I have an rc guys cessna agwagon arf. It's got a 97" wing and is 62" long, they say the flight weight is 14-15 lbs. but I think it's a little less. I have a o.s. fs 120 surpass that I got years ago and was thinking about using it in the ag. I'm just affraid that it might be under powered. Any advise would be great.

Just a guess, but I don't think it will be enough engine. Maybe a 1.80 4 stroke or a 1.60 2 stroke or even a light wieght 45cc gasser.

Considering where you are on the project, this is what I would do.  Find a way to estimate the weight if engine required for best balance.  That will give you a clue.  I agree with flamin that the 120-4stroke is likely too lo in power.  Ags are supposed to be hi powered planes.  If you can stand the weight, a G38 or G45 would be a nice match for the airframe.  If lower weight is called for there are a bunch of light weight gassers available in the same size class.

Looks like fun.

Bedford

a g26 is perfect on those airplanes, for power and balance

I've flown a 14lb bipe on a saito 120 and its just enough power, not much reserve.  I agree with the others, go bigger.  Cause its a lot more fun to fly a crop duster the way it was ment to be flown.
Edwin

A 30cc will do fine, or the new FG30 from saito, but any 1.50-1.80 4cycle will pull it around just fine with plenty in reserve.

Did anybody bother to check the recommendations from the manufacturer?

[link]http://www.rcguys.com/agwagon.html[/link]

Yes, the 120 will be on the low side of power.

Rafael

Then a light weight 45 would be perfect. Who wants an underpowered plane?

Yeah that's what I figured. I got the 120 yrs ago and I looked the price up on tower and its going for $379.99 now and just figured maybe I could put it to use. Couple guys I know were saying go with a g26, I've never had a gas plane, always glow. But comparing prices I can get a o.s. 160 2 stroke for $259 from tower but from them and a couple other sites I looked at I couldn't find a gas engine from much less than $350-400. I know gas is more cost efficiant in the long run but I'm not gonna be flying to often, probably once a week so I'm not worried about that. I know that the direction said if the motor weighed over 3 lbs. to do dual elevator servos at the rear of the fuslage, but I just did one up front at the servo tray. Though I think a g26 is under that so I'd still be safe.

Why do you insist in going to the bottom of the power band on an Ag wagon? I normally go to the top of the power recommendations even if the airplane was a slug for real. You can always throttle back, but when the power is not there......

Rafael

O.S. 300 Twin

We have a 3M53 Gasser on ours and find its about perfect. Anything less wouldn't be enough.

The plane takes up to a 4.0 hp engine and a o.s. 160 2stroke glow puts out 3.7, I don't think it would be under powered. And like I said before I can get it for $259, I can't find a gas engine for any less than about $350. I also only did one elevator servo so the engine can't weigh more than 3 lbs. unless I change it to dual and patch the hole where the push rod comes out.

I just maidened mine today with a Saito 180 in the snoot and all I can say is that ity flys awesome. Very Very scale like for power. The 120 4st would not be enough, but the 160 2st will work just fine. I did have to put about 2 1/2 lbs in the nose to balance. The plane came in at around 17lbs RTF.

If you look in the classifieds you will find a bunch of small gassers in the same price range as the large 2 stroke your looking at $260.00 +/-

Heres one for an example.
http://www.rcuniverse.com/market/item.cfm?itemId=527726

I'm not affiliated with any engine manufacturer... just giving you some advice.

John

Nice! I had a couple of ?'s What's mounted where in instrument panel would be? And what's mounted next to the on/off switch? I'm gonna guess it's a lead for the glow igniter

The thing mounted where the instrument panel would be is a Voltwatch. It is used to monitor the voltage of the onboard battery.

Yes, the item mounted on the dash is indeed a Voltwatch Battery monitor.
The plug next to the on/off switch is a remote glow ignitor plug. It was just a real pain in the a** to get the glow ignitor directly onto the glow plug and this is a lot safer and works awesome.

Cheers

Curt