SebArt Katana 30e

SebArt Katana 30e

She’s beautiful from any angle!

If ever a model has caused excitement among electric flight and 3D aerobatic enthusiasts, then it’s this one. In truth, from first impressions it’s not difficult to see why, for although there are plenty of Katana designs around this is arguably the most attractive example you’ll find.

The Katana S 30E was designed by Italy’s Sebastiano Silvestri, based on his Katana S Tournament of Champions model. It’s an extremely lightweight, electric powered aerobat that’s designed for brushless motors, 3s Li-Pos and 40A ESCs.

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It’s interesting to note that just about every new sports aerobat currently passing through the portals of RCM&E seems to be aimed at expert 3D flyers, although I have a feeling that there are far more 3D models than there are dedicated and accomplished 3D pilots. That the 30E isn’t a beginner’s model should be obvious, and whilst I’m more of a pattern flyer (some now call it vintage style would you believe) I’ve always wanted something that would prop-hang, so I was rather hoping this little piece of brushless bling would satisfy that element.

Just in case the 3D experts reading this are sceptical of my ‘club pilot’ assessment, top display flyer Dave Wilshere has kindly added his thoughts from a high-end user’s perspective, so all bases are covered. You’ll find Dave’s comments at the bottom of the page

BLING THING

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There’s no doubt that the 30E is pretty, and she’s beautifully built, too. The wings and fuselage are primarily laser-cut ply with a little balsa here and there, whilst the tail feathers comprise a light balsa framework. Unusually, the canopy and forward fuselage top deck are a one-piece tinted moulding, painted where necessary and supported by a laser-cut balsa frame, the whole secured to the fuselage with a magnetic catch. Removing this provides ample access to the innards for both radio installation and battery changes. Equally well presented are the glass fibre cowl and spats, the whole model complemented with good quality wheels, spinner, hardware and stickers. Rest assured, you’ll want to use the fittings rather than replace them.

BENCH SKILLS

Bench skills? Don’t worry, you’ll not be requiring any! Our review example needed a brief encounter with my heat iron just to seal a few covering overlaps, in addition to which the cowl needed a little tidying with a file around the underside vent. It should be noted, however, that these were nothing more than the minor fiddlings of a fussy modeller. The instructions are best described as adequate, this due to dark photos and vague text. Mind you, there’s so little to do that modellers with a few airframes under their belt won’t need to refer to the book very often.

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Constructing the 30E follows a typically standard electric ARTF construction process: wing and tail mounted servos, plug-in wings plus a little cyano’ and epoxy here and there. Straightforward enough. The level of pre-build and accuracy means that I really have nothing to report along the way except that the instructions suggest using 300mm servo extension leads in the fuselage, which won’t be long enough! Take my advice here and either go for 600mm, or make your own. Incidentally, at a suggested 100mm the wing servo lead length is just about okay.

KIT OUT

There’s a wide choice of servos you can consider for this model. Any mini or micro units pulling 2kg should be fine. The instructions actually recommend JR DS385s, which are micro digitals, and as these aren’t too expensive I decided to treat myself to a set. Ultimately this was a good decision as the servo cut-outs and mounts seem to have been designed specifically for 385s. If you’re fitting Hitec 81s however, you’ll need to remove a little ply to get them in. Don’t be tempted to use HS55s, as they’re just not man-enough to cope with those large control surfaces.

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SebArt suggest using a huge 14 x 7” prop – a real paint stirrer, if ever there was! As I’m sure you’ll agree, that’s big for a 49” span model, even with a brushless motor up front and a prop-hang remit. At first I was concerned that the motor might pull more amps than the 40A ESC could handle, however since the motor is a low Kv unit I found that 40A was only drawn at full throttle, so I wasn’t too concerned. My 30E weighed in at 3 lb (1.4kg) with the battery on board – a little more than the 2.64 lb that the instructions led me to expect. I was a bit surprised at this as everything on the model was as suggested, right down to the servos. This wasn’t a concern though as a sparkling figure of 140W/lb had been rung up on my calculator.

There’s bags of room for a 3s Li-Po or indeed something a little bigger although extra battery weight will affect the performance

The 3s (11.1V) 2000 – 3000mAh Li-Po is fast becoming the standard power source for electric models of this size, so my two FlightPower EVO25 2500 and 2170mAh packs were just the ticket. My Futaba 6EX 2.4GHz system was in need of a permanent home, so a high-powered electric application seemed appropriate given 2.4’s indifference to interference. With servos housed at the extremities, the little R606 receiver had literally acres of space in the fuselage, which meant that finding positions for the twin 13cm internal aerials was easy.

3D FOR A NEWBIE

Seeing those large control surfaces flapping about had me a little worried that the 30E might be a bit of a handful, so I decided to use dual rates for the first flight (something I don’t usually bother with), employing a safe 60% movement on aileron and elevator with 40% negative exponential on aileron and 25% on elevator. At the flick of a switch I’d have 100% available. Like most electric models, a happy C of G is found by shifting the battery position so I decided to play safe and move the pack a tad forward to have the model just a fraction nose heavy for the first flight.

The climb-out was impressive, vertical, very fast, and the model felt beautifully set-up. A few clicks of trim soon had her flying hands-off so it was time to treat the airframe to my aerobatic repertoire!

Easy to fly yet so capable too

Since the low rate set-up was a little too sedentary, I flicked in the high rate, which seemed very comfortable. Roll rate in this setting is impressive, the elevator very responsive and, while we’re on the subject, the expo’ was about right, too! As you’d expect, the stall handling is very good, indeed the model will drop her nose if provoked but she certainly won’t flick or bite, at any stage. Until the Katana came along I’d never had a maiden flight where I’ve ventured into a low inverted pass, but the model is so confidence inspiring I just couldn’t resist. Actually, the Katana holds inverted well with just a touch of down elevator, which suits my pattern aerobatic flying style.

The 30E’s low weight is certainly reflected in the flight characteristics, this being particularly evident when I pulled a loop and cut the throttle at the top. Expecting the momentum to pull her over the top, she simply stopped! Clearly, the prop was acting as a brake at low throttle and the light airframe just sat there, upside-down in an inverted hover! The feather-like airframe was undoubtedly boosting my confidence, especially low down, where whatever manoeuvre I performed was always done in the knowledge that a quick burst of power would have the model punching skywards and away from terra firma. I’ve even been practising my parachutes and have found them pretty easy, albeit with a little wing rock on the way down.

I’ve left the C of G in its original position although a battery shift should bring about a neutral inverted feel for those who prefer it that way. Whilst landings are pretty straightforward, the model does need to be ‘flown in’ using throttle. Once on the ground the small spats and wheels have coped better with the long grass than I’d have anticipated, indeed neither has sustained damage and I’d hasten to add that the metal undercarriage has barely been tested by the lightweight airframe.

Landings are pretty easy, just remember the throttle

HEY, GOOD LOOKIN’

I just love this model, mainly because it makes my flying look so good! The 30E reminds me of a Shock Flyer; it has the same flying characteristics, albeit in a larger airframe. Make no mistake, this is a stunning model that I guarantee will grab attention on any flightline.

The motor package seems to be perfectly matched to the model so unless you have your own set-up in mind, look no further than that suggested. Add a 14 x 7” prop, pop in the servos and receiver and fly.

Both the FlightPower packs have delivered 7 – 9 minute flight times, although the lighter 2170mAh pack does seem to deliver a slight performance improvement for a negligible reduction in duration.

The 30E’s incredibly low weight combined with a 400W power system mean that this model is quite a revelation in flight. Don’t be intimidated though, it’s equally at home with a club pilot at the controls as it is with an expert and it’s as responsive as you care to make it. What a fantastic machine, it’s already teaching me a thing or two.

THREE MONTHS ON….

The time taken to get a review into production can sometimes mean that by the time it’s published, the model has seen a significant amount of flying time. So it is with this Katana which I’ve been flying since oh, let me think..May. Although the patch I fly from is suited to electric and i.c. models, I’m more of an electric flyer these days.

Summer sees me rushing home from work, throwing a model into the back of the car and heading off to the patch for an hour or so’s flying. Over the last few months I’ve found myself reaching for just two models, The Seagull Decathlon and this Katana. It is this Katana though that has really stolen my heart.

Practicalities first, it taxies really well, those wheels and spats havn’t posed a problem although I should add that the grass at our patch is always very short.

In the air the model has been a revelation to me. It is just so precise, so smooth and with all that power on tap….so incredibly able. Yet at the same time it is so very easy to fly (not for beginners mind) My knife-edge, prop hanging and all number of things are progressing nicely.

The little JR 385 micro digital servos have impressed

I’ve read in another review that the user felt the undercarriage isn’t strong enough but I really cant agree here. The u/c on my model is just fine, the low-weight of the model means it’s never going to have to work very hard to provide support although I’m speaking from having used a short grass patch and long grass landings will obviously test the structure a little more.

An amazing model then and my model of the year so far by a long way.

DAVE WILSHERE’S THOUGHTS

I’m always on the look-out for new toys, and over the last few years these lightweight 3D electric models have proliferated whilst their performance has continued to improve. For me this type of aeroplane provides a great practice vehicle for the larger petrol models in my fleet.

PRE-FLIGHT

I used the recommended JR digital DS385 servos (rated at 2kg) and have flown the model using both 35MHz and 2.4GHz radio, with perfect results. You need powerful servos for the huge ailerons just to stop any blow-back, so don’t be tempted into using servos with less torque than 1.3kg. Digital servos should ideally be used though. I experimented with a couple of propellers but kept coming back to the recommended 14 x 7” ‘E’ APC. Control movement was set to the maximum possible, with 40% negative exponential on ailerons and 35% on elevator. Examining the wing section made me realise that the 30E wasn’t going to be an out-and-out 3D aeroplane, indeed the design is very thin with a really wide wing chord at the root. The tail moment arm is also quite long, hinting at smooth flying characteristics.

IN-FLIGHT

The take-off run is short. Pulling vertically and banging in aileron shows a good rate of roll, whilst that low Kv Hacker motor swinging the large propeller provides plenty of pull. Snaps, spins and a Hanno Screw descent show the 30E’s forte very quickly; it handles all the snap manoeuvres very well.

Pulling into the prop-hang requires a fair amount of stick-stirring to keep the fuselage vertical, but once locked in, the model can be held and torque-rolled down the patch with only minor corrections. Harriers are performed with a virtually no wing rock and she can be brought down quite slowly with minimal power. Knife-edge was better than I expected. The smaller Katana / Funtana models don’t normally knife-edge that well but this one is sweet, with a minimal amount of mixing required to allow hands-off passes (hands-off apart from the rudder, that is). Around 8% up elevator is about right.

Back to the prop-hang again and the lack of control response from the tail group does become more apparent, a factor of the long moment arm keeping the tail away from the prop-wash.

If you hold off the touch-down too long during landing, the thin wing stops working quickly with a sharp drop, so it’s best to fly the model in, with blips of power. In a nutshell, this little Katana is a nice, smooth flying aeroplane that is probably best described as a good artistic aerobatic machine. I like it.

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