Why Single-Bevel Broadheads? (http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=24;t=000005)
Awesome report. Thanks Doc Ashby. You've made a yet another believer... :notworthy: :notworthy: :notworthy:
I am a believer...even before this report. Now if I could just learn how to modify these broadheads...or better yet...the manufacturers actually make them like that and deliver them sharpened and ready to go! I attempted to modify a dozen heads to take to Africa with me and could not get them shaving sharp...they wouldn't even cut a rubber band.
Good stuff Doc! :) ....O.L.
I use ceramic rods on my Woodsman and it sounds like the rods would work with this head. Generally speaking, what weight bows do 170gr heads prefer?
Should the arrows have left or right helical for the broadhead to spin in the right direction?
I believe even more penetration could be achieved by rounding the back corners of the head slightly.Aerodynamics should be considered whether flowing through animals or air. I remember reading a penetration test in Bow and Arrow magazine in the late 60`s and again in the late 70`s and the same broadhead won both times. I can`t remember the name as it was`nt in production even during the first test but the only difference between it and the other heads was rounded back corners. And because of those tests I`ve always rounded the back corners of my Deltas.
troutms, Grizzlies need right wing (right helical) to optimize the benefit of the single bevel.
I found it interesting he said using the wrong direction on a single beveled head actually reduced performance below a double beveled head. I used left wing with Grizzlies for years before I knew any better.
That's what I thought but I wanted to be sure. Thanks.
Anyone know if you using right wing feathers with a straight fletching (instead of a helical or offset) will diminish the performance? -Chad
That's good stuff right there! Very well done.
Ok, I'm new. Can someone show me the difference in the broadheads and how you make a single bevel broadhead out of a double?
Very well done! IMO this report covers all the bases: theory, testing and example. Made a beliver out of me. Thank you for sharing!
Dave, you don't have to make a single out of a double. Grizzley and A-bowyer make single bevel heads. Grizzley makes a RH bevel and A-boyer makes a LH bevel. Doc Ashby takes a 190 grain Grizzley El Grande and modifies it to his specs. The Grizzley comes unsharpened and is high Rockwell hardened so it is hard work to sharpen and modify each head. But Doc Ashby has proven that the resulting modifications make a superior broadhead that will split bone that gets in the way, either by poor shot placement or the animal moving during the shot.
Grizzly 145 left side Abowyer 125 gr right side as they come from the makers. As far as sharpening my Lansky Knive sharpener works well, with a strop or crock stick.
(http://i94.photobucket.com/albums/l101/GUNSMITHAMMO/P1010001-11.jpg)
Brent
Great report Doc!!!!
Ashby definitely deserves a broadhead named after him. Great man and tremendous contribution to our sport! :thumbsup:
STD, You got that right. What few are aware of, he does this almost completely out of his pocket along with a huge investment of time.....O.L.
Well, true to form, there's a typo in the single-bevel article - and a huge thanks to Sean for finding it. On Page 21, 2nd Para, last sentnece: "None of these are exhibited with single-bevel broadheads"; "single-bevel" should (I hope obviously) read "double-bevel". (I'm sure my highschool English teacher would be amazed that I can even write - incorrect or otherwise!)
I hope Dave is correct, and that someone - anyone - will make a HIGH-QUALITY off-the-shelf broadhead based on the Modified Grizzly design ... and with a Teflon coating too, like that on the Eclipse. Sure would save me a bunch of time reshaping broadheads - and I could care less what they named it! If everyone interested in seeing one in production wrote some manufacturers, PERHAPS it would prompt a response (but I won't be holding my breath on that one). But, if there ARE any manufacturers intetested, I would be glad to pass along all the assistance I could give them! They could take advantage of twenty-five years of field testing and a few hundred thousand dollard of R&D - for FREE!
Thanks to each and every one for the kind words. Greatly appreciated.
Ed
Hello Doc
Even in France you become famous
Thank again for your help in the bowhunting world
I was thinking about the left wing thing and would suppose if one left the broadhead screwed on lightly the arrow wouldn't hinder the twisting action. You just wouldn't get the added benifit.
As to the manufacturing of "The Ashby", Knife companies seem to be hurting for business. One might talk a knife company into a single run of quanity to see how they would sell.
I suppose Tradgangers could form a company or provide backing for such a product. I don't know what the potental for sells would be for a single product like this. It may be hard to get backing. Now if one would "invent" a 3 and 4 blade version that would open the market. In theory the 4 blade version would have twice the twisting power of a two blade.
I suppose you would need to study the design of the front end a little to come up with the right angle to begin the fracture befor the second set of blades engaged to assist.
If someone was smart enough to patten the idea they could also sell this idea to folf like Muzzy, wasp, etc to be used on the screw on tip infront of their fixed blades. That would be a pretty simple addition to proven designed that may greatly add in penetration.
Someone needs to jump on this and make it happen. Once there is a product the other would follow or lose sales. At that point they would be require to pay you for your design.
Please tell me these modifications have been pattened? Add the screw on tip to the list if you haven't already. My undersanding is pattens can be granted for such modifications.
And now for the screw-in crowd (Is US$3.03 each, delivered to your door, too expensive?):
(http://i34.photobucket.com/albums/d106/Naphtalitlk/Single_bevel_Supreme.jpg) (http://i34.photobucket.com/albums/d106/Naphtalitlk/Single_bevel_Supreme-2.jpg)
Pascal, nice to know that the study information is getting around in France. The bulk of the bowhunters I guided in Africa were French; mostly guys from the Ivory Coast. How I do miss living in Africa!
Darke, I NEVER worry about a patent on anything. I keep both me and the study isolated from even any appearance of industry influence or persoanl gain - and that's why all the reports are offered free for publication too. The study is a work of love. I just want to have the best information I can provide 'out there' for the bowhunters interested. It's just my way of trying to give something back for all the joy bowhunting has given me over the half century I've hunting. There is one broadhead in the works and, while it's probably not precisely the head I would design myself, it MIGHT just turn out be a very good head (I'll let you know after there are some to test). I'm told it has to have 'market appeal' too. If it's good, it won't bother me that it's not an 'improved copy' of the Modified Grizzly. The more 'best broadheads' available the better. More to work with and chose from!
Lance, I talked to Woody and he's going to be looking into offering the Outbacks in a steel-ferruled version, like the prototypes I tested this year.
Ed
Thanks for all the work Doc. I read the article last night and was completely convinced. But, all my feathers are LW. Lots of them. So, I just modified a 160gr Ace Standard to a single bevel in about 10 minutes.
My 12 yr old shot it into a layered foam target along with a double bevel. The single bevel had to turn to pullout, and the double pulled out straight. I now have five more BH's to rework.
The altered head still has a 1 1/8" width, but that should work well on deer. And now I can use all my LW feathers.
Java Man
I have a half dozen of those sent to me for some testing Naphtali.
Since the right bevel and right helical are needed for max penetration, what about the threads on a a broadhead adapter? Are they left or right twist?
Alan,
If you use a right bevel (i.e., Grizzly) on a screw-in BH adaptor the BH rotation DOES tend to unscrew the adaptor from the insert during penetration. Secure them together. LocTite works perfect. Be sure to thoroughly degrease the threads and thread-groves on both insert and adaptor before using the LocTite.
Ed
Ed:
Just before he went on holiday, Woody wrote to me ruling out steel ferrules for my Supremes. He informed me he made your ferrules from steel broadhead adapters he bought from 3Rivers Archery.
He told me the main reasons for not having them available are:
1. He cannot automate assembling ferrules to blades with existing machinery;
2. Steel is very taxing on his equipment while returning a nominal (for the adapter's structural strength) improvement in broadhead strength of assembly.
***
I was interested in him using steel primarily for enhanced broadhead strength. Unless your testing shows something different, it will be a L-O-N-G time before Woody can deliver that product efficiently. And, unless he'll be retiring soon, he's not a full-time broadhead manufacturer. Just doing my special order set him back -- we're at six months, now. Fortunately, I'm confident my broadheads will be worth the wait.
Lance,
I just had a long phone conversation with Woody this past weekend. He said he would take another look at the steel ferrules. The biggest problem is with slotting them for the balde, with the equipment he has. However, he said he would talk to the fellow who makes his aluminum ferrules to see if he could do them in steel, if so, they may be a 'go'. I hope so. The steel ferruled prototypes held up much better than the aluminum ferruled versions. The 'bottom-line' outcome was higher average penetration and far more consistency in the penetration shown.
Ed
Ed:
Many thanks. I've got to E-mail Woody immediately to adjust my order. Since the Supremes cannot be used this year, with luck everyone comes out smelling like roses.
I have read through the studies quickly again. Did any BHs have convex edges?
Alan,
I've tested single-bevel vs. double-bevel on a number of different broadheads. Included were both high mechanical advanatge and low mechanical advantage designs with straight edges and with conves edges. I statred trying to do some testing on a concave profile and three blade designs this year. At this point all I can conclusively say is that the single-bevel advantage holds for straight or convex blades, regardless of whether they are of a long-narrow design or a short and wide design. The poorer the BH's MA, the greater degree (percentage) of improvement they show in penetration, but they won't show a greater amount (actual inches) of gain than the higher MA broadheads.
Lance,
I think Woody is off on a hunting trip at the moment; affter a buffalo, I think. But talking with him is a good idea. I'm not sure about any time-frame for starting to offer a steel-ferruled version of the Outbacks, and it sounded like everything hinged on whether he could get steel ferrules with blade slots already cut in, from whomever it is that makes them for him.
Ed
That is some good research there. I have the wide Magnus I broadhead and I was wondering if anyone has sharpened it to a single bevel or if I should just keep them double-beveled.
Michael
Michael,
The Magnus I has a pretty low mechanical advantage, only slightly better than a Woodsman; and penetration outcomes reflect this, with the Woodsman penetrating almost as much as the Magnus I. However, the Magnus I shows a big gain (percentage wise) in both penetration and frequency of heavy bone penetration when single-beveled, but it won't come up to the penetration a high MA broadhead shows. I've used them in testing, and Troy Breeding has used them a fair amount in his hunting.
No doubt whatsoever. Changing your Magnus I's to a single-bevel is a worthwhile improvement.
Ed
Judging from the volume of questions I've received, I need to clarify the effect and importance of matching the arrow's fletching-induced rotation to that caused by the broadhead's single-bevel as the arrow penetrates. I'll try to make them as clear as I can.
(1) Use right-wing fletching with a right single-bevel, such as the Grizzly.
(2) Use left-wing fletching with a left single-bevel, such as the Abowyer.
(3) If you mismatch fletching and bevel induced rotation, penetration decreases dramatically. The average penetration loss ranges from 42% for the high mechanical advantage (MA) broadheads to 67% for broadheads having very low MA. When you consider the average outcome for a verity of possible hits, by failing to match fletching and bevel-induced rotation you're cutting your arrow's penetration potential in half!
(4) Yes, even when mismatched, many times the penetration will still be sufficient when fletching and bevel-induced rotation don't match – but it will be far less than when they match.
(5) Yes, the big difference is on bone-impacts. The penetration difference is smaller on shots having only soft-tissue impact.
(6) When everything goes right, it will make little difference if bevel-induced rotation matches that caused by the broadhead.
(7) When things go wrong, it can make a BIG difference.
(8) With broadheads having equal mechanical advantage, a double-beveled broadhead will average more penetration than a MISMATCHED single-bevel.
(9) Yes, despite the penetration loss, you'll still gain many of the other single-bevel advantages listed in the article. But what you've lost is a lot of 'force advantage'. You've wasted a lot of arrow force that you could have usefully-applied to penetration; but the biggest thing you've squandered is much of the single-bevel's bone-splitting potential.
(10) One of the big variables in bevel-induced bone splits is the amount of force applied by the bevel against the bone. It determines how hard the bone's resistance 'pushes-back' on any given degree and amount of bevel, which, in turn, determines the blade's rotational force and the amount of torque the broadhead's face will re-apply onto the bone. This is a huge single-bevel advantage you're depleting when your fletching rotation and bevel-induced rotation don't match. The heavier the bone involved, the more difference the arrow-force you've lost is going to make in the outcome.
(11) Absolutely. If you don't match the arrow's rotation in flight to that caused by the bevel in tissue, you'll get more average penetration using a double-beveled broadhead of equal MA - and, as Howard Hill stated regarding the outcome of any given hit; "all else being equal, penetration is the name of the game". He was absolutely correct ... and that's precisely why it's so important that you match the rotation your fletching causes and that your single-bevel broadhead causes.
I hope this answers most of questions.
Ed
Dr. Ashby,
I just read your report and found it fascinating, and applaud you for producing such thorough reports and research in such a selfless manner for the benefit of bowhunting. Being relatively new to bowhunting, however, I noticed there is only one cutting edge on the Grizzly or Abowyer broadheads. If those broadheads, or a Magnus were sharpened on either side of the broadhead, creating single-bevels on both the left side of the broadhead and say for example the right rear side of a broadhead, wouldn't that assist in inducing greater rotation, and would this additional rotation be worth the additional effort to create. I may not be very clear in what I am trying to describe, if so please let me know and I can elaborate.
Brian, all the single-bevel broadheads have a bevel along each of the blade's edges; with each being on the oposing blade face from the other. When you look at the blade face, you only see one edge bevel. The other bevel is on the opposite side of the bevel-less edge you can see. I think that's what your asking (?).
Regardless, the bevel-configuration used is going to generate the maximum amout of torque the broadhead is capable of achieving, at any given rate of blade taper and bevel-angle. Any degree of partial-beveling will show less bevel-to-bone contact at some point during penetration; which means less torque.
Hope that answers your question.
Ed
Yes, that answers my question.....I did say I was new to this... :knothead:
Thank you
My pleasure Brian. I started out at this a bit over fifty years ago. There were only two 'bowhunters' in the whole county - James Hayes and I - and neither one of us had any idea whatsoever of how to go about anything to do with bows and arrows. I STILL remember how hard it was back then to find out even the simplest things about archery or bowhunting! God Bless Tradgang!
Ed
Dr. Ashby, would you care to give me a call this next week to discuss this?? I am a custom knifemaker that is getting back into traditional archery in a big way.
I would be more than happy to see if I could do the modifications to an existing broad head. I am used to working in large batches so I could possibly take care of this. I promise I can get them sharp enough to scare you!
Tom
Just saw that you are in Australia, the call is probably out. Maybe shoot me an email then.
If one of the other people posting on this thread want to contact me about this project my cell number is... 479-233-0508
Tom
Here's a pic of ours from a winter hog hunt. The Grizzly 125 pierced the heart from the rear on a hard "raking shot" that entered behind the last rib. It continued forward and lodged in the sternum. If you look closely you can see the rotation as it passed through the heart, on the upper right and lower left. The arrow was an Easton 2016 fletched right helical, from an old 50# Hoyt recurve.
(http://i106.photobucket.com/albums/m276/BraveheartArchery/Grizpigheart.jpg)
The arrow was losing steam at the point it did this but you can still see the rotation.
Ed,
I am back from my buff trip, managed a small buff and had a great time.
Brad Kane was my guide and Wolfgang Kimmel the other hunter in the team. Both top blokes and a pleasure to share the hunt with.
Several stalks had me very close to bulls but the oppurtunity for a clean shot eluded us for several days.
At one point a large bull we were stalking got it in his head to chase a subordinate bull, which decided to run our way,the bulls saw my bow and Brad's rifle lifting, and we had a staring match at 7 metres.
Asat camo and face masks are good gear, lol.
I have spoken to the man who does the ferrules for me, and he thinks it is doable to make steel ferrules with slots cut to fit the blades.
They will be slightly more expensive to produce due to slower machining of steel versus aluminum.
He is flat out for the next 5 weeks, but then his machine is free to play with broadhead ferrules again.
In time I will be able to do left and right wing bevels easily, but until I make a better surace grinding bevelling machine, its right wing only.
I cheated with the buff and used a 72lb compound, because I am not presently strong enough to draw a trad bow with the grunt required.
However your advice on arrow weight and broadhead worked well.
Arrow specs were 840 grain total weight, speed 182 feet/ sec, single bevel, 170grain, 3:1 broadhead. Shot distance was 20 metres.
If I hunt buff in the future I would go up to a 1000 grains for arrow weight next time.
Arrow placement very close to centre of front shoulder one third of height of chest. broadside.
The tip of the broadhead was almost through the far side hide, the last 8" of arrow broken by the action of the shoulder as the buff ran off.
He went down in 40 metres, a matter of seconds.I was very pleased to kill such a large animal so cleanly. Thanks for all the good advice.
Woody.
Dr. Ashby,
Concerning the Magnus 1: I have removed the factory edge and I'm now working on the single bevel (left hand). Question is what would you recommend on the triple thickness front section. Without having an edge on the off side in the same plain, I can not get a cutting edge without putting at least some angle on the off side front section. Will this have a big impact on performance? Hope what I'm trying to describe makes some sense to you. Thanks, Dave
Hello Woody,
Sounds like you had a great hunt! Buffalo are increadibly tough critters. Now that you've 'been there', take a look at Photo three in the new updates, Part 8. After seeing first hand what buff are like, you'll now have a special feel for what a HUGH difference a fully penetration maximized arrow can make! Those are just 790 grains, and carry just under 39 foot-pounds of kinetic energy. "Impossible", all the folks who lean on kinetic energy as an indicator of an arrow's penetration potential would say ... but those arows did that; and exit wound on EVERY SINGLE SHOT!
That's great news on the steel ferrules. After testing the steel-ferruled prototypes I know that this one change will place the single-beveled Supreme VERY HIGH on the list 'Best Broadheads", and certainly place it as the top choice in overall performance among screw-mount broadheads.
Tique, are you adding a Tanto profile tip? That's what I did during the modification, and I DID double bevel it on the triple-thick section. I'm just beginning to look at what affect the dimentional size of the Tanto and the type and position of the bevel I place on the Tanto, might have on performance. It will be a big part of next years testing. Until I know otherwise, I can't really say that double-beveling the tip causes any problem. Wish I could give you a better answer, but just don't know what is the best way to go yet. Perhaps by the end of the next round of testing.
Tom, check out the post I added about how I modify the 190 Grizzly. I gave some specific dimensions there. If you have any specific questions, send me a PM. I'm headed bush again very soon, but will get any PM sooner or later, and back to you as soon as possible.
Ed
Where can I get some of those "Abowyer" heads???
JRH, I asked the same thing and there is a post, do a search but call the manufacturer. He may be hunting this week so you can't reach him for now. I like the heads and got the 135 gr. He said he doesn't have many now due to demand but will be making more.
Here is a thread I just started with pics of a Grizzly 190 gr broadhead that I modified per Dr. Ashby's instructions...
LINK (http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=050127)
Let me know what you think.
Tom
Thanks for the info...
Has anyone tried modifying a Magnus, Tusker or any other reasonably priced readily available blade? I would think the Magnus I, or the Tusker delta types would be good candidates? I am asking only because left hand helical's shoot best and fletching last the longest through my longbow. I am sure Abowyer's are good heads however, at $40 for 3 heads, could there be a more economical alternative...?
JRH,
I modified one Ace Standard 160gr head. I'm going to do several more, and some Tusker Aztec's. Just need to find time. With a bench grinder, it took less than ten minutes to modify the head. I'm still trying to figure out the Tanto point, but its probably not so necessary on deer size critters.