I must confess to having had a healthy cynicism concerning the alleged success of the European and American electric jets featured occasionally in Electric Flight International. However, my visit to the World Jet Masters changed all that. I took a couple of daysí holiday especially to visit the event on Thursday and Friday, and boy oh boy!! What a revelation!! The e-jets were completely mind-blowing.
Though it may sound daft, all the glow and turbine efforts paled into insignificance compared with the electric models, which easily matched the in-flight realism of the others. There was a larger number of e-jets there than I expected, ranging from the Schlosser F-16s to a massive Antonov. I wish now that I'd taken a lot more notes and photos, but I wasnít intending to burst into print.
The most popular power units in use were Lehner pylon race motors, and the Antonov had 6 of them. Also on Lehners were a Gloster Meteor and an A-10. Chris Golds showed his B-52 and Concorde, each with the correct number of Wemotec 480 fans and Sp 480 motors, and Ralf Dvorak's P-80 was there with its twin motored fan unit. Of the aforementioned models, I only saw the Antonov fly, and what a captivating sight it was! The huge model sounded and flew exactly to scale. Picture a full size 747 flying a circuit, and the Antonov flew exactly the same. Even the droning whistle from the motor units sounded right. By complete contrast, there was a big model 747 with two gas turbines, which flew just like a jet fighter, and looked horrid doing it. Unfortunately, I donít know the source of the Lehners, but a request on the EFLIGHT Mailing List may prove worthwhile.
Ralf Dvorak displayed his Su 35 with twin Ultra 930/7s, 30 cells at 27 amps, and home made fans. He delighted everyone with some great flying early in the week, but crashed on Thursday, having forgotten to extend the RX aerial from within the fuz. Damage was not too extensive, however, and he reckoned that he would repair the airframe and use it as a plug to make a grp mould.
Jean-Paul Schlosser brought a pair of his all-grp Jepe F-16s, one of which had an Aveox 1406/2, and the other an Ultra 930/6. The Aveox machine is advertised as having 12 cells, but I reckon I counted 14 cells when I looked inside the Ultra-powered one. The fans were Schwerdtfegers, and the models were bungee-launched and belly landed on the grass at the side of the runway. Unlike most fan rotors, Schwerdtfeger ones have adjustable pitch which you optimise to suit the motor/battery combination in use. How you go about this process is described in the fan unit instructions, and it certainly works!
Talk about performance! I saw these two models fly one heck of a co-ordinated aerobatic sequence, their dynamism breathtaking in its power and elegance: great long climbs until the models were mere specks high in the sky; massive loops and Immelmanns; multiple rolls of all types; and all of this performed in an eerie silence that seemed to herald the dawning of a new age even more significant than the advent of model gas turbines. There wasn't too much to choose between the way the models performed, so it wasn't obvious which motor was which. Admittedly, no extended verticals were flown, but the flight capabilities would readily satisfy all but the most cynical onlooker.
Anyone who wants to buy what may well be the world's best electric F-16 kit should contact Jean-Paul at: JEPE Fiberatelier, Engelseweg 3b, 5705 AB Helmond, Holland, Tel/Fax
F-16 specs from Jean-Paul's JEPE brochure are: Span 30in; weight 3lb 12oz; fan - 90mm Schwerdtfeger; motor - as above; cells - 12x1900 mAh. Two series-connected in-line 6- or 7-cell packs are located in F-16ís generously proportioned wing root fairings, one each side, just above the wing, and the rest of the avionics is disposed on or around the duct and fan unit.
Two more impressive e-jets were a Vampire and a MiG 15. I didn't get any details on Reto Senn's Vampire, but it was about the same size as Jurgen Tuchler's MiG 15. The MiG was the better performer of the two, the Vampire seeming light and draggy to my eyes whereas the MiG knifed solidly though the air.
I had noticed the MiG in the pits, but only spotted it flying quite by chance. I happened to look up, and there it was - a very quiet MiG speeding through a display of large expansive manoeuvres with consumate ease. I stood, completely absorbed and rooted to the spot whilst it flew for an age, and I must confess to thinking that Dave Ribbe had brought his version from the States (ed note: Dave's Mig, displayed in the E Zone's coverage of the 1996 KRC electric fly-in, has since been obliterated in a fatal crash at a ducted fan rally). I was quite elated to discover afterwards that its superlative performance came from an ancient fan rotor conceived almost at the genesis of ducted fan technology! Even the motor isnít that recent, or hugely expensive, meaning that this level of e-jet performance has been available for over 3 years. Looks like e-jet enthusiasts have some catching up to do!!
The MiG spans 50in, weighs 9lb 14oz, has Merati pneumatic retracts, and is powered by an HP 355-30-6, which is a 6-wind motor, identical to the Ultra 3300-6. It uses 30 cells at 34-37 amps, and a Kress Axiflo RK-40 fan, slightly reduced in diameter from 5in to 4.3/4in. The duct unit and motor mount are home made, and thrust is about 6.1/2 lb. I think the model is all built-up from ply and balsa, based on the Pavel Bosak plan in the British RC Model World plans range. Retracts are Meratis, which are pneumatic "up" and spring "down", akin to Spring-Airs.
A large hatch, which extends from the front of the canopy to just in front of the fin, gives good access to the avionics. The battery pack comprises three10-cell packs in series, each pack made up from two parallel 5-cell sticks. One pack rests atop the duct beneath the canopy, and the other two are disposed each side of the duct, at about mid wing-chord, and slotting down between the duct and the fuselage skin. The top of the nose, just in front of the windscreen, has a 2in square of wire fine mesh let in for ventilation, and all fuselage formers have many lightening holes, which also allow free airflow through the battery/avionics compartment. The avionics was mounted on the duct, with servos spread around the model where required. The esc was mounted flush in the duct for good cooling. A Wemotec RK-740 fan would no doubt be a good starting point if any of you wished to make something like this.
And how did it go? Thereís only one word ÖÖ AWESOME!!
Jurgenís MiG performed just as well as many of the IC-powered models there, and its quietness of operation combined with an impressively powerful performance was a very telling feature. I have flown quite a bit of IC ducted fan, and never found the tortured sound of K&B 6.5 or 7.5 and Turbax, or OS 91and Ramtec, all of which I owned and flew in various successful models, remotely attractive to listen to. But an electric RK40 powered machine? Gimme more, more, more!! This model flew exactly the same schedule as the IC and turbine jets, so duration wasn't a problem. As with the F-16s, no extended vertical climbs were demonstrated, but that wasnít an obvious omission by any means.
After seeing these e-jets in action, I just couldn't resist taking a Wemotec RK 720E home with me from the event to try out with my Ultra 930/7! It took me half of Sunday to get the unit together, despite not understanding a word of the all-German instructions, and you should feel the thrust! I can't wait to get my own electric jet flying.
And what will that be?
Well. I havenít actually decided the subject at present, and it isnít important at this stage. My line of thinking is first to use what Iíve got - and the 930-7 with FX-35D esc should fit the bill. Hand or bungee launch will suffice to save weight, and I have no suitable runway within a reasonable driving distance anyway. Next, I want to run about 35 amps, so will use enough RC2000s to get that - probably 15. This will give me about 500 watts input, and to match the performance of the F-16 and Mig just described, I know I need a power loading of at least 110 watts per pound. So the auw should be less than 4.1/2lb. As regards wing loading, up to 30 oz/sq ft will be ok. My little twin OS 15 P-38 Lightning published in RCM weighed around 4lb, had a wing loading of 30 oz/sq ft, and it hand-launched quite well, though props are more efficient than fans at throwing speed; hence the likelyhood of needing a bungee.
So I need about 2.1/2 sq ft wing area. As an example, a Mig 15 with this area would come out at 1/10th scale, ie about 40in span and length, and 15 cells would just fit. But ideal though the Mig is, I feel like doing something different, and will finalise that decision in a couple of months - when I have finished my Duncan Hutson electric SE5a review kit.
A What!!! An Electric SE5a as a kit??
Yep!!. The model is to 1/6th scale, spans 53.1/2in, weighs about 7.1/4lb, and flies like a real bird of prey. Stateside readers should contact Lou Proctor Specialities for availability information, and on the UK side of the pond, give Duncan a ring direct. Suffice to say that the CAD drawn and cut kit is a beaut, and is just falling together. Duncanís prototype uses an Astro 40G on 20 cells, and mine will use a Max Cim 15-13Y 3:1 on the same pack. The wings are done, and the fuz gets started tonight.
Cheers for now.
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