Post by: UCBerzerkeley on October 12, 2009, 03:16:00 PM
But if you take a look at basically any cutting instruments you see curves - knives, axes, a variety of swords (yes, some are straight). Curves creates a shearing motion, so that the edge slices through the target as the weight of the blade drives it deeper. It is the principle reason a kukuri or katana make such effective slicers.
Seeing as not all broadheads exhibit this curvature, I must be wrong. Can someone please set me straight? (haha...get it...straight...straight-edge...nevermind)
Post by: George D. Stout on October 12, 2009, 03:23:00 PM
Post by: VAFarmer on October 12, 2009, 04:03:00 PM
Most other "stabbing" blades are straight.
I would venture to say Mr Stout is getting close when he speculates that cost is a factor. Not to mention sharpening. MUCH easier to sharpen a straight blade than a curved, if you ask me.
If anything were to be more effective, it would seem like something that would create less drag.
farmer
Post by: Gary Logsdon on October 12, 2009, 04:15:00 PM
Post by: freefeet on October 12, 2009, 04:27:00 PM
I wouldn't buy a curved bh simply because it would be a pain to get them sharp in comparison to a flat edge. So if i were to design or manufacture one that would be the first priority that i would presume my customers would want.
As a chef i can tell you why large knifes have curved edges. Because you can do more with them on a chopping board. The only straight edge knives i own are carving knife (that never touches a chopping board) and bread knife, which has a very specific role and serves no other function. All other knives are curved for use with the chopping board so i can roll from one end of the blade to the other cutting a bit at a time instead of struggling to cut all at once. A broadhead, whether curved or not, has to cut all at once so i can't see that curved will make any difference.
I can see some bh makers going for the curved trad look of a knapped flint head as a style thing and people buying them as such. But the steeper you make the angle of the cutting edge the less sharp the cutting edge is.
Post by: Jason R. Wesbrock on October 12, 2009, 07:32:00 PM
Post by: Ragnarok Forge on October 13, 2009, 01:30:00 AM
Post by: UCBerzerkeley on October 13, 2009, 04:39:00 AM
Quote
Originally posted by Clay Walker:You say that pretty convincingly. In a double pass through, a large amount of slicing goes on. Basically all the damage happens after the initial penetration. That is what you want, yah? TO do as much damage as possible? Curved blades slice better.
A straight edge in a thrusting weapon cuts and penetrates far more effectively than a curved edge. A 3 to 1 length to width ration with straigh edges will provide maximum penetration.
Post by: GingivitisKahn on October 13, 2009, 07:38:00 AM
When you slice a piece of meat with your knife, you tend to start with the back end of the blade and draw the knife towards you over the meat. A broadhead must penetrate and clear the way for all of the broadhead and the arrow shaft behind it. I doubt you could easily take your curved knife and push it and the handle and your arm through the meat.
There are others here that have experimented extensively with different sorts of broadheads and their penetration qualities. You might want to have a look at what they say on the topic.
Post by: DuffyRP on October 13, 2009, 07:48:00 AM
Post by: lt-m-grow on October 13, 2009, 10:53:00 AM
Quote
Originally posted by UCBerzerkeley:So how did the 3 to 1 ratio get dubbed "perfect" and who said so?
QuoteOriginally posted by Clay Walker:You say that pretty convincingly. In a double pass through, a large amount of slicing goes on. Basically all the damage happens after the initial penetration. That is what you want, yah? TO do as much damage as possible? Curved blades slice better. [/b]
A straight edge in a thrusting weapon cuts and penetrates far more effectively than a curved edge. A 3 to 1 length to width ration with straigh edges will provide maximum penetration.
No intention to hi-jack UCB's thread. This seems pertinent to his comment here.
Post by: JimB on October 13, 2009, 11:11:00 AM
It is all in the Ashby reports.
I have no idea if curved vs straight makes any difference.I can't see it if it does.It seems like thousands of animals are taken with both.
I'm guessing that how sharp the edge is and possibly how structurally sound the tip is,would far outweigh this issue.
These days,I gravitate toward the straight edge because I can sharpen them easier and have been putting a big emphasis on getting and keeping them sharper than I ever have.
Post by: hickstick on October 13, 2009, 01:21:00 PM
Quote
In a double pass through, a large amount of slicing goes on. Basically all the damage happens after the initial penetration. That is what you want, yah? TO do as much damage as possible? Curved blades slice better.by 'double pass through' I'm assuming you mean complete penetration? and yes I'd rate it 1) getting complete penetration first 2) doing the most amount of damage to Pulmonary and Circulatory systems as possible (but not in any way negate #1)...
right now I'm shooting the orignal woodsmans. and I like what I've seen so far.
Post by: Bill Carlsen on October 13, 2009, 01:51:00 PM
Post by: UCBerzerkeley on October 13, 2009, 02:49:00 PM
Quote
Originally posted by GingivitisKahn:The ashby reports are what got me started thinking bout this in the first place. i'm not doubting the 3:1, history has proven it works. but the curves I was unsure about, specially since i've read that ashby has used the nanook (from ABS) on some very big game (nanook is curved, single bevel).
T
There are others here that have experimented extensively with different sorts of broadheads and their penetration qualities. You might want to have a look at what they say on the topic.
i threw this out as food for thought, i don't claim to be an expert or even particularly knowledgeable. So thank you for all the well thought out responses! i feel smarter already
although, if knives are not a good example for curved blades, i dont think the guillotine for straight blades is either. i might be totally daft, but it would seem that penetrating curves blades mimic the draw motion of a curved knife on meat just fine
i admit, i feel this is a pressing matter in an age when deer, boar and elk have all began to acquire impenetrable body army :bigsmyl:
Post by: Soilarch on October 13, 2009, 10:08:00 PM
The curvature (or lack) is not the secret.
The angles between the line of motion (path) and cutting edge ARE.
Kukari and Samurai Swords are curved because when you add in our human anatomy they allow the angle between the path of the blade and the cutting edge to be lower. (Our wrists our only so flexible.) Hence, better slicing.
3:1 heads have a lower angle between the path and the cutting edge than say a 2:1...Hench, better slicing.
Sure, with a convex broadhead you have a lower angle towards the outside of the head. But you also have a higher angle towards the inside of the head. On a straight edged broadhead you keep the happy medium from the tip to the outside.
Six of one, half a dozen of the others.
Post by: Ragnarok Forge on October 14, 2009, 01:37:00 AM
If you look at any of the swords made for penetrating armor they have diamond shaped tips with straight edges at the tip of the blade and then a radius which transitions into the full width of the blade.
the 3 to 1 width the length ration was discovered thousands of years ago and used in both spear heads, knife ti, and sword tip designs. All of these weapons need to penetrate on a hard thrust. Check out a Roman Gladius some time. The tips are really close to 3 to 1. Recent research has verified what has been known for a long time. Physics also verifies the testing without having to perform it. Any time you make something narrower at the same thickness of material it will penetrate further. Less friction means more penetration. Newtons laws and all that.
3 to 1 is a compromise between adequate width and reasonable length of broadhead. why not 4 to 1 or 6 to 1. We would all look prettys silly shooting knives on the end of our arrows.
Oh and just for reference, I am a civil engineer by trade and a blacksmith by hobby.
Post by: freefeet on October 14, 2009, 05:50:00 AM
Quote
Originally posted by Clay Walker:More length = more drag! Shorter length = less dynamic sharpness or weaker edge.
why not 4 to 1 or 6 to 1. We would all look prettys silly shooting knives on the end of our arrows.
Post by: Bill Carlsen on October 14, 2009, 08:49:00 AM
Post by: Butch Speer on October 14, 2009, 09:38:00 AM
The 3:1 thing. I don't have enough experience with them to make a statement. The native Americans & earlier people killed a few animals with arrows. Check out some flint heads sometime. Definitely not 3:1. People usually refer to Howard Hill when it comes to 3:1. The man killed a lot of animals. So did Fred Bear. His heads weren't 3:1. I believe that what these two & many others proved is that it' shot placement & sharpness that kills.
As far as using physics instead of testing. I might be wrong(sure wouldn't be the first time) but, I believe a bumble bee can't fly.
This is all just my opinion.
Post by: Dave Bulla on October 14, 2009, 09:52:00 AM
A couple things come to mind when comparing curved to straight.
Straight is cheaper to manufacture I'm sure. Since a die can be shaped almost any shape, I don't think that straight or curved is the issue as far as "easy" to make goes. However, straight means less waste of material when the pieces are stamped out of the sheet metal. Picture your kids making Sugar cookies at Christmas time in some rolled out dough. Lots of space between the little Christmas trees and snowmen. If they made the cookies square or triangle shaped, an entire sheet of dough could be used with no waste. In manufacturing, waste control is a huge issue.
On curved blades such as swords and kukaris, think about how they work. Sure they can be used to stab but I think that by design they are slashing weapons. Go one step farther and picture the "flight path" of a sword slash. By anatomical default we swing in an arc. Usually, the blade is angled slightly trailing at the tip which creates a cutting angle between the blade and the object being cut. The blade of an experienced swordsman does not hit the object at 90 degrees but at closer to 30 or 40 dgerees. Thirty three degrees would be the same angle as a 3 to 1 blade on an arrow. As the swords curved swing passes the target, the curve of the blade maintains that efficient cutting angle. If the blade were straight, the angle would increase as the blade was passing through the cut object. Maybe the ancients knew what they were doing, maybe they figured it out by accident but they stuck with it because it worked.
Now picture the path of a broadhead. The arrow travels in a straight linear path. There is no sweeping motion like swinging a sword or knife. Therefore, by design, the cutting angle of a broadhead does not change as it passes through an animal. Sure it does in reality when it contacts bone or if the animal is moving but in a best case scenario, the arrow path is linear.
As for the 3 to 1 angle, I expect it is a compromise of strength, mechanical advantage and damage to tissues. 3 to 1 seems to be the angle at which you can get enough width to do maximum damage while maintaining enough metal in the blade tip to reduce curling and have a low enough blade angle to cut well without making a head too long or too short. If you tried to make say a 5 to 1 head, it would have to be 5 inches long for a 1inch wide cut. Not only would it have to be heavier steel to avoid folding the tip but it would weigh too much for most archery setups. It's all about trade offs.
Post by: freefeet on October 14, 2009, 12:52:00 PM
Quote
Originally posted by Butch Speer:Flint is a very different material to steel. Different drag/friction, different edge retention and a very different edge altogether. I don't believe that one can realistically compare a flint head with a steel one.
Check out some flint heads sometime. Definitely not 3:1.
Post by: Seven on October 14, 2009, 01:27:00 PM
Quote
Originally posted by freefeet:Ishi used a 3 to 1 ratio.
QuoteOriginally posted by Butch Speer:Flint is a very different material to steel. Different drag/friction, different edge retention and a very different edge altogether. I don't believe that one can realistically compare a flint head with a steel one. [/b]
Check out some flint heads sometime. Definitely not 3:1.
Post by: Butch Speer on October 14, 2009, 04:29:00 PM
I got this from http://www.archerylibrary.com/books/pope/hunting-with-bow-and-arrow/chapter02_2.html The general size of these points was two inches for length, seven-eighths for width, and one-eighth for thickness. Larger heads were used for war and smaller ones for shooting bears.
I really don't see why you can't realistically compare flint to steel for penetration purposes.
Again, it's just my opinion.
Post by: Fletcher on October 14, 2009, 04:37:00 PM
Post by: Dave Bulla on October 14, 2009, 09:56:00 PM
Again, it's just my opinion."
Well, you could. I expect that a 3 to 1 steel and a 3 to 1 flint that is expertly crafted and truly sharp would penetrate close to the same. But I think steel would have the edge most of the time because of all the flint points I've ever handled and many were by guys who were supposed to be some of the best in the country, I've only ever felt one that seemed good and sharp. Now, before the flames come out, I understand that flint cuts different than steel but I also know that I could drag almost any flint head across my skin with light to moderate pressure and it wouldn't cut me but a good steel head razor sharp will cut almost with it's own weight. How does it compare when shot? I don't know. I've never shot stones. Just stating an opinion based on what info I've gathered for myself.
A better comparison would be a 2 to 1 vs. a 3 to 1 stone head or the same comparison in steel. That would solve the angle question.
Post by: ChuckC on October 14, 2009, 10:31:00 PM
Actually, if I am not mistaken, Ashby changed the 3/1 shape even more by reducing the width of his broadheads to less than an inch.
If the projectile will handle the stress and not cause a damage related collapse, it would sure seem that the longer and narrower (and sharper) the blade, the easier it should penetrate anything. There rides the problem.
That is partly why Ashby wants a 53 or so Rockwell hardness, so that narrow, very fine point holds up better. The single bevel not only does its thng by spinning as it travels through something, but by sharpening only one side, the edge is half the thickness. . . but it has to be able to hold up.
Flint of that thickness would never hold up. Obsidian could conceivably get sharper, but not on a broadhead, but rather from a flake, which is also a single bevel.
ChuckC
Post by: Jason R. Wesbrock on October 15, 2009, 01:04:00 AM
Post by: Butch Speer on October 15, 2009, 08:31:00 AM
I hope there isn't a tussle either. I sure didn't do it for that. I don't even use flint heads(use bear heads).
Dave
"A better comparison would be a 2 to 1 vs. a 3 to 1 stone head or the same comparison in steel. That would solve the angle question."
That would be a much better test.
Again, I wasn't trying to stir it up, just wondering why.
Post by: Dave Bulla on October 15, 2009, 10:15:00 AM
Post by: ChuckC on October 15, 2009, 11:41:00 AM
Sometimes we have bad days and we need to be careful we don't let them get away from us.
That hasn't happened here yet.
One thought to ponder is. . . Ashby's thought (NOTE these are MY words, telling what I THINK he was saying) is that a very sharp projectile passing through certain areas of a body will cause unrecoverable damage.
By passing completely thru you have two holes, one of which is likely to be low and allow blood escape. If the area was the chest, it will also cause pneumothorax and not allow or cause labored breathing, which hastens the act of death.
I do not believe he thinks a wide head with a bunch of cutting edges (hence more tissue cut) is as important as two holes and a pass thru in the right area.
If I recall well, his testing also showed a certain "rounded" broadhead did very well in penetration also.
I personally think all of this stuff, Ashby's, yours, mine, is all interesting and good information, and adds to our knowledge and experience base.
I also think that there is no perfect, right, exact answer for all situations.
Take from it what you want and learn some more.
ChuckC
Post by: Butch Speer on October 15, 2009, 03:02:00 PM
Thanks. I know some people like to stir it up but, i normally don't. Just didn't want to start a whizzin' contest.
!["[dntthnk]"]("graemlins/dntthnk.gif" "\"\"")
Chuck,
"I do not believe he thinks a wide head with a bunch of cutting edges (hence more tissue cut) is as important as two holes and a pass thru in the right area."
I never thought about looking at Dr. Ashby's reports like that.
"If I recall well, his testing also showed a certain "rounded" broadhead did very well in penetration also."
I was just reading that part of it this morning.
I think a lot of confusion happens with the idea that Dr. Ashby says' this is the way it worked best for me. I don't remember him writing that it was the only way. I'm not saying you shouldn't pay attention to what the Doctor says, just temper it to what you're hunting.
The Doctor did a bunch of very comprehensive testing & he should be commended for it. If I were after 1000lb. buffalo, I would do just exactly as he writes.
But, I only hunt whitetails so I believe for me & most other people on this board, Dr. Ashby's studies are a little overkill & should be adjusted to what you're hunting.
Again, Just my opinion.
Post by: Jeff Strubberg on October 15, 2009, 04:23:00 PM
Try and stab with a scimitar, the do it again with a rapier.
Either sword will stab, either will cut. But stabbing weapons have a strong tendency to be straight, while slicing weapons have a strong tendency to be curved.