REFLECTOR: Propellers 1 2 3 4 Blades

[Bob Jackson (Jax Tech)]

Ron,

We have ~500 hrs on an MT 3-blade, and ~300 hrs on an MT 4-blade.  The
4-blade is quieter and smoother (and there don't seem to be any 'beat' noise
effects due to wing interaction, like you hear on Cozy's and LongEZ's with
two blade props).  

We also seem to have fewer FOD issues with the 4-blade, even though the
diameter is only ~1" less (the big difference between MT 3 and 4 is the
smaller blade area of the 4-bladed prop.

What we didn't get with the 4-blade was the 'dramatic' performance
improvement at altitude (above 15 Kft) that we were hoping for.  And no
dramatic changes either in take-off roll, climb rate, top end speed, etc..
Maybe a small improvement in engine cooling (better low pressure draw from
the cowling ducts).

Bob Jackson
'Turbo Cross Country' Velocity XL-RG
N2XF  TNIO-550N


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Velocity
Sent: Saturday, November 17, 2012 11:46 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Propellers 1 2 3 4 Blades

I am working on making my second propeller. My first one is a three 
blade. I works just as
it was designed for,  great take off performance. I  now think I would 
like to have one that has
a bit more top speed. Now a single blade propeller is the most efficient 
but a little
impractical and hard to balance. So my question is a 2 bladed propeller  
would be the next most efficacy
and easiest to build but my fear is having both blades traveling through 
the wake from the wings.
at the same time . A four bladed propeller  has the same issue as a two 
blade just twice the frequency .
  Any thoughts on the choice of number of blades.

More blades equals smaller diameter but I have enough room to swing a 2 
blade so that is not an issue .

Long easy guys seem to have no issue with two blades . Any one in the 
velocity world
use a two blade propeller with or with out success?


Ron

Velocity XLFG  Chevy LT1  300 hp