Gonna pick up a 3 blade prop tomorrow (if they got the right size) for a scale look, but still want to fly with it. I was thinking a 12x6 MA 3 blade, its going on a OS 70FS Surpass 1 on my kyosho focke wulf. I think it will be about right for not being too big or too small for that engine. What do you guys think?

As a general rule: whatever two blade prop you use decrease the diameter by one inch for a three blade with the same pitch. So, would you use a 13x6 on this OS 70fs? It probably can handle that.

Bret - what he said!

Mr67Stang - you just beat me, and almost word for word what I was going to put.

Hogflyer

You know what they say about great minds although I'm sure there is a converse saying as well

Come on guys !!!!

Brett : I did a lot of playing around with 3 bladed props a while back and here's what I came up with for myself.

On all the engines I used below 90, I didn't really like the performance I got, it was ok but not real good. ( the 70 wasn't out yet, I had 56's )

On the 90 and above I liked the response and used 3 bladed on a couple planes. I liked the braking effect they gave me.

Not much help but that's what I came up with. What they said about sizing. ENJOY !!! RED

From Master Airscrew ;

To convert form 2 blades to 3 blades you want to decrease the total blade area and
increase the angle of attack (or pitch) to overcome the increased drag of the third blade.
The general rule is to DECREASE propeller diameter by 1-2�, and INCREASE by 1-2�
the propeller pitch. It is all right to keep the same pitch when going from 2 blade to 3,
however you will not want to decrease pitch.

http://masterairscrew.com/images/selecting_a_prop.pdf

Works very well for me.

That's the way I learned it. Going from 3 blade to 2 blade. Decrease diameter by 1" and increase pitch by 1.

Good luck.

I'd actually heard decrease diameter by 2" and increase pitch by 1". Not that it really matters that much - unless you want to do some REALLY complicated math (which probably won't have any effect in the real world) it's all just guess work and "rule of thumb". Try a couple of sizes and see what you like. If you want to get into the math side of it find a copy of the ThrustHP program, punch in the range of "ideal" 2 bladed props for your motor and note the disk load numbers, then start punching in available 3 blade props and compare disk load numbers. The same load should theoretically give the same power at the same speed. (Don't pay too much attention to the max speed ratings in that software though, ThrustHP is a bit optimistic there.)

Great minds think alike.
Fools seldom differ.

This is what I was taught and what I do but today on some of the prop sites I keep seeing them drop the size and stay with the same pitch. From my own testing I find adding pitch worked best??
I was running the 13X6 APC on my OS .70 and tested the MAS 12X6 and 8, both worked out fine. Problem is I was flying a 66 inch Tiger Moth so it doesn't mean anything at all to Brett, apples and oranges but the different pitches are worth trying to see what you like. MAS props are cheap enough to test several and well worth the effort!!

I run a 14x7 3 blade with my O.S. 91 FX Ringed and my plane flys very well with it. I love the looks, the sound of the prop wash when I do a slow fly-by. And the whine it produces when I do a high speed fly-by with it. The Evolution 3 blade has more of a breaking effect then my Master Airscrew 3 blade. My plane does not slow down like my old PTS did when I cut the throttle. The cause of this is the width of the blades on the Evolution. It's designed to slow the trainer down for landings, where as the Master Airscrew it's designed for preformance and scale looks, rather than just for training. JMHO




Pete

Evolution 3 blade ????????????
The only ones I've been able to find are the thing that comes on the Raptor and the "Evolution Alpha 60" 3-blade. That Alpha 60 is listed as a 12x4. That seems a bit small and flat to use on an OS91FX. All of my OS91s like the 14x7(3) Master Airscrew. They're on the H9 Spitfire, P47, and Corsair, and a Hobbico Sukhoi31. I'd tried the MA 13x8(3) that the OS75AX likes on one of those but it acted small. I can't imagine a 12x4 even coming close to applying the power of a 91FX, so what Evo(3) are you referring to and where can it be found.

I believe you've might have mis-read my Post? I didn't write I used the Evolution 3 bladed Prop on my O.S. .91FX Ringed True the Alpha has the Evolution 12x4, the PTS Raptor and Mustang have the 3 bladed Evolution 10.5x4. I ment 14x7.

For those who don't know, Evolution does not make a 14x6 or 14x7, I suspect most people knew that, so I didn't bother to spell it out better than I did. The one I'm using on my O.S. 91FX Ringed is a 14x7 Master Airscrew.

Just wanted to clear things up.

Pete

Well, I was cutting the spinner for the new MA12x6 3 blade the other night and screwed up. The spinner that comes with this focke wulf is made for either 2 or 3 blade props. I marked it for a 3 blade and then promptly cut it for a 2 blade.[:@] DANGIT! I was miffed. I guess I had something else going on in my mind. I ended up cutting it out for both, I'll have to check the balance on it, I hope it won't make a major vibration. Got the LHS checking on ordering another one. It has a snubnose that is specific to the focke wulf, I can't find an aluminum one that has the right shape.

A Scale Aluminium spinner is pretty easy to get, not cheap but easy; http://www.skysharkrc.com/shop/?shop=1&cat=15

Thanks vet, those look nice.

Here's what it looks like;

what did you use as a pilot?

In China I bought, and sold, a bunch of generic WWII pilots. I just repaint them as needed.