The flight times and characteristics of the Cub and Junior sound like the perfect trainers for our classes.

From : Don Stackhouse

Time for some info about the RK models' characteristics to help your planning.

The easiest to build and fly in this series are the Cub and Junior with the "no ailerons" option. The Cub is in production now, and I'm finishing up the instructions for the Junior this weekend, so those should be available within the next few days. If I had to pick one or the other for training beginners, I'd probably pick the Junior, but it's a very close decision.

Next in the ease of flying category would be the Lockheed Model 10 Electra. It's relatively big, with a huge tail and very long tail moment, so the stability (especially the dynamic stability, which in my experience is an even bigger issue in a trainer than the static stability) is rock solid, but the control response is still very quick and crisp, but not at all "touchy", even with the throws set for basic aerobatics. It has lots of wing area and good tip chords, so the low speed performance and handling are among the best in the RK series (it will even turn as tightly as the long-wing A6M2 Zero, ten foot diameter turns are no big deal for either of them), but its top speed is nearly as good as the DC-3 (currently about the fastest in the existing series), so it handles wind very well. It cruises on 1/4 throttle and gets about 20 minutes or more on a 170 mah NiMH pack. Prior to the Cub and Junior, the Electra was the plane we recommended for beginners. Joe also uses his to drop one of those 5" plastic skydivers, and typically gets about a half-dozen climbs, drops and landings per charge. The setup for that is very simple, just a servo, two paper clips and a rubber band. We can send you a .JPG of Joe's setup if you're interested.

From what we've seen so far, the handling of the Boeing is similar to the Electra, other than the roll rate being rather "scale". It's very smooth, but not as nimble as the Electra. It's also a bit too expensive and complicated for a beginner. It might make a good second airplane. It's very impressive in flight, very scale-like. It's also very efficient, typically using only 1/2 throttle for takeoff and cruising on a little less than that. Climb angle with the throttle wide open is pretty steep.

We're talking about flying a formation of two or three of them along with a pair of P-38's and a pair of the FW 190A's that we're working on at the indoor demo at the Toledo show this year. The B-17's will simulate a raid on a collapsible cardboard ball bearing factory, while the P-38's will defend them from the Focke-Wulfs.

The Long-wing A6M2 Zero is very good in tight spaces. So is the Jenny, although the Jenny is probably a bit too complex for a beginner's first airplane. The Zero has a very tight turning radius, and is extremely maneuverable. It is also very efficient (as could be expected with all that wingspan), with flight times on a 110 pack in the 15 minute category.

The control response on the Corsair is similar and the turning radius is close (although I think Joe has finally learned to not try to dogfight my Zero with his Corsair, but stick to the "slash and dash" tactic - if I can get him into a turning fight I've got him!), but the Corsair likes to cruise at a faster airspeed. Joe really likes his Corsair, while I really like my A6M2. Both are good second airplanes. For outdoors the short-wing A6M5 Zero is a little faster but still very stable, very close in performance and handling to the Corsair. Both of these have a bit more induced drag than the long-wing Zero, so flight times on a 110 pack tend to be more in the 10-12 minute category.

However, both have plenty of chord and lots of wing area, so like the A6M2 they do seem to carry weight well. Joe has flown both of them very successfully (even in a basketball court) with a 170 mah pack and a Hitec 555 Rx. The larger battery can supply more current, so the extra power offsets the extra weight. This principle seems to hold true for most of the RK models, except for the ones that don't have enough wingspan to carry the extra weight (in particular the Triplane).

This is less of an issue now that the FMA M-5 receiver is available, since it doesn't add nearly as much extra weight as the bullet-proof but relatively heavy 555. We're testing one of these in the Boeing, and so far it hasn't had a single glitch. (of course when we fly the Boeing, everybody else seems to land their planes so they can watch it fly!) If you're in a high-density RF environment that gives single conversion receivers a difficult time, the M-5 could be a very worthwhile investment. We're hearing rumors that some of the other manufacturers may be coming out soon with dual conversion receivers of similar sizes and weights.

The Jenny is a delightful plane, and would be a good trainer if it was a bit less complex to build. It's not all that difficult, the structure essentially jigs itself to get the correct incidences and alignments, but it does have a lot of little plywood parts (even the valve rocker arms and the radiator cap!). It's surprisingly durable, despite its appearance. Handling in flight is very stable and scale-like, not unlike the A6M2, although the drag of the extra wing and all those struts tends to reduce flight times a bit. It likes to cruise at about 5/8 throttle. Its long wings with ailerons on only the top wing don't help the roll rate (although barrel rolls are still possible) but it does some of the tightest loops of the entire RK series, 6' diameter or less if you have enough elevator throw, and it will do a half dozen or more of them in a row with only a modest amount of altitude loss. Just relax the back pressure on the elevator for about one fuselage length during the vertically downward portion of each loop, and you can do loop after loop until you run out of altitude. Its top speed isn't as high as the WW II warbirds, so it's comfortable outdoors in winds of up to about 5-7 knots, where the monoplanes can typically handle 8-10 or more.

The Camel has better roll authority than the Jenny, and its shorter span requires more power for cruise (about 3/4 throttle), but otherwise it's similar to the Jenny in handling. It's very nimble and fun to fly, a bit faster than the Jenny, fairly easy to build although not really a beginner's airplane. Because of the higher power requirements its flight times tend to be in the 6 minute category. It's very comfortable in a basketball court or outdoors, up to about 8 knots of wind. Ground handling is actually fairly good, much better than you might expect from such tall, narrow gear.

Joe tested the Camel with a 6-cell 110 mah pack with good results. While we usually see improvements from the extra power of a bigger battery, in this case the Camel's short span responded very favorably to the reduced weight of one less cell. Cruise throttle settings were reduced and flight times improved. I'm also looking forward to trying this in the Triplane. One other option will be an MPS-2A with a 7" prop (normally we use a 6-5 on the MPS-2A), made practical by the reduced RPM of the 6-cell pack. Maybe this spring, when it's warm enough outside for the batteries to perform normally again, and after I finish some of these other projects...

The Triplane is delightful in flight, although it's even draggier than the other two WW I models and needs to cruise at about 7/8 throttle. Flight times tend to run around 4-5 very exciting minutes. It will loop and roll, although it does not retain energy well, so multiple loops are usually not a good idea unless you have lots of altitude or a very fresh battery. In a turning fight it's unsurpassed, as you might expect. It's one of the few airplanes that can turn inside the A6M2, and anyone foolish enough to try to jump you is going to have their hands full. A dogfight between my Triplane and Joe's Camel is a lot like the dogfights between his Corsair and my A6M2. If we're indoors and he has to turn soon after his initial attack run, I can usually dodge his initial attack and then whip around to get on his tail as he goes by.

If you haven't noticed already, the performance and handling characteristics of the individual RK models tend to mimic their full-scale counterparts, as do the relative differences between the different models. This tended to happen naturally to some extent, but we also tuned the individual designs to encourage this property.

The Triplane's ground handling is rather scale-like as well. It's downright intimidating at first, but becomes rather fun once you get used to it. When the tail is down, the two lower wings and that big stab blank the tiny rudder, making it very prone to ground looping, which then usually ends in a nose-over. On takeoff the trick is to hold full down elevator as you open the throttle ALL THE WAY, then neutralize the elevator as the fuselage comes up to a level attitude. This gets the rudder immediately up into some clean airflow. Be ready to use lots of rudder as required to keep it straight, hold the tail slightly low as the speed builds up, and it will lift off nicely by itself. On Astro-turf it's probably better to hand-launch, but on any reasonably smooth surface it will ROG quite nicely if you use the right technique.

On landing, keep plenty of speed, leave the throttle at about 1/2 (yes, I said one half!), and fly it on in a "wheel" landing. Leave the throttle at 1/2 during the landing roll and hold the fuselage level with elevator as long as possible during rollout. If you're really good, you can do high speed taxi including great big turns and figure 8's on one wheel in this mode. Flip from dual rate to full rate on the transmitter after touchdown to get more rudder authority. When the plane decelerates enough that you can't hold the tail up anymore, put the tail down with "up" elevator, back off to 1/4 throttle and let the plane slow to a stop, or at least a very slow taxi. Don't cut the power completely, or the windmilling prop will block off all the airflow to the tail. The Triplane's ground handling is fine at high speed with the tail up, or at very low speed with the tail down, but positively atrocious in between those two conditions. As long as you plan your ground operations so that you always operate at one of those two conditions and only pass through that dangerous middle area momentarily during the transition, everything will be fine. It's a fun and challenging model to fly, although it requires that you stay in practice with it, even after first getting used to it. It's a great airplane for keeping your skills sharp. Now that I'm used to it, it's one of my favorites in the series. However, it is NOT a primary trainer.

Building the Triplane is not too difficult. On the Camel and Jenny the wing struts are designed to act as a jig to get the wings properly aligned, but the single struts used on the Triplane don't lend themselves to this technique. Instead we include a laser-cut cardboard jig that holds all three wings in alignment while you glue in the struts and the fuselage. One thing that's very important on the Triplane, as well as the long-nosed models like the P-51 and the Me-109, is to get the correct trim adjustment between the rudder and ailerons. This is also true of the other models with coupled ailerons and rudder, although not as pronounced. With coupled rudder and ailerons, any roll trim you add also adds some rudder. If you don't readjust the rudder to eliminate the resulting yaw and get the fuselage back in line with the airflow, that profile fuselage makes horrendous amounts of drag. The airplane acts like there is a serious lack of power, suggesting a battery or motor problem, when in fact the problem is the drag from all that yaw. Long noses hurt yaw stability, which is why the Mustang and Messerschmitt are vulnerable to this. In the case of the Triplane, it already has all the drag from having to pull three sets of wings through the air plus the induced drag from that short span, so the drag of a yawed fuselage is just a little more than it's willing to tolerate. If your Triplane seems sluggish in flight, experiment with its rudder's neutral setting.

Getting back to the WW II ships, the Spitfire is really a nice model if you keep it light. The long tail moments make it surprisingly stable, and its handling in flight and on the ground are both quite good. It was my personal favorite before we developed the A6M2. Building it is really not too difficult. It's a little tricky gluing the basswood strip to the curved edge of the lower skin, but after that it's easy. The ribs are designed so that the upper skin is actually just a 2-D curve, not 3-D, so it curls into place without significant fuss. The resulting model is quite beautiful and is very nimble in flight, just like the real one.

The Mustang flies well, although it does not like to have a ham-fisted pilot on the controls, just like the real one. Typical cruise is about 5/8 throttle. Too much aggressive control movement will make the plane squirm around in the air, and that causes that big fuselage to generate gobs of drag, which then kills all your airspeed. The key is to use small, smooth control inputs and learn to manage your energy well. It's very fast and nimble if flown well, but tends to get very grumpy with pilots who just bang the sticks around. The biggest mistake with the Mustang is overcontrolling. Try to yank it off the ground and then do a max-performance pylon turn before it's finished accelerating (it continues to gain a fair amount of speed after the initial liftoff), and you're likely to see a low altitude tip stall. Go get the glue...

A Mustang flown with finesse is a thing of beauty.

The same is true of the other long-nosed models in this group, the Me109 and the P-40B. Both have relatively high wing loadings, so are very nimble but like lots of power and airspeed. Slow them down too much and they can turn and bite you. Cruise them at about 3/4 throttle until you get used to them, and land with about 1/3 throttle.

We're expecting to have the MPS-2A twin-motor system in production very soon, and the Mustang, Me109 and P-40B are all good candidates for it. Joe's son Terry has been having a ball with an Me109 and an MPS-2A with a 7-cell 230 mah NiMH pack. We're still experimenting with it in the Triplane, where more power could help but its short wingspan has trouble carrying the 7-cell 230 mah NiMH battery we recommend for the MPS-2A. Like I mentioned above, a small 6-cell pack and an oversize prop might work with the MPS-2A in the Triplane.

The P-38 has longer wings with a lot more mass mounted on them and more aerodynamic roll damping than the single-motor WW II fighters, so the roll rate isn't as good (although I've watched Joe roll his under a 20' ceiling), but the P-38 has reserve power like a turbocharged Corvette. Energy maneuvers are its forte. It's a little faster in cruise than the other WW II fighters, so it does very well outdoors (I successfully flew one of the prototypes in my backyard once in 12-gusting-to-20 knots and blowing snow, but it wasn't fun). With enough ceiling height it does BIG loops and in general it handles like it was on rails. The best battery for it is probably a 170 to 230 mah NiMH, or possibly one of the Li-poly batteries. It pulls about 2-2.5 amps at full throttle, and cruises on about half that. One thing I'd like to try sometime is a P-38 with two speed controllers for differential throttle to augment the rudder. That should make some very interesting maneuvers possible, but it requires some tricky programming in the transmitter.

The new Ryan ST has a big fuselage, long nose and all that side area in the wheel pants. It flew OK on an MPS-1A, but not as energetic as a Ryan ST should be, so we're equipping it with an MPS-2A right from the start. It has lots of power with that setup, plenty of wing area and span, and is very stable but very responsive, a lot like a good .40 size sport model. The wing loading is high enough for it to ride turbulence and wind well, but the low speed performance is good enough for indoor flying. I flew it recently in a very constricted and crowded basketball court with excellent results. It also does very well outdoors, as could be expected. We have the instructions nearly done, and expect to have it in production soon.

The DC-3 is awesome to watch. It can be flown in a basketball court (in fact the very first test flights were in one), but it's really better suited for larger rooms and outdoors. It's the fastest of the current RK models, even faster than the P-38 and Electra. It's cruise speed is also fairly fast, and although it has a fairly tight turning radius, its roll rate is fairly scale. In a tight flying area you need to plan ahead and allow enough room to roll in and out of turns. It's very stable with its long tail moment. Handling in the air and on the ground is impeccable. Despite the narrow tips, it is nearly immune to tip stall, thanks to the generous washout and the use of progressive airfoil changes from root to tip. The biggest problem with it in a tight flying area like a basketball court is landing. It's quite efficient, so finding enough room to roll level at a safe altitude, then getting it to come down, land and stop within the space available can be a real problem. I've flown the prototype quite a bit in the gym at our local high school, and found that the best technique seems to be to make a circling touchdown on one wheel (you may actually have to touch the inside wing tip a little before the inside main wheel), followed by a circling rollout. It can do full-stall landings, but a scale-like "wheel" landing seems to work best. Just fly it on with the fuselage level, then gently set the tailwheel down after it's decelerated a bit.

Leave some power on (that advice seems to apply to nearly all of the RK models). The area of the prop disks blanket a large portion of the wing and most of the tail. If you cut the power completely, the props will windmill by extracting power from the airflow, which will essentially shut off the airflow to everything behind them, including the part of the wing that does most of the work of supporting the airplane, and virtually all of the tail.

One of the biggest problems with the DC-3 is that it looks too good in flight. It's easy to get mesmerized watching it, and forget to fly the plane! I was flying it in the big indoor hockey/basketball arena at Wright State University one night, and got so enthralled watching it fly so smoothly off towards the far side of the arena that I almost forgot to turn at the far end! I realized what I was doing just in time to avoid the seats.

I suspect that the Boeing could have that same effect. These big airplanes are just too pretty in flight.

The DC-3 carries weight well, and I'd like to try one with an extra servo to operate some scale split flaps. That should make it much easier to fly in small rooms. Another option might be to rig scale flaps with a 2-position ground-adjustable linkage. For big rooms and outdoors leave them retracted, for flying in small rooms leave them down.

All of the earlier (i.e.: prior to the J-3 Cub) RK models use very light 1/32" balsa for the top and bottom wing skins. It isn't too hard to work with, but might be a bit challenging for an absolute neophyte. The Cub and Junior were intended for training, so they use .050" upper wing skins and tail surfaces along with hard 1/32" balsa lower wing skins, for better durability and easier construction. Because of their greater speed/size, we use this same setup on the Boeing and the Ryan ST wings. BTW, we specify a range of balsa densities on virtually all parts in our RK kits, typically a total tolerance of about 2 lbs/sq.ft. for any particular part and tailored to each individual part's structural needs. If you find a piece of heavy balsa in a RK kit (wheels on the larger models, for example), it's because that part needs to be heavy. Depending on the individual situation, we might go with thicker, lighter wood or heavier, thinner wood.

As far as the newer models are concerned, the Cub and the Junior are both very stable and docile (the tail moment on the Junior is 1" longer than scale just to make certain of this, and there are subtle deviations in the Cub as well), with good handling on the ground and in flight. Both are easy to build, with some novel self-jigging features built into the parts. For example, both have small supports built into the wings to help set the dihedral at either the with or without ailerons settings during construction. The Junior has tabs and matching slots built into the aft fuselage, fin and stabilizer to help ensure proper alignment, and the Cub has reference marks cut into the stab for the same purpose. An experienced builder could assemble either of them in about a day, and a reasonably adept and properly coached beginner could probably do it in a few days. Although these two are easier to build than many of the other RK models, there is still enough commonality with the other models that folks will find them quite familiar after building a Cub or Junior. As I mentioned above, the Cub and Junior are very docile with the no ailerons option and reduced control throws, but they can become very aerobatic with increased throws and with ailerons. They will loop like the Jenny, but can do respectable axial rolls with the right technique (plenty of speed, and LOTS of down elevator during the inverted portion), and retain energy much better than the Jenny. They also thermal well, even with the wing struts installed. Glide angle completely power-off is steep enough to get them reliably into a tight landing area, but with the throttle cracked open just enough to eliminate the propeller drag they become quite efficient.

The Ryan ST uses construction very similar in most respects to the Cub. However, its higher weight and wing loading along with the Ryan's bigger powerplant probably make the Cub or Junior a better choice for a beginner. OTOH, an experienced gas flyer might prefer to start with the Ryan.

There's probably a few more details I've left out, but this should give you the general flavor of the models in the Roadkill series. If you have a REALLY big hangar to fly in or plan to fly outdoors, you might also want to consider the 2-meter Chrysalis. It was designed for beginners, with excellent plans and extremely gentle handling combined with excellent performance. We included spoilers as standard equipment because a beginner would probably have trouble getting it to come down in a typical small flying area without them! One of our customers described it as having the float of a Gentle Lady but with twice the range. The dynamic stability is extraordinarily high, so high in fact that first-time beginners have flown it successfully even with the C/G set so far aft that it was slightly divergent in pitch! Even so, it is very responsive and maneuverable.

We have Speed 600 electric version of the 2-meter Chrysalis in development, and it isn't difficult to ad-lib your own electric version if you don't want to wait for the official factory version (probably a good idea, given our schedule!). Just shorten the nose 3.5" and mount the motor with 2 deg. right thrust and 5 deg. down thrust.. Folks have also successfully electrified the hand-launched Chrysalis, typically with a Speed 400, but some are also happy with a GWS drive from an old Lite Stik, mounted on a stick in the front of the nose block. Both versions of the Chrysalis could also be powered with a 1/2A gas engine on a pylon over the wing or on the nose.

Lots of options. Probably the Junior is the best overall starting point if you want to do training and need to fly both indoors and outdoors. After that, obviously the sky is the limit!

Don Stackhouse
DJ Aerotech