Ultra EFOC - How?

[Greg Skinner]

I have several bows in the 52#-57# range that I have been experimenting with on the EFOC principle. Here is my experience FWIW. I have tried in vain to get GT 35-55's and CE 150's to fly well regardless of how I try to stiffen up the front. However, the GT 55-75's shoot well out of all of the bows by varying length and point weight slightly.  The best I have been able to achieve so far (EFOC) is a shaft cut to 28 1/2 with 100 grain brass insert, 100 grain steel adaptor and 190 grain broadhead.  This gives me a total arrow weight of 650 grains (the magic number for bone threshold) an EFOC of 29.8% and a gr/lb of 12.2 from my 53 @ 27" Moosejaw. My chrono says the arrows are traveling at 154 fps and the Grizzly El Grande 190's shoot right with the field points, using 3 4" shield cut fletches. My "lightweight" setup is my 52 @27 Liberty Elite with the arrow cut to 29 1/4, a 50 gr brass insert, 100 grain steel adaptor and 160 grain broadhead (Grizzly or Ace).  Total arrow weight is 566 gr, giving a 10.9 gr/lb, 27.8% EFOC and flying at 160 fps, requiring virtually no adjustment in aiming between the two bows, both of which are cut 3/16" from center shot. I'm using 3 3" parabolic  fletches on the arrows for the Liberty. I really like how these combinations are shooting, but I love to play around with this stuff, so I'm sure my experimenting is not over. Getting the right arrow and having it tuned correctly has helped my shooting consistency immensely.  Now I know that if I miss my target it is not the fault of the arrow and I can critique my form to determine why the miss.

[Ragnarok Forge]

Ok,

So the arrows are made up.  

I have two dozen full length 30.5 inch beman ICS Bowhunter 550 shafts.  100 grain brass inserts, 3 - 3 inch shield cut fletch, standard Beman nocks, and a 4 - inch flourescent orange tiger stripe tape on each arrow.  YAH I KNOW, I should drop the tapes to increase FOC.  Especially since the arrows cost less than half per dozen what my FMJ's were running.  I just like tapes on arrows, particularly when I find myself searching for them behind a 3D target.  I have the arrow shafts within 0.2 grains of each other.

So based on the last posting above I can say the actual FOC% numbers are pretty darn close to the calculated numbers.  I am just waiting for Brock over at Bull Mountain Archery to complete a new 8 strand TS+ and a 12 strand TS+ string for me.  Once I get those shot in and fully stretched.  The bow and arrows will be ready for my testing runs.

A buddy is building me a tall sawhorse to build an arrow holding / firing device.  I plan to set it up so I can draw the bows to specific draw lengths in half in increments.    

Real world results for the EFOC arrows will be posted before long.  I want to get the tuning process and final arrow lengths / weights figured out before posting any numbers or results.

Deer and Elk hunting are almost over here so it is time to get on with this process.

[jdemoya]

Is any of you still using the turbulator? Thanks.

God bless,

José

[elktalker]

I made a 29" gold tip ultra lite that flies great out of my bow. 365 grains up front 640 total can you tell me my foc and would that be concidered extreme?

[Rob DiStefano]

Originally posted by elktalker:
I made a 29" gold tip ultra lite that flies great out of my bow. 365 grains up front 640 total can you tell me my foc and would that be concidered extreme?

you need to first find the arrow's balance point in order to determine its foc ...

 http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=2;t=000089

[Prairie Drifter]

Originally posted by elktalker:
I made a 29" gold tip ultra lite that flies great out of my bow. 365 grains up front 640 total can you tell me my foc and would that be concidered extreme?

According to stu miller's calculator, you have about 26.4% . W/O knowing which spine I played a little. Are you shooting the .300 spine? Your bow is about 55# at 28"?

[elktalker]

the arrow is a 300 my bow is about 62# @ my draw.(65# @ 28)balance point 22.5

[Rob DiStefano]

the ONLY true way to calculate foc is to know the total arrow weight, the precise arrow length (from the depth of the nock groove to the end of the shaft (in the case of carbons or alums, end of the arrow insert), and the distance between the depth of the nock groove and the arrow's balance point.

 

 foc and gpp spreadsheet

[elktalker]

thank you for the foc and gpp spreadsheet I didn't know you could input #s in the first time I looked. My foc is 27.5

[Rob DiStefano]

Originally posted by jdemoya:
Is any of you still using the turbulator? Thanks.

God bless,

José

HAH!    

sorry, just had laugh.

'turbulator'?   ummm,  no thanx.     :rolleyes:      

[Doc Nock]

What, Rob? You still havin too much trouble getting the J4 bottles to balance on the rear of your shaft and clear the shelf???

[Rob DiStefano]

Originally posted by Doc Nock:
What, Rob? You still havin too much trouble getting the J4 bottles to balance on the rear of your shaft and clear the shelf???

   

[chopx2]

This is my first post ever on trad gang so hopefully no social faux pas will be committed.

I just decided to get back into traditional archery after a 15 year hiatus and hit the net to research what's changed in that time. I too became intrigued by the foc studies Dr. Ashby has done. (BTW Dr. Ashby my thoughts and prayers go out to you. I hope 2010 returns you to full health and faculties.)

Like a few other posts here I have been struggling to break the 30% barrier. Last night I came across Dr. Ashby's notes on the Papua New Guinea hunters and their equipment...check out his post on Alaska bowhunting  http://www.alaskabowhunting.com/PR/Ashby_Papua_New_Guinea_Bows_and_Arrows.pdf

After reading that it dawned on me the reason this Ultra barrier is hard to breach is because our broadheads size (length) and weight is inadequate.

Much of the weight we add is in the shaft (heavy inserts) where it loses much of it's effectiveness due to it's proximity to the balance point. Basically we need our broadheads weight to be further forward.

Tonight I got home from work to find my 190gr Grizzlies and 125gr broadhead adapters in the mail. While dry fitting the insert I noticed that there was a void inside the ferrule in front of the adapter.

It dawned on me I could add weight to the ferrule near the middle of the broadhead moving the extra weight forward of the insert.

What I did...turns out #6 lead bird shot weighs about 2gr per pellet. I was able to melt down 16 pellets (32grs) in the ferrule with a propane torch and not interfere with the adapter. My FOC went from 29.5% to 31.2%

Here is the arrow set-up:
Beman Bowhunter 400 (8.4gr/in)
Shaft 28.5"
Nock throat to end of insert 29.25"
100 grain brass insert (sticks out 1/4"from end of shaft when fully inserted)
125gr steel insert
190gr Grizzly glue on heads
16 pellets of #6shot (although you can use any size since it will be melted)
3-5" feathers
Factory nocks (direct fit super nock)
Total Arrow weight 730gr

The result is 31.2% FOC

So a couple lessons learned...
1. have a plan on what to do with the left over powder if you cut open a shell like I did
2. don't melt the lead inside the broadhead. I fear I may have killed the tempering on the braodhead...now have a practice only head

Once I find a suitable vessel to melt the lead in, I will finish up a few more heads to see how they fly...I'll let you know.

Maybe I can get 1 or 2 more pellets in too....

Sorry for the length of the post.

[Earl Jeff]

Antonio great setup you might want to look at some Victory archery HV Shafts they have 350 spine shafts that are 6.4 GPI and try putting smaller shot in the insert you can fit more in to start and after they melt just keep the heat on them and those little buggers melt quick.

[chopx2]

Do you know if my ICS inserts will work on their arrows?

With a slightly lighter nock and shaft I might be able to pick up a couple more %

Thanks for the tip!

[Fletcher]

I'm kinda curious as to why the length of the point is not used in computing FOC.  The point is used in the total arrow weight, balance point, and is a part of the flying arrow.  Why is the point not a part of the arrow's length?

[Richie Nell]

Chopx2,
I mentioned that in another thread. It does work.  Textbook physics.

posted December 20, 2009 02:41 PM                        
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I totally agree with 30coupe.
Your FOC will increase the quickest if you get the weight literally out in front of the arrow instead of inside the arrow...AS IN...the broadhead and adapter. Then work backwards to 100 gr. brass insert and then weight behind insert if needed.

With glue-on Grizzlys I have put 15 grains of lead from bullet worm weights in the ferrule before glueing in adapter. Works great by adding more weight in front of arrow.

--------------------

[Richie Nell]

Chopx2,
You can also use 3" feathers instead of 5" and cut 1/8-3/16" off male part of nock.  That will decrease a few grains from long lever and add to the heavy or short lever.  Increasing FOC.

[evincen3]

Hey everyone, I am brand new to this website, and relatively new to traditional archery, and as you can imagine, I need endless help!
The Dr. Ashby studies got me fired up about trying to shoot a heavy arrow with Ultra EFOC. I would like to shoot 650 grains total (to reach heavy bone threshold) and 30% FOC. I have a bear Montana longbow, I am pulling 50# at 29 inches, I have easton aftermath 400's at 29.5 inches, but 225 grains is as much I can put up front before the spine gets too week. Total weight is only at 512 grains with FOC only in the low 20's. How can I increase my overall weight by 135 grains and keep my arrow stiff enough? From what I have seen, people are using as low as 7 GPI arrows achieving UEFOC, but my arrows are 8.8 GPI, so if I increase my spine to 340's, it will be that much harder to achieve UEFOC.
sorry for the long post, any thoughts or ideas will be greatly appreciated.

Thanks

[**DONOTDELETE**]

Here is my question. Since the foot can stiffen the arrow a bit and I need to stiffen mine to be able to add more weight up front, Would gluing in 4 to 5 inches of a 7 inch oak footing stiffen and arrow enough for me to put 350 or 400 grains up front which would push me towards the 30% Ultra Extreme FOC mark?

I haven't read through this whole thread because i'm not much interested in the Ultra EFOC thing at all..... But..... to answer the question you asked here would be "Yes" it will stiffen things up, BUT.... running an over footing past your insert like that put's a hinge point on that arrows flex point, and under extreme impact conditions, will snap off right behind the footing....

I think i would look into possibly using full metal jacket arrows, or a tapered shaft like Grizzly makes rather than a long footing that cause a weak spot in your shaft.... food for thought.