I agree. There is no doubt in my mind that the small diameter carbon arrows I use now penetrate better than the aluminums I used years ago.
This is in spite of the fact that the Aluminum arrows had a higher momentum rating than my current carbon arrows. There are other factors beyond just KE or momentum. A stiffly spined carbon arrow that stabalizes quicker off the bow, flexes less on impact and is subjected to less friction because of its smaller diameter has some of those "OTHER" factors going for it. IF I'm wrong then you explain how I get consistently better penetration from the carbons fired from the same bow, using the same broadhead even though the aluminums were much heavier and had a far better momentum rating?

Agreed... this is my experience as well. And when I used to manage the shop, I saw plenty of similar evidence from customers too...

That said, I believe alum has way too much going for it otherwise to dismiss it

BPS, that's not what I meant or am trying to do at all.

My question was entirely serious. I thought we were discussing momentum vs. KE as a better indicator of penetration potential. In order to do proper testing, one needs to eliminate as many variables as possible. Since you are stating stiff spine is where it's at, I am wondering if you've ever tested your current speed pro arrow against say perhaps one just like it only with the internal cavity filled with some weight bearing medium, such as fine sand or even lead powder (no idea how much space is available in these things, never seen one). That should yield similar spined arrows with the only difference being weight and fps.

It's not a set up question, I'm genuinely curious...

In my mind, I would suspect the heavier arrow to have slightly more ke, but a lot more momentum, giving us a closer glimpse at the truth.

That is why I asked, not trying to whiz on the speed pro parade. I just feel that until such an in my mind more accurate test is performed, everything else is just apples and oranges...

BPS...

Perhaps you missed what I said in an earlier post:

Nobody is discounting speed or trying to discredit the phenomenon. Speed plays a crucial part in the whole energy/momentum thing. Without speed there is no KE or momentum. But it's part of the formula, not the product of the equation.

By definition, KE is scalar. You have a certain amount of energy in an arrow, some of which is going forward, some is rotating around the axis of the arrow as the fletching spins it, some is being transferred into noise and heat from it's interaction with the atmosphere. You've got energy going in all directions.

That's because KE is a scalar quantity. Momentum is a vector. Momentum is mass and speed in a specific direction over a specific amount of time. BY SCIENTIFIC DEFINITION, momentum is the deciding factor when it comes to penetration potential. It's not my opinion, it's physical law. Blame Issac Newton. It's his fault, not mine.

So.... Your results are due to the momentum your speed is giving you, not the speed itself.

Your momentum for those 350 gn arrows at 350 fps and 95 ft lbs of energy is .54 lb/secs. Let's look at some other setups that will give the same momentum:

400 gn arrow at 304 fps and 82 ft lbs

450 gn arrow at 270 fps and 73 ft lbs

500 gn arrow at 243 fps and 66 ft lbs

550 gn arrow at 221 fps and 60 ft lbs

In other words, my 2315's at 220 fps from my Accuwheel mounted ProTec at 60 pounds and 33" draw will skewer any critter just as easily as your 350+, 95 ft lb arrows. What's the problem?

Can you do things your way? Certainly... but your way keeps taking archery and bowhunting closer to the realm of brain surgery and rocket science.

On the other hand, if one can't handle the draw weight or the draw force curves that come with the cams needed to get that kind of arrow speed, then the bowhunter can easily achieve exactly the same penetration potential you've got with much less extreme setups by increasing their arrow weight.

I've got other issues with high speed arrows, as an archery club officer, that are totally unrelated to bowhunting. Specifically, safety issues and being able to contain stray arrows within the club's boundaries. We're on the verge of having to enact speed limits at our club's range because our formerly rural location is rapidly becoming suburban. Someone with a rig like yours would be limited to our practice area only.

I have Norb Mullaney's take on KE vs. Momentum in a nice article he wrote about all this. Anyone want to read it? ....(waiting for the roar of the crowd pleading for more......) [8D]

:Yawn:

[&:]

What was that you said Todd?



:yawn:

Oh...ok..sure...go ahead..



Seriously..I'd like to see what Norb has to say, or anyone else for that matter. I don't always agree with what I read, but I always enjoy seeing other's perspective

It's a rather lengthy 3pg article- after lunch today I'll scan it in 3 jpeg pics and post them on our band website for everyone to read. Good article and he makes some interesting points....

'Ol Norb is pretty thorough.

Before I read it can you tell me who Norbs data supports.....................us light fast guys or the heavy slow guys

I don't like reading material that contradicts my open minded beliefs......LOL

okay, so what's the argument here? is it carbon vs. aluminum for better penetration, or is it which is the better indicator for penetration, ke vs. p? [&:]

What? You expected this to stay on topic?? Well, you're fairly new to the forum. Once you've been here a spell, you'll find out these KE vs momentum discussions always devolve into aluminum vs carbon, old school vs new wave, science vs sci-fi...

[8D]

I think I read Norb's treatise on this subject and he came down on the KE side. I'd like to see Norb and Sir Isaac debate the issue.