Wednesday, February 10, 2010

Prop Size and Other Prop Info

I just found out recently that I have been using props too small for my glow engines. Years ago, when I started flying .60 sized airplanes, the guys I flew with used 11x7 props. That is what I have always used, without asking any questions. A few weeks ago, I was reading a review of a .40 sized aircraft and they recommended a 12 inch prop. I have always flown 10x6 props on .40 sized aircraft. Well, the other day, flying my floatplane, I was having problems with the floats sticking to the water so I put a 12 inch prop on the plane and I got better takeoff performance. Tonight I decided to lookup recommended prop sizes and this is what I found:

From the OS Engines website:

.40 No info
.46 10.5x6, 11x6-8, 12x6-7
.61 12x6-8, 13x6-7
.91 13x8-9

Propeller Pitch
Pitch is the same on model airplanes as it is on real airplanes. Pitch is how many inches the prop will move in one revolution. So a propeller with an 7 inch pitch will move 7 inches in one revolution.

Lower pitches are better for climbing and power maneuvers. Higher pitch props are better for speed.

Prop Blades
The fewer blades a propeller has, the more efficient it is. Ideally, the perfect propeller would have one blade but balance would be a major problem. So, a two bladed prop is more efficient than a three bladed prop.

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