Im getting this plane here in the next week and i want to put a 2 stroke on it...
Im either going with a OS .91FX or 1.08 FSR. Whats going to be best. I would get the .91 hands down because i know it will fly the #### out of this plane but people are HAVING PROBLEMS with the engine. Has Os fixed the .91FX.

My only other question is if i go with the 1.08 will the plane balance, or will i have to put a bunch of led in the tail.... Its quit a bit heavier than the .91fx but the plave may need some weight up front to balance it...

I can't imagine that the 1.08 is any heavier than a 120 Surpass or Laser 150 (both around 30 ounces). I have used these engines in the two Ultimates I owned/own, with no balance issues. In fact, the ARF/Laser 150 combo I'm flying now needs the CG moved aft a bit.

I have seen this plane fly on both. Eather one will make you happy. I've not heard of any proplems with the 91, and I sell them. Dennis

I fly mine with a ST.90. It needs 90% throttle to hover. Anything else the .90 is fine. If you go with the 1.08 think about putting two ELEV servos in the tail. This will make up for the weight and is a better setup anyway.

David

I have a O.S 91 in mine and it balanced right on no wieght. The 1.08 is heavier.You'll need to ad tail weight. Mine flies great and I'm at damn near 4000 ft. I'd go with the .91-Mike

Oh yea, What problems are they having, O.S's are great. I love them. -Mike

Well in the past people have complained about this particular engine overheating and having fuel problems... Just look in the engine forum. There are alot of people who seem to hate them.

rcmiket, can you hover your plane with the .91fx. What kind of prop do you use. As long as you say I want limit the plane due to the engine then i'll go with the FX. I don't like the extra weight of the 1.08 anyways.

Also how easy is it to do flat spins with this particular plane...

Thanks

You didn't ask me but mine will flat spins OK, not great. It's easy to get in and out of but it's about 30degrees nose down. Not real flat. Also mine will hover with either a 14x6MA or a 14x4W APC. The APC will do it with a little less throttle.


david

I have a YS 120 (32oz) in mine with twin elevator servos and battery under the canopy, it balances no problem. As for flat spin; I don't no how daveopam's is set up but mine flat spins super. It takes about 30º of elevator. Power is the key, it take about 75% throttle to flatten out. With a less powerful engine I don't think it could overcome the drag. I would go with the 1.08.

Wow a YS120!!! I bet that plane is a beast!

I run a ST2300 in a modified CG ultimate (longer fuse, (5") dropped the top wing 1" and set the elevator at 0deg ) with the twin elevator servos and the battery under the canopy like the other guy.
I am flying pattern with it hence the mods. (till I get another 2 m pattern ship this winter) the 1.40 is very nice, I wouldn't want less motor.
That said I had a stock one with a Saito .91 and it would hover and pull out a little and flat spin etc fine , It is really dependent on CG and wieght .
the one with the ST in it is 9Lbs 12oz . The stock one was quite a bit less if I remember right.
(they do not need to be modified to fly hotdog stuff great either.)

No it can't hover but either could the full scale. If thats what your looking for than keep lookin. I have never had a O.S give me or anyone around here any trouble. Were using Cool Power 15% and a wide ranch of props. Belive me at 4000 ft. and 100' degrees of heat we find O.S.'s very user freindly. Hope you find the right combo. Good luck.-Mike

Oh yea 14-6 Apc Prop. Sorry -Mike

David, here is how I answered the question for myself. I asked how much heavier is the 1.08 over the 91FX? Then I asked if the weight increase is worth the increased power.

I have the ARF with; OS 1.08/Pitts Muffler and dual elevator servos with FG push rods. Mine balaced with a 5 cell 1800mAh battery under the back side of the canopy. I am using an APC 15x8. This is my first real high performance machine and it will require some work on my part. I have four areas I am work on after flying it this summer are:

1) Covering scheme. It is not the best for visual orientation. Will recover this winter.
2) Weight. I want to investigate reducing weight with;lighter landing gear/wheel/axles. Eliminate FG push rods by moving elevator servos to rear and using smaller battery more forward. Small receiver, mini throttle servo.
3) Dead stick glide is about 1:1 (45 deg angle!!!!) Nothing I can do about this but point nose down and hope I make the field.
4) Try different props. This thing is pretty fast even at 1/4 throttle. May be a 16x6??

Marcus

Marcus it sound like your on the right track. My covering is yellow with navy blue on the bottem of the fuse, lower wing and stab bottem. This is the best combo I've had for a fast rolling plane. I'm sure reducing the weight will help some areas. Under power though most ULTs fly the same. I have flown 10-12 of them over the years. Unless they are going up the .75ST ones fly as good as the YS1.20 ones. If the glide rate is what your trying to improve then save yourself some time. They all glide that way. I caution most guys not to test fly one at the reccomended low rate ELEV. It wont hold the nose up in a turn when it dies. The prop I like the best on mine is only a 4" pitch. I dont care how fast it is.
Good luck with Ult. It's a great airplane.
David

I fly mine with OS 90 FX 15X6 sea level, I love it. Yes it used to get hot, just opened much more the cowling on the bottom part, I have tried 13X8, 14X6, 15X5 I stick to 15X6, top flite and Zinger are fine, APC give you more rpm but idle goes up. Right about the color too, it is not a good one to see,
Mine is ready for general maintanece, will go to white and red colors.
I had problems with regular servos, one aileron`s stripped, rudder is not too good.
beatiful true-turn Ultimate spinner, try it it enhance it a lot!

My last recomendation CHADWICKZ 71 is to keep it light, I enjoy it more than the 120 4-s, Although it all depends on how hight is your flield located.

Well, my airfield is about 350ft... Anyways, I plan on putting futaba 3004's on the control surfaces. They should hold up fine.