Hi all!I'm thinking of getting back into this after many years of being away and am somewhat rusty on the acronyms.What does EFOC and FOC stand for,what importance do they have,and how do you figuer the percent of FOC (whatever that is)?I love this site and have learned alot!Thank you for helping!Steve.

Figure FOC (Front of Center) with this.  I have no idea what Efoc means.

If your arrow's weight was "even" throughout the arrow....the arrow would want to tumble in flight.  When the tip end is heavier...it'll want to guide the rear end (nock end).  Think throwing a bare shaft through the air v. a bare shaft with a FP/insert on it.

This is crude, admittedly (my description).

Do a search on here, heaps has been discussed.

QuoteOriginally posted by GMMAT:
 

Figure FOC with this.  I have no idea what Efoc means.

EXTREME FOC

EFOC is extreem forward of center.  The Grizzly Stick woven fibre carbon arrows have this quality because they are continuously tapred from the point to the nock, meaning more weight is up front.  I've never tried them, but have heard that they perform well.

Thank you all!Steve

Steve -- Actually, this is a darned important concept, and very complex. In his ongoing "scattered series" of articles for TBM, where he breaks it all down and tells it where we can all understand (with as little math, etc. as possible), Ashby has a detailed FoC article, though it will likely be a few more months before it runs. Meanwhile, you can check the Ashby forum here, I believe the 2007 test results, for details. EFoC, definited as 20% or more forward-of-center balance, not only makes arrows fly better with less fletching (due to a long rear lever-arm and a short front lever-arm), but also greatly increases penetration by reducing arrow flex and vibration. Nothing I'm capable of explaining, but something I can understand when plainly put, and something I can darn sure see when my arrows group better and slug plumb through the backstop and 3" into a tree (target points at that). I have tried the GrizzlyStiks, with a 300-grain field point, and am amazed at the accuracy and punch they deliver from a 55# longbow. Bitter medicine for an old-school woodie shooter like me. Consequently, I am experimenting with ways to get more weight up front on woodies, as are many others here. It's great off-season fun, and good exercise for long-closed minds like my own. Dave

I just did some calculations (brain now hurts    ) and came up with 24.2% front of center on my 726 grain Beman MFX Classic's.  31" from nock groove to BOP.  

Arrow is a Beman MFX Classic 340 31" long with a 100 grain brass adaptor and a 250 grain field point.  They hit like a hammer.

I found this to figure it out.   FOC  

Also here is a thread I did on my arrows...  my cold day experimenting with EFOC  

Just need to get some sleep now!

Josh

here's an excel spreadsheet i created for calculating foc - you may find use for it ...

Arrow FOC