Your bow is now a 72" bow, not a 70" if you have a 27"+long limbs.

Easton shaft selector program 2011 indicates you should be using a 500 spine CarbonOne.

 

^^^

And with all due respect, I find the Easton charts off by 2 spines in many cases. My math, right or wrong, has you at 660 or 600s, assuming some tuning required.

I also had a similar question last week and received some good feedback:

http://www.archerytalk.com/vb/showthread.php?t=1671624

 

Thanks for the suggestions.

Today I did a bare shaft test at 20 yards with my GT ultralight 400's. The bare shaft would strike ~20 inches left of the fletched shafts and obviously not flying well. I repeated this many times and the results were consistent.

Does this result provide any insight into the spine of some new arrows? Right now I think the 660s or 600s would be close.

Thanks,
Matt

As a side note, today I found that by weakening my my plunger a lot I could improve the alignment between my arrow and sight. With the stiff plunger, my sight was about a 1/2 inch left of alignment with the arrow. Now with the weak plunger the arrow and the sight are roughly in alignment. Even with the week plunger, the bare shaft was still ~20 left of the fletched ones, so better, but not a good final solution.

 

I want to report my results in the hope it might help someone else looking for long arrows for a ~40# draw weight. I settled on the following setup and am able to make them tune well at 20 and 40 yards.

27" riser
long SF premium wood limbs marked 30#
my draw length is 31.25"
measured bow weight at 31.25" is 39.5#
70" 14 strand d97 string with no twists
10" brace height
nocking point +9/16"
tiller set to +1/16"
beiter plunger with medium spring set to 1.0 tension (almost all the way weak)
center shot set such that looking at tip of arrow, the arrow is one arrow width outside of center
using the plunger hole closest to the target

carbon one 660 spine shafts
shaft length is 30.25" (uncut)
nock groove to end of shaft is 30 11/16"
nock groove to tip of point is 31 5/15"
3 x 1.75" X-Vains are 12 grains total
g pin nock is 4 grains
pin bushing is 8.5 grains
stainless steel point is 110 grains

Initially the arrows tuned stiff, so I increase the bow weight to the max, used a lighter string with higher brace height, and moved the plunger to the hole closest to the target. Now, the bare shaft is just slightly weak at 20 and 40 yards (3-4" right at 40 yards) and the fletched and bare shafts fly visibly true. They are visibly much better than my old GT ultralight 400's.

Here is a picture of bare shaft tuning at 20 yards using a completely stiff plunger (matchstick instead of spring) and exactly center shot.

At Lancaster you can order these shafts individually and I only bought 4. Now, I'll buy a full dozen.

Thanks for everyones help,
Matt

 

raising your brace height will make the arrows tune more stiff not less stiff.

dropping your strands and increasing the weight is probably counteracted a lot by raising the brace to 10".

i dont think you need your arrow that far outside of center but maybe some more experienced shooters can tell you better.

if you just want things to tune better i would:
return to a more conventional brace height,
put a few twists in your string,
use more than 14 strands,
and simply use the weight and brace height adjustment to improve the tune of your arrows.

all of these tuning modifications lean towards stability.
tiny strings are usually less accurate.

i think some of the things you are doing (smaller string, no twists, front plunger hole) wont be needed if you just up the weight and dont put your brace height so high.

when you noticed the bareshafts were stiff did you change everything at once or one, single change, at a time?

nock height seems a tad high for those arrows but that may be because tiller needs adjustment (or its fine and a result of how you are pressuring the grip).

 

brace height seems high try lowering bh to 9.25 inches or 9 then try...

 

Thanks for the suggestions.

I was making one change at a time (going from 90 to 110 grain points and increasing draw weight to the max from 37# to 39.5#) and the arrows were still tuning stiff. The bare shafts were hitting left of the fletched and slanted nock right. That is when I got a little impatient and changed the string and the plunger hole together. Then the arrows were tuning just slightly weak, only hitting a few inches right and not slanted. I thought it was much better. My bow spec has a brace height range up to 9.65" and the reason I raised it to 10" was because my other string is too short for a lower brace height. I'll go back and try the 1st string and try a lower brace height.

What is normal way to set up center shot? I may not have described it correctly, but I set it up per page 8 of the following tuning guide.

http://www.hbvachilles.nl/downloads/recurvebowtuning.pdf

Also, I may be have a clearance issue. For 2 shots out of about 200, the arrow came out of the bow very badly and the bottom vane was damaged.

This seems to be a work in progress

Matt

 

you dont HAVE to be a full arrow diamter outside of center shot, its just a good place to start. you can move it in some.

if you didnt maintain your degree of centershot by adjusting your plunger when moving to the higher brace height then going to the higher brace height in effect moves your center shot.

this is where you can see the merit of finding the correct spine to begin with insted of adjusting your bow so much to fit the arrow. BUT since you have the arrows you may as well make em work carbon express medallions are in the same price range and may come in longer stock lengths..im not sure though.

..when you return to the lower brace height or go even lower than your original brace height then you will need to re adjust center shot to maintain the same amount of offset.

or better yet, move plunger in half the distance again of the arrow diameter. you will still be well outside of true center.
go to a lower brace height like suggested above, something lower than your original tune.
keep the heavier weight on your limb bolts.
if your comfortable with the smaller diamter string it WILL help i was just playing devils advocate. its up to you.
dont go overly tight with nock fit.
figure out contact issue.

thats about all i got im not advanced enough to give better advice.

 

raising your brace height will make the arrows tune more stiff not less stiff.

Exactly backwards, I'm afraid.

John

 

What is the normal brace height range for a 72" bow? Something like 8.75" to 10"?

Matt, did you buy more arrows already or do you still just have the 4 test arrows?

 

sorry if i gave bad info, matt (and others).

john (others),
now im confused.

i am a part time shooter. no where neer the level of most of the people here but i can shoot ok. i can score 270s on a 300round (and am currently reworking my form and seem to be improving)--most of my shooting is indoor as well. i shoot at 50m for fun and dont score but i can group arrows and bareshaft and tune and read whats going on.

i have never shot a bow/arrow combination where lowering the brace height made the arrow act more stiff. in my experience lowering the brace height, increases speed, increases the power stroke and makes the arrow behave less stiff.

that is, if i am shooting my bow at 9 3/4 and my arrows are tuning stiff and i cant go up in point weight, i lower the brace height and adjust the center shot in some (maintain it at the same point/string distance i had before) and the arrow is now flying straight. even without adjusting centershot (ex longbow), lowering the brace height makes the arrows bareshaft weaker. if this really isnt the case and im just crazy (im willing to accept that lol) will you or anyone else please explain to me why im observing this. there is just no way i saw this happen. last good weather i shot at 50m and was playing with things and dropping the brace height by almost an inch on my 70" bow made me have to go 25gns lighter on my point weight to keep the bareshaft flying true. decreasing the point weight by 25gns (not quite sure on the exact weight but i definitely had to lower point weight) INCREASES the dyanamic spine of the arrow, right? i am assuming i had to go lighter points (increase dynamic spine) because the 1" lower brace height made the bareshaft tune too weak.

sorry i cant edit and if i caused confusion. i was going off what i thought ive been observing and understood.

 

anyone?

 

try 780 spine with 65 grain nibb 3 inch feathers are you still in the 30 lb range of dr weight...

 

My riser lists the max brace height at 9.6 inches.

I have ordered more carbon one 660's but they are not here yet. They are on back order at Lancaster.

I would like to order the right shafts instead of trying to make my bow work with the 660s, but I can't find anything weaker that is long enough.

I haven't had a chance to try anymore changes but I'll report back if I learn anything new.

 

I didn't have much time, but I changed back to my 18 strand string and twisted it up to a brace height of 9 9/16" (max spec for my riser) and shot about 30 arrows (half fletched and half bare). The below picture is about average.

This is a 80cm face (i think) shooting at 20 yards. With this string and brace height, the bow is quieter and I didn't have any clearance issues.

Looks to me based on bare shafts consistently hitting left and nock right that the arrows are still a little bit stiff. Is this close enough?

I wish that carbon express listed their uncut shaft length on their website. I now believe that the Medallion 700 comes 31.5" uncut. If this is true and I would have know, I probably would have tried them. At 31.5" and 700 spine they would surely be weak enough and I could cut them down a little at a time to get them just right. My dozen carbon one shafts just shipped yesterday, but I could send them back and try to carbon express ones. I wonder if I could use the carbon one pin bushings, nocks and points with the medallion shafts? Would it be worth that effort?

Thanks,
Matt

 

I didn't have much time, but I changed back to my 18 strand string and twisted it up to a brace height of 9 9/16" (max spec for my riser) and shot about 30 arrows (half fletched and half bare). The below picture is about average.

View attachment 1290595

This is a 80cm face (i think) shooting at 20 yards. With this string and brace height, the bow is quieter and I didn't have any clearance issues.

Looks to me based on bare shafts consistently hitting left and nock right that the arrows are still a little bit stiff. Is this close enough?

I wish that carbon express listed their uncut shaft length on their website. I now believe that the Medallion 700 comes 31.5" uncut. If this is true and I would have know, I probably would have tried them. At 31.5" and 700 spine they would surely be weak enough and I could cut them down a little at a time to get them just right. My dozen carbon one shafts just shipped yesterday, but I could send them back and try to carbon express ones. I wonder if I could use the carbon one pin bushings, nocks and points with the medallion shafts? Would it be worth that effort?

Thanks,
Matt

I would live with that. Maybe try dumping the nock pins and pin nocks, and try an insert nock, such as the Beiter 12/2 nocks or Easton insert G nocks, the dynamic spine will be a little less stiff with less weight at the nock end of the arrow. Another way to lower the nock end weight is to switch to Spin Wings from vanes.

 

Matt,

I just had lancaster give me precise measurements on the medallion xr's the other day. here is a link to the measurements:

http://tradtalk.com/forums/showthread.php?t=32347