Pay attention! (I didn’t)

[Starz]

In a recent video, the host proposed another theory having to do with 'hard' flying.

He noticed that when flying in Sport mode and making hard turns, starts & stops, he noticed afterwords some marks on the body of the quad. He speculated that those hard movements cause the props to flex to the point of contact.

Extrapolating further, perhaps flying into strong headwinds could have a similar stress effect, even if flying under normal "P" mode.

No hard fly in my instance. Sport mode wasn’t needed. I had other fly toys that I could pour the coals to if speed was in the plan.

 

[TDZHDTV]

The problem I have with that theory is that bending the prop to hit the body would require a downward force, and it would seem to me that as long as the prop is spinning, there should be an upward force on it. However, the props get to be nearly flat near the tips, so I wonder if there's some condition that causes it to get twisted enough that the tip actually is generating a downward force while the rest of the prop is still generating an upward force. That would probably bend these props quite a bit. The alternate theory is that it's caused by twisting or bending of the arm, but it's hard to see how there could be enough of that to cause a prop strike without breaking the arm.

I’ve been experimenting with making the arms more ridged with tape, I’ve found that it is possible to set up a resonant frequency in the arms (in hover state) that manifests in the propellers to an extent that you can see them flexing +/- 3-4mm (total 6-8mm).

 

[s2seyecle]

The problem I have with that theory is that bending the prop to hit the body would require a downward force, and it would seem to me that as long as the prop is spinning, there should be an upward force on it. However, the props get to be nearly flat near the tips, so I wonder if there's some condition that causes it to get twisted enough that the tip actually is generating a downward force while the rest of the prop is still generating an upward force. That would probably bend these props quite a bit. The alternate theory is that it's caused by twisting or bending of the arm, but it's hard to see how there could be enough of that to cause a prop strike without breaking the arm.

Your point is well argued. If you've watched the video (painful as it is long) he's pretty convinced that the props were flattened by spending a month cramped in the case (positioned longitudinally). The 'force of speed' causing prop strike isn't as well argued.