Popriv

3D Profile with an OS .50SX .
Setup weights about 5 lbs ( Solid fuse,,,)

I maidened this last saturday with a 12x5 prop... It flew at idle with this prop... Suggestions at the field were to try a 13x4 ...


OS lists the prop range as:
sport - 11x6 thru 11x10 and 12x6
Arobatic - 12x7 - 12-9


For this slow flying 3D plane what would be a good choice. can I go with a 13x4?

thanks

G.Barber

My Feedback: (1)

APC makes a 13x4 wide blade prop that works very well. I used to use this prop on an O.S. .60 FX on a U-CAN-Do .46 - it was a great combination! Give it a try - you'll like it!

One more suggestion - if you do use the APC props, "dull" the edges of the blades with a piece of sandpaper. The APC props are WAY too sharp, and can cut you just tightening the prop nut!

ES CONTROL

Yea 13x4 .   If more RPM is needed. or it cuples bad on knife edge 12x4

ES CONTROL

Yea 13x4 .   If more RPM is needed.  12x4

RCKen

My Feedback: (9)

The best bet for finding "the best" prop for your particular type of flying is simply to get out and try. Select several different sizes, and even different manufacturers, of props and then head out to the field. Fly with each prop and then decide which one suits you best. While we can all sit here and say one size is "perfect" for your setup, it's really difficult for us to accurately predict what's going to be best for you.

Popriv

Ken, I guess my question is what range of props can I safely try on this engine.... Is it just a matter of staying within the rpm range OS lists for this engine? OS doesnt list 13x4 as an appropriate option....

steve

Gray Beard

My Feedback: (-1)

Just keep it in it's working RPM range and your good to go. Keep in mind, a longer prop with a smaller pitch gives you more thrust with a slower speed. 3-D props are smaller pitched for a reason. Not all props are made the same or just made of plastic. You can try a lighter wood prop like a Xoar after you try the same size prop from APC. Prop testing takes me the most part of a long day. Over the years we all end up with a good selection or props and sizes. Once you know a general size you like then you can sell or give away your over stock. I'm low on prop sizes I usually don't use, I give them to friends at the field as they need them. For buying a big stash of props RC swap Meets and auctions are a good place to buy them. Different makes of props are more efficient. APC is better then Master Air Screw but MAS are bullet proof. Xoar are way better then Zinger but you can find Zingers in most any hobby shop.
See why there is no one magic prop anyone can say is the best. Engine/plane combos are all different and one engine/plane combo may like a different make of prop better then the same combo someone else owns.
As long as you don't over rev the engine or bog it down too much you will be OK. The manufacture can't list all the sizes. They list the sizes they found to work with the engine during there testing. You should be OK trying out a 13 inch prop. I don't think I would try anything bigger. Look at some of the smaller pitches of the 3-D props too. They are made in smaller pitches then 4.

delman

I have had good performance with the apc 12x4 prop on my 50sx's. If you try a 13x4, I would try the thin blade as the 13x4 wide blade was better on my 61.

jimmyjames213

My Feedback: (2)

i found the 12.25x3.75 to be the best for hovering while the 12x4 is best for high alpha (torques slightly more than the 12.25x3.75 making hovering slightly more difficult but high alpha easier)
either way 12x4 or 12.25x3.75

jaka

Hi!
Two-stroke engines do not have "Safe working range"! You can use what ever prop you like as long as the engine likes it! That means using a small 8x6 or a big 15x4! As long as you do not set the needle to lean and over heat the engine it will be jsut fine.