Carbon Tuning "Easy?" Well....

[J. Clabaugh]

I've been shooting some Cabelas SST 240's and have discovered that they are apparently too weak of a spine in how I have them set up.

31", Cap Wraps, 250 gr. heads.

Originally, was shooting some Cabelas Maverick 220's.
30", 125 gr. heads. -not much in overall, combined arrow weight.

I'm using a Bear Montana Longbow, 55# @28". I have a 29" draw.

The nocks were very, very tight, and were causing some "crazy" inconsistant arrow flight. I've filed them ope to where I can make them drop off the string with a slight rap.

After, the consistency improved dramatically. Now, through paper-tuning, the arrows show weak spine. It improves, somewhat, by using the 125 gr. heads instead of the 250's.

I went to the SST 220's because I wanted to increase FOC and head weight. The spine charts available from Cabelas at the time of purchase originally made me concerned that I was risking too stiff a spine.

So, from the info I've got here, and from undoubtedly much more experience that most of you beyond my own with set-ups and tuning, would you confirm/agree that I need to increase spine? If so, how much of an impact does shortening "skinny" carbons by one inch have? I don't remember the weight of the SST 240'S. (Also have never put my bow on a scale- so don't know if it's pulling at the poundage marked).

I'm going to make the investment in the near future of getting some of the Three Rivers Test Kits. I figure to give the mfx Carbons a go first, then wood, then aluminum. I thought of trying out the Grizzly Stick Alaskans- but right now cost is prohibitive.

Again- advice? Opinions? Similar experiences?

Thanks!!!!!!!!!!!!!!

[BigJim]

If you can cut the shafts any, it will make a dramatic change. Very few things make as much of an impact as shortening the arrow.
As far as the arrow go, I am not experienced with the brands mentioned. I would look into the arrow dynamics before buying the Grizzly sticks. Much more consistent and less expensive.
There are a few carbons out there that won't break the bank and still give you a quality shaft.
thanks, bigjim

[Andy Cooper]

What sort of increments should the shafts be cut at, if they can be? 1/4", 1/2"??

[machomanandysavage]

You should cut them 1/4" at a time.

[JimB]

The carbons I have aren't real skinny but chabging an inch could equal 18-25 grs of point weight or roughly 5# of spine.I'm sure every setup would be different.Don't go cutting an inch off though.I think the 1/4" advice is good.I play a lot with different point weights and even fine tune with 1,2 or 3,5gr weight washers before I do any cutting.That gives me a better feel for what I need.

Take the time to read the tuning information on bowmaker.net

[Andy Cooper]

Here\\'s the link!

[Bowwild]

Changing arrow length has much more impact than simply changing the weight of the total shaft.  Length changes moves bending characteristics (actual spine) of the shaft.

I get terrific results with Beeman MFX Carbons.  However, my set-up is dramatically different from yours.

[chopx2]

Originally posted by Bowwild:
Changing arrow length has much more impact than simply changing the weight of the total shaft.  Length changes moves bending characteristics (actual spine) of the shaft.
 

I would add that MY PERSONAL & UNPROVEN experience with EFOC carbons it that you need to keep all the point weight in front of the riser so I would keep a minimum of an 1-1.5" depending on insert length sticking out. It seems to ME that when I pull the carbon shaft portion including 100gr insert to the shelf it doesn't paralax correctly. I think it's because that last 1-1.25" of shaft is ultra stiff.

Again seems to me. My FOC is over 30%.

[chopx2]

You can also build out your side plate with a toothpick or thicker leather and see if that improves flight. If it improves flight then I would try cutting 1/4" at a time. Might need a little of both to make them fly.

Going to skinnier shafts will only make the weak spine problem worse.

[J. Clabaugh]

Wow- great feedback and advice all- thank you!!!!

These are the old Poltruded (sp?) shafts that have outserts, instead of inserts. I just measured diameter of the SST 240's and they measured 1/4"- pretty "skinny."    

Chop, I did try a toothpick taped to the side plate, and flight improved. Still much better with the 125 gr. heads than the 250's. I can take off a total of about one inch and still keep the point weight ahead of the riser due to the outserts.

Jim, thanks for those figures on an inch at a time results. Thanks for the website reference- I'll take a look at it in a few minutes.

BigJim- Thanks for the suggestion on Arrow Dynamics- I'll look them up. Suggestions on the best site/web address to do so?

Don't know how I'll proceed with trying to cut the shafts though. I don't currently have access to a high speed saw as typically recommended for cutting carbons, nor a dremel. I have a broken shaft out of the Maverick 220's though (a doe rolled over on it and broke of a portion of the arrow). I could try experimenting with some "creative" methods of making the cuts. Any suggestions?

Side Note- I pointed out to my daughters the kind of responses you gave, and the wide spread of points in the country that we're all located. It's encouraging to them, and I think this example is good for any of us, to see that there's still a lot of good in the world in the midst of the bad.

Again, thanks all. I greatly appreciate the help!
Jeff

[Andy Cooper]

Side Note- I pointed out to my daughters the kind of responses you gave, and the wide spread of points in the country that we're all located. It's encouraging to them, and I think this example is good for any of us, to see that there's still a lot of good in the world in the midst of the bad.

The posters here have better manners and are more considerate than than are the posters on many of the Bible study boards I frequent. FWIW

[chopx2]

Jeff,

Those are very skinny shafts. You could probably improve your spine issues with a 5/16" carbon shaft (the most common size). The ADs Jim recommends would probably be even better for that. These larger diameter shafts will shift the arrow left like the toothpick (if you are RH) making it act much stiffer even at the same spine.

For example I use 350 spine 5/16" shafts and they fly fine. If I go to a 340 spine (slightly stiffer) Beman MFX with the small diamter shaft my arrows act a little weak spined because it is closer to centershot.

I'm sure you can find someone on here near you who'd be willing to help or even let you try their shafts to see how they work.

You could also try bareshaft tuning or bareshaft planing to see if that confirms your paper results.

I just hate to cut arrows until I am absolutely sure...have about 3 dozen arrows sitting in the corner that'll never get used...lol

[mahantango]

Carbon shafts are not that hard to cut. An abrasive wheel in a Dremel, Abrasive/carborundum blade, or diamond blade in a cut-off saw or miter saw all will work fine depending on what you have available. I usually wrap the shafts w/ masking tape before cutting, and avoid breathing the dust!

[J. Clabaugh]

Again, thanks Chop. I'll play with them some more before cutting them down. (Lighter heads/building up the strike plate). I'm not sure I'll be able to save the outserts, and I'm not sure how many spares I have. (Glued the originals on with epoxy).

I found that 3-rivers has Arrow Dynamics test kits. I'll probably order one of those and see what may work best, Then again, this might be the opportunity to test out woods and aluminums as well!

Mahantango, thanks for the advice- I may be able to go with your idea re: the miter saw.

Jeff

[bucksdown]

j i started out using carbons when they first came out, back when they wouln't let em compete with them. something that worked great for me was a fine toothed file. make circle around them and file a little at a time. you won't come out with a flush cut, but you won't have spilnters the way the wrong cutting blabe will leave.