated the this with a recurve and my Oneida . Both these bows did not display the same instability. Up until now I assumed that stability was a function of bracing height. but now I am thinking left right stability may depend more the ratio of string to limb distance of a drawn bow.
If you consider a compound bow with a very low bracing height and parallel limbs most of the draw consists of string and little or no limb component. As a result there is very little correcting force on the tips to bring the bow back into line if it is deflected.
At the other end of the scale there is the Oneida it has a very large backwards movement of the tip during draw. Based on my observations I should say about a third or more of the draw lenght is due to limb movement. so the string component of the draw is much less. Any deflection causes a large correction force hence greater stability.

[pwiles1968]

I have a parallel limb bow with thin handle, that I guess matches your description, I do find it can be sensitive to hand position but don't have any of the left right instability/wobble that you describe, though I have not fired it without a stab.

[Jerry Tee]

Next time you take it out of the box before you put the stab on draw the bow with fingers and your usual open hand grip, move your draw hand left and right and see what kind of sympathetic oscilation you get at the riser and then let down again And let me know, Stabs wil only minimise what is there, not remove it.
I am trying to under stand more exactly the the qualities that give a bow tolerance and how they work.

[buzz lite beer]

Are you talking bow hand Torque here, or the ability to "yaw" a compound around the cams/wheels where the string comes off, which I think is normal on most compounds except Oneida's

[Jerry Tee]

Yes. Up unitil now I have always thought bracing height and A to A (deflex and reflex taken into account by bracing height)were the main factors in tolerance and stability and most of the posts I have read on the various forums seemed to back this up. But badly drawing that compound bow has caused me to think again and come up with the idea that the horizontal ratio of limb extention to string extention in the draw lenght is going to have a far greater effect. comparing say the Bowtech constitution and the Hoyt Montegra both are 40" or better A to A but on the Bowtech there is very little to no limb deflection in the draw lenght. The Montegra on the other hand has a shorter riser and longer limbs and therefore the limb deflection is a much greater percentage of the draw lenght. So if what I am thinking is correct then it should be much more stable even thought the bracing height and the A to A are similar.

[pwiles1968]

Originally Posted by Jerry Tee

But badly drawing that compound bow has caused me to think again

You could Try drawing the bow properly and then see how they shoot .

Sorry Could not resist.

[geoffretired]

Jerry Tee I think I can see what you are getting at. Does it follow that a recuve is less liable to the wobbles for the same reasons you put forward?
Once at full draw I would suspect there is no difference between the different bows; everything is being pulled into line by the positions/directions of the forces. As the first few inches are pulled I suspect the slim grip will allow the hand to wobble on the grip rather than the grip to wobble in the hand.The wrist can flex allowing the forces to act down one side of the thumb bone then the other. The body is not so well in line at that stage and the draw is not so controlled or in line either. It's an interesting idea. Perhaps more bows with slim grips could be used to gain more data.

[Jerry Tee]

I would have thought so Geoff recurves do bend their limbs back. Once draw and settled yes all should be calm and straight. how ever a little face contact with the string a bad release, or anything else that causes a little miss alignment or a bad finger loose and some component of that wobble will be back again.Yes stabs will attenuate it but on a bow with less string extention should be less prone to it.

[geoffretired]

Jerry, I'm not getting my head round this as I would like.One month old Granddaughter is visiting so I could be getting distracted!?
Perahps there are two things going on here. One is the wobble as the draw is first started, the other, as you say at full draw when things can go out of line so easily all over again. I need some thinking time on this I feel.

[Jerry Tee]

Probablely me not typing exactly what my brain is thinking. I got the wobble at full draw. I tried to find a reference point on my face, when trying this other compound and at full draw I moved my draw hand out and back in again to another point a little quickly and I was supprised to feel the amount of left right wobble that caused at the riser.