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Discussion Starter #1
Did some bare shaft tuning last week...my bare shafts are hitting about 3" higher than fletched arrows. Did some checking and noticed that my timing was off a little (the bottom cam is slightly advanced)...also noticed that my ATA was slightly long, brace was slightly short and tiller was shorter on the bottom. I am thinking that a few twists in the buss cable is the answer to bringing the bow to specs and fixing the timing...my question is...will this bring the bare shafts down with the fletched? I have a perfect bullet hole thru paper (or at least as perfect as my eyes can detect!)...
 

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cam timing will surely have an effect on bare shaft tuning! hitting high should be giving you a nok low impact.
 

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Discussion Starter #3
that's correct...the bare shafts are hitting tail low. I am hoping that correcting the timing will also correct the bare shaft impact point but that may be wishful thinking. When I shorten the buss cable my nock point location will shift downward which would seem to the opposite from what most bare shaft tuning guidelines indicate. But perhaps the normal guidelines are only valid with a timed bow...not sure. Going to fool with it this evening...
 

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You may have to raise your nock point or lower your rest ever so slightly after correcting your timing. Don't get too caught up on ata and brace height, most of the time those specs are only approximate. Get your timing right first then shoot it and adjust as needed. If you are only a couple inches off on target with bare shafts it will not take much to get it perfect.
 

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One thing to do is check the bareshaft flight at various distances - at long distances, you can actually get an incorrect diagnosis. Case in point, with my genesis pro, I've been getting a slightly knock high bare shaft at my indoors distance of about 8 yards. The groups are ok, but, at 20 yards the bare shaft was in fact hitting low in about the 7 ring.

So last night I went about trying to debug it by resetting the knocking point back to 90 degs to the string (this is on my genesis pro) to establish a baseline. Still was getting a slight knock high impact on the bare shaft. However I've been noticing a "clink" on release for a while and it was still there after this adjustment. So I suspected that maybe I wasn't just hearing things, and perhaps the knocking point was actually too low causing the arrow to bounce off the rest. As an experiment, I tied down the launcher (Spot hogg prong rest) with some serving so it was solid with no spring action. The idea here is, if there is rest contact, this will really aggravate the trajectory of the arrow. Sure enough, now the bare shaft was going way knock high at my 8 yards, indicating significant rest contact. It was coming off the string knock low, bouncing off the rest and going knock high by the time it got to the target.

I dialed it out by actually lowering the rest, and sure enough I arrived at an acceptable shaft after a few turns on the elevation knob on the rest. The "clink" has gone away plus or minus a less than perfect release.

So sometimes it ain't what it appears to be lol....

LS
 

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Discussion Starter #6
So I did some adjusting last night...put 2 twists in the buss cable which corrected my tiller, timing, ATA and brace height. Looking at the arrow on the rest it was now at pretty close to 90 degrees with the string whereas before it was pointing "downhill"...so shortening the buss in effect lowered my nocking point. So i'm thinking that since my bare shafts were hitting high before that should be hitting really high now because I lowered the nocking point instead of raising it per bare shaft tuning accepted practice...NOPE...the bare shafts were still high but not bad I had still had pretty close to a bullet hole thru paper. So I lowered the arrow rest slightly and bingo...bare shafts and fletched shafts same place. Only thing I can figure is that the higher thrust on the bottom was causing bare shafts to hit high even though the arrow was pointing downward. i'm glad I went through the process...even though I probably could have lowered the rest initially I would have had an arrow pointing significantly downhill to counter the tiller/cam imbalance. Here is the final result at 20 yards:

IMG_0984.jpg
 
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