Single Bevel vs Double Bevel

[TurkeyBowMaster]

I've often wonder if the s cut is more a product of increase rotation in flight due to the head helping the feathers rotate the arrow. It would seem this might also help flight, as the feathers are not fighting to rotate the head...the head is helping in rotation. Of course this would be an easy theory to test...just shoot a helical opposite of the heads rotation.

 

[Jeff Martin]

I've often wonder if the s cut is more a product of increase rotation in flight due to the head helping the feathers rotate the arrow. It would seem this might also help flight, as the feathers are not fighting to rotate the head...the head is helping in rotation. Of course this would be an easy theory to test...just shoot a helical opposite of the heads rotation.

TBM, Dr Ashby papers state: Not only does he expound on why the single bevel rotates, he states the more pressure on the blade the more perpendicular force the blade will apply. In other words, the blade will turn with more force in harder mediums (bone, tree, dense foam) over softer tissue. Frankly, that is why on smaller deer, the affect is probably not as drastic as larger animals.

Btw, test bare shaft , that would better test for your comment above. I am not experienced with SB but I have read hours of the science behind them. It is 100% not not the blade helping fletching.


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[Beendare]

I just wonder how much of that bone splitting is due to simple leverage...vs the head twisting.

The leverage from a heavy arrow putting all of that force behind a smooth tapered 2 blade head would seem to me to be a much higher number than the force derived from the 2 beveled edges.

Then there is the issue of how that leverage is utilized. The photo of the elk vertebra I posted was with a Steelforce Phat Head and it has the blade then a distinct bump out at the ferrule where the head stopped dead in the bone.

Post it again here


edit; plus that SF has bleeder blades inhibiting penetration in bone.


A smooth taper like on the VPA design is going to utilize the arrows energy like a smoother wedge.....so how much more does the single bevel add at that point? I don't know. It must do something if folks are getting those curved cuts.... while the double bevel blade cuts are pretty straight. I bet the force exerted by the single bevel is measurable.....by a physics major....that math is beyond my paygrade

 

[Kevin Dill]

Simple physics accounts for the torque/rotation. As any SB blade cuts through any media, the cutting and movement results in greater lateral pressure against the bevel side vs the flat side. The tougher and more resistant the media, the greater the pressure against the bevel. That pressure encourages the bevel to move away from the resistance. Try cutting straight down through a block of cheese with a significant SB blade and you'll notice the blade travels in a curving fashion away from the bevel side.

A SB head has at least 2 cutting edges. It cuts through forward movement combined with a tapered overall design. It travels horizontally through the media but the tapered design results in progressive cutting along the length of the blade. As cutting occurs, the effect of the single bevel (per edge) shows up...but it is augmented by having multiple edges...as in a 2 blade or 3 blade head. Each blade edge adds to the torque/rotational effect. The more resistant the media, the more force it exerts on the blades...whether we can actually see it happen or not.

That said, I have no personal belief the S cut is a major advantage in soft tissue. It proves rotation exists but doesn't prove additional overall wound severity and faster or greater mortality. In hard or tough tissue...the game may be different. The rotation/torque may be advantageous in achieving deeper penetration or maybe dealing with bone. The problem is all the variables inherent in any broadhead wound...so many variables it really prevents proving...through reproducible results...just how any broadhead will act on a given shot.

 

[TurkeyBowMaster]

Talked a bit with the maker of Simmons and he said the single bevel Simmons didn't penetrate as well as the double when tested in a broadhead target. I think that could be because the blade edge is trying to rotate and that causes extra friction on the blade sides. I don't think the same results would be found in game, but I don't think it would result in more penetration either. He also found the wound channet to be more closed with the s cut.

This made me rethink sb in a Simmons, but I do like the tip of sb enough that I sb just the tip. Doing that sacrifice about 1/8 of length, but the Tigersharks are pretty long to start with. Being the tip was the weakest part of the Simmons this modification should sure that up some even though Dave said he hadn't had a problem busting bone. Simmons is 54 thousands and pretty hard Rockwell.

Another possible benefit of sb just the tip is it should stretch the hide a little more than the keener db and create a larger hole in the hide. Hopefully I will get to test soon as I am finally getting to hunt a little.

 

[TurkeyBowMaster]

Talked a bit with the maker of Simmons and he said the single bevel Simmons didn't penetrate as well as the double when tested in a broadhead target. I think that could be because the blade edge is trying to rotate and that causes extra friction on the blade sides. I don't think the same results would be found in game, but I don't think it would result in more penetration either. He also found the wound channet to be more closed with the s cut.

This made me rethink sb in a Simmons, but I do like the tip of sb enough that I sb just the tip. Doing that sacrifice about 1/8 of length, but the Tigersharks are pretty long to start with. Being the tip was the weakest part of the Simmons this modification should sure that up some even though Dave said he hadn't had a problem busting bone. Simmons is 54 thousands and pretty hard Rockwell.

Another possible benefit of sb just the tip is it should stretch the hide a little more than the keener db and create a larger hole in the hide. Hopefully I will get to test soon as I am finally getting to hunt a little.

 

[Steve O]

The Simmons is concave. Concave and convex briadhead designs will not penetrate as well as straight. Again, geometry and physics always work better than opinion...

Length:width is important for penetrating. Blade thickness and bevel angle are important for rotation. If you look at Abowyer, Tuffhead, and Grizzly broadheads you will see optimal designs proven out by math and field experience.

 

[Steve O]

Lots of good information here:


Dr. Ed Ashby, Kalamazoo, MI Jan 2012


Video 11 should be of great interest. Have not watched the videos but was at the talk. Hopefully the video captured the demonstration Dr. Ashly did in person by hand showing the "spiderweb" effect the rotation causes.


I've switched to SB heads because I've seen the Abowyers and Tuffheads made and understand the quality that goes into them. I've not been to the Grizzly shop but know the owner well enough to say they are certainly on par with AB and TH. There are no DISadvantages to the single bevel compared to the double, so I've decided to go with the advantages the physics and math show to be there. I've had very positive experiences with my Abowyers all the way up and literally...thru...Eland.

 

[TurkeyBowMaster]

Shot a single bevel Simmons through a doe and it stuck 7 inches into the ground. What is interesting is I missed one earlier and that arrow went 9 inches deep. Using that I should easily be able to shoot through 2 does , possibly 3 in 2 inches in dirt equalls one doe pass through. Single bevel all but the tip.

 

[Jeff Martin]

9" deep in the ground...you must be hunting the swamp


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[TurkeyBowMaster]

Sandy ground.

 

[TurkeyBowMaster]

I don't know if it's a coincidence, but I've been going between ribs a lot lately which adds to penetration a little. Could be something about concave that slides around bone. Didn't hit any on my elk either.