Hi-Fly (oz5111)


Hi-Fly (oz5111) by Fred Militky 1973 - plan thumbnail

About this Plan

Graupner Hi-Fly. Radio control glider model. Hi Fly from Graupner kit #4239.

Note the Hi-Fly was available in 2 versions: as a glider and as a twin-engined electric model (this is briefly mentioned in the review). See Hi Fly Twin Motor (oz15119)

Note the later Graupner Ultra-Fly (oz5086) design seems to be essentially the same airframe as the Hi-Fly, but with the addition of a nose-mounted electric motor.

Direct submission to Outerzone.

Update 07/05/2018: Added kit review from RCM&E, February 1974, thanks to RFJ.

Quote: "RCM&E Kit Review No 59: Graupner Hi-Fly, by Peter Russell.

THE review of this Graupner kit is rather different to earlier ones in the series, since it is really a review of two models. So to keep the whole thing tidy, it is proposed to deal with the building and flying of the glider in this article, and have a separate review of the twin-electric powered version, probably next month.

First impressions The Germans, and perhaps Graupner in particular, do such a thorough job on the 'paper work' in their kits that they often create an unfortunate illusion of complexity, and a cursory inspection of the kit, such as on the counter of a model shop, might easily discourage the potential purchaser, as it does seem to indicate that this is a complicated way to produce a fairly simple model. In fairness, it should be mentioned that this builder rarely tackles kit models, so the impression might not be typical.

Once construction is actually under way, however, it soon becomes apparent that not only is it not complicated, but, in fact, it goes together very nicely, providing that you stick to the 'book'. One wag, who saw the model in its very early stages commented If that's a 'Schnellbaukasten' heaven help the 'langsam' ones! There are indeed a lot of parts, but it was nevertheless completed much quicker than expected, in two weeks of leisure time, though it must be admitted that the evening sessions went on into the early hours, once or twice.

The die-cutting is very good, and as can be seen from the picture, there is a lot of it. Even the leading edge sheeting is die-cut and accurate. Some of the ply parts needed 'persuading' before they would leave their sheets, however. As for accuracy, the standard was very high indeed, perhaps half a dozen wing ribs needed minor adjustments, and the notches in the trailing edges were a bit generous. Of the construction itself, very little can be said, except that everything went together just as they said it should, and no errors were discovered either on the drawings or the in-structional leaflet. The 'Explosions-zeichnung' (exploded drawings) were particularly useful.

The kit is very complete and includes most of the necessary 'hardware' and two types of glue. For convenience, however, already-opened containers of 'Resin W' and Devcon were used, the former for most of the woodwork, and the latter for items like ply parts, wing and tail root fittings, and so on. One tiny nit-picking point that might bother some builders, however, was the rudder horn. The swept back rudder introduces a bit of very untidy geometry into the control linkage, in that the push rod has to go up, down, sideways and twist.

Since the sweep back is merely a whim of fashion, rather demode at that, it seems a pity that the elegant, straight-forward rudder of the type used on the Cirrus could not be used. All that be as it may, you can't use an ordinary linkage on a swept control surface, and it seems a pity that Graupner could not have included one of their own excellent `ball and socket' linkages, which was the item finally used.

The 'up-and-down' control is Graupner's well tested all-flying tail in which a large nylon bellcrank is pivoted in the base of the fin. The bottom end is connected, via a Quick-link, to the elevator push rod, whilst at the too end, the horizontal arm of the bell-crank has two wire pegs protruding, from it, spanwise, one concentric with the pivot and the other at the extreme end, the rearward end, of the arm. Onto these two pegs slip the two halves of the tailplane, or 'stabilator' as it is described here. All very neat and business-like, but it is essential to ensure that the whole thing is accurately aligned and without a trace of play. This, together with the wing root arrangement, is about the only item of assembly in the whole model that needs any great skill or care.

Of the wing, this is very similar to the Cirrus, with the same elegant and fashionable compound taper, but with a slightly shorter span and lower aspect ratio. The section is a thin, slightly concave underside aerofoil reminiscent of free-flight contest gliders. The construction is lighter than the Cirrus. Leading edge sheeting is confined, except at the extreme root, to the top surface only, and the heavy drag spar of the Cirrus is eliminated. The two halves are joined by a single approximately eight gauge steel peg, with two short 3/16 dowels at the leading and trailing edges to ensure alignment.

The fuselage is a very straightforward box-with-rounded-corners deal (which can be sanded to a surprisingly elegant section, possibly not much inferior to the Cirrus) about which very little can be said.

Graupner included some wood filler and Modelspan for covering, but since most people seem to use plastic films currently, the review model was covered with this material. This led to some problems as the shrinking of the film caused some warps and deformation of ribs, here and there. The warps can be removed, but short of re-covering, there isn't much that can be done about the other distortion. Also, since the Hi-fly wing and tail structures definitely come into the lightweight category, perhaps the wing would have had better torsional stiffness if it had been covered in the conventional way.

As mentioned earlier, this writer rarely builds kit models, but can say that of the ones he has built, this one was the best, from every viewpoint.

Flying: Although Graupner provided the entire 'Elektroprop' outfit, along with the Hi-fly kit, it was felt that it would be advisable to fly and report on the model as a glider first, as many people will want to build it purely as a glider. When complete and fitted with non-miniaturised avionics, the Hi-fly weighed a mere 31 ounces, an ounce or two lighter than advertised (the bare airframe, without covering, weighed an amazing 16 ounces) and the CG was spot on, without ballast. This must be just about unique. The first flight took place on a low hill where the terrain is not suitable for test gliding so after a careful check on the CG position and the tailplane incidence, the model was 'thrown over the side' into a wind of 5-10 knots.

From previous experience with other gliders, the lift was expected to he marginal, but the Hi-fly climbed steadily to about 300 feet, and showed itself to be near-perfect in trim, The control responses were OK, but the tailplane appeared to be quite sensitive to small movements. The model could, nevertheless be trimmed to fly hands-off for quite long periods. After it had been airborne some time, other models appeared, including a Cirrus, and none of them could out-soar the Hi-fly until a 'Wildflecken' appeared, and this did out-soar it, but it must be remembered that the 'W-F' with its high aspect ratio, 12 foot span and very light wing loading, would be expected to out-soar almost anything in these conditions.

After about 20 minutes, the wind got stronger and more turbulent. This was causing trouble for some of the other pilots, but the Hi-fly continued to handle well, and even penetrate quite well. At the end of 30 minutes it was decided to land it, and a combination of rather difficult terrain plus a, by now, distinctly turbulent wind led to some anxious moments on the approach, which took about three minutes. It was very difficult to hold the wings level during the final 20 feet, even with the stick thrashing from one stop to the other, and the landing was pretty rough.

A few days later, the model was tested on bungee and tow line launches. Looking at the model, it appeared that the suggested position of the bungee hook was perhaps a little forward of the ideal position, and this appeared to be substantiated by the flight testing, though the difference is probably so small that it's not worth going to the trouble of moving it. The bungee was quite short, just two strands of quarter flat and nylon filament line, but the launches were good and several flights were around or just under three minutes. Height on the launch was, perhaps, 300 feet, though some of this was wasted in getting the model to drop the tow. Perhaps the hook provided could be shortened a bit if a lot of bungee launching is contemplated. As it was, a 'normal' release required a quite breathtaking dive, so the 'turn-off-the top' method was tried. With this method, when you get to the top of the launch, you simply turn 180 degrees and dive off downwind. This is quite spectacular and possibly dangerous, because if it then failed to release, for any reason, you would be in serious trouble. With the Hi-fly, however, this method was used repeatedly without problems arising.

Finally, the Hi-fly was tested on a 100 metre tow line, and here the long hook was an advantage because it was possible to keep the model on tow as long as necessary without fear of it un-hooking itself. Although the wind was not ideal for good towline launching, several flights of 2+ to three minutes were possible. All this flying took place at below zero temperatures, and there was snow on the ground when the bungee and tow launches were tested.

Summing up, this is a simple, light, high performance model that will out-soar the Cirrus in some circumstances. It seems very satisfactory in all three soaring modes, and might be a real contender in thermal soaring contests. There are probably very few kit models available that fly better in weak to medium lift. The kit is well-engineered and complete, and represents good value, even at the current disadvantageous situation of the pound sterling relative to the mark."

Update 25/2/2024: Added zipfile of two exploded views (jpg format, low res), thanks to Pit.

Supplementary file notes

Exploded views.


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Hi-Fly (oz5111) by Fred Militky 1973 - model pic

  • (oz5111)
    by Fred Militky
    from Graupner (ref:4239)
    92in span
    Glider R/C Kit
    clean :)
    formers unchecked
  • Submitted: 03/12/2013
    Filesize: 1080KB
    Format: • PDFbitmap
    Credit*: LucVanAmmel
    Downloads: 11552

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User comments

Hallo Mary, hallo Steve. I think the picture is 30 years old [see more pics 003]. The builder is my friend "Volker Kirch". The Hi-Fly was powered by an electric engine.
BernhardDittmann - 23/02/2016
Love the Website. Thanks! Hi-Fly? Had one in back in 1975. Fond memories. First flight off bungee? 27 minutes. Way to go. Hint to builders: Keep the wing covering tight, or at high speed the wing-tips will flutter! My Hi-Fly didn't disintegrate, but it was mandatory to re-tighten the solarfilm periodically. It is very tempting to build another.
TimMorland - 11/08/2016
Hello, I am from Argentina and I am building the vintage Graupner Hi Fly. Here are some photos of the building [more pics 004-007].
GJoseRosalesRuiz - 12/07/2018
I have new photos of the glider almost finished [more pics 008-010]. In the new photos I am with my dog, Dana. Thank you. Regards from Argentina.
GJoseRosalesRuiz - 13/11/2018
I forgot to tell you the model ready to fly weighs 1100 g./39 ounces, and with a .049 Cox engine on a pylon engine mount and a 6x4 propeller about 1200g./42 ounces. I hope the engine can give enough thrust!! Anyway I can tow it.
GJoseRosalesRuiz - 20/11/2018
I had been painting my glider last week, it was my first time at painting a model so it it isn't perfect but it has a good look [model photo & more pics 011, 012]. It's finished now so the next step is: FLY!!! I put Futaba standart servos, FM radio transmitter and a AA battery pack. I hope the weather gets better here, it was so rainy these days. I will fly it in the school with my teacher, an experienced modeler, he helped me with the build of the Hi Fly, there is a big sport field there. In the last photo I am with my teacher [more pics 013].
GJoseRosalesRuiz - 24/11/2018
I am trying to learn to fly rc models. The model is not balanced with the rc equipment only so I had to put some lead in the nose, about 100g. And the Cox .049 is perfect for this glider. My teacher told me that gliders or powered gliders with .049 engines or similar are very easy to fly and learn. It took it very well with a lot of wind........ and I crashed it! It was a really windy day. I crashed it with a wall!!!! I almost crashed a teacher's car! (I was at the school sports field with my teacher.) But I think that I am very lucky because the Hi-Fly didn't have serious breaks. It only broke the left ply dihedral reinforcement and the hard balsa nose block.
GJoseRosalesRuiz - 27/11/2018
Beautiful model....good job
Xxx - 15/10/2019
It's me again, Jose. A lot of time has passed since the last time I sent emails. I was busy with a new glider. However it's the same plane, the Hi-Fly, but it has important modifications. One of them is that I put a bigger glow engine a .12 size with throttle control, an all flying tailplane as the original one, and I also installed a vintage fm graupner radio with old varioprop c05 servos. It's about 1.5 kg or 52 Oz. I made the fuel tank with a film canister. I suppose it'll allow me to fly 2 to 3 minutes. Your site is wonderful, with excellent content. I attach the photos of the new model and the transmitter [more pics 014-019].
GJoseRosalesRuiz - 24/01/2020
Hi friends, I really want to build a Hi-Fly. What is your experience with the .049 engine like a power option? Thank you very much
Gustavo Ruiz - 30/07/2021
Hello Gustavo. The 049 with a 6x4 prop is a good temporary option as the Hi Fly is a bit large for that engine. My experience with a babee bee (5cc tank) is that you need a bigger tank so that you have time to climb the plane in windy conditions. You may use a bigger engine such as a cox .09 or similar.
Jose - 07/12/2021
Hi Steve and Mary, I have rebuilt my Hi-Fly [pics 020-023], which I first built back in 1978. I painted my Hi-Fly in the retro look of that time with the original colour scheme of the Graupner company. In contrast to the original, I installed a front motor according to today's standards and added ailerons to the wings. I have just had the first flights, which were carried out to my satisfaction. Kind Regards,
Frank Schwarz - 17/10/2022
You can see it fly: https://youtu.be/29p-8d8oPIM ! I am not sure if it is a HI Fly or an ULTRA FLY ! The guy who built it passed away and took the secret with him. He sheeted top and bottom of wing and tail, gave it 20 cm more wingspan [pic 024]. This time I used the right transmitter mode !
Reinhard - 06/03/2023
Hello, Hi Fly flown again at "Graupner Classics 2023 Neuwied". Wing has been repaired [pic 025]... Greetings from Germany,
Reinhard - 03/06/2023
Hello to you 2. Today it is the turn of the HI FLY to be presented [pics 026-028]. It comes from the Aumann RC kit. I started with a Hi Fly in 1981. Good reception. Cordialement,
Jean Luc Folliguet - 10/12/2023
Hi, I found a rare image of the twin-engine version of Hi-Fly [pics 029, 030] in the Swedish hobby magazine ”Allt om Hobby” from 1975. Quite beautiful! Best regards,
Björn Löfving - 01/02/2024
I think that twin-motor electric system was sold by Graupner as an add-on for electric flight. The first photo was taken from a full-page image in the large (FS) Graupner catalogue. I don't remember the year, but I think it was a few years after the 1975 launch
Arno - 01/02/2024
1973, I've seen the double engined in flight in those years. Somewhere I had the 2 engined installation plan. I will search. Pit
Pit - 01/02/2024
about twin engined at the end: https://www.youtube.com/watch?v=62fsJ0WVXU0
pit - 02/02/2024
Have added a new listing for the twin electric setup, with plan drawing, thanks to Pit. See Hi Fly Twin Motor (oz15119).
SteveWMD - 19/02/2024
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