Differences in foc by playing/tuning

[Shadowhntr]

As most know, Ive spent the last 3 days getting my hunting arrows just right. Out of 6, 2 wouldn't fly quite perfect to the original arrow id tuned for specs,, and through testing I found one was too stiff, and one was too weak. Not by much mind you, but I could tell flight wasnt quite perfect. Only difference between these 2 ond others outside of spine, were by chance (or was it?) they were fletched with goose feathers, which is half the weight of tame turkey feathers.

Shaft #1.....On the stiff one I added 25gr to the point via woody weight to equal 450, and left it the same length as the other 4 at 29" to get it flying perfect. Its final weight was 853gr. Best I could do......
FOC=31.47%

Shaft #2....On the weak one, I kept the same weight at 425 head weight, and trimmed 1/4" off the back of the arrow...because as luck would have it, it was slightly heavy to begin with too so a nudge in downward weight would better match the main 4. Shaft removal brought total arrow weight to 825gr. at 28 3/4" long.
FOC=30.87%

Shafts#3-6... 29 "long, 425gr head, total weight at 822gr
FOC=30.17%

[Captainkirk]

Interesting!
Those be some heavy suckers, BTW. Ashby would buy you a beer.

[Carpdaddy]

Many thanks Jason; before you came along I was probably considered the one who went to extremes. You have made me appear almost normal again.
On a serious note; man I would love to shoot some of those just to see how I liked them. I know they will do damage and I'm looking forward to seeing the results on a critter.

[Captainkirk]

Many thanks Jason; before you came along I was probably considered the one who went to extremes. You have made me appear almost normal again.
On a serious note; man I would love to shoot some of those just to see how I liked them. I know they will do damage and I'm looking forward to seeing the results on a critter.

Me too.

[Shadowhntr]

What got me, was what small changes will do. By only taking 1/4" off the back of the tapered shaft, it raised foc by 0.70% !
It wouldn't take much to have changed it a full percentage point, seeing how all i did was remove the nock taper on a 5/16 diameter shaft.
In the case of the other heavier arrow, it remained the exact same shaft, and only by adding a mere 25gr, took it from 30.17 to 31.47. Thats a 1.3% raise, and a graduation from EFOC to UEFOC....Something many believe impossible with wood!

I dont have the stats in front of me, but on a previous tapered shaft, I had pre built an arrow and measured foc before I had put a laquer finish on it. I carefully removed the hardware, finished it with 3 coats of gasket laquer and rebuilt the arrow identical as before. Just the addition of laquer changed the foc by 0.60% (to the negative )

I realize those aren't bone breaking differences in pecentages...but its interesting to me to see how little it takes to change the numbers by a half to a full percent.


Something that many who pursue foc dont think about, is the nock end of the arrow, and instead put all the attention to the point end. Even length of fletching, heaviness of its quill, bird feather type (ex. goose is 1/2 the weight of tame turkey, I suspect there is even more difference in goose and wild turkey), all can change foc more then what you would even imagine...because fletching or anything else on that end, is on the long side of the balance. Thats why I go with shorter fletching x3. Any bits of weight back there make big differences in balance point from the leverage. Thats why tapered shafts make so much foc difference with the last 9"-10" being narrowed reducing weight back there. Plus you can then use 5/16 nocks which weight 9.7gr, while standard 11/32 nocks weight 13.5gr. (Classics) All these little things add upto big changes in foc.