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The Opel Sanders RAK.1 Rocket Glider

By Chris Banyai-Riepl

 

HISTORY

Fritz von Opel is best known for his cars and trucks, but in the 1920ís he experimented on new forms of vehicular power, most notably the rocket. Opelís first attempt at rocket power was with a car in 1928. Max Valier, Fritz von Opel and some others tested the rocket car in Berlin. Impressed by the speed, Opel started designing a rocket-powered glider, the RAK.1. This wasnít the first glider to fly under rocket power, as Friedrich Staner flew one in June of 1928 for a distance of about one mile. Opelís glider, though, easily doubled this distance, even though some of the rockets failed to fire.

The design of the RAK.1 was a basic one, featuring a high upper wing and a twin tail arrangement attached by twin booms. The pilot and rockets were housed in a small fuselage slung underneath the wing. For landing a skid was placed underneath the fuselage. Sixteen rockets were used, measuring 400 millimeters long and 90 millimeters in diameter. These rockets were designed to fire in pairs, with only two rockets firing at once. This prolonged the flight time and also reduced the initial G-forces that would result from all sixteen rockets firing at once.

The first attempts at flying the RAK.1 met with failure as the rockets did not ignite. After looking at the problem, it was determined that the battery was too weak to ignite the rockets, and the igniter was bent. After these problems were fixed, another flight was attempted. This time everything worked according to plan. On September 30, 1929, the RAK.1 became airborne, with the first two rockets firing for 25 seconds and lifting the glider into the air. When those rockets cut out, a further two were fired. To keep the plane within the confines of the airfield, a right-hand turn was performed, bringing it into a downwind leg. Another two rockets were fired, but only one actually burned, reducing the speed of the glider and bringing it down. The rough landing due to the tailwind damaged the RAK.1 to a point where much of it had to be rebuilt. Upon examining the plane, it was discovered that a total of 5 rockets failed to fire.

Nonetheless, the RAK.1 was a success, and just a couple weeks later the movie "Frau im Mond" was released, which brought rocket technology to the forefront of German public opinion. Opelís RAK.1 was rebuilt and capitalized on the popularity of this movie, making a couple more flights, each one more successful than the last. Unfortunately financial concerns brought Opelís involvement with the rocket glider to an end, but the concept remained in the German mind, with the result of such things as the V2 missile and Me163 rocket fighter becoming operational during the Second World War.

THE KIT

If you are waiting for an injection-molded kit of the RAK.1 to come out, youíve got a long time to wait. While it was a historically important plane, it wasnít important enough to warrant a large injection plastic production run. Luckily there is the resin kit companies out there to fill this gap. Czech Master Resins kit of the Opel Sanders RAK.1 comes molded in a greenish gray resin and like the real thing has few parts. The wing is one piece, with the fuselage comprising of right and left halves. A basic interior is provided consisting of a seat, stick, and instrument panel. The tail is made up of three parts, with the horizontal stabilizer being one piece and each vertical tail separate.

Construction of the kit is very straightforward, and started with the interior. No instructions are given as to what the interior should be painted, so I painted it a generic brown. Assuming the instrument panel to be wood, I painted it accordingly, then glued in into one side of the fuselage. Some trimming was needed to get the halves to fit around the panel, and once that was done, the two halves were joined. The rocket tubes are depicted by an end-piece with 16 holes drilled in it. I glued that in place, then drilled one hole all the way through the fuselage. This gave me a way to hold the fuselage while I painted it.

The wing didnít need much work, as it was a solid piece. Some light cleanup around the edges was all that was needed. I then started to look at the tail arrangement and how that was going to be attached. There are booms that go from the bottom of the fuselage to the tail and from the wing to the tail. These are provided in scale and in resin, which makes them rather flexible and not too sturdy. Rather than try to clean up the resin parts, I elected to replace them with something a bit more sturdy. Raiding the wifeís craft table I came across the perfect replacement for the upper booms in the shape of a couple beading needles. These are nice and long needles, without much of a taper to them. I was able to cut them to the proper length and then drill holes in the wing to take them. The struts going from the fuselage to the tail were then made up from styrene rod. Between the steel needles and the styrene rod, the tail structure went from being a weak link to an incredibly strong part of the model.

PAINTING & DECALING

The RAK.1 had a simple paint scheme, with the wings and tail being clear doped linen and the fuselage and wing leading edge painted blue. The CDL portions were painted with Humbrol 74, while the blue portions were painted up with Testors Acryl Insignia Blue. Once the basic painting was done, the final assembly took place, with the tail being attached to the struts, and the wing attached to the fuselage. Detail painting came next, with the booms being painted aluminum with satin black connectors. The rocket section was also painted satin black. The landing skid was attached with two pieces of plastic rod and painted up a wood color. Once everything was in place, a coat of Future was sprayed on in preparation for the decaling.

The decal sheet is like the model: small. All that is given is the tail inscription and the fuselage inscription. The decals are very thin and appear to have been printed by Propagteam, although they donít say. They went on with very little trouble and snuggled down nicely. A final coat of a satin finish, and the model was done. Setting it on the shelf, though, I noticed a rather peculiar attitude: it wanted to rest on its tail. So a display base was in order.

THE BASE

Not wanting to spend a lot of money on a display base, I wandered around the local Fred Meyer superstore looking for something that would work. Eventually I ended up in the picture frame area, and noticed that they had a bunch on sale, including one with a rather large, flat wood frame. The gears started turning in my head, and I decided that a 5x7 frame would make a very nice base for the RAK.1. I bought the frame and rushed home. The first step was to get rid of the bracket on the back. I knocked the hinge pin out and the bracket fell off. That was easy! Now to the actual base that the glider would rest on.

Using the cardboard insert from inside the frame, I cut two pieces of cardboard. The second piece I trimmed so that it would fit into the frame, as opposed to behind it. Once that was done, I taped the edges of that piece, then glued it to the second piece and placed them both inside the frame to dry to keep everything aligned correctly.

When that had dried, I moved to the grass. I used railroad static grass for the base, spraying adhesive on the cardboard and layering the grass on. It took several layers to completely cover the cardboard, but when it was all done, I had a nice lawn that fit perfectly in the frame. All that was left was to mount the model. I positioned the model on the base and figured out which wing I wanted down. I then drilled a hole in the frame where the wing touched, and drilled a corresponding hole in the wingtip. Taking a piece of the leftover beading needle (very useful item!), I glued that into the wing, then slid it into the hole. Now the RAK.1 has the right sit to it and is perched on a nice lawn. A very inexpensive way to really add some impact to a model.

CONCLUSIONS

This was my first 100% resin model, and it really was a great introduction to the medium. The kit was really simple, as was the paint scheme. The history of the type, while difficult to research (and I love those kind of projects!) was fascinating and relatively unheard of these days. The Czech Master Resin RAK.1 was a great diversion from the usual items, and now that I have one resin kit under my belt, I feel more comfortable with trying another.


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