Hey there people!!

I have a phoenix models sukhoi I crashed a while ago . I was flying the plane with a TT .42gp but it was kinda underpowered with that engine, after crashing it I thought I might get a bigger engine for my plane. I am thinking about a 4 stroke most likely and these are the options that have gone thru my mind: O.S. FS-72, Saito 72, O.S 61 FX, O.S FS-91 or Saito 100. I would appreciate if u guys could tell me which engine would be a better match. As you can see I like my planes overpowered so please dont tell me to put a .46 engine in there. Also... Do you think and O.S .91 or Saito 100 would be too much for this baby???? My plane is VERY tail heavy btw.

Thanks,

Willie

Loved mine with the Saito .82 in it. Had oodles of power. Too bad I ran it out of fuel at the wrong time.

Mine flew good with an OS46AX in the nose. But it could have used a bit more power. It balanced well with that ~18 ounce engine, but it happens that my ARF came with a huge hunk of lead hidden in the fuselage. (Had I known that, I wouldn't have moved the battery into the tail and wound up with a model that was carrying excess weight.)

There was room for the 46, so there would be room for an identically sized OS55AX, which is a moderately more powerful 2cycle. I think I would choose that over the OS61FX unless you really need a 23oz engine up front. Either the 46AX or 55AX would show you appreciably better performance than the TT42 had. They're not just larger displacement but seem to be about the most powerful for their displacement I've seen. I'm doing prop tests with the 55AX right now, playing around with 3blades, and that 55 is swinging some props my 61FX likes.

As for 4strokes..........
The OS FS91Surpass is also a heavyweight at 24oz. Either of the Saitos would be lighter by quite a bit. The 82AAC is 18oz and would give a bunch more power. I've not flown many 4strokes, but have flown that one and it's a HOSS. It'll swing a 14x6 without a problem. I'd go with that if I were doing what you're planning. The 100FA-AAC whould give even more power, but I'd bet it would be wasted. It could swing the same pitch in a prop with an inch more diameter, but is going to weigh 3oz more and cost more.

AS for your tail heavy airplane.........
If there is a lead slug hidden in your Sukhoi, like Phoenix did in a lot of them to make up for lousy wood/design, then punch it out while you're rebuilding. And then move the battery up there. And pick the Surpass if you still need nose weight. And put the lead in front of the firewall instead of on the fuselage floor.

You got 18oz, 21oz, and 24oz engines to pick from, and all of them excellent engines. And plenty of room for them. Also plenty of room in the cowl for ballast if that's needed.

BTW, what you see in that cowling picture is about 3" deep of pink foam. Yeah, it's painted black. It's there for two reasons. It fills the area where I want to block cooling airflow from going. And it helped round out that oblong fiberglass cowl that Phoenix QA should never have passed.

Where the foam is would be plenty of space for any forward ballast you might need.

BTW, any model airplane manufacturer who puts a slab of lead into an airplane to make up for lousy wood selection or poor design would be better lost to a hobby they don't understand. And a mfg that throws an egg shaped, poorly trimmed fiberglass part like I got really should shift their production to Barbie dolls. I've had two Phoenix ARFs and both showed a real lack of understanding of the hobby. It's pretty amazing what the ARF mfg's don't know.

Very nice reply Da Rock. I dont understand what ur sayin about the "slab of lead"... My english is not too good so I really dont get it. I would appreciate if you could explain a little further . And this means that the 91 or 100 4 stroke wont be too much power for the plane?

Ohh btw, am fixing my plane now but the fuselage is pretty messed up ... I hope I get it fixed soon and I gotta make sure that firewall is in good condition cuz my plane hit VERY hard in the nose and made like 2 star rolls on the floor.

Thanks!

Willie

Phoenix Models put lead into the fuselage at the factory. It's in the front, on the floor, just behind the firewall. They apparently did it when they discovered that their design or their choice of wood behind the CG created an airplane that was tailheavy. It is almost impossible to see. You will not notice it is there even if you look into the fuselage. It is a flat rectangle of lead.

I built mine with an OS46AX which is an average weight for the recommended engine size Phoenix suggests. Mine came out nose heavy. And I moved the battery back into the rear of the fuselage, actually behind where the trailing edge of the wing aligns. If I had known the lead was there, I would have removed it and not had to go to extra effort to build support for the battery so far aft. If they had included it in their kits for those that might need extra nose weight, I could have not used it. Had I needed nose weight, I would have placed it one the cowl side of the firewall and been able to use less than the amount needed to put it inside the fuselage.

Anyone who has not assembled their Phoenix Sukhoi has a chance to get that lead out while it's easier to do. And should, if they want the best performance out of their model and whatever components they choose. Less weight takes off easier, climbs better, and lands slower. Automatically sticking a hunk of lead into an unassembled ARF is a somewhat ignorant thing to do.

The Sukhoi is an aerobatic airplane. It's expected that they have more power than the average model. Excess power is more often what you want for an aerobatic model. That airplane will have enough excess power with a 60 2cycle or a 90 4cycle. And it will fly even better if that lead is removed if it's in your model.

BTW, crash damage is often increased when there are lead slugs inside the fuselage. For one thing, the airplane usually hits harder. For another, concentrated mass often blasts it's way through bulkheads and fuselage sides.

I don't think my plane has that lead you're talking about. Today I fixed my plane, the problem was much simpler than it looked... I fixed it pretty well and I mite be reonforcing dome areas later on. The plane unfortunately doesn't look as good as new since the monokote is broke in some areas but I really don't care much .My plane is actually VERY tail heavy, even with the tank full the tail slams into the floor. Now my mind is between the O.S .91 or the saito 100... I think the saito 100 might be better because of the weight savings. I have heard nothing but good about the O.S FS-91 but is the Saito 100 as good??

Thanks,

Willie

Since there is quite a difference in weight between the two engines, and you've got the airplane back together, why not figure out how much weight it will take to balance out the airplane and let that help you decide which engine to use. Since they both are excellent engines, and you don't have a preference, let the airplane decide.

Put whatever weight on the motor mounts that it takes to balance the airplane. Then see which engine is closest to that weight.

They're bot excellent engines. The OS is about 2oz heavier than the 100FA and is about $30 cheaper.

Alright!!! TYVM Da Rock your posts where very helpful .