Richard Riley wrote:
On Sat, 02 Jul 2005 22:19:43 -0600, Scott Derrick
wrote:

: I am working off dim memories here, but ISTR that Klaus had vibration
: problems with an experimental (in the deepest sense of the word)
: 3-bladed prop and that he recommended 2-blades only for the EZ series
: aircraft.
:
:Many pushers now use 3 bladed composite props. The most popular for the
:180 HP and up crowd is the Catto Prop, maple laminate core with 25 to 36
: layers of fiberglass over the wood with a 1/2" aluminum mounting plate
:embedded on one side. He makes them for 100 to 600 HP engines. They
:are known to be bullet proof.
:
:The lower power pushers use 2 blades because they can get away with it
:and they are much cheaper than 3 bladed fixed pitch props. The higher
:the engine HP the more blade you need. A two bladed prop on a 200 HP
:engine is just to long for a pusher, so 3 blades are required.

I've had 2 blade props on 540 Berkuts from Props, Inc and Klaus.
They've worked fine. 3 blade Catto's are a little faster than the 2
blades from Props Inc, but slower than the ones from Klaus.

2 blade props are more effecient than 3. In fact, 1 blade is, in
theory, more effecient than 2, they're just hell on engine bearings
(the Germans tried them in WW2).

I saw a picture years ago of a one-blade prop and it had a counterweight
on the other side. This shouldn't be a lot harder on the bearings, but
you would have some aysmmetrical loading from the asymmetric thrust. It
sure looked ugly though!


Matt