Re: [indoor construction] VP or VD

From: markdrela <drela_at_mit.edu>
Date: Tue, 24 Oct 2006 21:02:37 -0000

--- In Indoor_Construction_at_yahoogroups.com, "Nick Ray" <lasray@...> wrote:
>
> With the 9cm max blade cord, would you use a lower pitch prop
> than the typical 32-36" range seen with F1Ds?

For a given diameter, a wider blade dictates a higher pitch, not a
lower pitch. The baseline min-D prop I looked at has the following
chord and pitch angle distributions:


# r[cm] c[cm] beta[deg]
   1.79 3.53 83.72
   3.38 5.87 77.07
   4.96 7.54 70.81
   6.54 8.58 65.06
   8.12 9.05 59.87
   9.71 9.05 55.24
  11.29 8.68 51.14
  12.88 8.03 47.51
  14.46 7.14 44.30
  16.04 6.04 41.46
  17.62 4.67 38.93
  19.21 2.68 36.66
  20.00 1.46 35.62

The P/D is roughly 2.2 over most of the blade, hence the wide chords.


> Also, is a Symmetrical prop still the most efficient?

Propeller theory says nothing about the spar position on the chord.
That's a matter of flex under load.

> Lastly, how would gradual change in diameter verses
> a prop folding at set intervals of torque effect the efficiency?

How the diameter is scheduled shouldn't matter too much, since the
prop does OK at any diameter.
Received on Tue Oct 24 2006 - 14:04:58 CEST