Roskoe

One of my buddies came over today with his Mathews Switchback XT. The local archery shop (same folks who don't believe in paper tuning) had set up this bow. He couldn't get broadhead and field points to hit the same. His arrows (Vapor 4000) were marked as being for bows in the 55 to 75 lb. range.

First thing I did was check the pull weight. 51 lbs. Archery shop said it was 70. So we turned it up a little at a time until we got to 65 lbs. - a point at which he said it was the upper limit of comfortable. Then we started paper tuning. Moving the rest to the right a little at a time, we finally got to the point where the arrows were going through the paper straight. The rest was now so close to the riser (1/4") that a broadhead wouldn't clear - and the sight was maxed out as far as it would go to the right (RH shooter).

So we moved the rest back to the left until abroadhead would clear the riser. And started shootingfield point vs. broadheads. Messed around with it for about and hour, and finally got the two types ofheads shooting the same spot. The spot where this occurred was, incidently, almost exactly the same setting we started with initially.

I guess paper tuning is just a means to andend - and in this case, the bow shoots well and the field point andbroadheads hit the same spot. But what went wrong with the paper tuning here? Although I don't have any charts for the Vapor brand arrows, we were right in the middle of the range for pull weight - using 29" arrows and 100 gr. heads. Any ideas from you tuning gurus? Thx. Roskoe

TFOX

The arrow could be the culprit.It may be a spine issue or a quality issue,not sure.


Could also be excessive idler lean.


Maybe torque with the Mathews grip,they are notorious for that.


Now you can see what I say about using paper to check with and not to tune to.


I believe in paper and love using it but will not compromise centershot or tune to get a good tear.I will try to find the problem and it is usually torque or spine.

TFOX

I am thinking underspined so go back down with draw weight and see what happens.

Roskoe

Thanks, T Fox. We are pretty sure it's a spine issue. The arrows are 29" long and have 100 grain tips. This Vapor brand is one I'm not familiar with - an economy brand that they sell at the local archery shop - but if the "4000" designation is the same as Easton's spine charts for a "400" series, then it looks like the arrow may need so be a little stiffer. Torque isn't a problem for this shooter, I'm pretty sure. He shoots with an open hand a lets the bow sling catch the bow. We will have the pro shop check the idler cam. He doesn't want to go down on pull weight.

TFOX

You can still get quite a bit of torque with an open hand(especially if you hold the fingers stiff).The torque can come from too much palm in the grip.

If the arrow is a Blackhawk Vapor,the spine isprobably closer to a.440 spine which would be even more deflection.

Greg / MO

I'm curious as to a 70-lb. bow being turned all the way down to 51 lbs? I'm surprised the limb bolts didn't come out!

TFOX

Your right greg,I was wondering that to but got caught up int the question forgot to ask.[]

Roskoe

This is just one more episode from the local archery shop - the one that doesn't believe in paper tuning. They sold him the bow as a 70 lb. Mathews Switchback. All tuned up and ready to go.

We were looking at his arrows last night - I was trying to compare thespine to a known Easton arrow. Out of the three dozen arrows he got, most of them are 29". But at least seven of them are 27.5" long. Kinda makes you wonder about these folks . . . . .

I have heard of folks using the bare shaft method to determine how close an unknown arrow might be to ideal spine. Any comments?

ijimmy

For traditional archers , shooting off the shelf , with a finger release .
Cutting an inch and a half off an arrow greatly increases its spine , or bend/flexibility in other words . Put fixed broadheads on both length shafts and you will see , they hit different spots left to right , as most compound bows have cabelrod toqure , and grip toqure issues .

JOE PA

Sounds like a pretty bizarre "archery shop." FWIW, my experience with Vapor 4000 was not very positive. They could be more of a problem than the bow.