Assymetric Tillering

[Don Case]

I started wondering about this after staring a Gordon's beautiful Vine Maple for awhile. To maybe simplify my question, if you start out with a smooth "S" shaped stave so one limb is reflexed and the other is deflexed should you end up with a bow that is symmetrical or should the deflexed limb always bend more? Given the right amount of "S" I can see a bow that has one bent limb and one straight limb when it's braced. Aside from looking goofy would this have any effect on the bows performance?
Don

[Bryce]

No matter the shape of the stave the limbs should be as evenly stressed as possible. So some parts of the bow won't 'look' like there bending as much or not as much depending upon the reflex and deflexed parts if the stave. With asymmetrical, the handle is layed out a little different and the limbs bend under the same amount of stress.  Instead of a 1/4"+ tiller on the upper limb which seems to be the norm.

That's just how I understand it. If I'm mistaken, I hope someone has some better insight:)

[willie]

 Bryce

so would it be safe to say that, if you measured back in from the tips on each limb an equal distance, the limbs at that point should be bent the same distance from unstrung?

where does one measure the 1/4"+ tiller at?

willie

[Pat B]

I generally put a stave like that on a form and heat it so both limbs are the same or at least close.
 I never measure positive tiller so I can't answer that question.

[artcher1]

When you look at Gordon's bow you may get the impression that the drawn tiller does look goofy. But the real goofy part would have been if he had tried to make it look symmetrical. In other words, Gordon nailed that tiller perfectly.

Understand that that reflexed area on the lower limb was going to stress the inner limb/near handle and that he needed to apply the correct limb design to the upper limb to compensate. A good lessen in proper tillering there folks.

So to answer you question, no, there wouldn't be any performance loss if you design/execute tiller each limb appropriately. ........Art

[Bryce]

Bryce

so would it be safe to say that, if you measured back in from the tips on each limb an equal distance, the limbs at that point should be bent the same distance from unstrung?

where does one measure the 1/4"+ tiller at?

willie

Yes! On my tillering system the wall behind the bow is painted with with chalkboard paint. Iam able to outline the bow and visual see how the bow is bending from its original shape.(that doesn't always mean I get it right on, but close enough)

When it comes to 1/4" or even 3/16" positive tiller where you measure the tiller is completely based on the length of the bow. John Strunk explains it very well in his chapter on the yew longbow.




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[artcher1]

I measure the widest point outside each fade..........Art

[Gordon]

I like the limbs to be stressed about equally relative to the other and the stress to be distributed equally across the length of the limbs except for the tips (which I leave a little stiff). The result being the tiller will visually appear to be off when the limbs don’t share a similar profile. Such as the case with my latest vine maple bow where the top limb has a straight profile and the bottom a deflex/reflex profile. I do favor a slightly positive tiller which means that the top limb is slightly softer (bends more) than the bottom.

[blackhawk]

To add to the stuff already mentioned I tiller for a balanced in the hand drawn bow no matter if one limb is longer,or both the same length,or differing side profile limbs like Gordon s(which was tillered perfecto IMO)...which means as you draw the bow you don't feel one limb tip towards you as you draw it...and of course every part of a working limb must share its worth of the load properly pending on design etc...you match those two and you'll get a smooth drawing shooting bow...

[Don Case]

Yes! On my tillering system the wall behind the bow is painted with with chalkboard paint. Iam able to outline the bow and visual see how the bow is bending from its original shape.(that doesn't always mean I get it right on, but close enough)

When you do this do you have some kind of clamp to make sure the bow goes back on the tree in the same position? And you would have to mark the string to make sure you're pulling from the same spot?

[Bryce]

yes. the bow is clamped center and the string is pulled the same.