Bare Shaft Result Help

[Big Boy Blue]

I would like some advice on the following

I have been shooting now for about 3 months and I have now reached a stage were I can get consistent groups of a reasnoable size at 30M. I therefore decided it was time to have ago at tuning the bow.

The bow limbs are currently 28lb and my draw is 27inchs. Having looked at the Easton shaft selector and using Archers Advantage the spines I got and have been shooting with are 1816.

To my absolute amazement when I had a go at bare shaft tuning at 18M, the bare shafts went well to the left outside the 80cm butt. Flethced arrows group in the Gold with about a 3-4 inch group size. The bare shaft position indicates the shaft is way to stiff. I have now wound up the bow weight with the riser and I will try again tomorrow.

My question is how come the bare shafts were so far out when I was carefull to get the correct shaft in the first place ?

I have SO much to learn

Phil

Oh and I shot Right Handed

[morphymick]

28lb limbs @ 28"?
@ 27" draw, bow weight drops to 26lb.

1816 are at the stiff end of the selection range for 28" @ 28lb assuming a 28" arrow, 1813 XX75's or 1814/1912 X7's would probably be more appropriate.

If using Jazz's, then 1614/1516 would probably be better. I use 1816 Jazz 27 5/8", 30lb @ 27" draw, weight on fingers. So yours would be a bit stiff.

Which arrows are you using, and what length are they?

Increasing bow/point weight, faster string (dacron to fastflyte, less strands or lighter nocking points) or softer button would make them weaker. If using Jazz's then you are stuck with fixed point wt.

Lots of options to play with.

Good luck,

Mick

[Big Boy Blue]

Mick

I am using XX75's. Whats interesting is that Archers Advnatage has options for Inputting the arrow length and the draw length. It shows the arrow as just about in the middle of the green band certainly not to stiff. I tried putting in the weight you suggested and indeed the shaft goes to the stif end. It wound therefore suggest that the program is not taking the draw length into account as much as it should.

On another point how do you measure the weight on the fingers as I have been told that bow scales are very inaccurate.

Phil

[joetapley]

I guess you've learned the hard way that taking selection charts/programs at face value can drop you right in it. Whereas asking other other archers turns up the immediate response that 1816 is too stiff. (nudge hint to Dave about how an equipment database would be invaluable).

Best you can do is up the poundage and reduce centreshot and spring pressure as much as you can get away with - short of buying new arrows. As far as tuning goes your probably better off using a walk back approach rather than bareshaft with mismatched arrows.

[Jerry Tee]

I have just put your data into the Easton target shaft selector and come up with 1712 or 1714's. It is possible that you made a mistake with the Easton shaft selector program. If you have not selected the right type of bow in the first box then you will not get the right answer. I put your values in again but this time I selected hard cam( Compound ) and guess what it came out with? That's right 1816's. Never mind all is not lost you will definately progress to a higher draw weight and then you will need a heavier bow and stiffer arrows.

[LineCutter]

If you've overdone the spine & you're not too worried about cast then you could add weight to the points. You've probably got 7% NIBBS at the moment.
You can get inserts & screw in points that'll take you to 145gr (if you need that much) from Bowsports

[Marcus26]

Throw em out and buy the correct spine. 1816's are way too stiff for your setup. Like needing 900 ACE's and buying 720's they are that far out.
Don't try and 'fake' it with changing the plunger tension. It won't actually tune the bow to the arrows, just mask the bad flight.

[Big Boy Blue]

Jerry

I put the information into the 2005 Easton Shaft selector program which is based on 2005 data. Even with a draw weight of 26-28lb the target shafts recomended are the 1813 and the 1816 for my recurve. If you drop it dowm to 23lb then it recomends the 1716 for XX75's

I did find an old Easton chart ,dated 2001/2002 which seems to agree with what you said. So they seem to have changed the data a bit by the looks of things. The new online selector also drops out the 1813/1816 pair.

Phil

[cliveanne]

Found this in my files, don't know if it of any use to you, but a friend of mine sent it into another archery forum (Forget which one) some time ago. It is a copy of his own work.

Although this is not strickly about arrow stiffness it may be of some interest to those who advocate the use of bare shaft tuning. In 2000 I was supervising 2 PhD students, who, finding themselves with a little time on their hands, were involved in a discussion regarding the flight and mechanical characteristics of bare and fletched arrows. We decided to test a hypothesis that there was no difference between the two arrow types or the difference was minimal as advocated by coaches at the time. We mounted a Yamaha Alpha X riser with Super Ceramic Carbon Limbs to a modified steel frame previously used for testing balance recovery in subjects with long term head injury. The frame was a triangular construction of 75mm dia steel pipe , 5mm wall thickness secured to 1 cubic meter of isolated (mechanical and acoustic) concrete The frame was secured at 12 locations using 12mm bolts. The draw was achieved by the use of a linea displaced actuator secured to a free motion gimble mechanism The release mechanism for the arrow was a cartel release aid attached to a Z beam load cell (range 100 - 999 N) with a small servo motor activating the release cam. .The load cell activated the release at 18kg load (+/- 0.003 kg) with a draw speed of 0.2 meter/ sec. In order to dertmin the position of the arrow after firing a custom target was printed . The target had 72 radial lines (5 degree increments) and 30 concentric circles at 5mm intervals. This recording system would provide a two co-ordinate location system i.e. distance from the centre in mm and deviation in degrees. The entire mechanism was mounted on micrometer adjustments giving adjustment in all three cardinal planes. We began by shooting a single fletched Easton A.C.E. and aligning the mechanism untill the shot was consistantly in the centre 5mm ring (n= 50 arrows). We then carefully removed the fletchings and repeated the test shots recording the location of the unfletched arrow The unfletched arrow was consistantly 35 - 40mm at 285 degrees away from the centre. We repeated the testing again changing a single perameter on each occasion of a) button stiffness, b) botton position,c) nocking point . At each set of tests, we could not find a configureation that would put the bare shaft and the fletched shaft in the same location. We concluded that fletching an arrow changes the flight characteristics in such a way that setting up a bow with a bare shaft gave dissimular location results. If a bow was to be setup witha bare shaft, then using fletched arrows would give different results.

[gunmender]

A site i came across has some similar stuff on it

http://www.spot-hogg.com/

The newsletter pages are quite informative and although wheelie orientated are in quite depth on things, a lot of free time on their hands me thinks!

Worth a look