Author Topic: FOC question (Read 1933 times)

O.L. Adcock · « **Reply #20 on:** February 06, 2009, 08:56:00 PM »

Dave, "or it's weighted heavily up front so that's on contat it's "pulling" a straight chain, rather than "pushing" a chain that collapses on impact."

That's exactly it. If we put a sudden force on the back end, it bends and we call it pardox. But all we are rubbing against is air..Put a sudden force on the front it..It bends again but now we're rubbing meat and bone. More weight up front increases the bend during the shot but decreases it during the hit. The best shaft would be very stiff but weigh nothing!

....O.L.

Schultzy · « **Reply #21 on:** February 06, 2009, 11:46:00 PM »

Yes 100% would be better but 95% Isn't so bad either.

I know what your saying though and that's why I said I'm going to up my FOC on my 2216 shafts this summer.

Adcock, you've been very knowledgeable In this discussion and I thank you for that. I learned a few things today with this FOC stuff, much appreciated!!

Nope, I can't make It to the P&Y banquet In Colorado. I sure wish I could make It though. :(

Thanks everyone, very good Info!!

O.L. Adcock · « **Reply #22 on:** February 07, 2009, 10:32:00 AM »

"Adcock, you've been very knowledgeable In this discusion"

No biggy, just comes from screwing up a lot!

...O.L.

Hartlines · « **Reply #23 on:** February 09, 2009, 07:43:00 PM »

The point measure in length is not as important as the weight of the point itself, that affects the balance and ultimately your FOC calculation.!!!?? yes/no

Schultzy · « **Reply #24 on:** February 10, 2009, 12:37:00 PM »

As far as I understand It yes. The length of the arrow though will change the FOC.

Jerry Wald · « **Reply #25 on:** February 10, 2009, 03:00:00 PM »

ok so here's what I found...shed some light here please:

I went here and it said to measure to front of point: - http://home.att.net/~sajackson/archery9.html

Problem is between my field points and broadheads I have a 1" difference in length if I use the total length and not the BOP method.

this also changes the balance point...with the field point I get 11.5% and the broadhead I am getting only 7.3%.

Same weights just a longer length.

I need to add weight based on this, but my arrrows are showing weak (80#) wood arrows.

I can shorten them an inch or so, but I need more weight.

Paul has sent me some higher spined arrows to try and some assorted tips.

I will see how it goes - Might have to go to alluminums or carbons it seems.

Jer

metsastaja · « **Reply #26 on:** February 10, 2009, 04:01:00 PM »

Yesterday I took some of my CE 250 that I have been bareshaft tuning and decided to used 100g brass insert, 100g screw in adapter and a 125g magnus 2 blade glue on.

My arrows are cut to 30". I was surprised I did not have to change a thing while shooting out to 20 yards. The bow seemed quieter and the penetration was through the black hole target no matter where I shot it.

When I shot only 125g 3 blades snuffers I don't remember getting this type of penetration consistently. Using the measure everything FOC calculator I am at about 21 percent.

I am a believer! OL thank you for your tuning pages on the web.

Night Wing · « **Reply #27 on:** February 10, 2009, 05:42:00 PM »

I found this video and found it interesting for front of center.

http://video.aol.com/video-detail/arrow-front-of-center/1060945262

O.L. Adcock · « **Reply #28 on:** February 10, 2009, 06:25:00 PM »

Jer, A few % one way or the other doesn't matter near as much as good tuning, they are what they are. Doc Ashby didn't see a huge jump until 19% was reached so 7, 12, 15% doesn't make much difference.....O.L.

metsastaja · « **Reply #29 on:** February 10, 2009, 06:28:00 PM »

Very interesting clip. Thanks

O.L. Adcock · « **Reply #30 on:** February 10, 2009, 06:41:00 PM »

Nightwing, the link is good on the mechanics of measuring FOC but their thoughts on "trajectory" and stability are off base!

....O.L.

katman · « **Reply #31 on:** February 10, 2009, 07:37:00 PM »

OL can you elaborate on the trajectory influence of extreme foc? There are some, not I, that think an extreme foc arrow will nose dive. I believe I understand the stability, increasing the lever arm for the fletching. Thanks.

Pete W · « **Reply #32 on:** February 11, 2009, 12:33:00 AM »

When I started using 300 gr points / Broadheads and 100 gr inserts I stoped measuring and just match the arrows to the bows.

Pete

Pete W · « **Reply #33 on:** February 11, 2009, 12:55:00 AM »

When I started using 300 gr points / Broadheads and 100 gr inserts I stoped measuring and just match the arrows to the bows.

Pete

O.L. Adcock · « **Reply #34 on:** February 11, 2009, 11:17:00 AM »

Katman, It's been said over the years that lower FOC's will shoot flatter then higher FOC's...You'll see this in some of Joe Tapley's writtings, mentioned in that video, and generally quoted by those who don't know any better...They base this on the theory that lower FOC's will delevelop some type of "lift" and higher FOC's will rotate nose down quicker. This is the theory and it's totally baseless.

Arrows can not develop "lift"..That requires a surface to be held at some angle of attack and stabilized in that position. Arrows can have an angle of attack if disturbed from straight flight as in coming out of the bow sideways due to poor tuning or form or crossing air pockets of different velocities and direction. During that time the arrow is planing away from it's original direction and bleeding off energy at a rapid rate. This will go back to normal as soon as it stabilizes and the faster it stabilizes, the less it'll drift from a straight line and the less energy it will lose in the process. That's where higher FOC's shine. The higher it is, the faster it will stabilize, the less energy it will lose. To get the full benefits of it, a high FOC arrow can use smaller fletching and stabilize as fast or faster then a lower FOC with larger fletching.

I've only played with things that fly going on 40 years...From arrows to miniature aircraft to 100 million dollar jets. The notion lower FOC's will have a lower trajectory goes against every aerodynamic principle ever written. The real world proof....The best FITA archers are shooting target arrows in the 15-20+% FOC range now days where 7-10% used to be the norm. The flight shooters, the ultimate "flat trajectory game", read all this stuff and typically shoot arrows balanced at center or behind trying to get that "lift". Then some jerk comes along using arrows with much higher FOC's and starts gobbling up the world records by the handful with more to come. Some of the great record holders I have no doubt used high FOC arrows but didn't say much about it for fear of giving away their secrets. Anyway, it's fun and it'll take awhile to erase decades of misinformation and flawed theory...O.L.

NorthernCaliforniaHunter · « **Reply #35 on:** February 11, 2009, 11:32:00 AM »

O.k., I have three arrows, full length, Carbon Express Terminators 4560's. I draw 29.5 at about 55# with a brace height (as recommended by someone but perhaps too low) of 6 inches.

The first arrow is untouched, with an aluminum insert and 150 gr. tip. Flies like dung (actually, I've had cow pies hit what I'm aiming better). The second arrow has a one inch section of brass all-thread behind the insert, and a wooden dowel 7 inches long tapered as described in "the perfect arrow" thread. Flies better than the first but worse than the third arrow, which has a two inch brass all-thread 'plug' and a six inch wooden dowel behind it...

The third arrow, though heaviest, barrel rolls through the air and impacts the target at random angles, i.e. worse than the other two! WHAT AM I DOING WRONG?? Shouldn't the increasing FOC mean improved flight???

O.L. Adcock · « **Reply #36 on:** February 11, 2009, 11:47:00 AM »

Nope....Tuning is still #1 priority and FOC and tuning are unrelated...Pick one, then do what you have to do to tune it, be it point weight, length, side plate thickness or a combination of all....O.L.

O.L. Adcock · « **Reply #37 on:** February 11, 2009, 12:00:00 PM »

To add a little to the tuning thing..If a person doesn't want or can't change arrow lengths or can't or doesn't want to change side plate thickness for tuning purposes, only 1 point weight is going to tune for any given bow/shooter combination. In other words, you have zero choice what the FOC will be. Here in lies the problems...few over the counter prefab parts exist and there are no charts or "recipes" that will give someone pefect flight right out of the box. If a person knows how to tune a 10% FOC then tuning a 30% is exactly the same.

NCH, you say this arrow or that flys better or worse then the other..Are they weak?, Stiff? Or what?...You have to know that to know what you need to do....O.L.

dragon rider · « **Reply #38 on:** February 11, 2009, 12:07:00 PM »

I kinda feel like Dave2Old - I got mostly C's in science because I took only courses that ended around Christmas time - a good season for charity, but if I'm following this, if I increase the point weight on my Carbon 150's from 145gr to something higher, any suggestions on what would be appreciated, I should get better penetration with no change in arrow trajectory. Any chance that's right?

Thanks.

dragonheart · « **Reply #39 on:** February 11, 2009, 12:14:00 PM »

OL,

I really like the point you made about the FITA archers. These archers are pushing the evelope of recurve accuracy at extreme distances and increasing the FOC in the arrows just shoots more accurate. Why do they not just shoot as fast and light an arrow as they can? Becasue it does not work as well. Heavier points/more FOC has been around indoor target archery forever, because it makes the arrow more stabile to shoot and ultimatley more forgiving and accurate. Indoor is all about accuracy. In hunting we get the added bonus of more penetration.


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