N12932

I have a hanger 9 spitfire and at the moment only have a 2 blade prop on it. I want to get either a 3 blade, 5 blade, or 6 blade prop to make it more accurate to the real plane. However, I have a sato 100 on it at the moment and im not sure how to determine what prop to pu on it to achieve this or where to find such a prop.

carrellh

The "benchmark" two blade prop for this engine (according to Horizon) is 14x8 APC. I used 14x8 to do my software experiment.
Playing with "Prop Selector" software (you can find the download by using the RCU search feature) indicates a 14x6 three blade would put similar load on the engine. Dropping the diameter to 13, the pitch to create a similar load would be 7 or 8.

Of course this is just theory. You might hate the way the plane flies with any three blade prop. And, you may not find a three blade prop in the right size to load the engine to the right rpm.

APC does have a few four blade props.

They probably exist, but I've never seen a model prop with more than four blades.

N12932

Thanks, I Look up that prop selector program and then do a bit of trial and error work

carrellh

For three blade (and possibly four blade) props you can find popular sizes at:
www.horizonhobby.com APC, Master Airscrew, possibly others

www.towerhobbies.com APC, Master Airscrew, possibly others

www.hobbypeople.net APC, Master Airscrew, possibly others

www.hobby-lobby.com APC, Graupner, Master Airscrew, possibly others

bla bla

You will achieve nothing N12932 other than having something that, as far as you're concerned, appears more scale.
The truth is, any of those multi blade props mentioned above are about is as far from scale as you'll get!
To make mater worse, you'll only have this perceved scale effect whilst it's in the pits and then, only when being looked at by people that know NOTHING about scale airplanes!
It gets even worse. The flying will also suffer. Yes it'll fly but not as well. The engine isn't designed to be loaded up, it's a light weight motor, in a sports scale model.
You need a set up that is as efficient as possible. That's is going to deminish with every extra blade.
Do what you will, we've all tried it at some point.
I'd spend your money and energy on something else.

Robotech

My Feedback: (9)

I used a Master Airscrew 13X8 three blade with excellent results on my HAngar 9 Mustang / Saito 100.

jetmech05

I've heard the argument that a 2 blade prop is better than a 3 or more bladed prop.
I am not convinced as full scale aircraft are getting away from 3 and 4 bladed props and going to 5 and 6 bladed props.
The trainer that uses a 3 blade prop flies just as well with a 2 blade prop.
I've heard the argument that the second blade is passing through turbulent air, seems to me that no blade is getting into more turbulent air than another blade when you consider forward motion of the prop/airplane.
remember its not the whole prop blade that produces thrust but only about 1/3 of the blade, down from the tip about 1/5 length of the blade.

saramos

There's a big difference in full scale as compared to RC. Full scale engines turn at much lower RPMs but with much higher torque. The props have much larger diameters. For the RC Spit to have a scale prop, you would need to be able to turn a 4 blade prop that is closer to 18" diameter. I too have a desire for a closer to scale prop. The closest solution for this size model is to go with a geared RCV SP series engine or electric power. Conventional engines turn at too high an RPM which requires much smaller 2 blade props. They have too little torque to effectively turn a large 4 blade prop. Even the RCV with it's 2:1 gear ratio will probably have trouble with an 18" 4 blade when the recommended 4 blade is a 15.5 x 12 (this is the size APC I use).

Scott

khodges

My Feedback: (1)

Try the three blade, if the plane flies to suit you, don't worry about the dynamics and physics of two vs three blades. I fly a 60 inch bipe with a 14-7 3-blade MA prop using a Saito 1.00, and it moves along pretty well, plus climbs like a squirrel with a cat chasing it. My 1.00 will turn about 9200 rpm on 15% Cool Power with this prop.