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Discussion Starter #1
When I bought my Bowtech Old Glory last year I picked up a dozen Gold Tip Pro Hunters to go with it. I just downloaded the trial version of Pinwheel software and I think I'm seriously underspined. What are the down falls of an underspined shaft?

The particular of my set up are:

Bow:
05 Bowtech Old Glory
31" draw w/ loop
70 lbs
80% letoff

Arrows:
Gold Tip Pro Hunter Black 5575
31" carbon length
Standard GT insert and nock
85 grain tips

Thanks for your help,

Ron
 

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I just corrected a spine issue with that software.
I was using 75 gr. tips on 25" Carbon Express Predator 200s (= 500 spine) at the suggestion of the pro shop. I was getting 283 fps with these, which is pretty good for 60lb/27.5 draw.

The problem was that I couldn't get real good groups or consistancy. (Usually off to the left.)
When I plugged my info into the software, it told me I was overspined.
When I entered 85 gr. tips instead, it put me in the 'green' spine area.
I switched to the 85 gr. tips and Presto! Instant improved grouping and accuracy.
I was surprised at how much difference 10 grains made.

It's opposite of what you're dealing with, but the point is that a little bit off on the spine can make a definite difference.
 

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yes you are a lil underspined but not dangerously. I have a 31" draw with a wrist release and shoot my huntin rig in the 63-65ish lb range and own and have shot both 5575 and 7595 with inserts and 100 gr heads, they both fly fine and not much POA difference out to 30 yds. With light 85 gr heads I think you'll be OK. If you are using a mechanical with most rest set ups you should be able to cut the arrows down to 30" or a lil less also. If you were shooting a real heavy head that would be another story.
 

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Discussion Starter #4
I'm using a Golden Key TKO drop away rest.

My arrows weigh about 385 grains with tips installed.

Thanks,

Ron
 

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You are going to be underspined with that setup, but there are a few things you can do to try and stiffen them up a little. Keep the 85 grain points and add a wrap to the back and maybe try a heavier vane to add a little more weight back there to. Also, draw an arrow back and see how much you may can trim off of the arrows. Then use the shaft selector program and type in some different arrow lengths and wrap and vane combinations and see what is gonna get you close to the correct spine. Hope this helps.
Kody
 

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>>What are the down falls of an underspined shaft?

Probably have grouping problems...especially if you're trying to get broadheads and field points to shoot together.
 

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Discussion Starter #7
Yep, that's what I'm seeing. I pulled a couple, well 3, of my old carbon express CX400's out of mothballs and shot them at 20 yards. They were close enough for the feathers on all 3 to be touching one another. Shot the next group with my new arrows and saying that they were a 3" group would be generous.

The arrows only over hang the rest by about 1/2" at full draw so I'd be afraid of cutting them any shorter.

I'm so glad I found this site. No way I would have known what was going on otherwise. Anybody need a slightly used dozen 5575 GT Pro Hunters?

Thanks for the help guys!!

Ron
 

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I know this is not the norm but I always end up going a little underspined according to charts, etc. So if they fly and group that's what matters, not what a chart or program tells you. They are just a guide or starting point:)

Too many think it is best to go over spined and that is just not true in most cases:)
 

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Ron Meadows said:
Yep, that's what I'm seeing. I pulled a couple, well 3, of my old carbon express CX400's out of mothballs and shot them at 20 yards. They were close enough for the feathers on all 3 to be touching one another. Shot the next group with my new arrows and saying that they were a 3" group would be generous.

The arrows only over hang the rest by about 1/2" at full draw so I'd be afraid of cutting them any shorter.

I'm so glad I found this site. No way I would have known what was going on otherwise. Anybody need a slightly used dozen 5575 GT Pro Hunters?

Thanks for the help guys!!

Ron
Read Easton Tuning Guide on arrow dispersion. An underspined arrow will not have as tight of a groupings as a properly spine arrow at close distances. A stiff arrow will have good close range accuracy but the grouping will widen more over distances more than an underspined or properly spined arrow. The stiff arrow will show variations of release more.

So for the widest range of shooting you want to use a properly spined arrow. I you are primarily shooting close ranges then in my opinion a slightly over spined arrow might be a little better.

The reason for this is the amount of cycling an arrow does on release. The weaker it is the more cycling in will do and the longer distance it will take for this to happen. The properly spine arrow will be the most forgiving of a slight release variation because it cycles some and averages out the final heading better.
 

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Discussion Starter #10
That makes sense. These things are shooting all over the place at 20 yards. I put them away for good this afternoon. I was beginning to think that something was wrong with my bow then I remembered that I'd changed arrows for this season.

I guess the most obvious question for me is how can a so called "pro shop" sell me arrows that fall off the bottom of the chart for spine with my draw length and poundage. I took one of my CX400's in with me when I bought the bow and was assured that these were fine.

Oh well, at least now I have ArcheryTalk to help me keep my stuff fixed up. I'm going to have to join the ranks of those who work on their own setups I guess.

Thanks again,

Ron
 

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Ron Meadows said:
That makes sense. These things are shooting all over the place at 20 yards. I put them away for good this afternoon. I was beginning to think that something was wrong with my bow then I remembered that I'd changed arrows for this season.

I guess the most obvious question for me is how can a so called "pro shop" sell me arrows that fall off the bottom of the chart for spine with my draw length and poundage. I took one of my CX400's in with me when I bought the bow and was assured that these were fine.

Oh well, at least now I have ArcheryTalk to help me keep my stuff fixed up. I'm going to have to join the ranks of those who work on their own setups I guess.

Thanks again,

Ron
I have had the problem of underspined arrows before. A slightly underspined arrow will make you play head games with your form and equipment. You keep moving sights or change things which really are not the problem.

There are a lot of variables which an archery needs to be aware off in arrow selection. Since, I have had this problem, I have learned to use On Target and always have the numbers right before I start cutting.

Many archers have got caught up in the speed game. They think the most improtant thing is to get the lightest arrow and shoot it at the peak poundage of the bow for max speed. In actuality, the arrow and bow need to be tuned together to work as a team. IMO, the best way to achieve this is to find a arrow setup which is properly spined for your bow at about the middle of the draw weight poundage of the bow. Then adjust your limb bolts to achieve the best flight.

On Target is available as a trial download from pinwheelsoftware.com. It takes into consideration may variables which are not available in any chart. Where or not you use a wrap, what let-off percentage you are using, fletching weight effects, etc. It will probably be the best investment in money and time an archer can spend to achieve better results.
 
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