ponderings on high MA broadheads and sharpness

[ozy clint]

just recieved some tuffheads and i must say they look bomb proof. however one thing i noticed is the way the tanto tip is ground it wants to rotate in the opposite direction to the beveled edge. something i will fix with a file.

anyway, i got to thinking about sharpness on high mechanical advantage heads like these.
do you think that they would have a greater tendancy for tissue to ride over the edge because of the high MA? what i mean is, for anything other than scary sharp the tissue would have more tendancy to ride over the edge because of the high MA.
or are high MA heads better because they are acting upon the tissue for a greater length of time?

[Stumpkiller]

Mechanical advantage is a measure of resistance divided by force applied.  So sharp and thin will win over less sharp and thicker.

BUT, there are maybe 3,500 broadhead designs and if there was a perfect choice we'd probably have many fewer.  Whether mechanical advantage even applies to a cutting edge (is a blade a mechanism?) can be debated. I guess a wedge is a simple machine.

I use a file sharp edge that is more saw-like than razor sharp.  Still pops hair  I add a bevel ("tanto" for you oriental speakers) or chisel tip to prevent rolling if bone is hit.

And I use traditional, proven heads that I'm sure guys with slide-rules debated over years ago.  It ain't rocket science.  "New and Improved" should not be necessary in "traditional" archery or bowhunting.  ;-)  Folks were making this work successfully before the alphabet had been conceived.

Relax, looks like a great broadhead.  Get it as sharp as possible and kill game with it and worry not.

[ozy clint]

i'm not worried about it, i was just wondering if two heads the same width but different MA's would give different cut widths given they where the same sharpness, since the high MA head would have a greater tendency to push aside tissue? i'm thinking that all holes made by broadheads are actually smaller than the blade width since there would be some tissue displaced by the cutting edge but not actually cut. the difference probably isn't measurable but my point is- there is a difference?
i was thinking that the difference between hole size and blade width might be bigger on high MA heads??

consider this- i was just thinking that the velocity of the cutting edge will effect the cut width too. take your thumb and index finger and make a gap slightly smaller than the width of your broadhead. now slowly pass a sharp broadhead through the gap. it will displace some tissue but not cut it. now imagine that at 160fps! you would have a cut that extends almost to where the extent of the cutting edge was.

[Overspined]

Here's a blood trail from a diamond stone sharpened new grizzly 170.  I'd say you get them sharp, you have no worries. The other deer was a pass through lung and a blind man could follow it.

[30coupe]

 

Let me guess...it is not hunting season in Australia, correct?

[ozy clint]

sorry but your not seeing the point i'm trying to discuss.
doubts over whether they would work has never been an issue.
i'm was hoping for a discussion about it that was inline with my ponderings that come from a scientific point of view.

[ozy clint]

Originally posted by Stumpkiller:
Mechanical advantage is a measure of resistance divided by force applied.  So sharp and thin will win over less sharp and thicker.

that isn't what i was trying to compare.
what i was getting at was comparing the difference between the blade width and hole width (if there is one) between broadheads of different MA given the same blade width, same speed of cut and same sharpness.

[Stumpkiller]

If a head cuts a hole wider than that head it is because it pushed hide or tissue ahead of itself - showing it did not cut well on contact and demonstrating a lower efficiency.  

I actually prefer narrow heads (1-1/8" to 1-3/16") because, in my experience, they come out the far side and leave a better and shorter trail.  Two holes (enterance/exit) beat one hole every time.  They are also easy to tune to fly well.  I used Zephyr Sasquatch head for a while - extremely well made and super wide . . . until I lost a huge buck that only had a hole on the topside and no exit wound.  Spent two days of a canoe-in camping hunt trying to find it.  Bitter.  Granted - shame on me for bad angle - but the RibTek 125S (for Slim) heads I switched to, from your homeland,  never failed to pass through and drop deer in 25 to 100 yards.  I still use a bunch for my coyote and woodchuck heads as they take a beating and still sharpen up nicely.

My current favorite is the Stos.  Long, slim, sharp and rugged.  

       

I believe there are more good two-blade heads available now than at any time in the past.  This is good.

[ozy clint]

Originally posted by Stumpkiller:
If a head cuts a hole wider than that head it is because it pushed hide or tissue ahead of itself - showing it did not cut well on contact and demonstrating a lower efficiency.  

 

that is a good point. didn't think about that.

30coupe- it's hunting season 365days a year here. no cabin fever down here.  

[30coupe]

Originally posted by ozy clint:

30coupe- it's hunting season 365days a year here. no cabin fever down here.    [/QB]

Are you sure you aren't in heaven?  

[ozy clint]

australia is heaven isn't it?  :p

[pdk25]

As far as the bevel on the tanto goes, it is such a miniscule rotational force compared to the huge amount of surface area on the blade that I think you would may be a waste of your time to change the tanto.  As far as the difference in blood trails from broadheads with different "mechanical advantages" but with same blade number, width an a straight cutting edge, I can't imagine there is any significant difference in the amount of hemorrhage involved.  That being said, changing the shape of the blade can have a marked effect.  The Simmons style heads are a great example of that.  I would have to watch it in slow motion to fully understand it, but I believe that there is more 'dimpling' of soft tissue causing a wider cut than the blade itself, making for lots of bleeding and wounds that don't tend to close up.  I know that there are concerns with one hole as opposed to two, but there is lots of evidence to say that on most thin skinned game, a good shot with a light weight setup with the Simmons style heads will give you two holes.  Where the tuffheads really shine is on hard impact shots, such as buff ribs and scapula hits.  I don't really know that there is an animal out there where a different design of broadhead than the existing 300 grain head tuffhead will improve your odds of harvesting the animal.

[ChuckC]

Actually,  I don't see how a broadhead, no matter how sharp, can avoid pushing tissue ahead of it.  Unless it cuts on contact,  and i mean touch, no force at all, you are pushing some.

I agree Clint, although we strive for "as sharp as we can get it" the fact is, when you add 160 plus FPS to the stroke, even a duller head will cut.  A sharper one will just cut easier.

Another view.  Animals run when they need to get away.  They run faster and longer if they are scared by noise, big movement, or a large trauma to their body especially a large bone strike.

I wonder if a sharper head will cause less impact trauma (not beating it with a bat), thus causing less reactive running and shorter blood trail.

ChuckC