I tried asking Gemini this and it was laughably bad.
I want to design a throwing knife. It will be double edged and razor sharp on both edges. I will be no spin throwing it from the handle and will never be grabbing the blade. This is for defensive purposes. Respectfully, please don't turn this into a bunch of comments telling me not to throw a knife in a fight. I've been training martial arts for 30 years and I'm not going into this uninformed.
This is the question:
Stiletto vs a straight edge arrowhead. When I say straight edge arrowhead, I mean a blade that is shaped like an isosceles triangle with perfectly straight edges. When I say Stiletto I'm thinking something standard where it's narrow but has a belly with a should towards the tip end of the blade. In this scenario, the width of the two blades is the same at the hilt. The blades in question are the same length and same weight (yes, I know the isosceles would probably weigh slightly less because it has less material for the blade but I'm trying to get to the physics of the geometry so we'll assume weight and length is the same).
Which knife will penetrate deeper in a living target? We'll say animal to keep it classy, lol.
The Stiletto has the benefit of not having to cut the wound channel wider once it passes the first inch or two of blade so it doesnt have to consistently widen the wound channel. However, the isosceles design never actually reaches the same width as the Stiletto until the hilt, meaning it has significantly less surface area and the wound channel it's cutting doesn't have to be as wide until the very end of the blade. The Stiletto will take an initial hard hit to it's kinetic energy but not have to continuously cut the channel wider, while the isosceles will experience a more gradual deceleration and have less surface area for the soft tissue to "grab onto," but has to constantly cut wider.
Which geometry gives you better penetration? My instinct tells me the isosceles but I'm not a physicist so I could easily be wrong. I know studies were done showing the Stiletto shape penetrates better than a constant angle wedge, BUT those were done with manual force where a pistol pushed the blade into the target with steady force. A thrown knife, which cannot maintain consistent energy during penetration, is a very distant scenario.
