A heavy arrow that shoots flatter than a lighter arrow!

[Ed Ashby]

#4263

Here’s one to chew over. It is POSSIBLE (and, actually easy) to have a heavier arrow that shoots as flat, or even flatter than a lighter weight arrow! And that is when both are fired with the same launching force.

I just returned from doing a presentation at the ATA show, and was really pleased with how well the presentation went over with everyone attending – and even many who didn’t attend, but who heard about it from those who did attend.

I had a little demonstration in the presentation that I’d set up to show folks the effect on arrow flight that EFOC makes. It was a short, rubber tipped arrow with a movable rubber weight. By sliding the weight up or down on the shaft I could shoot the arrow at 6%, 11% and 24% FOC, without the mass of the arrow changing.

I pre-selected and marked the positions for the rubber weight for those specific amounts of FOC. Only a few compound shooters use over 6% FOC, and most use less than 6%. A typical traditional wood shaft with most commonly used broadheads show about 11% FOC. 24% FOC was with the weight as far forward on the shaft as I could slide it.

By using the same launching force and shooting angle on each shot I could demonstrate how much arrow energy is CONSERVED by using EFOC, and also demonstrate that front-weighted EFOC arrow DO NOT nose dive – indeed, they fly both flatter and farther than an arrow OF EQUAL MASS but with a lower amount of FOC. (Just as O.L. has repeatedly proven with his record-setting flight arrows.)

The small shaft was unfletched and, of course, the flight at 6% FOC was TERRIBLE, and it flew about half the length of the lecture hall. At 11% FOC it flew somewhat better, and traveled a bit over 60% of the length of the lecture hall. At 24% FOC the flight was great, and the small arrow HIT THE WALL at the far end of the lecture hall with a resounding thump! You could actually hear the collective gasp of the folks in the audience.

Now, this outcome logically implies that the energy previously wasted by an arrow with low FOC (and now being conserved by an arrow of higher FOC) can be usefully applied to propell a heavier, higher FOC arrow with a trojectory that is equally as flat as that of the lighter, lower FOC arrow. (Also, it must be remembered that the heavier arrow will retain its velocity better than a lighter arrow, continually gaining ground – velocity wise – against a lighter arrow as the range increases AND, the higher FOC arrow also stabalizes with less fletching, which translates to less drag during flight, which also aids velocity retentuion.)

That simple demonstration became the talk of the entire convention – even among folks who hadn’t attended, but who heard about it from those who had attended. During the balance of the day of the presentation and the next day I had a number of compound shooters tell me that they had changed to EFOC arrow and, to their amazement, had discovered that the EFOC arrows, though heavier than thier ususal, lower FOC arrows, were shooting flatter at long range. This they each had discovered because they were expecting to have to move thier sight pins DOWN (aim higher) with their new, heavier arrows, but ended up having to moving their sight pins UP (aim lower)!

Based on the information from several of the compound shooters who appeared to have done more extensive investigation of EFOC on their arrows it appears that the average ‘break even point’ was around 150 to 175 grains of increase in total arrow mass. That is; when changing from a low FOC (which was usually around 5%-6%) to EFOC around 24%-25%, or above, they each had found that an increase in arrow weight for the EFOC setup of about 150-175 grains resulted in the SAME SIGHT SETTINGS (same point of impact) at 20, 30 and 40 yards as they had been getting with their ‘customary arrows’.

This is good ‘food for thought’. If you are not already using EFOC, where is the break even point with your setup? Why would any hunter turn down being able to use more arrow weight if he can do so with no loss in arrow trajectory or point of impact?

This would make an interesting investigation with a shooting machine!

Ed

[Stephen Graf]

#28877

Seems obvious to me.

Whenever I would have my designs or analysis reviewed (engineering work) I would take it as the highest compliment when the person would say “seems obvious to me”.

The simplest design / concept is always the hardest to come up with. But once the idea has been had, and communicated, it becomes “obvious” to the observer.

Congratulations on your success at the ATA and I’m glad to see you are up and around!

[Bert]

#28888

Dr. Ed- It’s great to hear from you- we’ve all missed your intelligent posts. Nothing like the power of a demonstration to affirm your observations and experiments with EFOC- wish I could have been there to hear the collective gasp when the EFOC arrow hit the wall! Must have been much gnashing of teeth from the knitting needle, plastic-vaned, little lightweight mechanical machines they call broadheads fired from their overly complicated portable nautilus contraptions crowd!
Received some CarbonExpress shafts from Daniel(StandingBear) in a mutual trade and await eagerly my order from 3Rivers to experiment with EFOC- will keep you apprised of my results.
A belated Happy New Year, Doc, and may this post find you in good health and spirits- God bless- Bert

[Jason Wesbrock]

#29148

Edit:

Ed, I see you replied on the other forum while I was typing here. Thanks.

[Ed Ashby]

#29208

My pleasure Jason,

Just to save other folks the need to go back and forth, here’s the reply.

“In the simple demonstration arrrow used the dynamic spine on ALL the shots would be grossly over-spined. The propulsion system was a short section of modest strength bunge cord, drawn less than 10 inches. The shaft was a 20” section of dowel rod. The mass weight of the sliding weight is small. None of the shots represented a ‘tuned vs. untunes’ setup. All were ‘untuned’. It was a demonstration of the effect EFOC has on the flight characteristics of even a poorly tuned arrow setup.

I have, however, used matching arrows (same total mass and external profile, varying only in degree of FOC), equally well tuned, from the same bow and achieved the same results – the higher FOC shoots measurably (and significantly) flatter than the lower FOC arrow. To do so the higher FOC arrow has to be making better use of the force derived from the bow. This has been a 100% occurrance when testing with such matching setups.

Conversely, I have yet to see an equally well tuned lower FOC arrow that can totally recover from paradox as quickly (with the smaller fletching) as an arrow of higher FOC. That means that more of the arrow’s force is being loss to arrow flex. These results are not based on conjecture, but on repeated actual testing, from several different types of bows.

With big traditional broadheads (like the 190 Grizzly), Wesley Mulkey is getting total stability and can consistently hit 1″ dots at forty yards using a 2″ A&A pattern 3-fletch on a 28% FOC arrow setup. At lower FOC he can’t do that, even with considerabley more fletching and regardless of the tuning. That’s from actual testing too. Why does it happen? Because of the inate stability of a higher FOC projectile in flight. (Wesley is a three time Georgia 3-D champion, and by far the most accurate shooter I personally know.)

Talking with the folks at Win Win, most all of the South Korean FITA shooters are using well upwards of 19% FOC … and they’re the ones ‘taking the gold’.

Just as I told everyone at the seminar, there’s no trick or no magic. When we’re finished, feel free to come up and try it for yourself.

Hope that helps clarify,
Ed”

[Ed Ashby]

#29265

Because this is a subject not well understood the following is a follow-up posting I made in reply to a question about how this can be. How does it not defy the Law of gravity.

“Nope, the law of gravity is being well enforced. As you’ll remember from grade school science, the pull of gravity is a constant, not dependent on the weight (mass) of the object. The Gravitational Constant is 32.174 feet/second/second at sea level. A falling body drops at this rate, regardless of its mass.

(1) A higher mass arrow absorbs more of a bow’s stored energy, and will carry higher kinetic energy than a lighter arrow from the same bow.

(2) If more of the arrow’s energy is applied to the arrow’s forward motion then the arrow will travel farther before it drops to the ground. A more efficient arrow design does exactly that; it conserves energy otherwise wasted on ‘non-productive work”, such as recovering from paradox and/or stabilizing arrow flight.

(3) A heavier arrow which derives greater energy from the bow and which also is of a design that makes more efficient use of whatever energy it derived from the bow can have an equal or shorter travel time across a given distance; ergo, gravity has an equal or lesser time to act upon the arrow and the drop at that distance will be equal or less.

As previously noted, several compound shooters who approached me at the ATA reported that they were getting equal or less drop at 20, 30 and 40 yards with a heavier arrow having EFOC than with a lighter arrow at low FOC (and in one case the shooter reported that he had tested to 60 yards, with the same results). The aggregate of reported results indicated that an EFOC arrow in the 24%-25% range shot to the same point of impact as a low FOC (in the 5% to 6% range) that was 150 to 175 grains lighter. This is congruous with the results I’ve had with equally tuned, equal mass/profile arrows; the equal mass, higher EFOC arrows shoot flatter (drop less) than the lower FOC arrows. This can only occur when the flight time is less. Since I was testing with equal mass arrows, equally well tuned, the bow derived force would be equal. For the flight time to be less the EFOC arrow has to be using its bow-derived arrow force more productively than the lower FOC arrow. This additional ‘productive arrow force’ can equally well be applied to pushing a somewhat heavier arrow fast enough to result in a ‘total flight time’ equal to that of the lighter arrow, resulting in equal arrow drop.

Now those compound shooters are generally working with more ‘potential bow force’ than most of us traditional shooters. That means a higher potential ‘useful force’ gain (from the same amount of increase in arrow efficiency), but the effect would be the same for a traditional bow, but to a somewhat lesser degree – dependant only on the amount of available force (at equal arrow efficiency).

It’s all about total flight time. Ask any competition 1000 yard rifleman which .30 caliber bullet shoots flatter (has less drop) at 1000 yards, the 200 grain Match King or the 180 grain Match King, when fired from any of the .300 Magnum cartridges commonly used in 1000 yard competition. It’s the 200 grain bullet, even though it starts out well over 200 fps slower than the 180 grain version. Why? Because it makes more efficient use of the energy it carries. Indeed, beyond 600 yards it will be traveling faster than the 180 grain bullet. The net result is a shorter total travel time to reach the 1000 yard target, giving a sorter time for gravity to pull on the bullet, which results in a lesser amount of bullet drop. Bullets are a far more efficient aerodynamic design than an arrow, which also means that the potential for gains in efficiency are far greater for the arrow, percentage wise.

Hope this helps clear up the gravity question,
Ed”

[rayborbon]

#29352

When is too much EFOC?

[Ed Ashby]

#29755

So far no upper limit of arrow FOC has been found in the testing. The initial Ultra-EFOC (above 30%) are in the 2008 Updates, Parts 1 and 2, and there will be more in the next couple of 2008 testing updates. Results have been so impressive that I’m working towards developing some arrows in the 35% FOC range to test.

EFOC and even Ultra-EFOC are nothing new. I think use ‘moderns’ are just now rediscovering things some of the so-called ‘primative’ bowhunters have know for no telling how long. Check out the information on the Contemporary and Pre-WWII arrows of the Papus New Guinea natives! That article is in the library here.

Ed

[Bert]

#29791

Ray- You have too much EFOC when you have to aim and fire your arrow like a mortar round to hit a 20yd target! I’ll, of course, defer to the good Doc on this subject as he is our resident expert- those Papua New Guinea arrows look more like “spears”, but they work for them.
If you type in “english longbows and arrows” on Google on page 3 you’ll come to a very interesting PDF file on English longbow testing by Matheus Bane in 2006 whereupon he tests 4 different BH’s-short bodkin, needle bodkin, wide bh, and curved bh on 30″ ash shafts from a 75# yew longbow on various armor of the 14th century. No EFOC numbers but his arrows weigh, respectively, 1150 gr.,905 gr.,950gr., and 935 gr.
I’d like to get your opinion, Dr. Ed, on his testing as he lists alot of physics numbers of which you would be much more knowledgeable than us mere HS grads- all I know is that I would not like to be on tne receiving end of 5000 English archers firing at a rate of 10 to 20 shafts per minute unless I was in a tank!
Bert

[Ed Ashby]

#29867

Bert, that’s a good article, and with good testing and procedures. It sure makes a strong case for arrow momentum! Most interesting is that, if you take all the test collectively, the short Bodkin was the least effective, and the long (spike or needle) Bodkin the most effective. Can anyone say “broadhead mechanical advantage”? It made a difference, even way back then!

Ed

[Bert]

#29922

Dr. Ed- Thanks for your quick and accurate perusal and observations of the above mentioned testing. Having an interest in the historical, actual use of the longbow, the most formidable hand-held weapon until the advent of the gun during the middle-ages- but it required constant practice by a dedicated group of men over decades led by an intelligent tactician, which the English had during the 13 and 1400’s and the French almost never possesed.
A couple of interesting books on historical EFOC arrows and it’s effect in battle, and ones I highly recommend, would be Juliet Barker, “Agincourt”-written by a gifted historian and “Vagabond” by the equally gifted fictional writer who does his homework, Bernard Cornwell.
Essentially, the longbow archers were the light artillery of the age, used in the beginning of the battle( and usually outnumbered by their foes) to spread death and discord amongst the enemies’ heavy, knighted cavalry- could you imagine the panic as any of those heavy BHs by the thousands slammed and skewered armored men and more importantly- their horses, which promptly threw their weighted charges into the mud to be warhammered and pierced by the more nimble infantry-which included the archers when they had finished or run out of arrows?!!
May seem to be a bit off topic here but I think history has alot to teach us about archery and what kind,weight and shape of BHs and EFOC tested by men in battle when it really was life-or-death-or in your case, large, hairy creatures that wish to turn you into toe/hoof jam!
Soldier on, Doc!- as you stated, the word is getting out and we eagerly await further experiments and astute observations and conclusions. Thanks-
Bert

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