FOC Evolution…

[Bruce Smithhammer]

#6011

So, maybe it’s just because I still have 3-1/2 months until hunting season, or maybe I just need a new project to tweak about, but I decided it was time to start experimenting again, and see how I might be able to further increase my FOC and penetration.

Here’s what I’ve been shooting for a while now:

Shaft: GT 5575 (9.3gpi), cut to 28.5″

Combined Point Weight: 305gr.

Fletching: 4″ x 3

Wrap: 7″

Total arrow weight: 605gr.

FOC: 23.6%

I recently upped from 200gr. points to 225 gr. and got about a 2% bump in FOC:

Shaft: 5575, cut to 28.5″

Combined Point Weight: 335gr.

Fletching: 4″ x 3

Wrap: 7″

Total arrow weight: 633 gr.

FOC: 25.4%

Both of the setups above flew fine out of several bows that all have the same 3/16″ past center shelf cut, though I have seen a slightly more noticeable drop with the second variation.

But then I got to thinking about how I might increase FOC a little more.The caveat being that I plan to continue to use the same 225gr. broadheads I already have, and don’t want to invest in new, heavier heads. Which got me thinking about the other end of the arrows, and reducing fletching. I ordered some 2-1/2″ shields which will be fletched X4, and cut my wraps in half, which should reduce my overall arse-end weight (I know I could reduce it even more if I eliminated the wrap entirely, but they’ve paid for themselves many times over in otherwise lost arrows and I think a 3-1/2″ wrap is pretty nominal).

Haven’t fletched up the new arrows yet, but I’m expecting overall weight to be a little less, just shifted forward a little more. Target FOC I’m hoping for is 27%. I’m also curious to see if the increased FOC might flatten the trajectory a bit over the second setup above – Dr. Ed’s observations about how EFOC can actually flatten trajectory due to improved arrow efficiency/recovery has really got me thinking…

More to come once I shoot the new setup, and of course, any thoughts from the “FOC freaks” are more than welcome. 😉

[David Petersen]

#46845

Bruce — You can up the front weight and FOC by using heavier internals, far cheaper than heavier heads. If you’re hunting elk and a student of the Ashby study, you need to get total arrow weight to at least 650 before worrying a lot about FOC. I personally go for 700 minimum and my average elk arrow is 790-810 or so. I have proven to myself through experience, good and bad, that up to a point, weight indeed counts most. The sweet fix for you is if you can add front weight via internals enough to get total weight up to 650, at the same time increasing FOC … all with the same shafts you already have. 28.5″ doesn’t leave you much to work with unless you draw less than 28″. My el cheapo CE 350s provide an amazingly wide range of spine, which makes it all real easy. It’s woodies that continue to be a challenge, thus more fun.

[Bruce Smithhammer]

#46854

Thanks, Dave. I should have added that my “combined point weight” already includes 100gr. inserts and carbon collars.

I suppose I could switch to threaded inserts like the Gold Tip system that allow for add-ons. Or look at weight tubes, though I’ve heard mixed reviews on those.

Also, I draw 27.5″ Bare-shafting with the 28.5″ shafts that I’m currently using was good.

[Troy Breeding]

#46872

Bruce,

I know you may not want to hear this, but you can up your FOC as much as 2% by simply dropping those wraps. I fought hard and long before giving them up. After finally getting used to the non-wrap look I can’t even think about using them. They even look weard to me when I see them on other folks arrows.

As for gaining FOC, you will gain more with weight in front of the insert as opposed to behind.

Had to learn that one the hard way myself.

Troy

[Bruce Smithhammer]

#46896

Troy Breeding wrote: Bruce,

I know you may not want to hear this, but you can up your FOC as much as 2% by simply dropping those wraps….

Ha…yeah, I know and I probably will. I just need to “get over it” and kick them to the curb. 🙄

Troy Breeding wrote:

As for gaining FOC, you will gain more with weight in front of the insert as opposed to behind.

Had to learn that one the hard way myself.

Troy

Agreed, and that’s part of the reason I’ve been leery of “add-on” insert systems, and weight tubes, in the past. So I guess there’s really no escaping a heavier point, if I really want to get there…

[smiley1]

#46931

[quote=Smithhammer]Thanks, Dave. I should have added that my “combined point weight” already includes 100gr. inserts and carbon collars.

If you went to a 125gr adapter you would increase FOC and be right around 650 gr total weight.

[Bruce Smithhammer]

#46935

smiley1 wrote:

If you went to a 125gr adapter you would increase FOC and be right around 650 gr total weight.

So…hypothetically, I could go with;

125 gr. steel adapter

50 gr. brass insert

190 gr. Meathead

for a total point weight of 365gr, which would put my total weight just over 650…

Sorry, I’m just geekin’ and thinking out loud…

[Troy Breeding]

#47441

Careful Bruce,,, thinking will get you in trouble…:D

The only bad part about increasing point weight is the fact that often you end out with a shaft that is too weak. That is unless you have enough over hang to trim and bring the stiffness back into play. Sounds like your already at the point of not being able to trim. If so, get ready to move up one spine group.

Troy

[Bruce Smithhammer]

#47567

Yeah, I was thinking about that last night. They are flying just fine with 335gr. up front right now, and I would only be adding another 30gr. or so. But eliminating the wraps will likely also contribute to weakening the spine as well. Just have to see what happens.

My two recurves and my hybrid, being all cut 3/16″ past center, seem to be quite tolerant of spine variation. But of course everything has its limits. It’s my job to find them…8)

[Troy Breeding]

#48061

If they do turn out weak, you can always build out the sight windw alittle.

Troy

[Stephen Graf]

#48498

I can’t add much to the good advice and experience given here, but I’ll add maybe just a little bit…

I started using a 1″ aluminum sleeve over the end of my arrow a couple years ago to strengthen the shaft and keep it from breaking when hitting rocks,etc. It worked really well. So the next thing I did was get rid of the brass insert and go back to the aluminum inserts that came with the arrows. That way I could increase the weight of the point and increase the FOC of the arrow without increasing the weight of the arrow.

I basically moved the extra 25 grains or so (difference in wt between 50 grain brass and 25 grain aluminum) to the end of the arrow point. It gave me a couple percent and saved me about 12 bucks a dozen on brass inserts.

I have had no failures due to the aluminum insert. I know they are supposed to be a weak point. But I haven’t had that problem, especially with the added support of the aluminum sleeve.

[smiley1]

#48605

I agree with Steve about all the good advice given on this topic. I guess when I suggested using 125 grain adapters I should have also stated that you may have to compensate by building out the shelf as Troy stated or using an aluminum footing to help stiffen the spine. I am by no means an expert on this FOC stuff but have been experimenting with different arrow configurations for several years. In my observations it’s harder to tune an UEFOC arrow with a bow cut past center shot. Building out the riser helped me tune easier.

[Bruce Smithhammer]

#48710

Thanks folks. I think my next step will be to bareshaft with the added point weight and see how they fly, and then assuming that’s all good, go ahead and fletch them with the 2-1/2″ x 4, and check flight again. If they seem weak, I’ll experiment with building out the shelf.

[Troy Breeding]

#49117

A slight weakness in the shaft will only require a thin shim for the sight window. I normally use the tuffed side of velcro for my sight window strike plate. If more is need my first attempt is only add another layer of velcro. If that cures the problem I then pull the velcro and add a thin piece of leather with velcro over it.

Troy

[Bruce Smithhammer]

#51263

Well I bareshafted the 5575’s @ 28.5″ today, with point weight increased to 360gr, and they are definitely too weak – consistent nock right @ 10 yards.

So, I guess I’ll start building out the sight window a bit and see how that goes.

Or, I’m also considering just getting some 7595’s at full-length for cheap and then truly bareshafting them with the point weight above…

[Stephen Graf]

#51759

If you are right handed, then a nock right would indicate too stiff.

If you are left handed, then a nock right would indicate too weak.

I didn’t take note of the shelf on your bow pictures to know which way you shoot. So I thought I’d throw it out there, just in case.

[Bruce Smithhammer]

#51859

Whoops – typo above. I was getting consistent nock left.

This is what happens when I post at night after a pint of the strong local grog…:D

I am right-handed, btw.

[Bruce Smithhammer]

#61083

Today’s experiment:

650gr. total arrow weight

28% FOC

4 x 2-1/2″ fletch

Raining and blowing outside today, but I’ll test them out in the basement range @ 10yards for the initial test.

more to come…

[Bruce Smithhammer]

#61222

Got a break in the weather, so I got outside to shoot the new setup. Flying just fine out to 20 yds or so! In fact, I really don’t notice much difference at all between this and what I was shooting before, in terms of trajectory out to those distances. 45gr. heavier but another 5% FOC and the flight seems about the same:

[David Petersen]

#61326

Bruce — You’re looking good there! But to generalize your specifics, I since getting great flight, EFOC and most any arrow weight you want is easy as Grandma’s pie with carbon shafts. For elk, pump it up another 50 grains total(assuming best broadheads) and you’ll be a singularly murderous monster. (Which I hear you already are on upland birds.) For anything less, smaller “big” game, you’re already there.

One point you make is well worth repeating and emphasizing for the Ashby uninitiated, to wit: adding more point weight does not necessarily lead to “submarining” arrows, but rather, most often, to even greater accuracy. I don’t see any trajectory difference from my low-50# bows until I get beyond 800 grains. With more powerful and faster bows the front-weight limit should be even higher. Add small branches, wind, bone hits and other unknowns to the mix and the impact-accuracy gains are even greater.

But then again, it’s happy hour (when I should always put a lock on my computer … just ask our Beloved Webmother, assuming she’s back from surfing in Costa Rica) so I could be entirely and utterly wrong. But then, so long as we’re casting beyond the quiet water, it’s all an adventure and thereby good, enit?

[Bruce Smithhammer]

#61608

David Petersen wrote: ….adding more point weight does not necessarily lead to “submarining” arrows, but rather, most often, to even greater accuracy….

I had read and heard a fair bit about this, from Dr. Ed and others, and in theory it made sense, but now I’m convinced. The additional point weight, combined with reduced rear lever, really does “pull” the arrow along (and increases stability and tracking), rather than trying to steer the arrow from behind.

Of course, I had to endure serious skepticism from a couple friends who were utterly convinced that my arrows would nosedive 10 feet after leaving my bow, and who couldn’t understand why I would want to build a “less efficient” arrow, despite that fact that they’ve never tried it…reminds me of that quote about how minds are like parachutes – they work best when they are open. 😉

[Troy Breeding]

#61926

Speed freaks just don’t get it. Just think where we would be if Columbus hadn’t went against the others?

Troy

[Bruce Smithhammer]

#52289

Smithhammer wrote:

650gr. total arrow weight

28% FOC

4 x 2-1/2″ fletch

^ Been shooting this arrow exclusively for the last two months. A marginally noticeable drop in speed, but other than that, they fly great. They have no more drop than the arrows I was shooting before out to distances of 20 yards, very stable in flight (I’ve been intentionally shooting them in the wind at various angles) and the additional penetration is noticeable.

But perhaps the best affirmation is one of my frequent shooting buddies, who initially looked at me like I was crazy when I told him that I was going to try this setup. He’s been shooting with me a fair bit lately, and seeing how these arrows fly, and just the other day he said, “yeah, I think I’m going to increase my FOC…”

8)

[Author]

Posts