[Ed Ashby]

in reply to: Center Shot ain't always good! #38377

Patrick, there are a host of factors that enter into ‘the correct spine’, but it’s definitely not an ‘in and off itself’ situation of just the broadhead and the shaft. If that were the case all you’d every need is a way to measure the static spine and a point weight chart showing which static spine you need for that weight of point. Finding the correct dynamic spine is what tuning is all about. It’s why I bare shaft tune every setup, even those I only use in testing. Without the correct tuning of every arrow setup the testing would be more or less meaningless.

Every factor about the bow, the arrow, the setup and the shooter himself affects arrow tuning. Even the type and quality of your release and the bowstring you use becomes a factor.

Looks like you’re seeing that now! 💡 😕 😀

Ed

[Ed Ashby]

in reply to: A good product hits the market #38292

Steve, even from the limited testing I was able to do on the prototype steel one-piece adaptor/inserts I can assure you they are markedly stronger than those made from brass. As for aluminim, it’s no contest at all.

I’m pretty certain that we’ll see steel screw-in inserts in the not too distant future. One area that would have to be address is the potential for rust (between the threads of the broadhead adaptor and the threads in the insert). The very fact that this problem is being looked at, and different potential cures considered (such as the use of different steel alloys) tells me that a steel insert accepting screw-in adaptors (or broadheads) is being considered.

Ed

[Ed Ashby]

in reply to: Shoulder Shots 2 #38284

David, my point exactly! Regulate the arrow and it begins to pressure folks to use a bit more draw weight … or limit their shooting distance a bit.

As for trajectory with a 700 grain arrow from a 40# draw weight (traditional) bow I can pass along what I found when doing the buffalo testing. The 40# recurve used in the testing was a borrowed Bear Formula Silver target bow. The 2 sets of above threshold EFOC arrows used were each around 725 grains. I shoot all trad bows using instinctive aim (I use sights and a release when testing with the compounds). All testing was from 20 yards. My subjective impression was that, at 20 yards, I was still ‘pointing’ directly at where I wanted to hit; not allowing for additional any arrow drop; compared to all the other traditional bows I’ve tested at that same distance. It was the same subjective aim as I use with my heavier bows. I had no difficulty keeping the arrows ‘on target’ doing that. I’ll also mention that the velocity of those above threshold EFOC arrows was a blazing 119 fps from the 40# target bow!

Ed

[Ed Ashby]

in reply to: Center Shot ain't always good! #38268

Dave, you have the right method down. I routinely use layers of tape to build the arrow plate out when I need to tune in an EFOC arrow that’s shooting just a bit weak spine.

Jason, I should have made that point more clearly. Glad you added it! In the first post on this thread I put what I meant – “When a bow is TRUE center shot – that is, the center line of the arrow precisely aligned with the bowstring – it can cause problems with arrow tuning and arrow flight.” – but really should have mentioned that center cut and center shot are not the same thing. Thanks for the add-in and clarification. It’s an important point for trad shooters, shooting with the arrow in contact with the riser. Its real easy for filks to confuse ‘center cut’ and ‘center shot’.

Along this same line, whenever the arrow is in contact with the bow’s riser don’t overlook that shaft thickness also affects the degree of center-shot, and becomes a factor in tuning. The larger a shaft’s diameter the weaker the dynamic spine required to tune perfectly. Conversely, the thinner the shaft the stiffer the dynamic spine will need to be. The center line of the thicker shaft sits further from the center line of the bowstring, and it will have to flex more to clear the riser and flex back for perfect alignment. The thinner the shaft the closer its center line will be to the bowstring’s center line, and the less it must flex to tune correctly. Applying this to a ‘traditional’ riser cut beyond ‘center’, to ‘true centershot’, that ‘true center shot’ will be correct for only one diameter of shaft. Use a shaft having a greater diameter and the bow is no longer ‘cut to center shot’. Use a shaft with a smaller diameter and the riser is now cut ‘past center shot’.

Ed

[Ed Ashby]

in reply to: Shoulder Shots 2 #37638

David, it’s always a quandry, but I’d rather see that 35# D-shaped longbow WITH THE BEST ARROW SETUP POSSIBLE being used than I had a 70# compound with a 380 grain arrow and a poorly designed mechanical broadhead!:( Neither is an appropriate choice, but which is worse::?: not enough bow or not enough arrow? Bow’s don’t kill the animal. Arrows do:!:

Ed

[Ed Ashby]

in reply to: Center Shot ain't always good! #37593

Steve, some of both. Speed of paradox recovery with a tuned EFOC setup from a non-centershot bow will be as quick, or quicker than paradox recovery from a well tuned arrow from a center shot bow.

No question but that a mechanical release makes a huge difference in getting consistent flight but, at least for most compound shooters, there is also an illusion of tuning ease. That’s created by the ability to just move the sight a bit to have it coincide with the point of impact of the arrows. Combine that with the very consistent grouping of a release, which groups even moderately tuned arrows very close together, and you have what appears to be a ‘tuned’ setup that isn’t really tuned.

If you’re doing either careful bare shaft or careful paper tuning with a compound it can be (an usually is) an even more tedious job then bare shaft tuning EFOC arrows from a non-center shot bow. It’s amazing how many “perfectly paper tuned” setup’s I’ve seen that are no longer ‘tuned’ when you change the distance from bow to the paper! No matter how badly an arrow flys, chances are it can punch a perfect hole in the paper at some exact distance. It’s just like a broken clock; which has the percisely correct time … twice a day.

Deviations in the quality of flight of anything less than a very well tuned arrow are more easily visible to the eye from non-center shot bow. That’s because the initial degee of paradox is greater. This becomes even more pronounced on a bare shaft, where there’s no fletching to speed stabilization of the arrow’s flight. However, with a well tuned EFOC arrow from a non-center shot bow recovery from even a massive degree of initial paradox (the initial bending that the arrow has to do to clear the bow) occurs in miliseconds. From a center shot bow, which will tune correctly with a much stiffer spine, the degree of initial paradox will be much less, ergo, it is less visible to the naked eye, but full recovery (with a normal FOC arrow) from the paradox will take as long or longer as that of the EFOC arrow from the non-center shot bow.

In tuning arrows with high amounts of EFOC to compounds I’ve found it benificial (makes it easier to get correct tuning) if you first make absolutely certain that the arrow rest is adjusted to be slightly off of center shot (move the rest just a touch farther away from the bow than where center shot truly is). I like to move the rest away from the bow enough that I can just barely visably detect that the arrow’s tip is now definitely, without question left (or right, for a left handed bow) of perpendicular to the bowstring. That’s to avoid that ‘confusion’ of the arrow ‘not knowing which way to bend first’ that occurs when the arrow is at true centershot.

The first time I tried to bare shaft tune an EFOC arrow to a compound I hit that problem; a perfectly center shot rest alignment. It was a right hand bow, but no matter which arrow setup I tried, one shot would go markedly weak spine and the next shot would go markedly stiff spine. Adjusting tip weight was showing no logical effect on the bare shaft tuning. I could increase or decrease tip weight substantually and the same pattern would show up; one shot weak spine, then next stiff spine. It nearly drove me nuts until I figured out what was happening, moved the arrow rest out and, bingo, the compound bare shaft tuned just like any other bow I’d tuned. No problem at all.

Ed

[Ed Ashby]

in reply to: Center Shot ain't always good! #37259

OK, Ed, as your crash-test dummy, I must ask what exactly are you saying here? That my homemade longbows with no centershot perform with EFoC arrows just as well as a centershot bow

Yes. When tuned with EFOC arrows total recovery from initial paradox (to be distinguished from arrow vibration during flight) is as quick from a non-center shot as from a (near, in the case of your Shrew) center shot bow.

or are you saying that with my near-centershot Shrew longbows I might get better flight and/or be able to get good flight with higher FoC on a given arrow without that arrow falling underspine — by building out the back of the rest plate?

Correct again. By building out the side plate on your Shrew you will be able to make a too weak spined EFOC arrow (caused by the added weight up front) tune correctly to the bow.

This isn’t the easiest of concepts, so fire away if the’s stii not clear.

Ed

[Ed Ashby]

in reply to: Shoulder Shots 2 #37010

Looks like we were all posting at the same time! LOL.

Ed

[Ed Ashby]

in reply to: Shoulder Shots 2 #37005

Michael, MA stands for Mechanical Advantage. Any broadhead can be thought of as a series of inclined planes. As you’ll remember from grade shcool science, an inclined plane is a “simple machine” which multiplies the “work” that can be done with a given amount of “available force”.

The higher a broadhead’s MA the more productive “work” (penetration) it can accomplish with whatever ‘useful force’ (that portion of the arrow’s total force that’s not ‘squandered’ on non-productive task, such as shaft vibration and overcoming the drag shaft vibration causes during penetration) the arrow carries. Productive work includes such things as penetration, slicing tissued and breaking through bones – all those task the arrow needs to do to be lethal.

Huge sections of several of the updates are devoted to specific examples of how and why higher broadhead MA has made a difference.

Ed

[Ed Ashby]

in reply to: Shoulder Shots 2 #36899

As usual some great photos, David! That last one makes an important point. Though the BH has not pierced the spinal cord, the rotating single-bevel broadhead is exerting very substantial pressure on the spinal cord. As I can personally attest, merely placing such pressure on the spinal cord secondary to damage to the bone really has a slowing effect on movement. That’s precisely what happened with my back, and I was instantly and totally incapacitated! The corrective surgery totally removed the back 1/3 of 5 vertebras (L2 through S1), dorsal process and all. Two steel rods and a fistful of HUGE screws held everything together. After nine months of using a bone growth stimulator the bone has regrown to again cover the spinal cord exposed during surgery.

The point being; THAT’S A PRETTY EFFECTIVE HIT for slowing an animal down, if not dropping it on the spot! On a like hit, a double-bevel BH would also have exerted some pressure on the spinal cord, because of the wedge effect of the ferrule, but nowhere near the pressure generated by the rotational torque the single-bevel BH. Little things, but they are what so often make the difference between a successful hit and an unsuccessful hit.

And this concept relates back to the original point, bone skips, and the skip angle of the broadhead you choose to use CAN be a huge factor, and it becomes a factor on far more hits than most folks realize. That’s because very few folks closely examine the course of successful hits to see exactly what occurred on the hit, and even fewer ever get to see what it was that caused an unsuccessful hit to be a failure. More times than most want to admit, those unsuccessful hits boil down to poor performance of the arrow setup that was used, and not merely to a ‘bad shot’.

Ed

[Ed Ashby]

in reply to: Performance Differance between the 160 Grizzly and the 160 STOS #36176

Dude, have you tired one of the KME sharpeners? For single-bevel BH’s the KME KNIFE sharpener is the one you want. For double bevel heads the KME BROADHEAD sharpener works best.

If you have any trouble getting your BH sharp using the KME just call Ron and he’ll walk you through the process, step by step. I’ve used both types of KME sharpeners and I don’t see how you can fail to get a BH truly sharp if you follow Ron’s instructions.

On the other hand, if someone who really knew how to sharpen broadheads volunteered to do mine for free … King, you busy? 🙂

Ed

[Ed Ashby]

in reply to: Time to increase EFOC #35361

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

[Ed Ashby]

in reply to: Time to increase EFOC #34898

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

[Ed Ashby]

in reply to: Shoulder Shots 2 #34595

David, those are some outstanding diagrams! I’m pilfering those for my library of useful information! There are many useful applications for such great examples.

Next, let me sincerely apologize for ever mentioning the game I’ve shot. Keeping the focus on the Study and off my own hunting has always been a personal goal. My response was prompted because someone had posted that bowhunters W, X, Y and Z had each probably shot arrows into more animals than the total number of arrows I had shot into test animals. It was the downplaying of the Study’s validity; the extent of its database; that made it necessary to set the record straight on the sheer quantity of data the Study’s results are based on; and to make it clear that the Study results are also backed up by actual field results on hunted game.

Now, let’s move on to more important things. Look at David’s last diagram; the quartering from the front shot. The quartering from the front shot was the least effective shot angle in the original Natal Study, and nothing since has changed that.

The problem with the quartering from the front shot is not the quantity of bones presented; it is the angle of incidence between the broadhead/arrow and the bone’s surface. When the shot is quartering from the front most of the bone surfaces present a very oblique angle if incidence to the arrow. That means that it is very easy to exceed the broadhead’s skip angle.

A broadhead’s skip angle is determined by many factors; the broadhead’s length and width, the number and angle of attack of blades, the type of tip on the broadhead, the broadhead’s structural integrity, etcetera. The shorter and wider a blade is the poorer its skip angle. The more blades a broadhead has, the poorer its skip angle. A broadhead that bends redirects the arrow, giving even a poorer skip angle than the BH design would indicate. Even on a well profiled broadhead, the broadhead’s tip design has a marked influence on the skip angle. The very best broadhead designs have a skip angle of approximately 45 degrees. That’s from bone surface. It will be different from different materials. It’s easy to ‘demonstrate’ an arrow sticking at very, very steep incident angles … if you use a piece of plywood.

Skip angle becomes a very important factor when shooting at a downhill angle; regardless of the animal’s ‘quartering angle’ to the shot. I’m absolutely certain that many a ‘pass through’ shot from a tree stand that has resulted in a non-recovered animal wasn’t a pass through at all. It was a shot that skipped off the bone surface at impact, failing to ever enter the body. When such a hit occurs the bowhunter is left with a mental image of the arrow making what appeared to be a solid body hit and a bloody arrow stuck in the ground. The obvious assumption is a pass through hit. Without being able to examine the wound channel the hunter tends to categorize the hit as an unexplainable solid body hit pass through that somehow missed everything vital … or they simply blame that particular broadhead as not being very good.

Now, there will be times when your arrow is going to face a quartering from the front impact angle on an animal. Animals just don’t stand still every time. As with other shots, you want to be using an arrow that gives you the maximum chance that your inadvertent hit at the worst shooting angle will be effective. Fortunately for us shooting the penetration enhanced EFOC/Ultra-EFOC arrows with a weight above the threshold we’re already using that arrow! Our long, narrow, high MA, single blade, single-bevel, Tanto tipped broadhead shows the lowest skip angle of all designs tested. If the Tanto tip does take purchase on the bone’s surface our arrow’s mass above threshold gives a maximum chance of pushing on the bone long enough to exceed the bone’s structural integrity; and the time required for that ‘push’ has been reduced by the tendency of our single-bevel broadhead to split the bone before the arrow has to, literally, force its way through the bone. Our arrow’s extreme amount of FOC will give up greater post-breaching penetration in the even our arrow is successful in breaching the bone.

There is an additional factor worth mentioning. ANY single blade broadhead has an advantage on a quartering from the front impact; whenever they find a space between bones – whether that happens on impact or during a skid off the bone – they show a tendency to ‘right themselves’, aligning the broadhead with the space between the bones. They can’t do this every time. If they hit at a near right angle to an intercostal space the blades then to bite into the bone surface. In this case the arrow must carry sufficient force to drive the broadhead between the ribs, slicing into or chipping away bone, as needed. The rotation induced by our single-bevel broadhead helps here too. It forces the broadhead to rotate and helps chip away the bone as it does so.

If you want to see this single blade broadhead ‘righting effect’ for yourself, set up a series of 3/8″ steel rods, positioned vertically and spaced about 3/8″ to no more than 1/2″ apart. Place them in a securely anchored base, so the shots can’t knock the rods over (mounting the rods in a 4×4 that is secured in a BIG bench vice works well). Back off at a right angle to this steel rod ‘picket fence’ and shoot away with different broadheads. You won’t get any multiblade broadheads through without destroying the broadhead. You will be surprised at how many of the single blade heads ‘right themselves’ to pass between the rods. Should you want to carry this exercise one step further, make a second set of rods that are spaced 2″ apart. This time position the ‘steel rod picket fence’ at a 25 degree angle to your shot and repeat the process. Now turn the ‘fence’ to give a 30 degree impact angle, then on to 35, 40 and 45 degree angles of arrow impact. It’s an enlightening exercise into how drastically broadhead design can alter outcomes.

Now, don’t distort any of the forgoing as saying it’s alright to take quartering from the front shots. It’s not. They are the poorest shooting angle, with the lowest chance of success, and should always be avoided as a deliberate shot. Still it is beneficial to consider what is needed in arrow setup to give us the best odds of making a clean kill, in the event the animal turns towards you and you inadvertently end up making a quartering from the front hit. Fortunately, that ‘best setup’ for the quartering from the front impact is the same fully penetration enhanced EFOC/UltraEFOC arrow that works best on any other heavy bone hit!

Ed

[Ed Ashby]

in reply to: Time to increase EFOC #34350

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

[Author]

Posts