FOC question

[TooManyHobbies]

Is there a calculator for adding weight to broadheads to increase FOC. Or, would any of you be able to get me an answer?
Currently I'm shooting 33.75" (tip to tip, broadhead to nock), Woodies. Total weight approx. 652 gr. With 125 Zwickey Current FOC is only 5.9%. (just figured out how to do it). Obviously way light. How much do I increase? Do I just double the BH weight? Or add weight until the arrow balances?
Thanks, Brian

[Captain*Kirk]

Is there a calculator for adding weight to broadheads to increase FOC. Or, would any of you be able to get me an answer?
Currently I'm shooting 33.75" (tip to tip, broadhead to nock), Woodies. Total weight approx. 652 gr. With 125 Zwickey Current FOC is only 5.9%. (just figured out how to do it). Obviously way light. How much do I increase? Do I just double the BH weight? Or add weight until the arrow balances?
Thanks, Brian

Easiest way to increase FOC on woodies is to use Woodyweights on your current setup, which will increase FOC and total arrow weight and give you an extra inch or so, but this will also decrease your dynamic spine. Not sure if it will put you under your limit.

[Captain*Kirk]

https://www.3riversarchery.com/search.html?w=woodyweights

[TooManyHobbies]

Are the woodieweights permanent to stay on for hunting, or just to check what is needed to change the BH?

I just taped four dimes to the BH and got a new FOC of 13.3%. so a BH of 250-260 (or 125 woodieweights) should put me close?

Thanks Capt

[Captain*Kirk]

WW are a designed to be a permanent installation with a BH. You can get the test kit to find out which actually flies best with your combo instead of taking a stab in the dark at what you think will work best. They can be removed or installed simply by warming up the WW until your glue softens as with any broadhead. This will save a bunch of time and $$ over trying out different broadhead weights which may or may not work.

[Captain*Kirk]

https://shootingtime.com/archery/high-foc-arrows/

[TooManyHobbies]

 Awesome, thanks again.

[Captain*Kirk]

 
Let me know what you figure out.

[slowbowjoe]

And keep in mind adding that much point weight is going to weaken your dynamic spine a couple/few spine ranges.

[Jack Denbow]

I have found that for every 50 grains you increase point weight you need to increase spine weight by 5 lbs.

If you are shooting 125 grain point on a 50-55 lb. shaft and you increase your point weight to 225 grains
you will need to shoot 60-65 lb. spine.

Wood arrows are hard to get high front of center on. I used to drill a 1/8" hole in the end and glue in a
100 grain tungsten rod and the most I could ever get was 18%. It is a lot of work and the rod has to be perfectly centered.
My normal arrows run about 14% and I am happy with that.
Jack

[Jim Casto Jr]

I'm not sure what you're trying to accomplish.  With a 600 grain arrow, I'll assume you must be shooting 60+ pounds of weight.  Go up another 150 grains, and I would assume you much be shooting 70+ pounds. If I was hunting deer-sized critters FOC is nothing I would concern myself about. 

[flyonline]

Is there a calculator for adding weight to broadheads to increase FOC.

If you're into such things, there is an app called Archery Tune (search Archerytune) available on both Apple and Android that will do that for you. It can work out current FOC from measurements, tell you how much you need to add/remove to change FOC to desired % or work out your FOC for a theoretical/real arrow based on components and weights/lengths. It is in metric though 

[TooManyHobbies]

I'm not sure what you're trying to accomplish.  With a 600 grain arrow, I'll assume you must be shooting 60+ pounds of weight.  Go up another 150 grains, and I would assume you much be shooting 70+ pounds. If I was hunting deer-sized critters FOC is nothing I would concern myself about.

Well, my LB is 62@30, I'm drawing the BH right to my finger (31+), so a little more than 62#. My major problem is trying to figure out how to tune my arrows (or my bow). I sent Snag a PM, he made my arrows, and I'm hoping his records tell me what spine I have. Of course my field tips fly great, my BH's don't, so I assume the BH is the issue, but really, I don't have a clue. What I do know, is my FOC is 5.9. From what I've read, 12-15 is preferred. To be honest, I don't care where the weight is, I want my arrows to fly straight and hit where I'm aiming. At 15 yards, my arrows are all over the place. Not 6" off, more like 12-24" off. They're like a whiffle ball coming out of a pitching machine.
So, yes, I need help. 

[McDave]

I would say that your priorities should be first, to get your arrows into an acceptable range, i.e. more than 10% FOC, and second, that they are tuned to your bow.  You seem to be at a level where you should be doing some of these things for yourself, rather than relying on charts, calculators, or other people's advice.  Buying a spine tester is inexpensive and requires no particular skill to use.  Making measurements of FOC correctly is likewise not difficult, and is discussed in most instructional archery books.  Correctly measuring FOC is not magic; it just makes your FOC measurements comparable with everyone else's. Then we get to to the crux of the matter: bare shaft tuning.  This does require some skill to do correctly, but I have found that even done imperfectly, it gives me better results than other people's advice or calculators.  Ken Beck gives a good introductory discussion of this in Volume 2 of Masters of the Bare Bow, and his method is repeated an expanded upon on YouTube.

After you have done these things, then you can begin to play with higher FOC if you want to, making sure that your arrow stays tuned to your bow while you do it.

[Captain*Kirk]

I would agree with McDave that something is amiss. My immediate guess would be that the broadheads are wind planing, assuming they weight the same as your field points. Normal arrows fall in the 12% FOC range.
What configuration and size of feathers are you using? With a BH you need adequate stability as well as FOC to keep the arrow flying straight...not to mention you are using a longbow which is probably not cut to center, if at all. Do the arrows fly better off your Kodiak?

[Jim Casto Jr]

Thanks for adding more information.  Going to make a guess here from the added info you've given us assuming you've spun your broadheads and they're true.  It's a guess so please don't plan to take it to the bank. 

I'd suggest adding a Zwickey Delta or something even heavier and see if that helps.  If it does, your arrows are stiff; if it makes it worse, your arrows are too weak.

As a side note:  Field tip and broadhead tuning is very similar to bare shaft and arrow tuning with field tips.

Good luck to you.  Sometimes this simple stuff can make you pull your hair out.

[TooManyHobbies]

McDave, I do not have a spine tester, I will get one. I THINK they are 80-85, but still waiting on Snag's reply. And I will look up Ken Beck's discussion. Thank you.

Capt., my feathers are 3 @ 5". helical so the arrow will spin to the right.

Jim, spinning produces a very slight wobble, is that the broad head or the shaft?

Thank you all for the help, I don't think I'm as stupid as I appear to be, I'll learn.

[Captain*Kirk]

I made a spine tester. Cost me nothing, basically. Two cup hooks spaced 28" apart (26" for carbon or aluminum), centerline between the two marked, printed out a ruler I found online and filled a container with lead shot to total 1 pound (container and hook included...total weight). I found a chart online that calculates spine by deflection in inches. Not the greatest but gets me in the ballpark.

[TooManyHobbies]

Ok, I found one of my test arrows from Snag. It has 81# marked on it. That puts me in the 80-85 range. I stripped off the feathers on one arrow and shot bare shaft.
Surprisingly, my spine looks great. No left or right nock. BUT, my nock is HIGH after 10 yards. Repeatedly. My nock point on my bow is set at 3/8".

According to Ken Beck's video, adding a nock point below the arrow may help to lower the nock high impact. I put one on.
Well, it did bring it down, but now it's nock right on impact = stiffer spine. So my choices are a heavier point, a weaker 32" shaft or a longer shaft of same spine weight. Does this all sound correct so far?

[McDave]

I would try your nock point at 1/2” and 5/8”, to determine if you have a real or a false nock high.  If you have a real nock high, the nock high should increase at 1/2” and again at 5/8”.  If you get ambiguous results, then try the nock even higher until you get the expected results of increasing the nock high when you raise your nock point.  Make sure your bare shaft is straight and your nock fit is not too tight.  Some say the arrow should fall off when when you let it dangle straight down from the string and give the string a tap.  My nocks are a little tighter than that, but not much.  If you have two nocks, make sure there is a little play when you nock the arrow, maybe 1/32”, so you can wiggle it up and down between the nocks a little.