Why Magnus is not making a single bevel tanto tip head -

WoodySanford · 01-20-2010, 04:57 AM

The bulk of our testing is on animal carcasses, in light of other “Testing” that’s out there I feel I have to say something about that first. A carcass is quite a bit different than a live animal. Even five minutes after death there are significant differences that may make some variables more or less severe on a carcass than compared to a live animal, such as a lack of contraction from tissue being cut. Increasing variables like shaft friction. Also the manner in which a carcass is supported for testing has influence over the system of penetration.

A carcass is far more stable than a live animal and that can change the priority of variables as it reduces instabilities. We don’t use the information from carcasses to attempt to quantify anything; it gives us the tissue/broadhead interaction where we can observe what causes changes. It’s more an effort to understand the system better by studying the dynamics of it. Even though a carcass is more stable, it’s not a consistent medium and you get more of a range of results as each impact is different than another. This range will vary greatly depending on differences between species, sex and age of animals and by differences in equipment. So we don’t have any plans to publish data type results as they are not all that accurate even for the set up being used and can be misleading when applied to a change in equipment or animal. About all we can do is identify principals the consistently reoccur and what causes them to vary. We can make sense of it but there will never be “Concrete” answers.

There is no free lunch in life and that includes broadhead design. Each aspect of design coexists and supports another. With broadhead design, you’re trying to incorporate them in a manner to achieve a balance where they work. In applying the new trend in design to testing, we found some short comings where those aspects didn’t play well with others.

The first issue is in regards to durability, more specifically edge retention. Edge retention or sharpness is lost in two ways. Either by abrasion, which degrades the edge by rounding and making it thicker or by deformation. Deformation can be flattening, breakage or rolling of the edge. Support for edge retention is a balance between type of steel, volume created by the geometry of the edge and hardness of the steel.

The single bevel causes a significant reduction in volume of the edge, which lessens support of the edge. In order to get that support back hardness has to be increased. This is where the problems start. In lighter weight heads the blades are thinner. There is a threshold of hardness a design can support without becoming too brittle and you can sacrifice overall integrity just to get back to the level of edge retention you had in the first place.

In an effort to support the integrity of the blade you now have to make it thicker, which takes you out of the lighter head category or you will be reducing integrity of the ferrule by removing too much material to accommodate a blade that will survive the harsh impacts on animals.

The theory of the single bevels function is that pressure on an angled surface (the bevel) will cause the blade to rotate. Reducing blade thickness reduces the surface area of the bevel and would have the same effect as reducing the pressure, again making the single bevel less rewarding on the thinner blades.

From what we gather from our testing, the single bevel is best left to much heavier heads. By our estimation from using prototypes this weight begins approximately at 180 grains for a screw in head to ideally meet finished product quality standards. Note these are standards already met in lesser weights with a double bevel.

The next issue is the “Tanto” tip. Everyone who has any experience with two blade heads has at some point experienced tip rolling, a downside of the design. Tip support is much like edge retention in that it can be supported by an increase in volume. That increase can be by blade thickness or geometry and even type of steel. When we came out with the Stinger line and a stainless steel blade, it was quite apparent something needed to be done to support the tip. Given the limitations passed onto us by the consumer of popular weights we had to adopt volume by geometry instead of blade thickness.

There is a caveat here where you can have too much of a good thing. Increasing tip volume with geometry can lead to a blunter tip very quickly. Blunt tips have an advantage on bone as they have the ability to cause fracturing rather than penetrate into it. That may have some value on heavy bone but it is a disadvantage on flexible bone like ribs and softer more elastic tissue. Heavy bone also moves and regardless of tip design is well known for its ability to deflect an arrow or even a bullet for that matter.

Ribs are flexible and are allowed movement, they can be pushed. Pushing ribs increases the time resistance is present and also gives direction to an arrow that is counterproductive to efficiency in penetration. Blunt tips also extend hide beyond its limits to the point that it ruptures, much less efficient than piercing it and allowing edges to cut it. All arrows will take direction on impact with an animal. This direction will decrease efficiency and blunter tips tend to increase the severity of it greatly. To make matters worse the dynamics of penetrating the ribcage become even more complicated when animal movement is introduced.

There really is no best head; it’s more of a category than a single design. As I said, there is no free lunch and no head will be the best for all possible scenarios. In my opinion heavy bone is easily avoided for the most part with sound judgment in effective range and practice. Heavy bone, even if you do have enough ability to break, is a serious interruption of penetration and it’s a gamble as to maintaining direction of the arrow. Other than the spine, heavy bone doesn’t tend to be in the best location for a quick and clean killing shot either.

As for the new trend of design fitting in with our line of heads, we feel it’s best suited for much heavier heads and used with heavier equipment. The size of that market is pretty small and already covered pretty well.

Food for thought.
Woody

cartman308 · 01-20-2010, 06:28 AM

That's ALOT of fine information right there!! Thanks Woody!

WABOWMAN · 01-20-2010, 08:45 AM

WOW! My head is spinning!Great info had to read it a few times to get it all.Thanks woody

Gerhard · 01-20-2010, 10:35 AM

WoW!!!

Woody you rock!!!

Thanks for sharing the info it makes a lot of sense.

WoodySanford · 01-20-2010, 12:41 PM

Glad you fella's find it useful.

Red Feather Archery · 01-20-2010, 04:24 PM

Fantastic information there, Woody. Adds a lot of value to this site having expertise like this available.

Booner · 01-20-2010, 11:37 PM

Great content Woody.....Kudos. Do you feel that Magnus will ever venture into the 200+ gr category? I know you said it was covered pretty well...but there has to be room for modification I would think....not saying the heads out there are not towing the bill...trust me I LOVE some of the bigger heads...but It's just like the trad two blades moving to three etc.....Do you ever see a change in the heavy heads?

WoodySanford · 01-21-2010, 12:33 PM

Quote:

Originally Posted by Booner

Great content Woody.....Kudos. Do you feel that Magnus will ever venture into the 200+ gr category? I know you said it was covered pretty well...but there has to be room for modification I would think....not saying the heads out there are not towing the bill...trust me I LOVE some of the bigger heads...but It's just like the trad two blades moving to three etc.....Do you ever see a change in the heavy heads?

Anything is possible but I don't see it happening much. There is a reason you see most come out with a 100 grain model first. Customer demand sets most of the limits and you could easily have a hundred grand wrapped up in a head before the first one hits the market, you need it to move and support itself. I'm a heavy head guy myself but that starts getting into a much smaller market. There is a lot of things I'd like to be making but if it can't support the employee's effort to do so it not going to happen.

Mule426 · 01-21-2010, 01:40 PM

Woody,

What are the differences in shooting a double bevel head at say 100 grains and the comparable head with a single bevel?

Correct me if Im misunderstanding but I gather that the heaver heads offer more energy and thus alow the head to "spin" while passing through. Whereas a lighter double bevel head requires less energy to accomplish the same task.

WoodySanford · 01-21-2010, 04:53 PM

Hi Mule,

I've taken and ground a single bevel on stinger blades so I can get a real "All else equal" type of test and didn't see the merits of it. Testing on deer I set up a high speed camera to try and capture the rotation and couldn't. The single bevel acted just like a double. Heads will always take some direction when hitting an animal, even a deer. Sometimes as they deflect from a partial rib impact they will rotate some even when cutting the rib. I've seen the single bevel rotate the other direction than it is supposed to and seen many times they did not rotate at all, acting very much like a double bevel.

I've used moose carcasses and can't account for any consistency in the rotation. As heads go from one organ to the next you can see if there is any through a wound tract survey. You have its position in the hide, ribcage, then the lung and through the mediastinal plate (a membrane that divides the thoracic cavity) then the other lung and ribs/hide again. Its not that hard to keep track of.

The big thing though came down to edge retention. I have several methods of testing sharpness but there is no benchmark for such a thing, so I use these tests as an indicator of something I need to view under the microscope. It showed a lack of edge retention in the single bevel. We increased the hardness of the blade to get it back but then the blade was brittle and would break easier at the vents. I messed with cutting a slot for a thicker blade in the ferrule but it weakens the ferrule and you have to shrink down the over all size of the blade to maintain weight and that leads to a small cutting diameter.

Aspects of broadhead design kind of have to co-exist together and to get the popular weight, the durability people want and trying to match those to cutting diameter and effeciency is quite the balancing act. To get the best out of it and meet as many of them as possible, the double bevel won out.

Its not that a single can't or doesn't work. Its to get it to work has some requirements and to get what all the other aspects of a design require, it winds up with a much thicker and harder blade and to support that the entire head becomes much heavier. It would have been nice though as it is much easier to grind and has a faster run time on the machines and time is money in manufacturing.

Mule426 · 01-21-2010, 05:40 PM

I have been reading the reports that Dr Ashby has put out on the subject and I see the coralations between what both of you have stated. Basically a single bevel head maximises its effectiveness at higher grain weights, which is why I guess the majority of them are so heavy.

You brought one of my other questions, in your own tests did you have a helical on the test arrow? If you shoot an arrow with out helical on it, would the broadhead still perform the same way as if it was shot on an arrow that had helical. I would assume the effectiveness of the head would diminish if there was not any helical on the arrow.

WoodySanford · 01-21-2010, 06:30 PM

The problem without helical is quality of the arrow flight. The direction arrows take on impact has a pretty wide range. If you introduce a direction with poor arrow flight it only gets worse. Can't blame that on the head. I'll always use helical or offset if using the small fletching like blazers.

When your testing on animal carcasses, your actually testing the whole arrow and some variables can make it difficult or impossible to isolate aspects of the head. It actually requires a lot of testing to find things. I like to have sample sizes of 25 or greater because many times things might be caused by something else or be coincidence. I actually have to shoot multiple animals and catagorize the impacts as to their location and what was encountered. On a moose, hitting the heart can really slow down a arrow, where just missing it can be a difference of 50 fps or more with some heads. There are quite a few things that people believe about heads that there is no way to isolate to compare.

-bowfreak- · 01-27-2010, 07:03 AM

Personally, I love the double bevel and tanto tip. I will take "gouge on contact"(sorry I couldn't help myself

) over a weaker cut on contact tip every time. Great heads.....all of their heads are great.

Outbakbowhunter · 05-07-2010, 10:22 AM

Woody,
You said above that
"The single bevel causes a significant reduction in volume of the edge, "

I am not sure that I agree with that. What is the bevel angle you are talking about.

Is not the bevel angle adjustable by manufacturer to be as low or high an angle as desired.

Why cant a single bevel be made at a higher angle for better edge retention strength.

I dont agree with Ed Ashby on his lower edge bevel angles, ( from memory about 15 degress) but personally I like an edge angle of 30 degrees or higher.

Ed's opinions are mainly geared for uber broadheads on very big game, but some of his ideas are good (with a little tweaking) for guys shooting 125 grain models.

I dont really think single or double bevel makes that big a difference on deer sized game, if both styles are razor sharp and both are routinely giving pass throughs, the game is no more or no less dead.

I like them, because they are easier to sharpen, and I believe they also have a slight edge in accuracy ( I think they also spin more in flight ) as in tighter groups.

I hope to save up and get a Hooter Shooter before the end of the year, which will either prove or disprove it.

top dog rick · 05-07-2010, 10:45 AM

Makes sense How many single bevel Ax's have you seen ?

not many single bevel hunting knives I know of !

Also all of the single bevel's I have seen are steel .

How would Stainless hold up to single bevel ?

01-20-2010, 04:57 AM	#1 (permalink)
WoodySanford Broadhead Engineer Join Date: Nov 2009 Location: Currently in NC, during season...who knows Posts: 444	Why Magnus is not making a single bevel tanto tip head The bulk of our testing is on animal carcasses, in light of other “Testing” that’s out there I feel I have to say something about that first. A carcass is quite a bit different than a live animal. Even five minutes after death there are significant differences that may make some variables more or less severe on a carcass than compared to a live animal, such as a lack of contraction from tissue being cut. Increasing variables like shaft friction. Also the manner in which a carcass is supported for testing has influence over the system of penetration. A carcass is far more stable than a live animal and that can change the priority of variables as it reduces instabilities. We don’t use the information from carcasses to attempt to quantify anything; it gives us the tissue/broadhead interaction where we can observe what causes changes. It’s more an effort to understand the system better by studying the dynamics of it. Even though a carcass is more stable, it’s not a consistent medium and you get more of a range of results as each impact is different than another. This range will vary greatly depending on differences between species, sex and age of animals and by differences in equipment. So we don’t have any plans to publish data type results as they are not all that accurate even for the set up being used and can be misleading when applied to a change in equipment or animal. About all we can do is identify principals the consistently reoccur and what causes them to vary. We can make sense of it but there will never be “Concrete” answers. There is no free lunch in life and that includes broadhead design. Each aspect of design coexists and supports another. With broadhead design, you’re trying to incorporate them in a manner to achieve a balance where they work. In applying the new trend in design to testing, we found some short comings where those aspects didn’t play well with others. The first issue is in regards to durability, more specifically edge retention. Edge retention or sharpness is lost in two ways. Either by abrasion, which degrades the edge by rounding and making it thicker or by deformation. Deformation can be flattening, breakage or rolling of the edge. Support for edge retention is a balance between type of steel, volume created by the geometry of the edge and hardness of the steel. The single bevel causes a significant reduction in volume of the edge, which lessens support of the edge. In order to get that support back hardness has to be increased. This is where the problems start. In lighter weight heads the blades are thinner. There is a threshold of hardness a design can support without becoming too brittle and you can sacrifice overall integrity just to get back to the level of edge retention you had in the first place. In an effort to support the integrity of the blade you now have to make it thicker, which takes you out of the lighter head category or you will be reducing integrity of the ferrule by removing too much material to accommodate a blade that will survive the harsh impacts on animals. The theory of the single bevels function is that pressure on an angled surface (the bevel) will cause the blade to rotate. Reducing blade thickness reduces the surface area of the bevel and would have the same effect as reducing the pressure, again making the single bevel less rewarding on the thinner blades. From what we gather from our testing, the single bevel is best left to much heavier heads. By our estimation from using prototypes this weight begins approximately at 180 grains for a screw in head to ideally meet finished product quality standards. Note these are standards already met in lesser weights with a double bevel. The next issue is the “Tanto” tip. Everyone who has any experience with two blade heads has at some point experienced tip rolling, a downside of the design. Tip support is much like edge retention in that it can be supported by an increase in volume. That increase can be by blade thickness or geometry and even type of steel. When we came out with the Stinger line and a stainless steel blade, it was quite apparent something needed to be done to support the tip. Given the limitations passed onto us by the consumer of popular weights we had to adopt volume by geometry instead of blade thickness. There is a caveat here where you can have too much of a good thing. Increasing tip volume with geometry can lead to a blunter tip very quickly. Blunt tips have an advantage on bone as they have the ability to cause fracturing rather than penetrate into it. That may have some value on heavy bone but it is a disadvantage on flexible bone like ribs and softer more elastic tissue. Heavy bone also moves and regardless of tip design is well known for its ability to deflect an arrow or even a bullet for that matter. Ribs are flexible and are allowed movement, they can be pushed. Pushing ribs increases the time resistance is present and also gives direction to an arrow that is counterproductive to efficiency in penetration. Blunt tips also extend hide beyond its limits to the point that it ruptures, much less efficient than piercing it and allowing edges to cut it. All arrows will take direction on impact with an animal. This direction will decrease efficiency and blunter tips tend to increase the severity of it greatly. To make matters worse the dynamics of penetrating the ribcage become even more complicated when animal movement is introduced. There really is no best head; it’s more of a category than a single design. As I said, there is no free lunch and no head will be the best for all possible scenarios. In my opinion heavy bone is easily avoided for the most part with sound judgment in effective range and practice. Heavy bone, even if you do have enough ability to break, is a serious interruption of penetration and it’s a gamble as to maintaining direction of the arrow. Other than the spine, heavy bone doesn’t tend to be in the best location for a quick and clean killing shot either. As for the new trend of design fitting in with our line of heads, we feel it’s best suited for much heavier heads and used with heavier equipment. The size of that market is pretty small and already covered pretty well. Food for thought. Woody __________________ Best broadhead is a catagory not a single design! I am "Ferral" and I dig it baby! Last edited by WoodySanford; 01-20-2010 at 04:59 AM.

01-20-2010, 06:28 AM	#2 (permalink)
cartman308 Broadhead Mod Join Date: Nov 2009 Location: Fraziers Bottom, WV Posts: 1,201	That's ALOT of fine information right there!! Thanks Woody! __________________ Broadheadtalk Moderator Athens Factory Staff Shooter

01-20-2010, 08:45 AM	#3 (permalink)
WABOWMAN 130gr Join Date: Dec 2009 Location: port townsend,WA Posts: 504	WOW! My head is spinning!Great info had to read it a few times to get it all.Thanks woody __________________ Athens Field staff TRU-ball staff Vapor trail pro staff Broadheadshed staff Owner MAY'S CUSTOM ARCHERY ATHENS APROVED DEALER

01-20-2010, 10:35 AM	#4 (permalink)
Gerhard 145gr Join Date: Dec 2009 Location: Johannesburg (South Africa) Posts: 688	WoW!!! Woody you rock!!! Thanks for sharing the info it makes a lot of sense. __________________ Slick Trick Pro Staff, Broadheadtalk.com Field Staff

01-20-2010, 12:41 PM	#5 (permalink)
WoodySanford Broadhead Engineer Join Date: Nov 2009 Location: Currently in NC, during season...who knows Posts: 444	Glad you fella's find it useful. __________________ Best broadhead is a catagory not a single design! I am "Ferral" and I dig it baby!

01-20-2010, 04:24 PM	#6 (permalink)
Red Feather Archery Broadhead Maker Join Date: Dec 2009 Posts: 730	Fantastic information there, Woody. Adds a lot of value to this site having expertise like this available.

01-20-2010, 11:37 PM	#7 (permalink)
Booner Administrator Join Date: Nov 2009 Location: Arkansas USA Posts: 952	Great content Woody.....Kudos. Do you feel that Magnus will ever venture into the 200+ gr category? I know you said it was covered pretty well...but there has to be room for modification I would think....not saying the heads out there are not towing the bill...trust me I LOVE some of the bigger heads...but It's just like the trad two blades moving to three etc.....Do you ever see a change in the heavy heads?

01-21-2010, 01:40 PM	#9 (permalink)
Mule426 100gr Join Date: Nov 2009 Location: New Mexico Posts: 167	Woody, What are the differences in shooting a double bevel head at say 100 grains and the comparable head with a single bevel? Correct me if Im misunderstanding but I gather that the heaver heads offer more energy and thus alow the head to "spin" while passing through. Whereas a lighter double bevel head requires less energy to accomplish the same task. __________________ Athens Archery Field Staff/Smooth Stability Pro Staff/ Victory Archery Advisory Staff/Carbon Creations/ArcheryProstaff.com Accomplice 32" Camo on Black,Omega Rest Smooth Stability 8" Stabilizer Next G1 Camo

01-21-2010, 04:53 PM	#10 (permalink)
WoodySanford Broadhead Engineer Join Date: Nov 2009 Location: Currently in NC, during season...who knows Posts: 444	Hi Mule, I've taken and ground a single bevel on stinger blades so I can get a real "All else equal" type of test and didn't see the merits of it. Testing on deer I set up a high speed camera to try and capture the rotation and couldn't. The single bevel acted just like a double. Heads will always take some direction when hitting an animal, even a deer. Sometimes as they deflect from a partial rib impact they will rotate some even when cutting the rib. I've seen the single bevel rotate the other direction than it is supposed to and seen many times they did not rotate at all, acting very much like a double bevel. I've used moose carcasses and can't account for any consistency in the rotation. As heads go from one organ to the next you can see if there is any through a wound tract survey. You have its position in the hide, ribcage, then the lung and through the mediastinal plate (a membrane that divides the thoracic cavity) then the other lung and ribs/hide again. Its not that hard to keep track of. The big thing though came down to edge retention. I have several methods of testing sharpness but there is no benchmark for such a thing, so I use these tests as an indicator of something I need to view under the microscope. It showed a lack of edge retention in the single bevel. We increased the hardness of the blade to get it back but then the blade was brittle and would break easier at the vents. I messed with cutting a slot for a thicker blade in the ferrule but it weakens the ferrule and you have to shrink down the over all size of the blade to maintain weight and that leads to a small cutting diameter. Aspects of broadhead design kind of have to co-exist together and to get the popular weight, the durability people want and trying to match those to cutting diameter and effeciency is quite the balancing act. To get the best out of it and meet as many of them as possible, the double bevel won out. Its not that a single can't or doesn't work. Its to get it to work has some requirements and to get what all the other aspects of a design require, it winds up with a much thicker and harder blade and to support that the entire head becomes much heavier. It would have been nice though as it is much easier to grind and has a faster run time on the machines and time is money in manufacturing. __________________ Best broadhead is a catagory not a single design! I am "Ferral" and I dig it baby! Last edited by WoodySanford; 01-21-2010 at 04:56 PM. Reason: My grammer is horrible.

01-21-2010, 05:40 PM	#11 (permalink)
Mule426 100gr Join Date: Nov 2009 Location: New Mexico Posts: 167	I have been reading the reports that Dr Ashby has put out on the subject and I see the coralations between what both of you have stated. Basically a single bevel head maximises its effectiveness at higher grain weights, which is why I guess the majority of them are so heavy. You brought one of my other questions, in your own tests did you have a helical on the test arrow? If you shoot an arrow with out helical on it, would the broadhead still perform the same way as if it was shot on an arrow that had helical. I would assume the effectiveness of the head would diminish if there was not any helical on the arrow. __________________ Athens Archery Field Staff/Smooth Stability Pro Staff/ Victory Archery Advisory Staff/Carbon Creations/ArcheryProstaff.com Accomplice 32" Camo on Black,Omega Rest Smooth Stability 8" Stabilizer Next G1 Camo

01-21-2010, 06:30 PM	#12 (permalink)
WoodySanford Broadhead Engineer Join Date: Nov 2009 Location: Currently in NC, during season...who knows Posts: 444	The problem without helical is quality of the arrow flight. The direction arrows take on impact has a pretty wide range. If you introduce a direction with poor arrow flight it only gets worse. Can't blame that on the head. I'll always use helical or offset if using the small fletching like blazers. When your testing on animal carcasses, your actually testing the whole arrow and some variables can make it difficult or impossible to isolate aspects of the head. It actually requires a lot of testing to find things. I like to have sample sizes of 25 or greater because many times things might be caused by something else or be coincidence. I actually have to shoot multiple animals and catagorize the impacts as to their location and what was encountered. On a moose, hitting the heart can really slow down a arrow, where just missing it can be a difference of 50 fps or more with some heads. There are quite a few things that people believe about heads that there is no way to isolate to compare. __________________ Best broadhead is a catagory not a single design! I am "Ferral" and I dig it baby!

01-27-2010, 07:03 AM	#13 (permalink)
-bowfreak- 85gr Join Date: Nov 2009 Posts: 82	Personally, I love the double bevel and tanto tip. I will take "gouge on contact"(sorry I couldn't help myself ) over a weaker cut on contact tip every time. Great heads.....all of their heads are great.

05-07-2010, 10:22 AM	#14 (permalink)
Outbakbowhunter Trial Member Join Date: May 2010 Posts: 9	Woody, You said above that "The single bevel causes a significant reduction in volume of the edge, " I am not sure that I agree with that. What is the bevel angle you are talking about. Is not the bevel angle adjustable by manufacturer to be as low or high an angle as desired. Why cant a single bevel be made at a higher angle for better edge retention strength. I dont agree with Ed Ashby on his lower edge bevel angles, ( from memory about 15 degress) but personally I like an edge angle of 30 degrees or higher. Ed's opinions are mainly geared for uber broadheads on very big game, but some of his ideas are good (with a little tweaking) for guys shooting 125 grain models. I dont really think single or double bevel makes that big a difference on deer sized game, if both styles are razor sharp and both are routinely giving pass throughs, the game is no more or no less dead. I like them, because they are easier to sharpen, and I believe they also have a slight edge in accuracy ( I think they also spin more in flight ) as in tighter groups. I hope to save up and get a Hooter Shooter before the end of the year, which will either prove or disprove it. Last edited by Outbakbowhunter; 05-07-2010 at 10:24 AM. Reason: fixed a typo

05-07-2010, 10:45 AM	#15 (permalink)
top dog rick 100gr Join Date: Feb 2010 Location: Alabama Posts: 233	Makes sense How many single bevel Ax's have you seen ? not many single bevel hunting knives I know of ! Also all of the single bevel's I have seen are steel . How would Stainless hold up to single bevel ?

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