Limb Length

[bow101]

I place the arrow pass or shelf always 1 1/4" above center.   Would it be better if the Bottom limb was longer or shorter, for shooting 3 under.  I know I have read this one before somewhere.

[bubby]

I don't know about limb length but positive tiller is needed for 3 under

[PEARL DRUMS]

Only answer I can give is that I've seen plenty of 3 under bows that developed weak bottom limbs relatively quickly. I cant say the same for split finger bows, I've seen very few move. Maybe more important than limb length is tiller, as bub pointed out.

[bow101]

I hear ya, so make the positive tiller about 1/4"...?  I have seen a few bows on here that have unequal length limbs, was wondering why..?

[Del the cat]

One of my sweetest bows was made on the fly at a festival with no real measurements. It was just tillered to shoot, the next week I tuned it up and finished it... lovely bow, only about 35# but fast, no set and sweet as a nut.
I never really looked hard at it until one day I wanted to make a slightly heavier scaled up version.
It turned out the lower working limb was 3" longer than the upper!
The conclusion?... It doesn't matter a tinkers cuss... it all about how it's tillered.
There's a lot to be said for having the working limbs the same length, and it's up to you how much stuff you have in-between 'em
Del
BTW, I made the scaled up version with the working limbs identical length and that's a great bow too.

[Dances with squirrels]

The bows that balance best throughout the entire draw are those whose longitudinal center, string fulcrum, and dynamic balance point all line up. This is achieved by way of design(laying out bow center to suit the shooter's fulcrum) and balancing relative limb strength through tillering. When accomplished, there is no shifting from the static balance point(where it balances at brace) to the dynamic balance point at full draw. These are the sweetest drawing and shooting bows, and are quite inherently tuned... and this can be predictably done.


An asymmetrical bow exactly as you described, with the shelf 1 1/4" above bow center is a perfect layout for many 3 under shooters... assuming a 4" handle and average size hands applying even pressure because the string fulcrum is also at the 1 1/4" mark. The limbs then, if tillered/timed so the arrow nock comes straight back, will be harmonized while showing an even tiller as a result, and putting the dynamic fulcrum as well, at the 1 1/4" mark.... generally speaking.

[Badger]

  I have always felt the arrow should come straight back if drawn where the arrow mounts on the string but not necessarily when drawn. Regardless of how you draw the bow the bow will always return with the arrow holding the string back. It forgets all about how you drew it.

[BowEd]

bow101....Many good points made here.....Assuming your talking about durability then accuracy gets touched on here too.Tillering is the key here I think.Making bows over time will reveal this.I have always been pleased with how a bow feels and shoots when on the tillering tree while pulling the bow to full draw the point at where my hook of my poundage tester is the hook on the string travels in a straight line downward.That point is always close to where my fingers will pull when drawing and assume the arrow nock point will go in a straight line too right back to where I started drawing.The tips of the bow travel exactly even across from each other then every time.
My arrow passes are 1.5 to 1.75 above center of handle more so yet than yours but I don't really think it'll be much different.To me the bow shoots good at even, 1/8' or 1/4" positive tiller then with even length limbs.That's just shooting it 2 fingers under and one over but my one over is mostly just along for the ride.The two below do all the work.
If I shot 3 fingers under myself I would make the top limb longer.How much needs to be experimented with.With yours I'd try 1.25" longer.Just my two cents worth.I don't shoot 3 fingers under because sometimes an arrow nock fits too loose for me to trust[self nocks] and dry firing are no good for a bow......lol.

[Emmet]

I'm curious about people claiming to have the lower limb a little stiff when shooting 3 under.
I get the opposite results for some reason. I set the center of the bow as the pressure point on my hand. The arrow pass as close to that as I can get it, maybe 1" above center.
Even tiller and knock point usually shoots best square to the string. 3 finger under release. Anchor with the middle finger in the corner of my mouth, putting the arrow right below the eye.
 I've had the top limb get weak after shooting a few 1oo arrows and required re tillering the bottom to get it back to even. Never had  the bottom weaken.
Could the bottom limb be weakened from gripping and healing the bow with a high anchor.
Just trying to understand why, not trying to get off topic.

[Dances with squirrels]

The bottom limb more often gets weaker over time on symmetrical bows that are tillered positive, but it can happen sometimes on asymmetrical bows too. Depends on how far we pushed its limits, and how well it's tillered. A bow whose bottom limb gets weaker for no other good reason is trying to show us that relative limb balance is off.

Emmet, the 'relative' part of limb balance is indeed relative to the shooter's idioms, like healing the grip... among lots of other things. When a bow's limbs are fine throughout tillering, but then one of them gets weaker the more we shoot it, we're probably shooting it differently than we tillered it for. For instance, I see a lot of folks tiller symmetrical bows by pulling them at the center of the handle, and then when they shoot them, the pull the string 2" higher. That's a huge difference and can make the bottom limb lose strength over time.

[ryder]

I don't think having an 'ideal' limb length ratio is anywhere near as important as having the correct tiller for whatever design/ratios you use.

The Japanese were apparently not to worried about keeping things even, it worked out pretty well for them.

[Badger]

The bottom limb more often gets weaker over time on symmetrical bows that are tillered positive, but it can happen sometimes on asymmetrical bows too. Depends on how far we pushed its limits, and how well it's tillered. A bow whose bottom limb gets weaker for no other good reason is trying to show us that relative limb balance is off.

Emmet, the 'relative' part of limb balance is indeed relative to the shooter's idioms, like healing the grip... among lots of other things. When a bow's limbs are fine throughout tillering, but then one of them gets weaker the more we shoot it, we're probably shooting it differently than we tillered it for. For instance, I see a lot of folks tiller symmetrical bows by pulling them at the center of the handle, and then when they shoot them, the pull the string 2" higher. That's a huge difference and can make the bottom limb lose strength over time.

  Why would you tiller a bow based on how you pull it? We let go of the string when we shoot it so it should be tillered for wear the arrow sits, it instantly forgets where you lulled it.

[Dances with squirrels]

They weren't worried about keeping them even, as in equal length, but the great asymmetry means they have to concern themselves with other ways to achieve limb harmony, or suffer the same consequences we do. And like our bows, some Yumis are designed and/or tillered better or worse than others.

[Dances with squirrels]

Steve, with all due respect, we've had this discussion many times and I've told you each time why I don't believe your arrow theory. You'll have to kick that off with some proof one of these days 

[bow101]

bow101....Many good points made here.....Assuming your talking about durability then accuracy gets touched on here too.Tillering is the key here I think.Making bows over time will reveal this.I have always been pleased with how a bow feels and shoots when on the tillering tree while pulling the bow to full draw the point at where my hook of my poundage tester is the hook on the string travels in a straight line downward.That point is always close to where my fingers will pull when drawing and assume the arrow nock point will go in a straight line too right back to where I started drawing.The tips of the bow travel exactly even across from each other then every time.
My arrow passes are 1.5 to 1.75 above center of handle more so yet than yours but I don't really think it'll be much different.To me the bow shoots good at even, 1/8' or 1/4" positive tiller then with even length limbs.That's just shooting it 2 fingers under and one over but my one over is mostly just along for the ride.The two below do all the work.
If I shot 3 fingers under myself I would make the top limb longer.How much needs to be experimented with.With yours I'd try 1.25" longer.Just my two cents worth.I don't shoot 3 fingers under because sometimes an arrow nock fits too loose for me to trust[self nocks] and dry firing are no good for a bow......lol.

A lot of good points no doubt.  I have been shooting 3 under now for about 3 months and accuracy has improved, shooting split is off and on.

"I don't shoot 3 fingers under because sometimes an arrow nock fits too loose for me to trust[self nocks] and dry firing are no good for a bow......lol. "   Tighten the nock fit.