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Mechanical broadheads are junk

giles

Cull buck specialist
Supporting Member
My point being...some people rely to much on speed. Lighter arrows/bolts and light heads. Then complain when things don't work out. You have to find a happy medium for everything to work out.

My example is:

ever drop a razor blade?

You don't worry all that much, do you?

Ever drop a butchering knife? I bet your feet damn near touch your ears!
 

Blan37

Member
1,795
72
SW Ohio
Pretty cool stuff here imo:.

Here's one that happens every now and then to the international space station:

Objects as small as a fleck of paint can become a hazard once they reach orbital speeds of up to 22,000 mph (34,500 km/h).

This was shown recently by an image tweeted by astronaut Tim Peak in which a 7 mm-diameter circular chip was gouged out by the impact from a tiny piece of space debris.


Esa astronaut Tim Peake took this photo from inside Cupola last month, showing a 7 mm-diameter circular chip gouged out by the impact from a tiny piece of space debris, possibly a paint flake or small metal fragment no bigger than a few thousandths of a millimetre across. The background shows the inky blackness of space.
 
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giles

Cull buck specialist
Supporting Member
To me, this is like comparing the .22 and .45...one is fast and light, the other is fat and slow. Both have their purposes and both can be very effective. Just like its been said many times in this thread "shot placement is critical".
 

hickslawns

Dignitary Member
Supporting Member
39,919
260
Ohio
I saw it on a TV show one time. "Archers Choice" or something like that I believe. Good visual for explaining kinetic energy. Take a plastic practice golf ball. The ones with holes for chipping around the back yard. Throw it as hard as you can and see how far you can make it go. They did it down a runway or large parking lot. Then they took a normal golf ball and did the same thing. The example isn't perfect because the whiffle ball type golf ball has holes and wind drag. The point was both balls left the guys hand at the same speed but the regular golf ball with more mass was going to keep going much farther. That is how I look at arrows as well.

Agreed though. Still need good shot placement. Still need the broadhead to perform once it hits.
 

Jackalope

Dignitary Member
Staff member
38,924
260
KE = 0.5 • m • v2

m = mass of object
v = speed of object

Tinker around with it in grains and FPS. You'll find there is a sweet spot for KE where the grains you give up to gain the speed actually reduces your KE. And the opposite is true also where the grains you gain reduces your speed and thus reduces you're KE. At a certain grains and speed variable you can maximize your KE. It's going to be different for each rig dependent not only on how fast your bow is but how strong. For example a baseball pitcher can throw a baseball at 100mph. A bodybuilder can throw a bowling ball at maybe 20 mph. But a bodybuilder can't throw a baseball as fast as the pitcher, nor can a baseball pitcher throw a bowling ball as fast as the bodybuilder. Each will have their own sweet spot for KE.

As for broadheads robbing KE it mostly boils down to resistance. A BH that has more resistance will require more KE. It's easy to shove a pocket knife into a watermelon, it requires more force to shove in a butcher knife. The main reason I don't like mechanicals is the force required to open them is purely wasted KE. And it may not seem like much but it is. If you take your finger and deploy the blade it's not very hard at all. However the faster you want to open it the more force you will have to apply with your finger. The force required to open one in a microsecond and in less than an inch of travel time at 300 fps is actually quite substantial. But the worst part is it's completely wasted as it provides zero benefit to the intended use of the head, cut, penetrate, and kill. I would rather keep that KE and use it for penetration where it actually serves a purpose.
 

giles

Cull buck specialist
Supporting Member
KE = 0.5 • m • v2

m = mass of object
v = speed of object

Tinker around with it in grains and FPS. You'll find there is a sweet spot for KE where the grains you give up to gain the speed actually reduces your KE. And the opposite is true also where the grains you gain reduces your speed and thus reduces you're KE. At a certain grains and speed variable you can maximize your KE. It's going to be different for each rig dependent not only on how fast your bow is but how strong. For example a baseball pitcher can throw a baseball at 100mph. A bodybuilder can throw a bowling ball at maybe 20 mph. But a bodybuilder can't throw a baseball as fast as the pitcher, nor can a baseball pitcher throw a bowling ball as fast as the bodybuilder. Each will have their own sweet spot for KE.

As for broadheads robbing KE it mostly boils down to resistance. A BH that has more resistance will require more KE. It's easy to shove a pocket knife into a watermelon, it requires more force to shove in a butcher knife. The main reason I don't like mechanicals is the force required to open them is purely wasted KE. And it may not seem like much but it is. If you take your finger and deploy the blade it's not very hard at all. However the faster you want to open it the more force you will have to apply with your finger. The force required to open one in a microsecond and in less than an inch of travel time at 300 fps is actually quite substantial. But the worst part is it's completely wasted as it provides zero benefit to the intended use of the head, cut, penetrate, and kill. I would rather keep that KE and use it for penetration where it actually serves a purpose.

I wish I knew how to put words to thoughts...well put.
 

Milo

Tatonka guide.
8,185
157
It's the impulse, not the KE that delivers energy to target. The heavier or more cross sectional area available,the more energy it can produce or impart onto the arrow.
 

giles

Cull buck specialist
Supporting Member
It's the impulse, not the KE that delivers energy to target. The heavier or more cross sectional area available,the more energy it can produce or impart onto the arrow.

Do you mind giving an example? Not sure I'm understanding what the "impulse" is. Are you talking about knock down power, like a bullet?