I am putting together a Cessna 182 ARF by Great Planes. It calls for a .40 to .46 size 2 stroke. I have a O.S. Max SF .61 motor. Is this way to big, or could I use it if i stay out of the throttle? The O.S. Mas SF is an older motor that I bought 15 Years ago and never used. I have it on a test Bench and it runs great. Started up on the Second slap of the prop! If it would fit and if there is no weight problem, would this still be a bad move? Thanks for the help.

im not sure, ut i dont think there would be too much of a problem

in the 2nd world war the Japanese "Zero" fighter planes were roughly the same size as a cessna 152 but had about 5 times the power, so i dont see why not but if your using a bigger engine and prop there may be a little clearance issue and you may be more likely to hit the prop when you land

just my theory... correct me if im wrong

I don't know the wing loading of the kit offhand but you may be putting five or six oz. heavier engine in a plane that already has a hefty wing loading. If you have to add tail weight to balance it you're up 15 or 20% in weight and will have no low-speed envelope (scale models stall just like real airplanes do.) You'll have to land hot, and with scale landing gear that won't be able to take a lot of banging. If you're on a rough grass strip it may be trouble.

Or not.

Actually, you may find that there are a few major problems with doing this. Weight being probably the most important. You are going to be adding a large amount of weight to the nose of the plane. You are going to have to find ways of adding weight to the tail to compensate for this, which would probably end up being adding lead to the tail of the plane. Now you are increasing the overall weight of the plane which in turn increases the wing loading. The increase in wing loading increases the speed you will need to take off with, as well as causing faster landings.

Another thing to think about goes along with the increase in weight, and it deals with the structure being able to handle the increase in weight and power. It's possible that you could literally pull the firewall off of the airplane unless it's probably strengthened. This goes for the frame of the plane too. Will it be able to handle the extra weight and power?? Only two ways to find out. 1) pull off the covering and inspect the framework. 2) Fly the plane and see if it comes apart in the air.

Now don't get me wrong, I'm not saying that it's not possible to put a larger engine on this plane. I'm just saying that there are things that need to be taken into account when done. People put larger engines on planes all the time, but most of them have the experience needed to do this safely. A discussion such as this is usually above the level of experience of new pilots in the hobby.

Some things to think about.

Ken

The OS 61 weighs in at 23.6 ounces with the muffler. The OS 46 (not the LA) weighs in at 17.2 ounces with the muffler. That's an extra 6 ounces of weight that you may have to compensate for. Additionally, the OS 61 would use a larger prop than you may be able to use on that aircraft (ground clearance). If so, and if you go for a smaller prop, you could spin that engine to bits with over-speed.

I had an OS 61 on my Tiger 60. I played with props and almost destroyed the engine when I went to a smaller diameter than it called for. It screamed.. for sure, but I got nothing out of it other than a lot more noise (not good).

You are probably better off sticking with the recommended size for that plane. Save the OS 61 for something larger... like a Tiger 60 <GRIN>.


DS.

What no one has mentioned yet is that a 61 size engine is 3 engine sizes larger than 40. That means that unless you increase the fuel tank size to a 14-16 oz. you will have very short flight times. Most airframes built for 40-46 size engines won't accomodate fuel tanks that are this large. Even if you can do some mods and squeeze one in, now you will probably have double the amount of fuel in the plane than for the 40 size which also adds to your weight problem. []

Ruger,
That 61 shouldn't be a problem, in fact I think that's a better choice (especially since you already have it). The fuel tank will not be a factor, the airframe won't know the difference you can pull just as many G's with a 46 as a 61, beef up the fire wall with a little epoxy, move the battery back in the fuse and you might not have to add any weight.
I have a Flip and it calls for a 2 stroke 46 and I got a OS 91 4 stroke hangin out there!! No problem at all. I beefed up the firewall, moved the bat back and works great. I'm gettin about 10-12 mins out of it (stock fuel tank).
Besides your not adding that much weight and the 61 and 46 are similar in power out put, besides 4 strokes sound cooler anyway!!! JMHO

As far as fuel consumption is concerned, I once replaced the OS .25 FP in a Kadet Senorita with a OS .40 FP and used the same tank. Rather than shorter flight times, it seemed they were just as long or longer. That forty spent a lot more time at part throttle than the .25 did.
A .61 making about .8 horsepower at approximately 60% open throttle may well burn less fuel than a .40 making the same horsepower at near full throttle, and a larger diameter and slower turning prop turns a larger percentage of the shaft horsepower to thrust. That's why so many electrics are gear reduced, to couple the motor's power to a big, slow turning prop for maximum propulsion efficiency.
As far as weight is concerned, a lot of models seem to need that nose weight anyway in order to balance. If you need nose weight, it might as well be a bigger engine. Besides that, a plane that can go straight up vertically is so much fun.

Your right about the nose weight, most need it. I have only had one model that needed tail weight. [8D]

Thanks everyone for the Info. I think i will do the math for weight and look at the clearance for the prop. If the wing load and weight come out and the prop size looks cool then i might give it a try. Thanks for all the info, i appreciate it very much...

RugerFly

Ruger,
The wing loading thing is not real important, what I mean by that is you will not be able to fold up the wings with either of those engines. The prop clearance does not need to be huge, if you are getting like an inch and a half that should be good, more is better however. Let us know what you decide!

OK here is what you have to watch out for. I lost a plane this way: You increase the weight and landing and taking off have to be faster as stated above - no real big deal.

Here is the big deal:

It is tip stalls and spins that will get you!!! You are just messing around at half throttle at low altitude and everthing is going fine. You play around a bit. All the sudden a wing drops so fast you think your radio glitched. You put in up elevator and you now keep that wing stalled as you watch your plane pile into the ground. You will swear it is your radio and you will replace all the gear but you missed the real problem. Don't fly heavy planes slow unless you know exactly every way they will snap and tip stall on you and how to recover.

HA Ha, ask me how I know!

Ruger,
Chevy is right on!! No matter what engine you put in that bad boy I recomend you take it up reeeeeeeeeeal high and stall it, slow flight it, turn up the power and yank that thing. Every time you fly a new plane you have got to learn its habbits. Also on first landing (if you have the room) come in a little hot.

The OS 61SF is not a 4stroke, but a 2 stroke and a darn good one that deserves to be on a 60 size airframe. A Flip and a Cessna 182 are significantly different airframes. What's good for one may not necessarily be good for the other.

BUY THE RIGHT ENGINE AND BE HAPPY!!!

Gibbs

Jim,
My bad! I thought when Ruger said "61" he ment a four stroke. Yeah your right a 61 2 stroke is too big for that plane, way too big actually.

Ruger,
Jim is right and had I known at the time that you were talkin about a 2 stroke 61 I would have told you to save that bad boy for a different airframe. If it were a 4 stroke it would work but not a 2 stroke. Sorry boys! Guess I need to study my part #s on 2 strokers a little bit! [:'(]