Why do so many broadheads have straight edges?

[Dave Bulla]

Hey... interesting topic here today.

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.

[freefeet]

Originally posted by Butch Speer:
Check out some flint heads sometime. Definitely not 3:1.

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.

[Seven]

Originally posted by freefeet:
 

Originally posted by Butch Speer:
Check out some flint heads sometime. Definitely not 3:1.

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]

Ishi used a 3 to 1 ratio.

[Butch Speer]

Yeah, I guess I should have qualified the statement. Never say never. The majority of flint heads aren't 3:1.
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.

[Fletcher]

Because we've learned that they work.

[Dave Bulla]

"I really don't see why you can't realistically compare flint to steel for penetration purposes.
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.

[ChuckC]

Flint and steel is different.  The cross section of the projectile is different.  Hope we aren't gonna get in another tussle from this one.

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

[Jason R. Wesbrock]

.

[Butch Speer]

Chuck,
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.

[Dave Bulla]

Butch, no need to apologize.  You haven't done anything wrong.  We're all allowed to have an opinion and we all like to discuss differences in opinion.  That's one of the great things about this board.  All that is asked is to keep it civil which you certainly have.  Don't back off from a question just because one of us makes a comment about it.   :D

[ChuckC]

Butch,  like Dave said,  stir it up.  We learn from each other.  

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

[Butch Speer]

Chuck & Dave,
Thanks. I know some people like to stir it up but, i normally don't. Just didn't want to start a whizzin' contest.  

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.

[Jeff Strubberg]

**shrug**

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.