I am building a SSE from a kit, but I really wanted to fly it so I got the ARF version, too. Also, the LHS had a really great deal on it - $150.00. I could not pass it up. My power plant is going to be a OS FS-70 Surpass II. I wanted to know what prop size I should use. 12 x 6? 13 x 4? I know I have to change out the landing gear. I am putting in a Dubro landing gear.

Thanks in advance

EDIT: What size prop should I used to break-in the engine?

I would check with the OS to see what they recommend for a break-in prop. Here is the listing for that engine from Tower and it has some good information at the bottom of it.

http://www2.towerhobbies.com/cgi-bin...?&I=LXXA42&P=0

The 13x6APC is a good all around prop for your plane/engine combo. If you want to do a lot of hovering the the 13x4W apc is a little better. Either prop will work for break in. Just be sure to break it in at a very rich setting. the first two tanks should be 2/3 throttle @ 4,000 to 5,000 RPM. Then lean it out a little at a time.Not peaking the rpm for 10 tanks or so. Then to fly peak it out and richen it 300-400 RPM. If you havn't done this before see if someone can help you. It would be a shame to ruin a new engine.

David

I have an OS70-fsII and I use 13x6 props on it, I would think this is the standard mot people uses for this engine ?!?

Right now I'm too building the SSE kit and have ordered another OS70 engine for it, I plan to use the stock landing gear and a three bladed 12x6 prop.
I have used 3-bladed 12x6 prop on my other OS70 and it's a good match.... I'm not into 3D and need power to hover and I think the .70 will do just great even with a less effective, 3-bladed prop.
Advantage is that I can use the stock gear + it looks cool with three blades

My dad uses a 12-8 on the OS 70 in his Tiger. Great prop won't hover or anything but it will climb out of sight!