But animals aren’t made out of foam, and a heavier, high FOC setup seems to handle the variables of an animal better than medium to light and fast
I plan to watch the whole thing, but don’t currently have time. I watched up to 3:36.
First, I’ve heard of Joel’s test before, but could not find anything about it on the internet. Maybe I was spelling his name wrong. Seeing his graph, hearing a bread overview of what he tested and what his results were, and seeing one chart for the 35lbs stick bow, his results A) don’t violate my understanding of physics, and B) aren’t quite what you said, or what I’ve heard other claim.
You basically said(if I’m not mistaken) that going for speed instead of a heavier arrow resulted in better penetration. If that’s not what you meant I apologize. In my replies, I basically said that sacrificing momentum to gain velocity does not increase penetration, or if it does, it probably only does so in commercial foam targets for some strange reason. I have a hard time believe that it does, but I’ve heard the claim before, and I haven’t tested it myself.
Now for some physics, and why Joel’s data(from what I’ve seen of it) doesn’t equal speed being more important than momentum. In my physics classes, and in many others, it is taught that momentum better describes a collision than kinetic energy. When it comes to rifles, kinetic energy got popularized by non-physicists as a means of compared things by people who wanted to be scientific, but they should have been looking at momentum. To this day everyone cares about a cartridge’s energy. Somehow in the archery world, people actually talk about momentum, which it seems like they should. With rifles, lighter faster bullets yield a higher kinetic energy, but a lower momentum. KE=MV^2 Momentum=MV. With a bow, that doesn’t happen. With a bow, decreasing arrow mass does not increase velocity enough to increase KE. Decreasing arrow mass increases velocity a little, but KE and momentum both decrease. Joel’s chart for the 35lb bow shows exactly what physics would expect from a bow. When he increased arrow mass, velocity decreased, but penetration increased. That’s what everyone has always said about bows. If you decrease arrow mass, you’ll decrease penetration. What is interesting about Joel’s findings is that kinetic energy seems to be a better indicator of penetration than momentum, BUT every time he got more penetration he had more momentum. If you decrease arrow mass on the same bow, you’ll loose momentum. Any time you increase arrow mass, using the same bow, you always get a decrease in velocity and an increase in momentum and kinetic energy. Joel’s data doesn’t contradict that. It is interesting that it shows energy as a better predictor of penetration than momentum, because they teach the opposite about collisions in physics classes. They’re not teaching a scientific law when they teach that though. To discover that energy better described a situation in which certain things collide would not violate physics in a any way. What I will be interested to see when I watch the whole video is whether Joel’s data suggests that when changing bows, he can get increased penetration, with increased kinetic energy but DECREASED momentum. It’s not possible to create a situation in which you increase kenetic energy but decrease movement in the same bow, but perhaps by changing bows you could, and if so, I’d like to see what he gets for penetration there.
FOC isn’t mass. FOC is a measure where the mass is. You can shoot a 450gr arrow with 8% FOC and a 450gr arrow with 30% FOC. They both have the same mass. The 30% FOC has been shown to penetrate animals better than the 8% FOC even at the same mass. So there’s no such thing as “speed is better than heavy/high FOC arrows” because you have high FOC without reducing speed at all. That said, increasing arrow mass to gain FOC gives you two penetration improvements. 1) Increased FOC increases penetration, and 2) increases arrow mass(even if you left FOC the same) gives you increased penetration.
That said, I’ve heard a podcast or two involving complaints about high FOC and high wind. An arrow shaft that is misaligned with the arrow’s flight path is going to rob a lot of penetration.
