NEW Dr. Ashby report - check it out !!!

[Naphtali]

And now for the screw-in crowd (Is US$3.03 each, delivered to your door, too expensive?):

   

[Dr. Ed Ashby]

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

[Java Man]

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

[vermonster13]

I have a half dozen of those sent to me for some testing Naphtali.

[beyondmyken]

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?

[Dr. Ed Ashby]

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

[Naphtali]

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.

[Dr. Ed Ashby]

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

[Naphtali]

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.

[beyondmyken]

I have read through the studies quickly again.  Did any BHs have convex edges?

[Dr. Ed Ashby]

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

[Michael Peschek]

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

[Dr. Ed Ashby]

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

[Dr. Ed Ashby]

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

[MrBadExample]

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.

[Dr. Ed Ashby]

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

[MrBadExample]

Yes, that answers my question.....I did say I was new to this...    

Thank you

[Dr. Ed Ashby]

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

[Tom Krein]

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

[Tom Krein]

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