Arrow tuning question

[McDave]

I think I may have asked a similar question before, but I have never figured out why this happens.  You have two bare shafts, similar spine, point weight, etc., but either different brands or maybe one is carbon and the other one is aluminum.  One impacts unacceptably nock high, the other one is only slightly nock high.  I have had occasions where no matter where I adjusted the nock height, I get nock high, but by switching to another brand, I can adjust the nock height and eliminate the nock high.  Obviously, when that happens, I choose the one that I can adjust to eliminate the nock high, but I would like to understand why that happens.

For example, in the photos below, I selected a group of bare shafts that are close in spine to the extent that I could shoot all of them out of the same bow, by making appropriate adjustments to length or point weight.  They are a 1716, 1816, 1916, and a Gold Tip 600.  You can see from the side view that they all impact at radically different angles.  These angles were consistent over several different shots, and are not just one freak event.  From the top view, you can see that none of them are radically different in spine.  As expected, the 1716 is slightly nock left, indicating weak, and the 1916 is slightly nock right, indicating stiff.  Since I’m getting the expected reactions as I move from weaker to stiffer shafts, i don’t think I have a false weak problem.

[Crooked Stic]

3rd from the right in the bottom pic..

[McDave]

The 3rd from the right in the bottom picture is the GT 600, which is what I normally shoot from this bow. As you can see, it is pretty straight into the target whether from top view or side view.  However, I’m participating in a tournament later this month where recurve shooters are not allowed to use carbon, only aluminum or wood.  So I tried to pick a compatible aluminum arrow, which turns out to be the 1816.  It is heavier than the GT 600, so I have to adjust my trajectories, but the spine seems to be about the same.  It impacts more nock high than the GT 600, and I don’t really understand why it should.

[OkKeith]

McDave, just spit-balling here...

Nocks all fit the same on the string (none tighter or looser, same throat depth and nock diameter)? Could it be a shaft diameter thing (small diameter carbon vs larger diameter alum.)? Could it be a difference in the style, shape, construction of the insert? Could your release be slightly different with the alums?

That's an interesting phenomenon you have going on there. I have recently returned to alum. arrows as well in the search for new arrows for a new bow. They sure feel different when I shoot them than my carbons (could just be mental... probably is).

I will be very interested to see what others suggest.

OkKeith

[Hermon]

Following.  Have experienced the same thing and drives me crazy.

[The Whittler]

Are the shafts flying nock high or are you just judging how they stick in the target. I watch how the bare shaft flies not how they stick in the target.

[MnFn]

Could it be the rate at which the various shafts recover is different?

[McDave]

Are the shafts flying nock high or are you just judging how they stick in the target. I watch how the bare shaft flies not how they stick in the target.

Both, plus repeated shots where the result is the same.  This is a Rinehart target, and the arrows seem to maintain their orientation fairly well when they hit. The 1816's seem to have a nock high orientation when they leave the bow that I haven't been able to tune out, unlike the GT 600’s, that can be tuned to shoot flat.

[kenneth butler]

If you raise target to bow hand level does it lessen the nock high? >>>----> Ken

[McDave]

Here we have a different target, at bow hand level.  For this try, I shot a Victory Vap .600 spine shaft, the GT 600, and the 1816.  As you can see in the first photo, which is a side view, the VAP and the GT both impact the target pretty level, while the 1816 impacts nock high.  The GT and the 1816 have nearly identical diameter shafts, while the VAP has a much smaller diameter shaft.  In the next photo, which is a top-front view, you can see that the 1816 impacts slightly nock left, while the VAP and the GT impact almost straight on.

One might think the nock high might be related to the slight weakness of the 1816, but in the first group of arrows I shot, the 1916, which is slightly stiff, had as much of a nock high as the 1816.

Stay tuned!

[the rifleman]

I have found i have had to change nock heights for different shafts ( diameter seems to be a big factor).  Im wondering if the 1816s might be reacting with the shelf a bit differently than carbon--aluminum being a harder surface.
Just a thought-- you might try another softer rest material...
Like you, i can get multiple shafts to tune close, but it takes a lot to get one to tune near perfect with level nock height.  I generally don't worry too much about a little nock high...
Good luck.

[ozy clint]

different diameter shafts? are the larger diameter shafts worse?

[kenneth butler]

  Much better. Either of the 600's would be acceptable. Might lower your nocking point 1/32 and try again. good luck. >>>-----> Ken

[McDave]

  Much better. Either of the 600's would be acceptable. Might lower your nocking point 1/32 and try again. good luck. >>>-----> Ken

That’s a good suggestion, Ken.  I did some adjusting of the nock point earlier to try to reduce the nock high of the 1816, and think my adjustments were too large: I skipped right over the sweet spot and went from true nock high to bounce nock high.  My adjustments were about 1/8”. Following your suggestion, I moved the nock point down about 1/32” and it made a noticeable reduction of the nock high.  Actually, what I did was to tie off some serving below my regular tied on nock, so I can remove it later after the tournament and go back to the GT 600’s.  I removed my lower nock point, and will tie it on again when I figure out the best place for the upper nock point, 1/32” at a time.  Thanks!

[kenneth butler]

Glad it helped. I read your advice here all the time. You help a lot of folks including me. good luck in the tournament. >>>>-----> ken

[Jock Whisky]

I had the same issue a few years ago. A local bowyer told me to raise the brace height when all else failed. Worked for me. Maybe for you too.

[Wheels2]

Aluminum and carbons react differently even if same spine and diameter.
I find that aluminum recovers quicker and is more tolerant to spine selection.
I prefer to shoot woods, but the days of a 11/32" shaft in 79# spine are gone.  I have a friend looking for 85-90# cedars....  Good Luck!

[Crash]

Aluminum may be more spine tolerant but it does not recover quicker than carbon, slow motion video proves it.   Aluminum looks like a wet noodle coming out of the bow and again on impact with the target.

[McDave]

Not only are carbons and aluminum arrows different, but I have found that different bows react differently to the same arrows.  Normally, I have found that I can tune pretty well by making 1/16” or 1/8” adjustments in nock point, but in this case, thanks to Ken, I found that the correct nock point could only be found by making 1/32” adjustments. Maybe in the past I have had dumb luck, which ran out in this case.

[Hud]

I would suggest paper testing. If you haven't done it already tape or staple paper (newspaper, or heavier) to a open box, or wood frame, then set it 1.5 x longest arrow in front of your bale.  If your getting a high tear, you will see a round hole with the jagged tear above the hole, the direction of the tear will give you a true reading where a target will not. The round target is wound straw and has pronounced grain. Similar problems with Block, whereas an all foam target does not have a grain like layered targets. Secondly, carbons will fly different from aluminum, almost always. They will straighten out sooner, therefore stand fairly close to the paper, 5 - 10 ft.  Do you use a lot of pressure with your bottom string finger?  Are you shooting a light bow ie 35-40 lbs?  Make sure you are not causing torque on the string, consciously or not.