Carbon spine if shorten 2" ?

[Chad R]

I have some Easton Epic 600s that are shooting pretty good with 125 grains out front, but they are a little lighter than I like.  They are 29" and I only draw 26".  Anyone have thoughts on whether shortening them to 27" would stiffen them enough to offset bumping the point weight up to 250 grains?

Thanks
CR

[bayoulongbowman]

First what poundage? bow? prob leave em 29

[LKH]

Try it, but do so with only one or two arrows and cut them off about 1/4-1/2" at a time.  Do not make the 2" leap to begin with.

Carbons can be very finicky and get stiff quickly.

[Shawn Leonard]

Lighter meaning weak in spine or light weight. If ya cut 2"s off they will stiffen a lot and ya than could add point weight and get an arrow that flies good and weighs enough that ya don't hurt the bow. What bow and poundage are ya shooting? Shawn

[Chad R]

My bow is a Great Northern Fireball 45# @ my 26" draw.  The 29" arrows with wraps and 3 5" feathers weigh 225 grains without a point screwed in.

[Chad R]

Shawn - I was meaning light in weight.  Thanks - Chad

[BigAl]

I shoot Easton Epic 600s out of my Bear 48# @ 28" (my draw length) using 125 gr. tips. They bareshafted perfectly at full length. I also wanted a heavier arrow so stuffed two lengths of .080" weadwhacker thread down the arrow. That added 80 grains of weight such that I now have a 440 grain arrow which works out to 9 gr./lb. with a good FOC. Perfect.

[Yolla Bolly]

Chad---Listen to LKH ---a little bit of length decrease gives a big increase in spine. You can also add the weight tubes, they seem to decrease the effective spine, somehow.

[WESTBROOK]

Be safe! get the weight you want, THEN shorten the arrows a little at a time till they fly right.

Eric

[Whip]

Eric just said exactly what I was thinking - bringing up point weight will affect spine as well, so do that first.  Much easier to play with than trying to add length back on to the arrows when you cut them too short!      

[JRY309]

With tuning carbons it is best not to make big changes all at one time.Carbon spine is affected more by shortening then point weight changes.I find carbons with bows not cut to or past center seem to tune alittle differently.You need to flex around the bow(the paradox) and when a carbon gets cut alittle short it will bounce off the riser.I had some CX 45/60 that were alittle short and showing stiff.So I added more point weight to weaken the spine but they got worse the more weight I added.They were bouncing off the riser and with the heavier point the were showing stiff.The bow was a longbow not cut to center.On my longows not cut to center seem to tune better if I leave the carbon arrow longer,most of my carbons are 3" longer then my draw.To add enough weight to weaken the spine and to get the total weight to where I want.This has been my experience with carbons on bows not cut to center.

[Dr. Ed Ashby]

Eric and Joe are spot-on. Get the point weight you want first, start with a full length bare shaft and progressively shorten the shaft in VERY SMALL increments until you get the correct dynamic spine. I shorten the shaft 5mm at a time - that's taking off about one-fifth of an inch each time.

Ed
TGMM Family of the Bow

[Chad R]

Thanks Everyone!  I'll take your advice and start with one arrow and take off small amounts 1/4" or so.  To do that I'll cut them off with my dremmel tool while the shaft is spinning on my home made crester.  Unless someone has a better cheap way to cut them off.  I suppose once I find the right length I can take them to an archery shop and have them cut off.  Since my arrows are already fletched I'll paper tune to find the right length for the 250 grain tips.  How does that sound?

Thanks again,
Chad

[Chad R]

Thanks Dr. Ed!  Your work really made me think I want to have a heavier arrow with more weight up front (extreme FOC) instead of adding weight to the whole shaft with weight tubes, etc.

[Dr. Ed Ashby]

Chad, my 'at the range' carbon cut-off tool is a 'miter box' I made from a 3/8"x3/8" piece of channel rod. This "V rod" is mounted to a wood base with steel-putty; in three places. The right-angle miter cut is directly above a large steel-putty mounting point, and there are steel-putty mounting points at each end of angle bar. I use a hacksaw with a Rem-Grit blade to make the cuts. A regular hack saw blade won't wirk; you need an abrasive blade. Use just the weight of the saw against the carbon shaft. If there are any lose small fibers around the cut, remove them with the finnest toothed file you have (I use the one on my Swiss Aremy Knife). The cut isn't as precise as my regular cut-off saw, but no electricity is required to run it, and it's close enough to perfect for bare shaft tuning.

Ed
TGMM Family of the Bow

[Yolla Bolly]

Dr. Ashby---What kind of adhesive do you use tuning, that allows pulling insets to cut off small increments, then re-inserting the inserts, without damaging the carbon?

[BobW]

I've read that saran wrap will hold the point inserts adequate for tuning.

[Dr. Ed Ashby]

Bruce, during initial tuning I'm only looking for the correct dynamic spine. Since I'm not starting with a set arrow length and changing tip weight, etcetera, to match arrow flight, I'm not initially trying to match bare shaft flight to that of a fletched arrow. Therefor, I am only using unfletched shafts, and do the trimming from the shaft's rear.

I start out up close, and continue to bare shaft tune until I have dynamic spine showing about an inch or so weak-spine impact at 40 meters (about 44 yards). Once I have that, I fletch some matching shafts with field points and check that point of impact coincides. So far, it always has. I then verify the tuning with fletched shafts having broadheads, against the bare shafts.

It's different from the process OL has on his web site, but he helped me work out this method, so that one can start with a predetermined tip weight and tune, rather than starting with a set shaft length and tuning. Works very very well.

Hope that explained it clearly enough,

Ed
TGMM Family of the Bow

[Yolla Bolly]

Thanks, Dr. Ashby,  your explanation is very clear.  Does this method work on the tapered Grizzley Stick shafts?

[Yolla Bolly]

Thank you, Bob. A strip wrapped around the insert, or just cover the end of the shaft and shove the insert in?