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Author Topic: question about grizzly's  (Read 424 times)

Offline bm22

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question about grizzly's
« on: August 03, 2007, 09:22:00 PM »
according to Dr. ed ashby the grizzly picks up speed in rotaions when it enters the animal. so would adding bleeder blades to a grizzly negate the advantage of the single bevel design or would it still spin in the wound channel.

i think the grizzly are a great design but they just don't make a big hole or very good bloodtrails.

Offline Charlie Lamb

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Re: question about grizzly's
« Reply #1 on: August 03, 2007, 09:38:00 PM »
With all due respect to the good Dr. and his fine work, but on ANY North American big game out of reasonable weight and effeciency bows, the arrow will go through so fast it will be hard to tell if it was spinning or not.

The addition of a bleeder on a broadhead with as good a design as the Grizzly could only help. I'd want to keep the bleeders fairly trim and not overly wide....no more than the width of the broadhead.
Hunt Sharp

Charlie

Offline Mike Orton

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Re: question about grizzly's
« Reply #2 on: August 04, 2007, 03:33:00 AM »
BM,

I've been modifying the Grizzly Grande w/ my Dremel tool, cutting a short slot into the ferrule and inserting a Magnus bleeder.  A drop of epoxy holds the thing together nicely.  Awesome looking head as a four blade.

I've sent Shawn Schoonover (owner of Grizzly Broadheads) some modified Broadheads but I don't think he'll be adopting my technique.

I'm not condoning making the Griz into a four blade to use on large game, (elk and bigger) but for deer sized game is what I intend the four blade used for.

FYI, the Magnus bleeder is only about 10 - 12 grains extra, much of that weight is made up in the net loss of material removed from the Griz ferrule when the slot is cut.

 

   :thumbsup:      :thumbsup:      :thumbsup:
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Offline DarkeGreen

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Re: question about grizzly's
« Reply #3 on: August 04, 2007, 08:04:00 AM »
Quote
Originally posted by bm22:
according to Dr. ed ashby the grizzly picks up speed in rotaions when it enters the animal.  
Can you point me to a link where he made that statement? I'd like to read it.

Offline SlowBowinMO

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Re: question about grizzly's
« Reply #4 on: August 04, 2007, 09:47:00 AM »
I've always thought a 4 blade Griz would be a nice option for smaller stuff.  Mike, cool heads!

I wonder if bleeders off the center of the axis, on the right side, would let the Griz still spin?
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Offline Mike Orton

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Re: question about grizzly's
« Reply #5 on: August 04, 2007, 11:15:00 AM »
DarkeGreen,

I too was intrigued by that statement so I did some looking into the Ashby research I have accumulated.  The closest similarity I can come up with is the 2005 update1 discussion on Broadhead Lethality.  Even so, I could not find a reference to an arrow "pickup up rotational speed", however the Doc Ashby does make a reference to single bevel broadheads hold a clear advantage in penetrating bone and he suggests that right wing helical fletching be used to compliment the rotational force of the clock-wise twisting motion created by the Grizzly.  I don't think Doc Ashby was able to measure rotational speed, just penetration effects by way of torque.

Perhaps we're splitting hairs, if not bone....
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Offline vermonster13

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Re: question about grizzly's
« Reply #6 on: August 04, 2007, 11:18:00 AM »
I seem to remember him saying the entry wounds showed how the Grizzly was rotating but nothing about it picking up speed in rotations which would violate numerous laws of physics.
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Offline Mike Orton

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Re: question about grizzly's
« Reply #7 on: August 04, 2007, 11:21:00 AM »
Tim,

I'm not sure about off-setting the bleeders.  Personally I have trouble enough trying to keep the danged Dremel tool cutting straight, I don't think I could possibly hold, by hand, an off-set slot.  On deer sized game I'm not sure it would matter all that much anyway.

Personally, I'd like to find bleeders with a much less steep angle than the Magnus bleeders.  I'd prefer to find bleeders that more closely matched the angle profile of the Grizzly.

  :campfire:
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Offline Dave2old

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Re: question about grizzly's
« Reply #8 on: August 04, 2007, 11:57:00 AM »
I think the important distinction to keep in mind here is small game vs. big game. The whole point (sic) of Ashby's years of research has been to determine the factors, and the gear, that will best assure penetration and a clean kill with very common "bad" hits on big game, as epitomized by an angled shot into an elk scapula, which will turn most any normal head away, and/or blow it up (I've done it and seen it done too many times). Any broadhead feature that will slow penetration through heavy bone has to be eliminated, and multi blades and bleeder blades are at the top of the list. So yes, for hunting deer with plenty of bow and arrow weight, and you want more blood on the ground, they are good. But to max your odds of killing a big animal -- and I've seen some mighty big buck deer -- with a bad bone hit, you don't want bleeder blades or multi-blades. A theory I have proven to myself beyond doubt is that enducing max bleeding should not be our goal in setting up our gear and shots for big animals. Rather, we want to punch holes through both lungs -- complete pass-throughs. Do that and the lungs collapse and the brain shuts down almost instantly and the animal never gets out of your sight, making a blood trail superfluous. The absolute slam-dunk shot on elk is broadside and low, just behind the shoulder, so that you not only vent both lungs but get the top of the heart as well. The risk with this shot is that it's so close to the scapula, and the low front ribs over the hearts are extra thick and close together. For smaller game, deer and pronghorn, the Grizzly doesn't seem worth messing with to me, just too darn hard to sharpen, and I'll stick with such proven 2-blades as STOS, Eclipse, and Zwickie, modified to a tanto point -- still going for the pass-through and oxygen starvation rather than max blood. To each his/her own, so long as we aren't taking undue risks at the animal's expense. Cheers, dave

Offline DarkeGreen

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Re: question about grizzly's
« Reply #9 on: August 04, 2007, 03:08:00 PM »
Quote
Originally posted by vermonster13:
I seem to remember him saying the entry wounds showed how the Grizzly was rotating but nothing about it picking up speed in rotations which would violate numerous laws of physics.
I wasn't going to go quite that far because it is possible. You would need a design that used the force of the arrow moving forward applied to the angle of the blade to get it done though.

I just couldn't see Dr. Ashby making such a claim and if he did I wanted to know what broadhead...exactly and how it had been modified.   :)  

I have tested broadheads that increase the speed of the arrows rotation and didn't care for them. They do help arrows fly better no doubt about it. I shot severial into a box filled with cloth, foam, plastic, and other material. the head twisted all of that crap around the arrow and pulled it out side if the box. Even though it spooked me a little I had to know how it performed on game and shot some deer with a few of them. On deer penetration was greatly reduced over a standard head and they did at times pull "crap" out the exit wound. I found no advantage what so ever to having this happen as far as time to death was concerned or how far a deer traveled after the shot. Besides the disadvantage of less penetration the "crap" pulled out the other side often acted like a plug and you had no blood trail to follow. The trail was often a pin drop size of blood every 10 to 15 yards. Not good.

Anyhow, this result is much different than that tested by Dr Ashby in that he was talking about 2 blade heads with a very low rotational speed in the order of 3 turns per 10 yards, I believe. I highly doubt something turning this slow would cause the results I noted with the broadheads I was testing.

I believe the results Dr. Ashby noted were due to the machinical advantage of the offset angle of the single edge two blade design. I do believe this could be an advantage to breaking bone much the same as driving a wedge in wood splits it. I guess in theory if the angle is correct one might see a split second spike in the rotation of the arrow. This likely would be a one time event and would not continue to increase the rotation speed. I suspect it is a wedge effect more than anything with both edges applying force in one direction only when something hard was struct and would have no effect on soft tissue.

Just a wild guess though.

Offline bm22

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Re: question about grizzly's
« Reply #10 on: August 04, 2007, 09:56:00 PM »
i am sry if i wasn't clear in my post but what i wanted to state was that the rotation of the arrow increases due to the single bevel design i will try to find the quote.

Offline bm22

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Re: question about grizzly's
« Reply #11 on: August 04, 2007, 10:25:00 PM »
sry i couldn't find the quote, i am not sure if it was from his study or one of his posts.
but i remember a statement to the effect that a single bevel broadhead will increase its rotational spin when it incounters tissue,
a double bevel has an equal force applied to both sides of the head while a single bevel only has one, thus the tissue itself forces the head to spin at a faster rate.

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