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spine - need help!

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DC:
Maybe even more digression. When I started I could pull 40#@27". I figured that I would make each bow a little heavier and then my strength would build. After about a year and maybe 15-16 bows I took a picture for a bow I was posting. There was a lot of arrow sticking past the handle. I measured my draw length with a marked arrow and found that my draw length had dropped 2" so now my bows were 45#@28"  but I was only drawing to about 25". That equalled about 40#. My muscles were smarter than my brain. Still the same anchor point but my bow arm was swinging to the right just enough to limit my pull to 40#.

bownarra:

--- Quote from: stuckinthemud on April 11, 2020, 04:44:44 pm ---Slight digression but I cant reliably get my draw length locked in,  as I tire my draw shortens slightly, how do you keep your draw length dialed in with longish arrows?

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Can't means won't! Put a wrap of tape around the shaft and practise. It should be more about feel than some draw check anyway.

willie:

--- Quote from: stuckinthemud on April 11, 2020, 04:44:44 pm ---Slight digression but I cant reliably get my draw length locked in,  as I tire my draw shortens slightly, how do you keep your draw length dialed in with longish arrows?

--- End quote ---

use a clicker in practice sessions to help develop muscle memory?

Todd Mathis:

--- Quote from: stuckinthemud on April 11, 2020, 12:43:46 pm ---To avoid hijacking a thread, I'll post my question here. I have good Welsh legs, that is to say at 5'6" I am blessed with shortness! I draw 24" and my preferred draw weight is around 35#.  The arrows I have fletched so far have had sharpened tips, re-enforced with a triangle of bone or antler, so super-light-weight, and fine against targets - no hunting in the UK.  So, how would I calculate the spine for that - a 24" barrelled shaft with 2" feathers and a 1/2cm triangle of antler inserted in a sharpened tip bound with cotton soaked in ca  let into a shallow rebate (rabbet) ? I usually shoot elb

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I am a bamboo arrow maker, so there may be issues involved with other wood shafts which may alter this, but here is what I would tell you.  If I understand you, you draw a 35 pound bow.  Your draw length is 24 inches.  There is nothing that says you have to shoot an arrow the same size as your draw.  You might consider a 26 or 27 inch arrow.  If you shoot an arrow shaft which has a deflection of 35 pounds, then I assume this was done on a spine tester, which is normally measureing a 26 inch length.  Since it is unlikely to be easy to measure a 26 inch shaft on a 26 inch spaced spine tester, I will assume you might be slightly longer then that. 
The comment that your are not shooting a head which is light needs to be clarified.  Just how heavy (in grains) is the head?  If the balance points (FOC) are reasonable...anything above 10% would certainly qualify...then the comment by DC is an excellent one.  My suspicion is that your are shooting an arrow with a static spine of one number, but whatever that number is, YOUR DYNAMIC SPINE will probably be higher.  At least this is what I suspect.
Here is what I think I know.  You shoot a bow which is rated at 35 lbs @ 28 inches.  If that's correct, then you are shooting perhaps a 28 - 30 pound spine..  Have you ever measured the static spine of these arrows on a good spine tester?
This is an interesting question.   Here is what I want to know...
1-what are your arrows spined at?   What is the spine tester which is used?  Is it for traditional arrows on a 26 inch length or is it one of those spine testers designed for carbon arrows which use a different length?

2-What is the actual draw weight of your bow at 24 inches, and at 26 inches?  (this can be done at any bow shop)

3- what is the weight (in grains) of your arrows, and as a seperate number, what is the weight of your bone/antler tip? 

4- lastly, when you shoot these at 20 yards, where and how tightly do they group.  If you give me that info, I can give you a better opinion.
Great question...too many unknowns....Best of luck!

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