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View Full Version : Where and Why?



flytier17
11-22-2008, 08:38 PM
Do you place vanes on the shaft? I have a Bitz, and fletch the industry standard distance form the nock. I've been building arrows for quite some time, yet never experimented with deviating from this standard. Physics dictate that having the flethings farthewr bach will give them more of a mechanical advantage to spin the arrow for a given FOC value. However, when the vanes are moved rearward, FOC changes as well, however minimally. Where does the shift in FOC become detrimental to the ability of the fletch to spin the arrow? Obviously this is subjective to the individual FOC values and fletching types. Also, for 3-D shooting with a light fat shaft (CXL-SS), what FOC range is desireably and why? This will dictate the tip I put on it. I am matching 30grs. of Aerovanes on the back of it.

My questions summed up in a provisionally more concise manner:

How far do I place the fletch (from the base of the nock where the shaft material ends) to optomise my FOC's relation to the fletches ability to spin and stabilize the arrow?

What FOC range will provide the flattest trajectory of the arrow while not sacrificing its stabilization properties? (bearing in mind that the fletches have NO drag and spin the arrow more intensly than any other vane)

I am looking for input particularily from experienced arrow builders/arrow tuners and 3-D shooters, though any input is welcome.

I appreciate the effort to answer my questions at any level very much.

Alec

Montalaar
11-23-2008, 02:05 AM
I cannot answer all your questions as i do not care about my FOC. Spine is much more important for me. If the arrow brings good results while french tuning and checking the flight on long distance shots.. Why even care about it.

I place my fletching around 1,5cm that is 0.6" from the bushing. I use low profile feathers with my indoor arrows and low profile vanes with my outdoor arrows. If i would place the fletching to 0 cm from the bushing i would have massice face contact. This is the optimum position for my anchor.

I have read from a shop owner that he shot his arrows with a FOC of 14% and tuned them until every arrow had the same FOC. That was some years ago. I can tell you that most people here do not care about their FOC. I think it is something you CAN think about but it does not improve your flight at all if you change your FOC from 12% to 14%

flytier17
11-23-2008, 11:56 AM
HMMMMMMM, interesting. From a physics standpoint, it makes sense that perfect balance will ultimately achieve the flattest trajectory and the least wind resistance, but a higher FOC makes it easy for a vane to spin the arrow.

I can't wait to here bfishers take on this one. He does a lot of tuning and fiddling with FOC; at least thats the impression I got.

Thanks for the reply Simon,
Alec

flytier17
11-23-2008, 11:57 AM
Hey Simon, just curious; Do you have much of a flight difference between feathers and vanes?

Montalaar
11-23-2008, 12:47 PM
I have not tried to put feathers on my ACCs or Vanes on my Eclipse so i cannot tell you anything about that. Maybe i will try that in spring when my X7 will get replaced.

bfisher
11-23-2008, 03:16 PM
So what do you want me to say? I got Bitzenberger jig some 30+ years ago when I was shooting the best arrows available to man---Easton X7 with glue-on nocks. I drew a line on my clamp so that my vanes/feathers were
1 1/2" from the groove in the nock. With my form and anchor this kept the fletching from contacting my chin. To this day I've never changed.

Honestly, you give me too much credit in the tinkering area. I do know that the farther back fletching is installed should steer the arrow better, but does 1/4" or 1/2" on a 27" shaft make that much difference? I seriously doubt it. I can't shoot that well.

I've read several of your posts where you are getting pretty anal about spine, varying the length of your arrows by as little as 1/8" to get it "just right". I used to way back when, but probably for the last 20 years I just cut my shafts 27" from nock groove to the end of the shaft. I guess this is a way of getting that perfect spine for a given length, draw length, and bow poundage, right? I don't play with arrow length. I have limb bolts on the bow and set the bow to the arrow. I never care what the bow weight ends up at.

The other reason I leave my arrows at 27" is that for years I shot a 27 1/2" draw length, then 27", and more recently 26 1/2". I'm shrinking with age. Anyway, my arrows, at 27", will fit any bow I shoot with any rest. And I change bows at least once a year and may have a half dozen rests on a bow set at different lengths. The other reason is that I found a long time ago that broadhead tipped arrows are more stable if left a little longer.

I'm sure you also have read about me bare shafting out to 35 yards. Being truthful this is very difficult to do with many of the carbon arrows today as they do not spine consistently around the shaft. I can play around and get a particular shaft to shoot just right out to, say, 25 yards. Now turn it around (180*) and it'll shoot completely different. And this is with Pro series arrows.
That's why my all-time favorite arrows are ACC's. They are just that consistent.

Now, all this being said, my rep handles Gold Tip and I'm going to try some of their new arrows this year. They are now making a 30X Pro Lite. 27/64" outside diameter and a weight of 8.4gr/in. Spine ought to be way way too stiff for my setup (27" and 50#), but I'll bet you my bow I get them to fly well. I'd almost be willing to bet I get them to bare shaft almost perfectly, too. At least out to 20 yards. Some would say it's against the laws of archery, but that' what I like to tinker with. Just to prove that the rules aren't written in stone when it comes to archery. We'll see.

flytier17
11-24-2008, 01:10 PM
Thank you, that was very informative.

I am getting CXL-SS's for my Cougar. They are built to pretty rigid specs. I wonder how accurate a bareshaft will be with them?

I turned my FMJ's during bareshaft, and they were very consistent. They group the same @ 20.

I am running into the short length problem with my arrows. My DL is growing. I cut the arrows down till they spined right, and they sit with the point 1/16 off the rest, and the rest is as far back as it will go. Now, my DL is growing, but I have no room for adjstment. And, if I overdraw into the wall with a broadhead, it hooks the rest, and pops the arrow off the string. I have to be real careful when hunting that I don't get excited and pull at the wall too hard. Next year I am replacing the 340's with 300's and cutting them longer.