FOC

[Barry C]

I have just refletched with some ff187. I measured the FOC. My arrow is 29 inch long. The distance from nock grove to balance point is 20 Inches. According to the Easton program that gives a foc of 18.9%</p>

Before with spin vanes the balance point was 20.5 inch from the nock grove to balance point,#which indicated an FOC of 20.6%! I previously made it about 18... I must have been incorrect the first time. I have triple checked everything this time.</p>

Have I made a mistake?</p>

[morphymick]

Bang on Barry, give or take 0.09%.

Mick

[Barry C]

This is a really strange set of arrows. The guy in the shop commented how light they feel, but whats more I can tune them bang on with 50 pounds on my fingers... The bareshaft right into the group at 18m.#I havn't put them into the crono, but they seem much faster than a guy's whose flay at 220fps and similar to my brothers compound.

[Jerry Tee]

220 fps is not that fast for a compound. I estimate that my arrows take about a second an a quarter to cover 100 yds.I must se about getting the bow on a crono.

[Barry C]

I know, i meant mine are much faster than my friends at 220 he shoots recurve, mine are#about as fast as a compound my brother shoots, also with very underspined arrows. he shoots 560 acc with 82gr pound, 29 inch arrows at 55 pounds.

[Marcus26]

220 is terribly slow for a compound of those specs. I get 260fps with my Bowtech at 55# and a 360 grain X10 with full weight in the points. I only have a 28" draw so with a 29" draw I would get 270fps.

I don't see the need to fuss over FOC, none of the top recurve or compound shooters I know bother with it at all. Full weight points and that's it. More weight = less drift.

[joetapley]

I don't see the need to fuss over FOC, none of the top recurve or compound shooters I know bother with it at all

Australia is about the only place in the world where the bow was not invented - and as you can see they have not yet caught up!

[Marcus26]

Yep we just win with em while the english try to overthink things.
Sorry Joe but you have never proved IMHO that FOC matters. In my own testing I can vary the weights of my points by over 100 grains and the things still go where I aim them. The biggest impact is the point weight in relation to wind drift, but without wind my CXLs with 60 grain points shoot 10s at 70 just like my 110 grain point X10s do at the same arrow length, yet their FOC are much different.
Certainly adjustment of 2% makes no difference. You'll lose more points from increased drift.

Sorry guys, there is no magic formula, tune your bow poundage to the spine of the arrow, execute the shots correctly, aim at the 10 and you will hit the 10. Changing the FOC setting by 2% will not change your groupings if the above is held true.

[joetapley]

Yep we just win with em while the english try to overthink things.

I wish that were true but it's the Koreans, East Europeans, US and yes Australia etc. who win the (recurve) medals because they long ago moved (not entirely but to a significant extent) from top of the head opinions to trying to put things on a firm basis - would you scrap the AIS?

As for FOC the effects are masked by by the 'forgiving' aspect of the compound and the high arrow speed so you can get away with a lot. With lower arrow speeds from a recurve the main arrow flight performance properties are length, diameter, mass and FOC. You need a good combination of all four.

[Furface]

OK, on the basis that there is no such thing as a stupid question
What is "FOC"?