Arrow Flight problem

[Rock Crusher]

To start off I shoot left handed and I am shooting a Kohannah Kurve 60" long 49# @ 29". My arrows are CX Heritage 250 with 145 grains up front. Recommended brace height 7 1/4" - 7 3/4".


I was shooting the same shaft full length with 125 grains up front for awhile. They were flying nice I thought. I then found some 145 grain broadheads I wanted to try so I thought I would first see if I could get my arrows to fly with that much weight. I ended up cutting them down to 31" to get them stiff enough for that much weight but they would bare shaft nice all the way out to 20 - 25yds hitting the target almost perfectly straight. Then I started shooting the fletched ones and noticed that my arrow was wobbling in flight. Usually it was side to side but sometimes it would almost corkscrew. Not drastically but definitely noticable. So I raised by brace height one string twist at a time all the way from 7 1/4" - 8 1/4" and I can't seem to get it to go away. I messed with the nock height as well and even added an extra nock ring under the arrow so that the arrow couldn't slide down the string and then bounce off of the shelf.  I then went back and shot the full length arrows with 125 grains and they flew a lot better. But when I cut the feathers off of them and bare shafted them they appeared to be spined way to weak? So far nothing seems to work. I'm out of ideas and getting discouraged so any ideas and help would be greatly appreciated. Thanks RC

[Igor]

I'd have to say you should be shooting 150's with that bow and 145 grain heads. According to the spine calculator cut to 30" with 145 grain head would get you real close or you can stay with the same shaft but you'll have to use a 175 grain head and the length will be somewhere between 31.5 and 31" (I didn't know what the riser cut is on your Kohannah but that should be close)

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Glenn

[Rock Crusher]

How come then does the bare shaft fly so well? I obviously have a lot to learn on this spine thing. Thanks for the help I'll try it out.

[Steve B.]

You say you cut the shafts down to get them stiff enough for the 145's.  So you noticed a big difference in your arrow flight just by going up 20 grns. in point weight?  Is this a centershot bow?
They bareshafted nice out to 25 yds.?  The 145's that were cut to 31"?

They hit perfectly straight?  When the bareshafts don't hit perfectly straight are you calling those improperly spined?

Which system are you using to determine proper spine?  What flight indications?

You cut the feathers off and bare shafted them?  The 125's, or the 145's?

[Rock Crusher]

I went from full length 250s with 125grain heads to 31" 250s with 145 grain heads.  So not only did I add weight I also shortened the arrow about 2". I bare shafted them both and the full length ones with 125 grain heads wouldn't hardly hit the target at 25 yards and the 31" with 145 grain heads would hit almost perfectly straight. Wether they hit straight or not is the only thing I am going by to tell the correct spine. How else do you tell? My bow is cut a little past center I don't remeber right off how much but it is cut past center. Thanks RC

[Steve B.]

First, you should have just screwed in the 145's and tested them compared to the 125's, without cutting.  20 grn increase in point weight is not much and should not need a spine change especially with a centershot bow.
Not being able to hit the target with 125's is definately an indication of a problem but the other arrows hitting it straight is not how you bareshaft tune.
You get two sets of arrows that are identical except one set has no feathers.  You shoot all the arrows and compared where the groups hit in relation to each other and then adjust the dynamic spine until they hit in the same area.  There is more and better details on O.L. Adcock's website.

I'm betting the change in point weight is negligible and the shortening of the arrow shaft is what is making your 145's fly more true, either because of the stiffening affect or some affect caused by the lack of extreme overhang of your shaft past your bow.

I have a finicky flatbow that shoots much better with short arrows....??