hi there just tested my arrows for there foc% and correct me if im wrong, my arrows are 33" i measured the half way point 16.75" then the balance point and the difference was only 2" so i divide the 2" buy 33" and got a foc of only around 6, i know this is low. my over all arrow weight is around the 690gr how much weight should i add up the front and whats the easiest way about doing it?
what type of shaft?
point weight, insert weight, tub weight, footing
mnt ash wood shaft with 125gr point
Shoot a bigger point.
yea i figured that but i was wondering if there is some easy ways to add weight to the front as the broad heads i have are brand new.and how much weight ruffly should i be looking at
just ran some numbers for You and Your at 17.06% FOC
internal footing, split-shot (lead) in the point then remount.
There are jigs you can use to drill the end of the shaft. You glue in a nail, tungsten, brass, or other rod in the hole to increase the weight.
How did u get 17% foc mate my arrows are 33" and half is 16.75" and my balance point is 18.75" thats 2" infront of half so it gives me an Foc of around 6.8 % anyone have any quick or easy ways to add weight to the front?
Rob did a program that does the math to find FOC. You can PM him or email webmaster to get a copy..
If you're shooting a 690 arrow, that's a very heavy arrow. With my 42# @ 30" bow, I shoot very heavy 32", 2117 aluminum arrows weighing 637 grains. This only gives me 15.4% FOC, but a robust 15.16 GPP (grains per pound) arrow. My very heavy arrows blow through deer on broadside shots taking out both lungs. If I was you, I'd stick with your 690 grain arrow and wouldn't worry about upping the FOC percentage.
Might have to scrap the broadheads friend.
I have some 30" ash arrows.
With 125grn I was at 7%foc. (little shorter arrow is a way to increase FOC)
with 190grn tip on the same shafts I got 11.67FOC after I cut off some shaft length to stiffen the spine.
65 grains is a lot to add internally.
You could try woodyweights.
http://www.woodyweights.com/app/ProductDetails/tabid/57/Default.aspx
I worry about putting so much tip out in front of the taper. (it acts like a lever trying to break your tips off.)
Ash as you know is a whole different world from cedar though and you most likely wouldn't have a problem.
Just to be safe though you could put some steel in the tip with one of these...
http://www.3riversarchery.com/Arrow+Building+Footing++Internal+Point+Weight+and+Jig_c52_s224_p0_i5603X_product.html
And have a bullet proof aussie bomb lol
Obviously you might have to shorten your arrows a bit or get some stiffer spine.
Good flight trumps high FOC everyday.
But if you can have both..why not
Good luck!
:thumbsup:
How heavy is your bow? I know I've read the details before, but I can't remember. Chances are that it'll work just fine as is, on any game shy of camels and buffalo, and maybe scrubbers. So, it might not be necessary to scrap your arrows, and the next time you order shafts, you could get them five pounds stiffer and go up to 160 grain broadheads. That's all I have up-front on 690 grain to 745 grain wooden arrows, shot out of bows from 63# to 83#. I'm very confident with this sort of set-up. Ben Maher once told me that the only arrows people used were cedars with 125 grain broadheads, and they worked fine.
Bow is 60# at my draw 30"
well it looks like you can cut some off to stiffen the spine and add woody weights to get your %foc up. I use them on my carbons and love them .
Night Wing : I am shooting 840 gr out of my 42@28 mojo drawn to 31 so maybe close to 50 # at my draw and they shoot great. 690 is not all that heavy imho , I like heavy arrows . My setup brings my point of aim to 25 yds and works very well for me . Drew
FOC AMO Standard Formula
% FOC= (Dist. Knock throat to balance point - 0.50) divided by (Shaft Length BOP) X 100
download and run this simple foc spreadsheet calculator ..
FOC_CALC (http://www.tradgang.com/docs/arrow_calcs.xls)
foc should be your last consideration for a hunting arrow. you want an arrow of decent weight (at least 9gpp) that flies great outta your bow and has a sharp coc broadhead.
upping foc means sticking more weight on the arrow front end and/or reducing weight on the tail end.
you can increase front end weight with heavier points, nail internal footings, wood external footings, and "woody weights".
changing woodie balance can be critical to the arrow stiffness/spine, unlike carbs and alums. do the testing.
QuoteOriginally posted by Rob DiStefano:
....changing woodie balance can be critical to the arrow stiffness/spine, unlike carbs and alums. do the testing.
Really?
I've only shot wood out of tradbows.
I didn't realize adding wt to the tip of a carbon or alum shaft didn't change the spine much.
Seems it would no matter what the material.
Interesting.
QuoteOriginally posted by Zradix:
QuoteOriginally posted by Rob DiStefano:
....changing woodie balance can be critical to the arrow stiffness/spine, unlike carbs and alums. do the testing.
Really?
I've only shot wood out of tradbows.
I didn't realize adding wt to the tip of a carbon or alum shaft didn't change the spine much.
Seems it would no matter what the material.
Interesting. [/b]
yup, IMO, really. shaft material matters to a great degree. i use wimpy 500 spine weak/light carbons with very heavy front ends pushed by 55# - they fly like darts and kill things. carbon had a very large 'n' wide dynamic spine range (i.e. 35/55, 55/75) that you won't find with woodies. so, woodies are at least a tad more challenging for me when it comes to shaft spine and front end payloads. essentially, i don't mess much with woodie foc.
I see.
I've noticed some woods seemed "snappier" than others. I figured a little of this was to do with the elasticity differences between wood species.
I also thought more of it had to do with the density and or foc/size of feather differences.
Have to admit, I have seen the 35/55etc spine ratings on carbon shafts. I took it to mean the shafts weren't spine matched well from the manufacturer.
Guess I learned something today!
Thanks :thumbsup:
QuoteOriginally posted by Zradix:
I didn't realize adding wt to the tip of a carbon or alum shaft didn't change the spine much.
Seems it would no matter what the material.
Interesting.
You're correct; it does. You cannot take a well tuned arrow, add a bunch of weight to the front end, and still have a well tuned arrow. Physics is physics.
...back into the realm of confusion... :dunno:
Zradix,
Don't be confused by whatever number a manufacturer uses for their spine rating (i.e. 55/75). That doesn't mean they shoot the same over a 20# range. It's just a label the maker uses, which in the case of Gold Tips, means they spine at .400.
Carbon arrows have a lot of good attibutes, but they don't defy the laws of physics. As you add weight to the tip of an arrow, it will make it act weaker. The opposite is true is you use a lighter tip -- it will act stiffer.
Sambar, I think you may have thrown yourself a curve ball. You stated you have a 30" draw but you're quoting a 33" length...don't include the point in your length measurement. Measure to the back of the point. If you're including the point that is likely why your FOC calculation is coming out so low.
yea thanks mate i got onto the foc calculator and now measured it from the back of the point and got a foc of 9.67% and a gpp of 11.57 so that sould be fine to work with i think.
I have observed by experience that my Carbons with 200 grains up front penetrate the target better than my woodies which bounce off alot more. 48# longbow. After reading Dr. Ashby's reports it seems that EFOC is good for penetration. So for wood hunting arrows I am thinking about adding weight to the point (using a screw in adapter) rather than going for heavy shafts. But this increases the spine of wood shaft needed. So I need to go from Doug fir 60-65 spine to a 80-85 spine using 240 grains on the point with a total arrow weight of 600 grains.
Has anyone else tried this?
Jason....I think what Rob means is that Carbons are more 'forgiving' or 'tolerant' of head weight differences. Least that's what I have found with carbon....being able to shoot 100 grain differences with the same arrow....and not so much with the same wood arrow.
I also think that 33 inch wood arrow is not a worry if its flying good out of the bow. Unless its made of balsa :D
Just a suggestion but may be far off the mark for what you are looking for.
I shoot techno-hunt periodically and since the mushroom pts only go up to 145 grains and I shoot 300 grains I needed to come up with something. Took 300 grain pts, machined and threaded them to accept 100 gn mushroom pts. All 6 modified pt adaptors came out 202 to 204 grains.
Just a thought.
Note: Have extremely limited experience working with woodies. Haven't shot woodies since early 70's.