This may seem like a weird question, but I have been playing at bowjackson's site and found out how bad the foc is on mine and my husband's arrows. I'm going to switch to GT 3555 with 125 gr. tip and I think that is okay, but he shoots aluminum and there are a lot of variables! With the 2117 he has a stiffer spine, but the foc is only 9.4%. If he uses the 2213 the spine is listed as "C" on the charts, but his foc will be 11.1%. He shoots a 30" arrow at 55 lbs. currently a 2413 superlite with 100 gr. tips. What are your opinions?
Spine by far is more important than FOC. I'll bet dollars to donuts that alot of top shooters have no idea what their FOC is. For confirmation on this, go check out Bob Ragsdales page. He says that his son (a top shooter) has never verified his FOC yet he's still winning tournaments.
Actually come to think of it, I haven't the faintest idea what MY FOC is. I honestly don't care either. My bow seems to shoot perfectly fine and group broadheads very well.
I've heard that a FOC somewhere between 9%-15% for hunting arrows is recommended however, there is no such thing as an established perfect FOC for each setup.
L A, I think spine is more important. You can get acceptable arrow flight if the FOC is a little low. Underspined arrows will never fly well with broadheads. I don't shoot aluminums, but think spine is even more critical with them. It would seem to me a 3555 with a 125 gr head would have allot of FOC, unless they are very short.
Phil.
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Phil.
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My arrows are only 27" long, so yeah, they are pretty short! I really think maybe I read too much here on the boards and in the mags. because some people put a lot of emphasis on certain things like foc and then you three guys are like we were with really no concern about what your foc is. It makes it hard to know what is "right" or wrong. Heck, I had no idea that I should probably be shooting 2 blade broadheads instead of 3 with my setup. I think I have learned a lot, but there is always something that pops up I have no clue that I should worry about. Very frustrating!
FOC is more important in target shooting than it is in the majority of hunting applications. This due to the fact that the normal hunting shot is within 25 yards. If you get into a hunting situation where trajectory on very long shots becomes a norm (such as out west), then I would worry more about FOC. The weight at the front of the arrow is to facilitate proper flight on the downward trajectory. I could go into more detail but, I'd probably confuse you more.
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My answer would have to be that spine is most critical when dealing with the flight of fixed broadheads.
Broadheads will go crazy on a underspined shaft, because the arrow flexes so much that they spend much of the time turned sideways to the direction of movement. This allows the broadhead to begin to steer the arrow. If the arrow is too stiff, and your setup doesn't allow for a "straight ahead" release, then your arrow is going to start off flying sideways, the broadhead is catching air again, and things go downhill from there.
On the other hand, I think it's fairly uncommon for archers to end up with a completely unacceptable FOC. If you're sticking with common weight shafts in the normal cut range of 27-30", using a typical broadhead of 100-125 grains, and fletching with normal size vanes/feathers, then you're probably not TOO far from "good." I might be completely wrong with that last assumption, but I'll never know because I don't bother to calculate FOC.
Spine is probably more important, but you can't afford to totally ignore FOC. If I decided to shoot say, 75 gr broadheads on 32" aluminum arrows out of my bow, I could go with a 2020 shaft or a 2312 for extreme spread on arrow weight and be spined right, but wouldn't shoot worth a hoot.
With the 2312, using 4" vanes, the arrow would weigh 464 gr and my FOC would be 6.6%. Way too low, IMO. Going to 4" feathers would drop arrow weight to 447 gr and raise FOC to 8.5%. Still low, but better.
But that 2020 now... With vanes it would weigh 563 gr and have an FOC of 4.5%. Even with the feathers it would only make 546 gr and 6%.
The higher your FOC, the more stable the arrow is. Ever messed up and shot an arrow without a point on it? It goes hog wild. Ever thrown darts? They've got a very heavy point, so a very high FOC. Ever thrown one backwards? They almost immediately flip over, stabilize and fly point first into the dart board.
I don't doubt there's someone out there shooting very low FOC and doing just fine with well spined arrows, but anything that disrupts that arrow's stability, like a gust of wind, will throw it way off course or make it hit at an angle to it's flight path. Just like a lot of the other things that a lot of people seem to like in their hunting gear these days, it works wonderfully when everything goes right, but just one little something-or-other can go wrong and leave them scratching their head about why they missed... or worse.
If you'll notice from those numbers though, switching from vanes to feathers can raise your FOC by a point or two with little effect on spine. Reducing weight on the back end of the arrow is like adding weight to the front end. If I wanted to shoot a light arrow with a light broadhead, I'd definitely shoot feathers instead of vanes.
FOC or spine which is more important?
