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I would fly it!

earthsciteach

Moderator
Moderator
#7
My guess is that its likely a tradeoff between weight and efficiency. An electric motor capable of turning a prop of the size that would provide the performance desired my be too heavy. I've also read that the larger the edf, the more efficient the blades are. Fan swept area increases exponentially with increase in fan radius.
 

squishy

Pirate ParkFlyer
#8
very true, I was thinking that as well, the scale of RC ducts is so small compared to those on the airplane above...
 

tramsgar

Senior Member
#9
I've also read that the larger the edf, the more efficient the blades are. Fan swept area increases exponentially with increase in fan radius.
Pardon me and all, it was quite a while since I took my last math course, but wouldn't that be quadratic increase um or something?
 

squishy

Pirate ParkFlyer
#11
I don't even believe in math, stop forcing your beliefs on others...there's only one way to know for sure and that's real world testing..lol
 

tramsgar

Senior Member
#13
Yea I'm not picking on words here, just that exponential increase would require the radius as the exponent (and they engines would rip out and go to the moon =).

Still that thing didn't take off in the vid, what they're chicken or just trying to raise more development money?
 

earthsciteach

Moderator
Moderator
#14
Ok, going full out nerd here... Since the exponent is on the radius, doubling the radius increases the area by a factor of 4. Therefore, the area increases exponentially.

I get suspicious when I see airplanes taxiing but not flying. There seems to be a lot of fancy tricycles online.
 

tramsgar

Senior Member
#15
You're the teach, I won't argue... Oh who am I kidding =), I had to check Wikipedia as I didn't learn the terminology in English:
Quadratic growth, 2 as the exponent, like prop cross section surface area: πr[SUP]2[/SUP]
Cubic growth, 3 as the exponent, like volume of sphere: 4πr[SUP]3[/SUP]/3
Exponential growth, the variable as the exponent, like bacteria growing: a[SUP]r[/SUP]

Sorry if I just argue against the language barrier here. And I don't claim to know the formulas for drag, power, efficiency, prop specs et c related to the surface area of an EDF.