Terryh6336

My Feedback: (1)

Can someone explain when and why a three bladed prop would be used instead of a two blade. I am using a .70 4-stroke on a Senior Kadet. Thanks in advance.

pmw

My Feedback: (1)

A two bladed prop is more efficient than a 3 or 4 blade. A three blade would likely be used for increased ground clearance. Multi-blade props are a little quieter than 2 blade, but the difference is minimal. Some people will use multi-blades to achieve a scale look, but only when performance is not an issue. You'll notice that competition scale guys usually change to a 2 blade prop for the flying portion of the competition.

pmw

redfox435cat

on war birds were the look is desired.

again on a war bird if you overpower them and you need the 3 blade so the prop won't hit the ground

again on a war bird if you use the RCD geared motors. they are geared 2 to one so you they swing a bigger prop and again the prop would dig into the ground with a 2 bladed prop. the think the 91 pulled an 18 inch prop in 2 blade, you can get it down to 16in with a 3 blade


the GP sea wind requires a 3 blade because a 2 blade prop with the right load for the motor would cut into the top of the fuse. The os 91 swings a 15 in prop with a 2 blade, 13 in on this plane would just nick the fuse with the vibration, so a 12.5 is about as big as you can go. a 2 bladed prop with enough pitch to load the motor right would have so little torque it would be useless so use a 3 bladed prop.

actually just about every sea plane I got I use 3 blade for the most clearance from the water, the props just suck the water up


the 3 blade isn't done much on 40 sized and smaller planes with the exception of the pts system, those I rip the prop off the second I encounter them. 90's on up it's done when nessasary

da Rock

When one prop works better than the other. And there is no way to know just based on the number of blades.

The idea to not test one because it's supposedly less efficient than the other is BS. A 12x8 is more efficient than a 12x7 which is more efficient than a 12x6 which is............. but we don't refuse to test 12x6s simply because it's less efficient than 12x7s etc do we.

Three blades often work better than 2s. It's simply a matter of the prop suiting the engine and plane, not the number of blades. But about the only reasons that would call for 3 blades would be ground clearance and scale looks.

My Tiger60 flies better with the 3blader on it, especially in the summer when the air is hotter and thinner. I assume it's the extra blade area. Truth is, it works better in the winter too, but that's simply because that 3blader just suits the plane/engine as good as the best match the 2bladers I tested gave. But then, maybe I should have tried more efficient 2s. (which I did do, btw)