Don't trust the numbers, actually do the math yourself.

[KBC]

Just thought I would throw a tip out there that I just learned. I just put some new arrows together and this time instead of trusting the qSpine app numbers, I actually measured and did the math myself and found the FOC was not right in the app.

I'm not quite at the point of building my own arrows yet but I'm almost there. In the off season I'll get set up to fletch arrows but for now I just ordered this set from Black Ovis fletched and cut. I squared the ends and glued some 50 gr inserts in.

Last set was Easton 5mm Axis 29.5" long with 3 blazers, lighted nocks, stock insert, 125gr head and 10gr iron will titanium collar. 510 grains total weight and qSpine said they were 12% FOC.

New set is 5mm Axis match 29.5" long with 4 heat vanes, Easton nocks, 50gr brass insert, 125gr head an the same Iron will collars. 535 grains total weight and qSpine said 14.5% FOC.

When I measure the new arrows I get 12% FOC. I'll have to go back and measure the old ones to find the actual FOC.
Edit; the old arrows were about 10% FOC.

Maybe I used a different formula than the app is but I looked at a few and picked the one that made the most sense to me.

Sorry I'm long winded but the lesson is actually measure and do the math yourself. The app also said I would be borderline under-spined but my broad heads hit within 2" at 40 yards compared to my field points. Hell, I'm pretty happy if I can get a few field points to hit within 2" at 40 yards.

 

[Zac]

Are they consistently hitting in the same spot?

 

[KBC]

The broad heads? Yes, I will have to make some small adjustments to my bow since the BHs always hit a little right at 20, 30 and 40 but I think that's expected since I weakened the spine a bit taking a little weight off the nock end and adding some weight to the front end. It was pretty consistent with Iron Will 125 wides and 125 vented.

I'll figure that out in a few days when I get back to the range. Today I spent a bunch of time figuring out the new sight tape and getting my pins adjusted for the slightly heavier arrows. These new ones seem to fly much better. I'll edit the OP but I just measured the FOC on the old ones and they were 9.9% FOC.

 

[Mighty Mouse]

Maybe I used a different formula than the app is but I looked at a few and picked the one that made the most sense to me.

Out of curiosity, what FOC formula did you use?

 

[KBC]

I measured the entire length from the tip of the head to the back of the nock, not just to where the string sits.

Mark center
Find balance point and mark
Measure distance between the two marks
Divide measurement by arrow length
Multiply by 100

There's a few ways people measure FOC but I want to measure my whole arrow, not the arrow without point or just to the throat of the nock. Those parts are still a part of your arrow when you shoot it so this way made the most sense to me.

 

[Billy Goat]

Or you can not care what your foc is.

It's a cool number that gets thrown around a lot, I don't see a difference from 10%-18% with a hunting arrow.

 

[5MilesBack]

I'm a math guy and a tester, so I always do my own testing and math on things. I have some 30" Axis arrows and as soon as I saw you post your Qspine 12% I knew that wasn't right. But generally I ignore the FOC numbers.

 

[Mighty Mouse]

I measured the entire length from the tip of the head to the back of the nock, not just to where the string sits.

Mark center
Find balance point and mark
Measure distance between the two marks
Divide measurement by arrow length
Multiply by 100

There's a few ways people measure FOC but I want to measure my whole arrow, not the arrow without point or just to the throat of the nock. Those parts are still a part of your arrow when you shoot it so this way made the most sense to me.

The AMO standard method ignores the head. Including the length of the head will always result in a lower calculated FOC. Not that FOC has much practical significance, but including the head is likely why your numbers are coming out lower than what qSpine says.

 

[Zac]

What I'm taking from this is that you had an arrow that was spined appropriately. Then you ruined your arrow flight in order to obtain more front of center.

 

[sndmn11]

The FOC is also changed by the insert length or stacking multiple inserts in the shaft. I don't think those calculators account for those unknowns.

 

[5MilesBack]

What I'm taking from this is that you had an arrow that was spined appropriately. Then you ruined your arrow flight in order to obtain more front of center.

He added 25gr to his arrow.....I doubt he'll see any difference at all in flight, but if there is a change it wouldn't take much to tune that out.

 

[1sickLT1]

I too have found that the calculators can be off.
I built a setup recently that should have come out to about 13.5% FOC and really got 15.8%.

 

[KBC]

What I'm taking from this is that you had an arrow that was spined appropriately. Then you ruined your arrow flight in order to obtain more front of center.

Not really. The main reason I switched things up is that on my old arrows seemed to have a little flutter in the tail between 30 and 40 yards. I don’t know why they did it but I could see it or at least I think I could see it. I shot another guy’s arrow with the lower profile heat vanes and it flew great.

I wanted a 4 fletch so I had more options to nock tune them and since I shoot fixed blade heads, a little more surface area is nice since they are smaller vanes. The lighted nocks look cool but are a pain so I figured if I was getting rid of that weight I may as well try the 50 grain insert up front. I only added 25 grains total. I originally wanted to be in the 14% FOC range because I don’t know how much it matters but that is kind of the middle of the road of a lot of people who say it matters and all the guys who say it doesn’t.
Anyways, the new arrows fly great, my groups are smaller with them at all distances so I had to have done something right. I’ll just have some minor tweaking to do for BH tuning.

 

[Zac]

Not really. The main reason I switched things up is that on my old arrows seemed to have a little flutter in the tail between 30 and 40 yards. I don’t know why they did it but I could see it or at least I think I could see it. I shot another guy’s arrow with the lower profile heat vanes and it flew great.

I wanted a 4 fletch so I had more options to nock tune them and since I shoot fixed blade heads, a little more surface area is nice since they are smaller vanes. The lighted nocks look cool but are a pain so I figured if I was getting rid of that weight I may as well try the 50 grain insert up front. I only added 25 grains total. I originally wanted to be in the 14% FOC range because I don’t know how much it matters but that is kind of the middle of the road of a lot of people who say it matters and all the guys who say it doesn’t.
Anyways, the new arrows fly great, my groups are smaller with them at all distances so I had to have done something right. I’ll just have some minor tweaking to do for BH tuning.

If this is the reasoning that is fine I suppose. However the original post only mentioned that your original FOC was not what you thought it was. You don't need to try to cover this up, alot of people have been going down this road because they think it is appropriate. Your reply to me is very subjective at best. You have no real data or baseline. If your tail was fluttering it would be very easy to diagnose that through paper, bare shafting, or other various methods. Even if this was the case, what made you think it was an FOC problem? In the future you may want to utilize Archers Advantage other than some arbitrary FOC calculator.

 

[KBC]

The AMO standard method ignores the head. Including the length of the head will always result in a lower calculated FOC. Not that FOC has much practical significance, but including the head is likely why your numbers are coming out lower than what qSpine says. View attachment 307994

I will try again using this formula but it still doesn't make sense why you figure out FOC without taking into account the entire arrow. Is it just so guys can get a bigger number/measurement?

 

[KBC]

If this is the reasoning that is fine I suppose. However the original post only mentioned that your original FOC was not what you thought it was. You don't need to try to cover this up, alot of people have been going down this road because they think it is appropriate. Your reply to me is very subjective at best. You have no real data or baseline. If your tail was fluttering it would be very easy to diagnose that through paper, bare shafting, or other various methods. Even if this was the case, what made you think it was an FOC problem? In the future you may want to utilize Archers Advantage other than some arbitrary FOC calculator.

Well thanks for your permission? lol

I was trying to be less long-winded but here it goes on why I switched things up a little;
With the old arrows I got bullet holes with a bare shaft. I try and be as precise as I can so I even added electrical tape on the back end to make up for the missing weight. My BHs hit with my FPs out to 40 which was as far as I wanted to shoot last year so I didn't push them any farther.

Even with this I could see a small flutter in the tail between 30 and 40. My pin gap between 30 and 40 was a bit bigger than the 20-30 gap. I built a bow press, I built a draw board, I made sure it was timed properly and made sure there wasn't any nock pinch at full draw.

I think I might have had some slight fletching contact because the launcher on my hamskea has a little groove worn into it from the arrows which made them sit a little lower in the rest so I did have to adjust it up a little when I was getting it tuned again. I don't know for sure though because I never put lipstick on the vanes or anything.

All this and as I mentioned above I had wanted to hit about 14% FOC because it's around the middle of the range people who say it matters compared to the people who don't. I also was down to 6 arrows from the dozen I bought last year. I actually had 9 left but I shot the fletching off one(this was of course just after I had cut the fletching off of one to have a BS earlier in the day) and one arrow had damaged fletchings from the crappy targets at my range.

I played with the numbers in qSpine and although it said it would be a little weak I decided to give the new set up a shot hahaha dad jokes.... I don't trust stairs. They are always up to something....

Already mentioned, the 4 fletch for nock tuning, ditching the lighted nocks and according to qSpine hitting my 14% FOC goal.

QSpine calculates more than just FOC. Maybe I should have been more specific but the FOC doesn't seem to be what I thought it would be from that app and the spine doesn't seem to be weak like the app said it would be either.

I'm not sure what you think I'm trying to cover up and to be honest you come off a little douchey but thanks for the input. Did I add enough data? Is getting bullet holes with a bare shaft and having broad heads hit with field points out to 40 enough of a baseline? I'm not a pro by any means and obviously still learning so if you have any real input I would appreciate it.

Tonight I made a couple small adjustments to my rest and got my BHs hitting with FPs out to 50. At 60-65 they were hitting a little low but I think that would be from a little more drag. I finished the night with a 3 shot FP group around 3" at 65 yards. I think that's the best group I've ever shot at that distance so the new arrows couldn't have hurt.

 

[Zac]

Well thanks for your permission? lol

I was trying to be less long-winded but here it goes on why I switched things up a little;
With the old arrows I got bullet holes with a bare shaft. I try and be as precise as I can so I even added electrical tape on the back end to make up for the missing weight. My BHs hit with my FPs out to 40 which was as far as I wanted to shoot last year so I didn't push them any farther.

Even with this I could see a small flutter in the tail between 30 and 40. My pin gap between 30 and 40 was a bit bigger than the 20-30 gap. I built a bow press, I built a draw board, I made sure it was timed properly and made sure there wasn't any nock pinch at full draw.

I think I might have had some slight fletching contact because the launcher on my hamskea has a little groove worn into it from the arrows which made them sit a little lower in the rest so I did have to adjust it up a little when I was getting it tuned again. I don't know for sure though because I never put lipstick on the vanes or anything.

All this and as I mentioned above I had wanted to hit about 14% FOC because it's around the middle of the range people who say it matters compared to the people who don't. I also was down to 6 arrows from the dozen I bought last year. I actually had 9 left but I shot the fletching off one(this was of course just after I had cut the fletching off of one to have a BS earlier in the day) and one arrow had damaged fletchings from the crappy targets at my range.

I played with the numbers in qSpine and although it said it would be a little weak I decided to give the new set up a shot hahaha dad jokes.... I don't trust stairs. They are always up to something....

Already mentioned, the 4 fletch for nock tuning, ditching the lighted nocks and according to qSpine hitting my 14% FOC goal.

QSpine calculates more than just FOC. Maybe I should have been more specific but the FOC doesn't seem to be what I thought it would be from that app and the spine doesn't seem to be weak like the app said it would be either.

I'm not sure what you think I'm trying to cover up and to be honest you come off a little douchey but thanks for the input. Did I add enough data? Is getting bullet holes with a bare shaft and having broad heads hit with field points out to 40 enough of a baseline? I'm not a pro by any means and obviously still learning so if you have any real input I would appreciate it.

Tonight I made a couple small adjustments to my rest and got my BHs hitting with FPs out to 50. At 60-65 they were hitting a little low but I think that would be from a little more drag. I finished the night with a 3 shot FP group around 3" at 65 yards. I think that's the best group I've ever shot at that distance so the new arrows couldn't have hurt.

Yeah sounds like everything is fine. If I had to guess, the fluttering you are mentioning is simply your cock vane playing tricks on your eyes. Arrows don't just pick a random yardage to begin fluttering, and then tighten back up again once they reach 40 yards. You probably had a perfectly good set up before. However I can't criticize you for tinkering, I've dropped over a grand on 12 Valkyrie shafts with components because I got bored of what I was using previously.

 

[Metalhead12]

Are they consistently hitting in the same spot?

Yes

 

[Zac]

Yes

Broadheads consistently hitting away from the field tips.