what size 3 blade prop do I need ?

[planefixr]

Hello.I purchased a Tower Hobby F4u Corsair. It came with a 2 blade prop but was wondering if I can go to a 3 or 4 blade prop. How would you calculate the size needed. It came with a 9 x 4.5 slowfly. 1000kv motor and 30 amp esc. Thanks for any help, Steve

[JetPlaneFlyer]

Rule of Thumb is do drop 10% in diameter for each extra blade you add but keep the pitch the same.

So the (roughly) equivalent props would be:
8" x 4.5" three blade
7" x 4.5" four blade

Higher blade props are less efficient, especially so on a model with a big cowl like the Corsair where the blades are partly masked by the cowl. So watt for watt you would suffer a significant if not major loss of performance.

Why would you want to add more blades anyway? (bearing in mind you cant see the prop when it spins)

[rcers]

I usually go down and inch in diameter and increase an inch in pitch.

Three blades looks good on the ground, but understand they are nowhere near as efficient as two blades. Just be prepared for more power consumed and less performance in the air.

Mike

[JetPlaneFlyer]

Originally Posted by rcers

I usually go down and inch in diameter and increase an inch in pitch.

yeah, the inch rule is the 'other' rule of thumb, which works good for props that are is the 8-12" diameter range.... but the 10% rule I think works better over a larger size range

[planefixr]

Thanks for the info, I just thought it would look cool with a 3 blade. did not think of it being less effeciant. I will stick with the prop it came with. Steve