Heavy arrows and point of diminishing returns?

Yeah a lot of ppl miss the fact that Dr. Ashby's research is impact based, after the shot.

 

Exactly, it is about what the arrow is doing at impact, not at the bow. At the bow thinking sells bows. At impact thinking kills animals.

 

but the calculator you posted doesn't ask for weight on the string. it asks for everything else, IBO speed, draw weight, DL and arrow weight..weight on the string has an impact on ke/mo right?

 

Not enough to be concerned about down range at impact.

 

so what does this tell you about my set up?
using the calculator you sent

Calculated Arrow Speed

277 fps

Kinetic Energy

66.43 ft-lbs

Momentum

0.48 slug-ft/s

 

That you will successfully continue killing white tails, as you have already proven many times over, as long as the shot placement is good. Correct me if I am wrong, but I believe you mentioned losing deer from hitting them in the shoulder and poor penetration. The whole point of heavy arrows is to not be afraid of the shoulder because the shoulder covers the heart. With your set up, you have to shoot back and risk going too far back and into liver/guts. With mine, I can blow through the shoulders. I do not like aiming back and the fall out if I am too far back. I would rather miss forward if I am going to miss.

Here are the numbers from my three arrow set ups I have higher KE and MO than your set up. Speed is the only thing you beat with. I you refer back to the chart I made in post #26, you will see that at typical white tail distances, the time to target difference is so small, why not sacrifice speed for higher KE and MO? There is a balance point where both can be enhanced.

535 grains, 240 FPS, 68.41 ft-lbs KE, 0.57 slug ft/s

560 grains, 235 FPS, 68.66 ft-lbs KE, 0.58 slug ft/s

610 grains, 226 FPS, 69.17 ft-lbs KE, 0.61 slug ft/s

 

to me it says you could add some weight.

the 2 calculators give very close numbers, odd they arent the same
i have 64 pound draw 29.6 draw length 509 gr arrow, bow has ibo 335
265 fps from both calculators
79.36 ke and .60 mo from dynamic calc
80.29 ke and .598 mo from archery calc

i think of youre worried about MO you can sacrifice some speed by adding weight and increase your momentum

 

ok, makes sense.. I will say that two scapula failures were with 70+# bows and shooting 2" rage heads. at my draw length and those big rages are not optimal for that shot. I ain't sure that any mech is out out any bow. But rage has always done well with all other shots. I can never tell you or anyone when that next scapula hit will occur. I have always wanted to shoot what works best. I guess, a fixed head will work best 99% of the time. I do know this, I have made some bad gut/liver shots with the rages and recovered the animal...I don't know if I had been shooting a standard fixed head I would have recovered the animal.. the 2" slice sure did seem to help

 

A gut shot is the only time I can see a big mechanical being the broadhead you want. But, if the arrow is set up to go through shoulders, you don't have to aim back.

 

yep, thats true, I don't know if I would be comfortable shooting at the shoulders with 60# even with a fixed head

 

Thanks man. But do you see that it is like a fiber wrap around the insert? Haha.

 

I do not think you would have any issued if your arrow was 500+

 

so is KE just hype? sounds like all that matters is MO...

 

KE is good for selling bows. It is an indicator of how much energy the bow puts into the arrow at the instant of release. It loses are relativity the instant the arrow stops touching the string. Maintaining a high KE is dependent upon maintaining a high speed. Which is why bow manufacturers focus on KE and speed for marketing.

KE = (1/2)mv2 or (one half x mass of object x velocity squared)

At impact with an animal velocity slows so much it can be considered to be zero. So, at impact KE = (1/2)x mass of arrow x zero or KE = 1/2 mass of arrow

Momentum is used to evaluate impact of collusions. MO = mass x velocity

Remember at impact velocity = zero.

So, at impact the only thing that counts for penetration is mass of object.

Collusion is the momentum of two objects meeting each other. In a perfect collusion, both objects are equal and come to a standstill at the moment of collusion. But that does not happen when shooting a deer with an arrow, if it did, the every deer would immediately drop dead the instant the arrow hits it.

Collusion = Mass of object 1 x velocity of object 1 = Mass of object 2 x velocity of object 2

If both the deer and arrow are at a standstill at the moment of impact, than velocity is a nonfactor and again, mass is the only factor that determines penetration. But, deer often move at the shot, so deer have velocity despite the arrow velocity dropping to zero at impact.

So,

Mass of deer x velocity of deer = mass of arrow x velocity of arrow isn't true at impact. Again, if it was ture, every deer would drop on the spot.

Velocity of the arrow at impact is an non factor, only mass of arrow, but both mass of deer and velocity of deer can be because animals are not stationary targets.

 

so KE and MO do not work hand in hand? hum. interesting

 

How would you know.... Have you ever even killed a deer with a bow.

 

Could be worse brother, haven't had to endure rage thread in few seasons