Home Forums Bows and Equipment Time to increase EFOC

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    • Chris Shelton
      Post count: 679

      Well men, I have been waiting and watching patiently, and the season will infact be over for whitetail on Saturday! So now I feel safe messing with my arrow system! I am shooting Beeman ICS bowhunter shafts, with 100 grain stingers. 29.5 inches long 8.4 gpi, which translates to 247.8, for just the shaft:roll:

      Before when my arrows were the full 32 inches long, the EFOC was only a mear 8% I beleive, and after rechecking after I cut them to proper length(29.5), I was pleasantly pleased to see that my EFOC was bumped up to 13.56%!!!:D

      So my question is . . . do you guys think that bumping up the weight some more, would help? I am thinking weight tubes is the way to go, simply because I have alot of these shafts, and I love them, and they are flying great for me!

      Chris

    • David Petersen
      Member
      Post count: 2749

      Chris — I suggest easing into it by upping the weight of your heads (experiement with target points). If you’re using alum inserts, go to brass. You can easily double your FoC that way. My experience is that carbons are very forgiving in the spine dept. and the more weight I add up front, the better my accuracy with minimal trajectory change compapred to increasing overall shaft weight. In fac the easiest way to get EFoC is to start with a light shaft and add all the weight up front you can shoot well with. Dr. Ashby’s testing shows that 650 grains overall weight is minimal for assured slam-dunk penetration of heavy bones on heavy big game (assuming a high MA broadhead), and my own small experiments show that you want as much as that weight as possible right up front. Congrats on giving it a try! dave

    • L82HUNT
      Post count: 27

      Man thats some low arrow weight. WEight tubes will give you more weight but you will lose some of your foc. If you really want to get a EFOC as you said your going to have to get a stiffer shaft to get more weight up front.

    • Ed Ashby
      Member
      Post count: 816

      Chris, you didn’t mention the type and draw weight of your bow. Other factors, such as degree of center shot, also will affect the shaft you’ll need – or how much you’ll be able to front load the shafts you have. It’s all trial and error right now. Just start adding point weight and checking the dynamic spine with some bare shaft testing to see how much weight you can get away with adding.

      You’ll want to get to at least 19% FOC if you want to see some really measurable penetration gains.

      Ed

    • sapcut
      Post count: 159

      I made an arrow for my son’s 55 lb bow.

      Gold Tip Ultralight Entrada 400. 7.4gr./in. I think.
      513 up front and 781 gr. total weight with 32.7% UEFOC.

      That dude flys so stinkin good. It is amazing how well and fast that arrow can fling out of that little semi-recurve no name.

      Shooting Ultra EFOC arrows is kind of like Christianity…..You have to experience it to understand it.

      Richie

    • Chris Shelton
      Post count: 679

      O guys I forgot to mention that I was going to do what I and another fello figured out on another thread, I am going to get the heaviest weight tubes, and then probably the medium ones and split the tubes, and have the heavy ones up front.

      I shoot a 55# greatree takedown, 60 inches, I dont know the degree of centercut.

      Dave I forgot about brass inserts, they are definatly a good idea.

    • Chris Shelton
      Post count: 679

      Dr. Ed Ashby wrote: Chris, you didn’t mention the type and draw weight of your bow. Other factors, such as degree of center shot, also will affect the shaft you’ll need – or how much you’ll be able to front load the shafts you have. It’s all trial and error right now. Just start adding point weight and checking the dynamic spine with some bare shaft testing to see how much weight you can get away with adding.

      You’ll want to get to at least 19% FOC if you want to see some really measurable penetration gains.

      Ed

      Okay, we are getting somewhere now!!!

    • Chris Shelton
      Post count: 679

      Sapcut wrote: I made an arrow for my son’s 55 lb bow.

      Gold Tip Ultralight Entrada 400. 7.4gr./in. I think.
      513 up front and 781 gr. total weight with 32.7% UEFOC.

      That dude flys so stinkin good. It is amazing how well and fast that arrow can fling out of that little semi-recurve no name.

      Shooting Ultra EFOC arrows is kind of like Christianity…..You have to experience it to understand it.

      Richie

      How the heck did you get that sucker so heavy:shock:?

    • Ed Ashby
      Member
      Post count: 816

      513 grains up front. That’s how! Let us know how your duel weight tubes work out, Chris.

      32.7% FOC. That’s impressive,Richie. The higher I get into Ultra-EFOC the more impresses with what it does for both arrow flight and penetration.I don’t think there is an upper limit for FOC benefits.

      Ed

    • sapcut
      Post count: 159

      I first tried to find the lightest gr./in. I could find and I found these Gold Tips for $3.99/ea.

      I am using 190 El Grande’s and 125 gr. adapter. I put 15-18 grains of lead pieces in the ferrule of the Grizzly before putting in the adapter making it 333 gr. I then use 100 gr. brass insert and 1- 50 gr. lead bullet shaped worm weight behind the insert. I then use a 2.5 in. piece (30 gr.) of 2216 aluminum for the external footing.
      I keep the arrow full length and it flys ridiculously well and fast with 55 lbs. It does not fly like it is 781 grains.
      It looks like a 600 grain arrow in flight.

      I would hunt anything on the earth with that arrow.

      Richie

    • Chris Shelton
      Post count: 679

      Only one thing to say to that . . . WOW! You are right Doc I should have said how did you get 513 grains up front, lol. The adapter give u more than I can get, because I dont like adapters, lol. What is a external footing?

      And a generally question to all, I have noticed in the past that there is no back, at least to all the inserts I have had. Making a place to thread something into the back. Does someone make a weight that you can screw into the back of the insert to hide inside the shaft?

    • sapcut
      Post count: 159

      The external footing is basically a piece of aluminum shaft that fits nice and tight forming a sleeve on the end of the arrow flush with the insert. It helps strengthen the end of the shaft as well as add a little weight in the front. Another benefit…the location of the external footing’s weight is better than having the same weight farther up the shaft behind the insert. You have the weight in your arrow…. but FOC is not as good the farther away from the point you put the weight.

      Richie

    • Str8arrow
      Post count: 32

      Assuming your arrow is correctly spined for your set-up, I don’t know how you will be able to turn it into an EFOC arrow. If you have room, you can shorten them to get a bit more stiffness, but I doubt it will help enough.

      Experiment with one to be sure, but if it were me, I’d sell them and reinvest the money into a sustantially stiffer arrow that can handle a lot of weight up front. That is, is you really want to see what the higher FOCs will do for you. I also think you should strive to hit that 650 gr bone-breaking threshold. On your arrow, you’d have to get over 400 gr up front, and I can’t imagine that you will be able to.

    • Ed Ashby
      Member
      Post count: 816

      Chris, you MIGHT want to consider trying your current shafts with a built-out (thicker) arrow plate (and more tip weight). The farther your arrow is from center shot the weaker the dynamic spine your arrow needs to be. As you work with higher and higher amounts of arrow FOC the degree of a bow’s center shot becomes a big tuning factor.

      Contrary to ‘common knowledge’ having ‘center shot’ on your bow is not always a big advantage. With a normal FOC arrow it does offers some advantage. It forces you to use a stiffer arrow spine. That means less shaft bend at the release, reducing the degree of paradox (which also means less work for the fletching in overcoming the paradox – and the normal FOC arrow’s fletching needs as much help as it can get, due to the short rear leaver arm the fletching has). With normal FOC arrows this helps, because normal FOC arrows recover from paradox much more slowly the EFOC and Ultra-EFOC arrows. Even when used from a bow not having an arrow shelf (one having a peg rest) EFOC and Ultra-EFOC arrows still recover from paradox more quicly than a normal FOC arrow does from a full center shot bow. This is easy to see. Just test which can placed a well tuned arrow into a target absolutely straight at the closer distance. It’s no contest!

      When I was building up a barely above threshold Ultra-EFOC arrow (31.4%) for the 2008 testing (that information and the testing results will be coming in the 2008 Updates, Parts 3,4 and 5 – some really amazing results) I was able to get the same arrow tuned to both the 82#@27″ straight end longbow AND a 64#@27″ ACS-CX. The arrow was built up for the 82# bow. When I initially tried it on the 64# bow the dynamic spine WAS FAR TOO STIFF!

      The 82# bow, for which the arrow was originally built (tuned to), is far from center shot. When I first tried it on the 64# bow, which is far closer to center shot, the dynamic spine was way stiff, so I incrementally thickened the arrow plate on the ACS-CX until I got the arrow tuned to that bow too. Interestingly, when I had finished tuning the arrow to each bow and chronographed them, each arrow showed the EXACT same velocity. That’s an amazing degree of difference in bow efficiency; which is one reason it is very difficult to equate bow draw weight with terminal arrow performance. Here was an 18# difference in draw weight giving the same arrow exactly equal velocity. Once the arrow is launched it has no idea what type or draw weight of bow it was launched from. All that matters then is the arrow’s design and the force (momentum) it carries. As expected, when tested the arrows from each bow showed virtually identical terminal performance on the buffalo.

      Ed

    • Str8arrow
      Post count: 32

      Dr. Ed Ashby wrote: Chris, you MIGHT want to consider trying your current shafts with a built-out (thicker) arrow plate (and more tip weight). The farther your arrow is from center shot the weaker the dynamic spine your arrow needs to be. As you work with higher and higher amounts of arrow FOC the degree of a bow’s center shot becomes a big tuning factor.

      That’s a great idea, one that hadn’t occurred to me. I was under the impression that center shot gave a bit more flexibility in form errors, but I’m not really sure how much a difference it makes once you move away from center shot.

    • Chris Shelton
      Post count: 679

      I am a bit finicky about my arrow rest. I shoot a elevated brush rest, but it is a far down the riser as it can be. For some reason I can not get good arrow flight off the shelf of that recurve? And I dont understand why, it is just that recurve, I have tried everything from adjusting the nock point ect. But it didnt bother me, it was just a temp, untill my replacement brush rest came, unfortunatly that period of shelf shooting was during hunting season.

      I am thinking that with brass inserts, and my weight tube half and half idea, mixed in with a heavier tip, should increase my FOC a bit. I am thinking that I really want the arrow weight to be increased no matter what, because my shafts, since I cut them to proper length are a bit below the suggested minimum of 400 grains. I personally would like them to be around 500 grains, as a minimum.

      I seriously think that my current arrow system is good enough, but like almost all of you guys, good enough is not enough. I want it to be perfect. It is like using a muzzleloader with half the powder charge, sure it will probably work, but is it definate!?

    • Chris Shelton
      Post count: 679

      Alright, done some number crunchin. Here is what I got, with my weight tube idea only I am adding 237.2 grains. Plus the 247.8 of my arrow. I am thinking I will go with the 100 grain brass inserts. With my 100 grain broadheads untill I can buy new ones. SO i am looking at a total of 685 grains fo arrow weight. So Doc is there a way to caculate FOC without actually having the arrow??? If so that would sure be helpful!

    • Ed Ashby
      Member
      Post count: 816

      Not really. There are just too many factors; fletching weight and position will affect the total FOC, as will the weight of the nock used, the length of the insert (as well as its weight) and the amount (and sometimes the type) of glue used to attach fletching and insert. At every step it is truly a ‘balancing act’. Each small change in weight distribution changes the FOC which, in turn, alters the length of both the forward and rear lever arm, altering the force exerted by the weight(s) at each end of the levers, changing the effect the weight at front and rear has on the FOC measurement.

      As FOC increases adding weight to the arrow’s front has less effect on arrow FOC and the effect of adding weight at the arrow’s rear becomes greater. In the Ultra-EFOC range removing just a few grains of weight from the arrow’s rear has a much greater effect on FOC than does adding a lot of grains of weight at the arrow’s front. That’s because, at Ultra-EFOC, the forward leaver arm is already very short and the rear lever arm is already very long.

      So simple, yet so complex.

      Ed

    • sapcut
      Post count: 159

      Dr. Ashby that is exactly what I have noticed. I have even cut 1 grain of the male part of the nock, used 3 inch feathers, no wrap, etc. and it does make a difference. Like I mentioned once before, it is all about weight management when maximizing FOC.

      In your studies have you experimented with 1000+ grainers with 30+% UEFOC. Kind of the cake and the feast too.
      I just measured and made sure of details again….I am shooting GT Big Game 100 at 1029 gr. with 31.3% UEFOC.
      I know you have tested 1000 grainers and 31+% UEFOC but not sure if I had seen information where they were both crashing the party at the same time.

      Richie

    • Ed Ashby
      Member
      Post count: 816

      Richie, No I haven’t tried both together. There are a couple of reasons reasons. First, the Ultra-EFOC testing is still in its early stages but, second, and more to the point, is that I don’t have game big enough to test them on. At 790 grains and just under Ultra-EFOC I’m already routinely getting exit woulds on the Asian Buffalo. That’s with less than 37 foot-pounds of KE and 0.488 Slug-Feet/Second of momentum! Using Asian buffalo for the testing how would I measure the penetration of a 1000+ grain Ultra-EFOC arrow?

      At the ATA I had a change to discuss with Chris McDonald the pass through hits he had on his elephant. You might have seen the video on You Tube. He used a 90# compound, a 1100 grain arrow at 28% FOC and the Ashby broadhead. All three pass through shots penetrated through the Elephant’s ribs, both entrance and exit, and still achieved pass through hits. The ribs on that individual elephant were in the 2+ inch range in thickness. I was told that each shot “broke chunks off the ribs that were half the width of the rib”.

      No, I doubt that I’ll be doing too much testing of 1000 grain arrows at Ultra-EFOC. Not unless I find something a lot bigger than Asian buffalo to test on!

      Ed

    • sapcut
      Post count: 159

      Both arms are now up in victory. I officially have an arrow that will kill a T-Rex.

      I haven’t been fortunate enough this year to smoke anything with that setup but that IS my hunting arrow. It shoots extremely well and I just figured if I can create that type of arrow manhood….why not? No downside yet. I also just put on a SBD 10 strand skinny string. Maybe that will help even more.

      My goal is to be like King DeVille when I grow up and “not be scared of no shoulder”.

      Thanks for the reply,

      Richie

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