FOC discussion

[snowplow]

I keep hearing that to get into the 25-30% range you're going to need light weight shafts like the GT velocity shafts or others.

I just went way down that road to see how much FOC could be obtained at 10 gpp. So I figured 550-600 grains. I wasn't too terribly worried about getting to 650 (bone breaking threshold) as I dont hunt huge crazy things. I was hoping my arrow didn't really gain any weight, just redistributed to load the tip as much as possible.

Anyhow, I found a few of viable combos:

1. GT Velocity 500 29.5" with 300 gr tip package came in at 508 gr and 26% FOC. But it took 4 shield cut 4" feathers to straighten it out. Probably doable, but not ideal.

2. GT Velocity 400 30" with 300 gr tip package came in at 541 gr at 24% FOC. Great flight.

3. GT Velocity same as above but with heavier 310 gr tip package came in at 601 gr and 26%. Also flew great.

4. Arrow Dynamics Trad Lite 29" with 226 gr tip package came in at 580 gr and 26% FOC. Shoots best of all and is almost perfectly 10 GPP for my bow.

This trad lite shaft also flies just fine with a 300 grain tip as well, which puts the total weight at 626 grains and a full 30% FOC.

It seems to me that once you reach 24-25% FOC it gets much harder to advance. And for comparison with a GT Velocity ultralite shaft I would have to run a 485 gr tip package at a whopping 718 gr for the total arrow!

I haven't heard of guys pushing the tapered shafts for high FOC. It seemed like they would be good, but much too heavy compared to the light weight shafts. I didn't plan on testing one vs the other but I just happen to have some laying there. My data shows that at least in my application I can get a considerably higher FOC with lower overall weight. And I know for a fact that the AD shafts are as tough as any I have seen. And thought they might be fine, I doubt the lightweight shafts could compare to the AD shafts that department.

Have any of you guys noticed this same thing? High FOC with a AD shaft? How about the Alaskan's (I have never had them), with their full taper it seems like even more would be able to be had.

[Rob DiStefano]

imho, don't get too hung up on foc, efoc, uefoc, or lmnop.  high foc isn't *mandatory* criteria for killing deer and other more common critters.  millions of deer have, and will continue, to fall to 8% foc wood arrows.                

that said, going efoc or uefoc is easy with carbon shafting, any carbon shafting - just bump up the front end via the adapter and/or insert & point.

imo, a more important issue is understanding carbon shaft spine values - they have a very different dynamic spine (flying off the bow) than their static spine (on a spine meter), and they will typically fly *lots* stiffer than what the meter tells ya.  that sez to just load up the front end with confidence.

and, it's best to shoot arrows that have a goodly gpp weight (start at 10gpp) when compared to the bow holding weight at full draw.  this is where tailoring the gpp by front loading a carbon (or alum) makes shooting life far more easier than with woodies.  

the final shaft weight is predicated on the shaft's gpi value - the lower that number, the lighter the shaft and the more you can up the front end weight.  a carbon's high dynamic spine will allow much a "weaker" static spine range to be used, and therefore a much lighter raw shaft.  

ad and ad lite's will both have a higher gpi than (for example) the cheap beman bowhunter shafts i use ... a 29-1/4" beman 500 static spine with 350gns up front (100gn brass insert, 125gn adapter, 125gn woodsman) yields a 585gn arrow with a uefoc of 29.31% and a 10.6 gpp that i use out of a 55# longbow.  

i really think about this stuff once, build it, test it, then use it without having to revisit all the techie details.   :cool:

[snowplow]

Thanks Rob. Did you have to build out your shelf a bunch for that shaft?

I could get close to those numbers with a .500 spine GT Velocity but finally gave up because I built my shelf out so far I barely had enough room for my shaft and was still relying on the feathers to straighten out the shaft. The point would hit good but the shaft would be flying heavily nock left the whole time.

Have you experimented  with tapered shafts?

A bid drawback is how you cant use a calculator, it seems you must have them already setup to measure since no GPI can be had.

[Rob DiStefano]

most risers are built to +1/8" off the centerline, then add in a 1/32" to 1/16" arrow plate.  i rarely see a need to change or adapt to those parameters because when i shoot carbons i know after much trial and error over the years to avoid the high static spine shafts that all the manufacturers tell me i should be using because they're far too stiff in flight for me.  who ever heard of shooting a 29-1/4" 500 spine shaft with 350gn up front?  but it works for me.  i can go up to a 400 spine or even 350 spine and make either fly straight, but for those i'm tweaking my shooting form to do something that's not natural for me.  so i just shoot beman 500's - i still have about 6 dozen left, should last my remaining lifetime, they're cheap but good.    

i know that's not giving you the reply you wanna hear, but what i'm saying is in its own way quite related to your questions.  

IF i do my part, my arrows fly like darts on a rail and with the arrow/bow spex i listed above.  that just shouldn't be true, but it is.

i've trialed lots of tapered shafts, from woodies to synthetics, they all work fine for me, but if parallels work just as well for me then i see no need spending more dollars on the tapered variety.

after years/decades observing way more than a few archers who have fits with getting any shaft material arrows to fly well for them and their bows, most of their problems are really form related, not arrow related.

i avoid those arrow calculators like the plaque i believe them to be.  yes, sometimes they're right, but sometimes they're SO wrong.  it is impossible for software to define and predict all the unique possibilities of combining humans and arrow flight.  *cant* be done - pun intended.   :cool:

terry green posted this years ago, and i'm paraphrasing - "get yerself a dozen ad's, fletch up, point up, go kill something."  he's dead on.

[katman]

snowplow, maximizing foc and keeping at 10 gpp is a good thing imo.

Rob, I believe you that for you your arrow choice flies great but I have tried 500 spine carbons and 54# bows and if they were wood they would break entering then target at such a weak angle, heck the bare shaft missed a 3.5' bale, right, at twenty yards. But we are all different. Everyone must find what works for them with spine, foc, total weight.

[snowplow]

Thanks for the comments guys.

Rob, I cant quite make what you say work but I got close. That's why I asked the nock left question a bit ago. I really wanted to make 500 shafts work (at 6.3 GPI) because 26% FOC would be a piece of cake at 10 GPP. But it seemed too light to me. My point would hit right where I wanted but the odd thing that I have never experienced was the shaft would fly nock left the whole way to the target. It wasn't form because I would do the same thing with stiffer shafts and they would fly fine. At a highish FOC they would still enter the target perfectly straight but i figured that flight was not idea. I called that too light of a spine. Would you call that too weak? It took 4 4" feathers to make that go away. That was also with a built out shelf. I had never seen an arrow bare shaft that way before. That was with 300 on the front.

In contrast the AD for instance had a higher FOC and bare shafted like bullets with 200 or 300 on the front. So I dont thing the nock left flight was due to just being a FOC setup or form. So I figured it had to be spine.

Just for clarification I wasn't using any calculator for spines if that is what you meant. Just the GT calculator that totaled component weight for a total arrow weight and then FOC %.

Rob did you measure your FOC by balancing the arrow or in a calculator such as the GT? Your numbers are a lot more generous than the calculator.

Has any of you tried getting EFOC with tapered shafts? I understand if you find the average GPI (total weight / length) it will certainly be higher than a ultralite shaft, however where that weight is concentrated matters. I wasn't going to consider an AD shaft because they were so heavy, but then when I measured one that I happen to have right there, it ended up being better than the best ultralite package that I could come up with (GT velocity 400, 300 point, 540 gr total, 24% FOC). My point is that when considering FOC I immediately considered the tapered shaft, but then immediately dismissed them because I know they are heavy. By chance I compared them (which is hard because you cant imput them in a calculator). But I was very surprised because the numbers were much better than anything else I could find. Now I am trying to figure out if others have done this, or if it is coincidental to my setup.

PS what is IMNOP?

[Rob DiStefano]

i measure foc via the arrow's physical balance point, and arrow length is is its total aerodynamic length, from nock groove to the back of the point.  

i just checked that 585gn arrow and my calc was wrong - it's actually 26.07% foc for a 29.25" arrow (nock groove to back of point) with 350gn total up front that balances exactly at 22.25" from the nock groove.  here's a pic of the actual arrow, and where i found it after i released it ...

   

... and its 17 yard flight flew straight and true and completely through this li'l piggy ...

   

... and minutes later i flew another shaft at a much smaller pig that hung around after the otheres scattered - you can see it's feet sticking up behind the bit larger pig.  i don't think it would have mattered much if the foc was 30% or 25% or 10%.      

bare shafting has its place, but when a fletched arrow consistently flies true to the mark without fishtailing or porpoising then i could care less how that bare shaft performs.

all of the above is the bottom line point i'm poorly attempting to make ... i would argue that if you have an arrow that consistently flies straight and is of at least 10gpp, there is no need to be concerned about foc.  chasing efoc or uefoc can be like a don quixote quest for chasing windmill dragons, and counterproductive to what matters most.  just get the arrow to fly straight no matter what the shaft or foc values are.          

HOWEVER, i freely admit it can be great fun to test out and build a high an foc arrow that flies true for the builder, but that's just locker room fiddling when compared to being afield and playing the game for real.

"LMNOP" is just a bad joke of sorts.  it's just my bad take on all those letters - FOC, EFOC, UEFOC - that really aren't quite that critical for going out and killing critters.     :D