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Author Topic: limb length?  (Read 5265 times)

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Offline cryostallion

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limb length?
« on: November 10, 2010, 11:11:26 am »
hi guys, another question-
i'm sort of following the yew longbow build along in TBB 1, and can't figure out this one little detail.  it says when i'm laying out the bow, i should mark the 4" handle out thus: one line 1" above center, and one line 3" below center, thereby giving me an upper limb that is 1" longer.  for the life of me i can't figure out how the hell he gets a ONE inch longer upper limb.  any way i measure it- whether it be from the center line, the middle of the handle, or from either end of the handle- the upper limb is 2" longer.  now am i missing something here?  is this a typo? 
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Offline Josh

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Re: limb length?
« Reply #1 on: November 10, 2010, 12:41:19 pm »
if both limbs were equal length, the handle would be 2 inches above and 2 inches below the center line.  If you move the handle to 3 inches below and one inch above, you are basically shifting the 4 inch handle area down one inch giving you a one inch longer upper limb.  Does that make any sense?  Hope this helps.   :)
« Last Edit: November 10, 2010, 12:51:22 pm by Josh »
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Offline cryostallion

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Re: limb length?
« Reply #2 on: November 10, 2010, 12:52:28 pm »
makes total sense in theory!  doesn't change the fact that if you then measure from either end of your handle out to the tips you are going to have a 2" difference!  paradox!! 
thanks for confirming that i'm doing it right.  :P
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Offline Josh

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Re: limb length?
« Reply #3 on: November 10, 2010, 12:54:41 pm »
...not if you only shift the handle down one inch like you originally said.  look at the drawing above. 
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Offline Josh

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Re: limb length?
« Reply #4 on: November 10, 2010, 01:07:12 pm »
i dont see how it is a paradox but you do end up with 2 inches less bottom limb.   Lets say you have a 70" bow.  The center line divides both limbs to 35" each.  add a 4" handle area in center of bow and it brings the limbs to 33" each.  if you were to move the handle to 1" above and 3" below, i.e. shifting it down an inch, you would gain an inch for top limb (34") and lose and inch for the bottom limb (32").  That is where the 2" deficit comes from.  (Sorry I had to work it out in my head too.)  It was confusing me too.  :)
« Last Edit: November 10, 2010, 01:15:39 pm by Josh »
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Offline Josh

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Re: limb length?
« Reply #5 on: November 10, 2010, 01:17:46 pm »
I get what you were originally saying now.  Sorry.  :)
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Offline cryostallion

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Re: limb length?
« Reply #6 on: November 10, 2010, 01:18:29 pm »
here's my take on it...
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Offline Josh

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Re: limb length?
« Reply #7 on: November 10, 2010, 01:21:30 pm »
you lose an inch on bottom and gain an inch for top limb.  that's the two inch difference you are seeing.
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Offline cryostallion

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Re: limb length?
« Reply #8 on: November 10, 2010, 01:27:54 pm »
  the paradox is because you move your handle an inch to make one limb 1" longer, but you actually end up with one limb 2" longer.  i just wanted to clear this up for my own peace of mind, because i kept reading this build along and couldnt figure out why my limbs were coming out different!

-in the book it says you will end up with the upper limb 1" longer than the lower.  that's not the case.  i'm just glad that i can go back to it and know i'm not doing it wrong or differently!

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Offline Josh

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Re: limb length?
« Reply #9 on: November 10, 2010, 01:32:29 pm »
you would if your arrow pass is 1 inch above center (top of handle). if you hold the handle the arrow pass would be above the handle one inch above center... that would give you a one inch longer top limb.
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Offline Josh

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Re: limb length?
« Reply #10 on: November 10, 2010, 01:36:12 pm »
If you measure from the arrow pass not the center of the bow you would have a 1 inch limb difference if the pass was right above the handle.  :)
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Offline Josh

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Re: limb length?
« Reply #11 on: November 10, 2010, 01:54:06 pm »
last pic I promise!  ;D
« Last Edit: November 10, 2010, 02:05:46 pm by Josh »
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Offline Michael C.

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Re: limb length?
« Reply #12 on: November 10, 2010, 02:06:58 pm »
As long as when you add the bottom limb length and handle to center ie 34 + 3 = 37 and 36 + 1 = 37 your good. It is a bit confusing and I went through this same thing recently with my first asymmetrical build; I thought I forgot how to measure. The harder part for me was figuring out the tiller because one limb seemed a lot stronger than the other, just take your time though and if your lucky you won't break your first one like I did. I had mine tillered out and I thought everything was good but I didn't give a knot I had enough thickness and it pulled apart from the back. I shot two sweet arrows out of it before I gave myself a heart attack from the pop the bow made.
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Offline Cameroo

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Re: limb length?
« Reply #13 on: November 10, 2010, 02:51:54 pm »
I would say it's not a paradox, just a brain-fart on the author's part.  The top limb would be two inches longer than the lower limb.  If you actually wanted a one inch difference, you would shift the handle down half an inch.
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Offline cryostallion

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Re: limb length?
« Reply #14 on: November 10, 2010, 03:08:38 pm »
cam- not a true paradox i suppose, but for whatever reason my intuition tells me if i move the handle down one inch from center, then my top limbs gonna be an inch longer than the lower.  my brain farts too, i guess. :D

thanks for all your thoughts guys.

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Fanatical ethnic or religious or national chauvinisms are a little difficult to maintain when we see our planet as a fragile blue crescent fading to become an inconspicuous point of light against the bastion and citadel of the stars. -Carl Sagan
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