The issue comes up often... tuning... I'm making this thread because of a classified ad thread and I feel bad enough hyjacking as much as I did. I'm not trying to be the 'expert', just a fellow hunter passing on hard learned lessons. I have in person helped folks, even members here, find their bows tune. Explaining in writing it is much harder and longer than just having the bow and doing it.
First it's not tuning the bow, it's making adjustments for optimal arrow spine on release, which then relates to optimal arrow flight and hitting square on the target for optimal penetration... example, if an arrow is overspined it will fly sideways all the way to the target, hitting sideways and losing penetration... think of an overspined arrow as a small car pulling a big trailer, going down hill the trailer tries to pass the small car getting sideways, the car doesn't weigh enough to keep the trailer straight or pull it straight without more speed.
In my experience and therefore opinion, overspine is worse for hunting and much more prone to wounding.
A friend of mine that ran dogs for bear and lion and had in the past guided rifle elk hunts, was an experienced hunter. He decided to put in for archery elk and was drawn. He asked me to call for him, plus I knew the area well. He had a new Drenalin and could shoot it well at 60 yards in camp, standing in perfect form, sometimes he'd have a flyer to the right, but if his form was perfect he shot fine... but seldom are we able to stand in perfect form to shoot at animals, plus add the mental stress of shooting at one. If your arrow isn't tuned to fly straight at any angle or position on release it could be a disaster or outright miss.
He had multiple opportunities at big bulls, one morning there were bulls screaming at each other just over a rise, I stayed back and called to the side to cover my buddy sneaking over for a shot. He comes back soon and the bulls are still right there screaming, I raise my hands up in a question on why he came back, he raises his bow and I realize he has no arrows left, he missed with every shot. Eventually he shoots a bull but in the front shoulder, is disgusted with himself and quits hunting.
Though I had been archery hunting since '84, killed 7 deer and 5 elk, thought I had put aside all the BS that is written by supposed experts and wannabe's, I truly didn't know what happens when the string is released. I was on a quest of understanding in simple terms.
So here it is, take it or leave it.
You are not tuning a bow you are tuning an arrow. There is an optimal flight for whatever arrow you nock and shoot. Every arrow flexes on release so there is an optimal flex, if you shot a concrete arrow it would flex some. With a finger bow it's side to side and needed to clear the riser, archer's paradox. With a compound and release it is up and down. Like barrel harmonics and arrow has harmonic nodes, on a gun shot the node will travel the barrel a couple times and you want the bullet leaving the muzzle when it's the calmest. I started watching super slow motion arrow videos, on release the arrow would flex and jump a couple times before it left the rest. On a compound the middle will hump up, front and back go down, then reverse, porpoising across the riser and down range, settling down. Ultimately you would want to have the arrow at level when the flechings passed the rest... this would have been much more important in the old days when we used prong rests and such.
There is no such thing as a dead straight arrow on release. Imagine there is a rock and you have a stick and you want to roll the rock with the stick. When you push on the stick to get the rock rolling it will bend until the rock rolls and as the rock gets speed the stick will bend less to keep it going... spine. Now how much it bends depends on the thickness of the stick, how long or short it is, what size rock it is pushing and how hard you push. If the stick is to thin and/or long it could break on a large rock... underspine. Underspined arrows generally stay straight at the target but are jumping up and down, often folks would say, my arrows group better farther out, well they had settled down by then. You would have to be fairly underspined to see a problem on target... the energy from the sting on the arrow at full rest during launch is violent.
There was a really good video on an overspined arrow at release over 10 years ago but I can't find it now. On release the front didn't cause enough resistance and weight to stay ahead of the back, it left the rest nock left, head right as the torque of the string even with a release forced it that way, the front could never pull it straight and it hit the target a bit sideways. Sometimes pins were set at an angle in the sight to chase the drift. But no matter what they had to lose penetration, and if on an animal the excitement or improvised shooting form would enhance the issue of drift.
One other thing before I quit the Blah Blah Blah. A guy buys a bow, has it setup at a lower poundage to start, bow shoots good but hey let's up or max the poundage... just changed spine... can't get the arrows to shoot as well now. If you are in tune and then change one of the 3 spines issues you have to change another. I'm guilty of buying different arrows but that is the most expensive chase there is, changing field tip weight is the easiest way to change spine while testing.
Paper testing in my opinion is a waste of time, with the arrowing flexing in flight I just have to move forward or backwards until the arrow isn't in a flex when passing through. It can tell you if you are overspined but so will a walkback of a couple shots after you centered the rest as much as possible and still get a drift. Some of the worst tuned bows I've had to retune were paper tuned professionally.
Bare shaft tune...
first eyeball center and level while on the rest.
Cut the vanes off 1 or 2 arrows, I like 2, use a field tip not a broadhead. first shots should be at close range, maybe 10/15 yards. Keep you eyes open to try and see arrow flight/nock. Do not be surprised to see your arrow sideways and miss the target, shoot in a safe place. It's going to be harder to see the arrow fight at close range but you should see the nock to shaft if it's really bad.
Use the closest pin only, after rest adjustments you may need to adjust that pin to keep it on the target, or just aim left or right whichever to compensate.
Go back to 20 then 30yds, I fine tune a 30.
At each level adjust your sight right or left, up and down small increments at a time. I'm looking for arrow flight, pretty soon it will just pencil down there to the naked eye, bare shaft, no fletchings to straighten it out. I like 2 or 3 bareshaft arrows to get a group, usually they will group well at 30 in a few minutes of tuning.
Shoot fletched arrows in a walkback or at 40 and 50, fine tune if needed. If you string vertically at longer ranges you may need to barely adjust the level of the arrow, if it drifts horizontally on the 20 pin at longer ranges it could be overspined.
I probably left something out but have to go fishing at Roosy soon.
Kent
