another tuning questions

[amicus]

I have heard of people tuning with one arrow. Adding/subtracting weight or playing with lenght of arrow until the arrow hits the target straight. That is how I tuned my first batch of arrows. And everything seems good. Now with all the talk of FOC and new fletching I wanted to tune up a heavier arrow. Im trying to get the best set up as possible. And I really appreciate all the knowledge that has been posted here lately on tuning. I currently shoot a bob lee 66# @ 30". Im drawing 29". My current arrows are beman 400 ICS Hunters cut to 29 3/4 with 250 grains up front. When I bare shaft these arrows they hit the target straight and maybe a little nock high. I used the same method with full lenght ICS Hunter 340 with 100 grain inserts and a 250gr point. This arrow hits the target nock left and high, which I take to be a stiff. Is this right? Am I doing anything right? Should I tune with multiple bare shafts  and fletch shafts like OL suggest? Im sorry for the ramble. I started to worry about my tuning method when the 340 was hitting left and high and I was up to 650 grains. I didnt know how to add more weight. I would like to shoot the heviest arrow I can. Any suggestions would be greatly appreciated. Thanks Gilbert

[Aggie1993]

If it is impacting nock left and you are shooting right-handed then that would indicate a weak spine.

[snag]

Too stiff if hitting left. Hitting right is weak for righthanded shooter.

[O.L. Adcock]

You guys are "mixing" 2 different methods..."grouping left" is stiff for the planning method..."Nock left" would be weak for the "kick" method. (rt handed shooter)..Pick one and don't mix them....O.L.

[amicus]

Thanks guys, This can get confusing real quick.
O.L. am I using the "kick" method? If so, what I thought to be a stiff spine is actually weak. Cutting the shaft should fix this, right? Do you perfer on method over the other?

[Diamond Paul]

Less point weight will correct weak spine as well, as long as they are not ridiculously weak.

[Dr. Ed Ashby]

I'd say to wait for OL's 'definative' reply. He understands more about tuning than I ever will.

However, if you're looking to tune the dynamic spine for an Extreme FOC arrow, I'd say to start with the point weight you want and tune by progressively shortening the shaft in small increments. Look only at your 'right-left' impact and ignore the nock's position (other than for any 'up-down' adjustments of the nocking point). Even if you normally shoot with a canted bow, this spine-tuning seems to work best when done with the bow held vertically.

If you shorten the shaft all you can and still show a weak dynamic spine, then you'll need to start all over, with a stiffer static spined shaft and the same total point weight.

Once dynamic spine is correct, fletch up some shafts and compare the point of impact with the bare shafts. I finish by comparing the grouping of fletched broadheads against the bare shafts. To date, once I had the bare shafts flying right, the fletched shafts have all shot to the same impact.

It all sound a bit harder than it really is. I've done enough of them now that it's a pretty fast and simple processs to find the correct dynamic spine for the Extreme FOC's. After I got through the initial learning curve, it's been as easy as falling off a log.

Ed
TGMM Family of the Bow

[amicus]

Dr. Ashby, thats what I would like to do. Right now my weight with the 400 bemans is around 500 grains. I would like to bump that up to 600-650. The last arrow I tried was a full lenght 340 with 100 grain insert and 250 field point and I was getting nock left. Which would mean weak spine? Since I was thinking my shaft was stiff I didn't try shorting the shaft and using the same weight. I try it when I get home. Thanks.

[Dr. Ed Ashby]

Gilbert,

One thing I should have mentioned. In the initial testing, with the shaft still very long, a way under-spined shaft (for that length) can slap the arrow plate, ending up with an impact that suggest a strong spine. Don't discount what you think SHOULD be a 'tunable' weak spine until you try shortening the shaft some. In instances where the shaft is slapping the arrow plate, shortening the shaft can often give a sudden shift from 'strong spine impact' to one that shows weak spine. From that point you can then shorten the shaft progressively until the spine is correct.

I like my final bare-shaft dynamic spine to give a slightly weak-spine impact at 40 meters (about 44 yards). Adding fletching has a slight stiffening effect on the dynamic spine. By 'slight', I mean a 'group center' impact that's about 1 1/2 to 2" right at 40 meters (for a right handed shooter).

Hope that helps,

Ed
TGMM Family of the Bow

[amicus]

ttt

[R H Clark]

amicus
before you cut that 340 just make sure that it is really weak.A nock left for a right hand shooter is showing a weak shaft.However as DR Ashby mentioned you can get a false reading if the shaft is striking the riser.

Sometimes a too stiff shaft will show weak if it is hitting the riser.Lower the point weight a little at a time as much as possible to see if it will change the nock position.If you can lower the point weight a lot and it still shows weak you have a clue to a false reading.

By lowering the point weight you are in effect stiffining the shaft.If it doesn't respond and continues to show weak or it could even show weaker,more nock left,you are probably getting a false reading and need a weaker shaft.

Hope this helps more than confuses.

[amicus]

Was hoping O.L. would respond.