Is there a chart or a method to determine what 3 blade prop that could be used on an engine?
Thanks for your help.

Start with your known appropriate 2-blade prop.

At appx .40 size engine... you drop one inch dia to add one blade.

Somewhere near (slightly above?) .60 size... the loading changes such that you drop one inch dia AND 1 inch pitch to add a blade.

From the 2 blade, drop 1" dia, and increase pitch by 2"

At a .40 size engine... you drop one inch dia to allow a 1 inch pitch increase...

Dropping one inch dia, increasing pitch 2 inches and adding a blade will put one heck of an extra load on the engine.

FH,

We're Awaiting too.

Mine came with the three blade 12X4 and it's not that easy to turn,i just put on a 11X7.5 and it runs faster at idle,wide open it don't push that much air but i think i need a bigger two blade.

Yes 3 balded props are a little less efficient. I tried one on my trainer and there were a few slight advantages, a little bit more ground clearance, a little less noisy, and I personlly like the look of a 3 bladed prop better. But these aren't worth, IMO the loss of performance you recieve.

Keep in mind that the 3-bladed prop that comes with the Alpha and related planes (in both .40 and .60 sizes) is NOT a typical 3-bladed prop, and doesn't exactly follow the same "rules" when converting back and forth. That 3-bladed prop is made to put a lot of load on the engine.

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