Re: Prop Efficiency

From: markdrela <drela_at_mit.edu>
Date: Thu, 24 Aug 2006 01:30:08 -0000

--- In Indoor_Construction_at_yahoogroups.com, "John Kagan"
<john_kagan_at_...> wrote:
>
> Is that why I'm getting huge cords when I enter Indoor type
> parameters? I'm using:
>
> 2 blades
> 50 rpm
> .5m diameter
> .5m/s velocity
> .0025Nm torque

With these inputs, I also get max chords of 35 cm with the modified
method.

Your 0.0025 Nm = 0.354 in-oz, which I assume this is an F1D at max
torque. In that case your velocity is much too small I think. Let's
do the level cruise case first, since there we have a better idea of
the CL.
S = 0.11 m^2
W = 0.018 N
CL = 0.6 (wing should give about 0.5, stab about 0.1)
CD = 0.12 (L/D = 5)

These specs imply
V = 0.67 m/s
D = 0.0036 N = Thrust

I think this will give much smaller chords, and a torque closely
corresponding to the cruise torque.
Received on Wed Aug 23 2006 - 18:42:03 CEST