Limbs

[Woodely]

Who builds the lower limb shorter and why...?   I put my arrow shelf at 1 1/4" above center.

[Del the cat]

Most of the time the lower will automatically be shorter. If the arrow pass is say 1" above center and the grip is say 4" Then the lower is 2" shorter than the upper.
I've made a few with the lower limb deliberately an inch or so longer than the upper (the first was by accident) and they shoot very well... but it's all about the tiller.
Del 

[PEARL DRUMS]

Yup, its all about tiller. You can make any limb length combo work by balancing the tiller in your bow hand. That's how those wacky looking Yumi bows work so well. Balance in the tiller. 

[PatM]

Yup, its all about tiller. You can make any limb length combo work by balancing the tiller in your bow hand. That's how those wacky looking Yumi bows work so well. Balance in the tiller.

  Not so sure about that.  In slow motion  they appear to show that balanced tiller is not as big a deal as some would believe.

 The violent kicking forward of the lower limb on the loose is quite apparent.

https://www.youtube.com/watch?v=L6P2xNzqyFg

[High-Desert]

Del, it has always seemed to me the lower limb ends up longer if your arrow pass is 1” above center, your fulcrum, where the bow balances, is pretty center, but you draw the arrow slight above center, that shortens you upper limb, hence the reason the upper limb has to be slightly weaker. Let’s here why I’m wrong, my logic may have been wrong all this time.

[Del the cat]

Del, it has always seemed to me the lower limb ends up longer if your arrow pass is 1” above center, your fulcrum, where the bow balances, is pretty center, but you draw the arrow slight above center, that shortens you upper limb, hence the reason the upper limb has to be slightly weaker. Let’s here why I’m wrong, my logic may have been wrong all this time.

I'm not arguing with your logic. BUT.
That pretty much what I said... except for the wording.
" but you draw the arrow slight above center, that shortens you upper limb"
errr... No it doesn't... it doesn't change the length of the limb ... it changes the length of the string above the hand and changes the leverage/string angle on the limbs.
The actual limb length is as I described. E.G
Say 64" bow... 4" rigid grip... arrow pass 1" above center.
Lower limb is 32"-3" = 29"
Upper limb is 32"-1" = 31"
Del

[PEARL DRUMS]

Yup, its all about tiller. You can make any limb length combo work by balancing the tiller in your bow hand. That's how those wacky looking Yumi bows work so well. Balance in the tiller.

  Not so sure about that.  In slow motion  they appear to show that balanced tiller is not as big a deal as some would believe.

 The violent kicking forward of the lower limb on the loose is quite apparent.

https://www.youtube.com/watch?v=L6P2xNzqyFg

Im talking about the feel in your bow hand. Not timing of the limbs. Meaning you can draw the bow without it flipping forward or backwards out your hand.

[Dances with squirrels]

We should be careful comparing our 'relatively' straight and equal length limb bows to Yumis. Look at them unbraced... i.e. each limb's length, shape, and amount of reflex relative to the handle. Much different animal. A Yumi could never balance the way I like.

I make my bows with a slightly shorter lower limb for two main reasons.

1. It perfectly balances it in the bow hand while carrying, balances the same canting any degree, while swiveling, pointing, following moving targets. It's as effortless and natural as pointing a finger. Symmetrical bows aren't balanced like that... for me. Some folks don't notice the difference, but it screams at me.

2. It moves the bow center and static balance point upwards slightly, nearer my bow hand and string hand fulcrums. This makes it possible to dynamically balance the bow very early in the draw.... with no, or a very, very minimal sliding of the fulcrum under the bow hand during the draw.

In other words, the static balance point, bow hand fulcrum, string hand fulcrum, and dynamic balance point are all in, and stay in, exact or very close alignment... beginning to end... and I very much appreciate the effects this has on how the bow carries, points, balances and feels throughout the entire draw, feels at the shot, and affects the arrow.

It's not 'all in the tiller', as I've heard touted many times. Parts of the balancing act are determined in large part by geometry, and if it's to be addressed, needs addressed in the design/layout.

[PatM]

Yup, its all about tiller. You can make any limb length combo work by balancing the tiller in your bow hand. That's how those wacky looking Yumi bows work so well. Balance in the tiller.

  Not so sure about that.  In slow motion  they appear to show that balanced tiller is not as big a deal as some would believe.

 The violent kicking forward of the lower limb on the loose is quite apparent.

https://www.youtube.com/watch?v=L6P2xNzqyFg

Im talking about the feel in your bow hand. Not timing of the limbs. Meaning you can draw the bow without it flipping forward or backwards out your hand.

 That too.  I'm pretty sure the Yumi does roll forward in the top on the draw.   I do think that movement and feel is much less noticeably  unbalancing  on the draw than the reverse since  it fits with the natural inclination of an extended gripped hand.

 It naturally mimics the shape a pistol grip helps the hand assume.

 A bulbous grip  also seems to let movement happen without it being noticeably felt since it provides more of a pivot point without a larger flatter surface moving the wrist.

[Woodely]

For some reason I would rather not make the lower limb shorter,  if a limb breaks it's 80% of the time the lower limb,  that's why I never shoot a wood bow 3 under.  I could build the lower limb longer I guess,  something to ponder on my next build.

[Mo_coon-catcher]

2 reasons for me.
First the lower limb being 1” short means I can squat 1” lower in awkward field positions. It’s not much, but can make a difference.
The second reason is that I seem to get better balance both in the tiller tree and the hand, leading to a smoother shooting bow for me. On the tree I hang the bow from a rope on the center of the handle so it’ll pivot. With a shorter lower limb I have an easier time getting everything lined up when I hook the pull rope from where my middle finger will sit when drawing. Because I’m pulling from offset points, the bow starts with a cant, and as I pull back it’ll level out. When I have the limbs balanced I will have the back of the handle perpendicular to the direction of pull with the string angle on both limbs being equal. With then top limb longer and at the same string angle the tip will end up a bit further back than the bottom limb. With equal length limbs I have a more difficult time getting all those things matched up, even getting a bow that shoots well with the same amount of set in each limb after shooting. Typically it’ll be the handle not wanting to pivot flat even with the everything else looking good.

Kyle

[bownarra]

They carry much better.
If your 80% thing is correct then your lower limbs are over strained. You need to address this and make the strain even upper to lower. Wood can stand a certain amount of strain...it doesn't matter which limb it is in
If one limb was shorter than the other but are being drawn the same distance then simply make the shorter limb a shade wider and therefore thinner.
Thinner wood can safely bend further.
There is much more to this than just the length of the limbs!