Where to experiment?

[James Harvey]

#6985

Fellows,

I want to try setting up some efoc arrows for my long bow. My biggest drama is going to be shaft spine as it’s a heavy bow and I have a long draw.

My plan is buy the heaviest head I can (300 grains) then buy a range of adapters and some footing kits to use as the weight variables in the set up. I understand I may have to build out my sight window as well as I’m pretty limited in how much I can chop off the shaft (I have some uncut 340 carbons but I’ll probably end up getting some 300’s).

My question is am I missing something, or is this a reasonable way to experiment? Given that the best ‘bang for your foc buck’ is going to be in the head (as there aren’t many things that go more forward than that) I figure a heavy head with light internals is going to be a better compromise if I end up having to cut weight to tune.

Sorry if I’m covering old ground, I just had moment when I was about to place my order where I felt like I knew exactly what I was doing. Experience has taught me that generally means I’m about to make mistake 😉 Thought I should ask some wise heads to confirm I’m not being a total idiot…

Jim

[James Harvey]

#61594

Perhaps I could ask this another way 😳 Is there a good reason to use a head less than the heaviest one (300grain) available?

I figure the worst case is if I use the lightest adaptors I can get, shortened my shafts to the limit and they’re still underspined. However I can build out my sight window as Troy Breeding has mentioned if that occurs.

Perhaps it is simply time to get amongst it and start experimenting 😉

Cheers,

Jim

[Bruce Smithhammer]

#61614

Jim –

I’ll chime in since no one else has, though I’m obviously still learning as well (and hope to always be). I think that having an idea of what point weight you want to start with, and a ballpark idea of the FOC % you are striving for, is a good place to start.

I think that getting as much of the weight forward in the head (as opposed to the internals) is definitely beneficial.

Unfortunately, there really isn’t any spine chart for EFOC setups, and it seems to just take a fair bit of experimenting with your particular setup, given that there are so many variables.

The more of those variables that you can share – your bow poundage at your draw length, shelf cut, etc. the more that those more experienced than I may be able to help you narrow it down, based on their own experiences.

Good luck and keep us updated with the ongoing experiment – I think we all learn from seeing how others are figuring it out.

[James Harvey]

#61758

Cheers Smithy 😀

So I guess in principle, I want as high a FOC as I can get with commercially available bits and still tune for my longbow. I know that sounds like a pay-off answer but that’s my goal 🙂

So just from a numbers perspective, my 340’s are 11.2 gpi. Uncut that shaft is 360 grains. With a nock and 75 grain insert/adaptor it’s 447. If at that point I use a 225 head I’ve only just slipped over the 650 grain threshold with just the fletching to add. I’m fairly certain I’ll be cutting an inch or two off the shaft, which is going to drop me down to ~660 or 650 plus fletching. Which is really only ‘just’ there in terms of total weight.

If the 340’s are underspined (I’m confident they will be, they’re pretty spot on now with a 190 grain head) and I get some 300 shafts, the new shafts are only 9.5 gpi which will drop total weight again by about 50 grains. So in the 600-620 range with 225 grain head.

With a 300 head, even my lightest scenario is still over 650 and with the lightest shaft I foresee using, I could still get very close to 800 grain total using heavier adaptors and footers.

I guess a 300 seems to cover all my bases?

My bow is a centrecut, 70# longbow that I draw to 29.

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