Do you recommend aileron plus rudder on the RK Cub?

From : Don Stackhouse

It depends on what type of flying you plan to do. The ailerons on the Cub are fairly effective, but the roll rate for the no-ailerons version is also very respectable, and of course the stability is better because of the extra dihedral. If you plan to do a lot of aerobatics, it's probably worth building it with ailerons, and (especially now that there's all these 3.5 gram servos available) you might even consider adding the third servo and setting it up with independent rudder and aileron. It will do all sorts of wonderful basic maneuvers with the stock setup of coupled aileron+rudder on one servo, but adding the extra servo lets you do things like knife-edge, forward slips to landing, "flat" (zero-bank) turns, and other stuff along those lines.

Of course the other thing you should consider if that's the kind of flying you want to do is the upgrade to the twin-motor MPS-2A powerplant, and maybe even a 3-cell battery. Just to put that in perspective:

The stock single motor system on two cells pulls about 6 watts at full throttle (which is plenty for puttering around the sky, that's what I have in my no-ailerons Cub). That equates to about 32 watts per pound, which in this model is about equal to the results you get from about 50-60 watts/pound in a larger model. So much for that old rule of thumb!

The MPS-2A twin-motor system on two cells pulls about 15 watts, more than double that of the single motor. The difference at the propshaft is even bigger because the lower current per motor on the twin motor system improves the electrical efficiency of the motors.

The MPS-2A on three 250 mah cells pulls about 25 watts. That's the system you want to use if you desire a Cub that can hover and do unlimited verticals.

However, if you just enjoy puttering around the sky with a really friendly little airplane, with an occasional loop, barrel roll or hammerhead, touch and go, playing keep-away with the family dog, etc., I'd recommend the no-ailerons version. For that kind of flying, the stock single-motor system is fine, unless you're flying in La Paz, Bolivia (I'm not kidding, we do have a customer there).

I built the first prototype with a single motor (we didn't have the twin motor back then), scale dihedral and coupled ailerons and rudder. It's the yellow one in the photos on our website. It was a ball to fly, did all sorts of maneuvers and flew in all kinds of places, got 18 minutes on a 110 mah NiMH 7-cell pack, and handled all sorts of weather both indoors and outdoors. It's down now for a major overhaul, mainly from "hangar rash".

The one that I fly the most now is the no-ailerons version with the extra dihedral. I have some little lights on it for night flying, and I'm seriously thinking about making some skis for it. I've flown a full-scale Cub on skis, and it's a real blast, should be fun with a model as well. I'm thinking about writing a magazine article once I get them sorted out. I built this model at the JR Indoor festival in Columbus a year and a half ago, in four hours start-to-finish (no paint, I just left it bare wood, which looks and holds up just fine) including a break to narrate an airshow, and talking with customers most of the time I was building. It has taught my youngest son to fly in one weekend (20 minutes of dual instruction in the backyard Thursday night, maybe an hour in the golf dome at Waterford Michigan Friday night, several more hours of mostly solo flying on Saturday, by mid Sunday morning he was flying in and out among 6-8 other planes, doing loops and touch-and-goes, while I was busy flying formation with him with my Stearman prototype). It's also taught a number of other folks of a variety of ages the basics of how to fly. Like I said, it's a good trainer, as well as great for puttering around the back yard and doing touch-and goes on the picnic table.

So, it all depends on what sort of flying you want to do.

Don Stackhouse
DJ Aerotech