I just received a Great Planes Ultimate bipe for fathers day. I was wondering what engine to put in it when I am done building it? I was thinking of an OS 46 or 50. Would an os 61 fx be too much for this plane??

Thanks, Eric

I originally had an OS .46 on mine and changed it to an OS .61. It was definitely better. Wing loading went up, so when you chopped t he throttle, she is coming down fast.

Congratulations.
I got a GP Ultimate for Fathers day last year. Put an OSFX.46 in and its just great. Won't hover but does everything else. Great flier.

Just went back and forth between several engines on my GP Ultimate last night. I was pretty pumped on putting in an OS 61 FX until I noticed that it was just barely too big for the cowl even without the glow plug. [] If you don't want to cut the cowl out, be prepared in case your cowl may be a bit too small. I had to settle for a Saito .72 4strk....I wanted my 61 or my 91 4s, but my 91 4s found a home. Oh well, hopefully I'll only be denying myself the hovering.

I have the GP ultimate and I put the OS 61 in it and it flys pretty good. It won't hover but other than that its great. If you want it to hover put the OS 91 in it. The 91 is just a hair lighter than the 61 and has more power.

I have a GP ultimate and it started out with an OS 46 FX in it. This engine flew the plane pretty good and it fits nicely inside the cowl. I recently put a Saito 72 4 stroke in it and wow what a difference. I absolutely love this bipe now. It was already my favorite plane but now it is even better. The Saito gives me unlimited vertical performance and it is very good on fuel.

Rick

If you don't mind, what prop size where you using on that Saito .72 GP Ultimate?

I'll be using a new YS63FZ on mine. Lighter and stronger than the OS61FX; a little heavier than the Saito 72, but stronger. I have read a thread somewhere in RCU about at least one person using a Saito 91 in their GP Ultimate.

Mine is getting the OS .70 Surpass II...

I was using a Zinger 13x6 wood prop on it until I broke it on landing because I stalled it about 1 foot off of the ground. I have tried an APC 13x6 and an APC 13x4W. The 13x4W seems to work the best and gives the best vertical performance. Has anyone else used any other props on this engine plane combo and what results did you get.

Rick

I have an OS 70 FS on mine
flies great need to change the location of the battery
for better balance (middle of fuse.)
With two aileron servos in the bottom wing!
Cheers
Hisham

I put a Saito 91S on mine, and it flies like a dream!

Mike

The gp Ultimate that I have now had a saito 91 on it.