I'm in the process of finishing up my first venture into the electric world, a Great Planes Fun Force EP P-51.
I notice that the prop that came with the kit, a 10 x 4.5 S has the end tips bent at a 90 degree angle rear wards. Here is a pic:
Thanks for any insight..
I don't know if it's normal for Great Planes' props, but I've never seen one like it and I fly lots of electrics. I'd suspect it's damaged...
PCPhill
"Winglets" to increase efficiency...
Or it's defective. :)
David Hopper wrote in news: snipped-for-privacy@4ax.com:
Well, I had a GP prop (10x3.8, I think), and it was exactly the same, so I don't think it's damage or a molding error.
I'm guessing it was intended to improve efficiency by providing winglets, as another poster suggested. It may also be an effort to make the prop more resistant to tip damage.
However - from my one flight with that prop, it seemed to underperform its GWS and APC counterparts.
They're made that way. I don't know the reason .
Ken
It looks to me like the tips were bent after the prop was molded, notice the light colored stress marks at the bend. I've never seen one made like this.
Red S.
That's a standard Electrifly prop, my Flatout Cap 580 came with the same style that you're describing. I simply assumed the design was cosmetic and somebody at GP simply thought it looked cool.
I suspect that this type of tip design, if intentional, would be less efficient that a more conventional design. My reasoning is that any incremental "tip efficiency" gain (I doubt if there is any) would be negated by the incremental torque ( i.e. power) expense to overcome the added drag. Any added tip drag is an efficiency killer because it acts at the longest moment arm. Your observation confirms this.
Winglets have to be just right to increase efficiency. "Real" airplane winglets require lots of experimentation (and sometimes lots of computer time) to get just right.
Turned-down times are used on full-scale props, but they also need to be done right. Like winglets, they would improve things when the propeller's induced drag is greater than its parasitic drag, i.e. for high lift situations. If you just bend the end to make it look cool then chances are you'll get it wrong.
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