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Heinkel He162 Salamander
How a Kyosho T-33 was recycled into a sort-of-Salamander

By Andrew Gibbs

This article was written way back in 2001. It’s still relevant to electric modelling today, so here it is, in a slightly revised format.

Introduction
I’m one of the many modellers who bought and enjoyed Kyosho’s T-33. I admire the company for having brought to the market such a bold and easy introduction to EDF flying. I have been impressed with the model in many ways – it was quick to build, inexpensive, good looking, easily hand launched and well mannered in the air. A great combination of properties and the model was deservedly very successful.

However, the one thing it did not have was a scorching performance. I flew mine about a dozen times and on the recommended 7 nicad cells my example had little more than minimum power to maintain flight. On 8, things improved somewhat but not enough to maintain my interest in continuing to fly the model.

Analysis of Kyosho’s T-33 design
Examination of the T-33 showed that some elements of its design were excellent and others, in contrast, seemed to be rather poor. For example, the wing, judging from the model’s airborne manners, appeared to be of excellent aerodynamic design and was a very light and beautifully made structure.

Kyosho’s ground-breaking T33. This all-foam EDF kit made a huge impact when it was released around 2000.

The fan unit, judging from its appearance and construction, also seemed to be well designed and the motor seemed powerful enough, especially since it was capable of emptying a fully charged pack of 1700SCRs in 3½ minutes.

On the minus side, it appeared that the design of the long ducting was causing a considerable amount of thrust to be lost and that the airframe, while generally clean, had a number of details causing high drag. One example of this was that the wing and tail were both joined at acute angles to the fuselage.

T-33 thrust measurements
I planned to develop the model in the quest for more performance. On the T-33’s box Kyosho claim their fan unit produces 400g of thrust, presumably on the recommended 7 cells.

My thrust measuring rig, which I believe to be quite accurate, showed that the installed thrust of my model showed an initial peak of 312g and averaged 277g over the first minute, using a freshly charged 7 cell pack. On 8 cells the initial thrust was 340g and averaged 325g over the first minute. Here are the figures in table form:

The reason for the model’s lack of performance was now clear– a T/W ratio of 25% is considered the normal bare minimum for flight.

Design of the new model
I then decided that it would be more interesting to design a new model using the best of the T-33’s components, i.e. the fan, motor and beautifully made wing. I realised that if I could mate these parts with a new, lower drag fuselage and some efficient ducting then the resulting model would be significantly livelier than the T-33.

My design criteria for the new model were:
1. It should still be able to be hand launched.
2. It should use at least some of theT-33’s components
3. It should be reasonably simple and easy to modify if initially unsuccessful
4. If possible, it should resemble a real aeroplane.

The full-size He-162
Towards the end of WW2 the German aircraft industry produced a number of remarkable designs. The He-162 was one of these and was designed and built in late 1944, in an incredible time of a little over 2 months.

This design seemed to have a suitable configuration upon which to base a model – its jet engine was located in a short straight-through duct located on top of a slim fuselage – ideal! It also had extraordinarily small, short wings, but these could be enlarged for the model.

Heinkel’s He163 Salamander.

It was made largely of wood, a non-strategic material. It weighed up to 5,940 lbs and was powered by a BMW turbojet providing 1,764 lbs static thrust. This gave the machine a T/W ratio of only 30% and consequently it suffered from a relatively poor rate of climb, although it was fast with a top speed of 560 mph at 20,000 feet. Very few of the machines saw active service and of this small number it seems many were lost due to accidents and in-flight break ups. I was hoping for a better record of success, but the project was not to be without a few problems.

I made some sketches and then I drew out a full-sized side view of the new fuselage on an old bit of cardboard box (no expense spared in my workshop). This looked quite attractive (the design, not the box) so I decided to build it there and then from the sketch. This was is in stark contrast to my usual process of drawing up a proper plan and thinking the whole thing through before a knife gets anywhere near balsa.

The wing and tail are both set at +1 degree incidence. I made the tail moment slightly longer than on the donor machine. The thrust line is at +3 degrees to compensate for the high thrust line of the “piggyback” fan position.

I checked that the CG would end up where I wanted it by placing a balsa plank over the side view on the bench. A pencil was located under the plank at the required CG and the plank was balanced with small weights. I then added all the required components and balsa sheets to simulate the weight of the airframe and its contents along the length of the plank. This showed that moving the battery would cater for any likely CG adjustments necessary. No way was this aeroplane going to be carrying any ballast!

Wing loading
I wanted to reduce the span of the T-33 wing a little to get more of the visual feel of the Heinkel and also to increase the model’s roll rate. This decision would of course reduce the wing area and consequently increase the wing loading. I felt the model would probably tolerate this provided I could get the fan to deliver substantially more thrust, and if the airframe’s drag was minimised.

Weight target
After much weighing of the components at my disposal, I set an ambitious target weight of 1,100g for the model. Even if the weight went to 1,200g I felt I should still have a flyable model. All wood would be weighed before use, and cyano used for much of the construction.

Construction - Fuselage
First I set about building a fuselage from the side view that I had sketched. This is a simple balsa box, using 3/32” (2.5mm) sides with doublers of the same thickness. I used a generous (but light) triangular section along the corners so that the shape would be nicely rounded, for low drag, when sanded. A fillet is fitted to the outside of the wing seat to reduce the drag of the wing-fuselage junction.

The canopy is the T-33 item, suitably cut down and stuck to a removable balsa frame so that it becomes the battery hatch. I fitted a sprung locking pin to the rear edge of the frame. Three holes are drilled in the flat front portion of the canopy to admit cooling air.

Motor, Fan and Pod
The motor pod is made from the rear of the T-33’s fuselage. I cut through the fuselage 15mm aft of the original motor mounting slot, and discarded the last 80mm of this portion. This gave me a duct about 180mm long, into which I cut a new motor mounting slot using a Dremel-type tool further aft. An additional 30mm of soft balsa was added to the front of this tube and shaped to form an elliptical intake.

The duct for the Salamander was cut from the rear portion of the T33’s fuselage.

The overall length of the completed motor pod is 210mm. Power was fed to the motor through a pair of steel blades that had come from a windscreen wiper. These were located one behind the other and formed a thin low drag strut. The fan blades were carefully cleaned up and the fan checked for balance. Also the stators were slightly re-profiled to try and reduce their drag.

Tail plane and Fins
These were simply cut from 5mm thick medium balsa and shaped to a streamline section. The tailplane spans 320mm overall with a root chord measuring 95mm. Each half is blocked up 25mm to set the dihedral. Anti-warp strips were inserted in the 125mm high fins.

Wings
Having finished the fuselage, I still had some doubts about going for a reduced wing area. I put these aside and sawed the wing in to 2 panels, which when placed together again gave a straight leading edge, a distinctive visual characteristic of the He-162. Each new panel weighed only 64g, and the material I had removed weighed 40g including the aileron torque rods.

The centre section of the T33 wing was removed to save weight and drag.

The removed centre section was 105mm wide at the leading edge. I consoled myself that the lost area was less than it appeared since the fuselage was quite narrow in comparison to the T-33 and I had reduced both weight and frontal area. In any case, there was no going back now!!

Each wing was sanded overall and carefully trimmed so that the roots mated accurately with zero dihedral – the top surface of the wings is flat. The panels were then joined with epoxy and joint was reinforced with 1.5mm balsa, also epoxied. A single mini servo and new lightweight linkages were installed to operate the ailerons.

Preparation for flight
The controls and equipment were then installed and the aircraft readied for its first flight. The speed controller was located under the wing, behind the receiver and in front of the elevator servo.

I had decided not to paint the machine until I was satisfied it flew well. I range checked it at half power and found that the receiver that I originally planned to use gave a range of only 18 meters with the Tx aerial retracted. However, range improved to 70 meters with a different receiver. I also covered it in cooking foil to give it further protection from its proximity to the speed controller. I used the rest of the foil in the preparation of a tasty roast dinner that I put it in to the oven for my supper! In my excitement to fly the model, I forgot to photograph it or put it on my TMR. The ready to fly weight had come out at 1,100g approx with an 8-cell pack.

First flight – April 1st 2001
I range checked the machine again at the field at half power: 70 meters again with aerial down. The equipment inside the machine was the same as I had used in the T-33 and I felt confident that all would be well.

Confident the model would fly well, it was nevertheless tested without paint, just in case. A wise precaution as it turned out

The model was hand launched into a light southeasterly wind. It was slightly sluggish for a second or two and then climbed away strongly. A little trimming of the controls saw it flying smoothly around, and I felt confident to try loops and rolls. All who saw it were very impressed with its performance. It was easily able to maintain height on half power and loop from level flight. A couple of times the motor slowed momentarily before regaining full power, but other than that, no problems were evident.

I continued to enjoy myself but then suddenly, at a distance of only about 50 meters away with down elevator selected, the Salamander stopped responding to the controls. I attempted to pull up and shut the motor off but without success. I could only watch as my beautiful aeroplane developed an almost vertical dive in to the concrete runway from some considerable height. The entire airframe was wrecked – wings broken in two, fuselage all broken up, tail snapped in three places, flight battery and aileron servo both totally smashed up. Strangely, the nylon M4 wing bolt was undamaged. I felt thoroughly dejected. My dejection was all the worse because I had not photographed the finished model or measured its thrust on my thrust rig.

Ouch! After the first flight.

Back home things went from bad to worse – my roast dinner had burnt! However, all was not lost. In some ways the day had been a great success – the aircraft had flown very well and appeared aerodynamically sound. And I had not invested any time in painting it!

After consuming the edible portions of my dinner, I went to my workshop to survey the wreckage in search of clues. I could not definitely ascertain the cause of the crash, but, being brutally honest with myself, the cause was probably something for which I was somehow responsible. After much thought and discussion, the following theories were formed as reasons for the disaster:

1. The speed controller BEC function had failed.
2. Loss of signal due to the transmitter aerial pointing directly at the model (this would give a very weak signal in the direction of the model)
3. The elevator linkage had become disconnected in flight.
4. The battery pack had moved during the negative g manoeuvre
5. Radio interference
6. Poor equipment installation, particularly the speed controller’s position, sited as it was, amongst the rest of the gear.

I also discovered that the balsa in the vicinity of the blade supplying motor power had become burnt, which I could not account for.

Rebuilding
In spite of the extensive damage, I decided to rebuild the model. Amazingly, this proved to be a much quicker affair than its initial construction. The wing was epoxied back together and a spar inserted locally across the break to help carry flight loads. I also applied 2 thicknesses of tissue with dilute PVA across the centre third of the wing to help reinforce the joint.

At this point I decided to replace the single aileron servo with a pair installed one in each wing. This would give the ailerons the ability to act as flaps - this might be useful since the model’s wing loading was climbing still further with the weight of all the repairs!

The wrecked fuselage was rebuilt, this time with a better battery retention system (Velcro and small polystyrene locating blocks) and an all-new elevator linkage. I installed a dual conversion receiver with a new crystal, again wrapped in foil. A new elevator servo was fitted, relocated to just behind the receiver. The speed controller was relocated well to the rear and away from any other radio equipment, to a position directly under the motor. The motor was fitted with additional suppression, now comprising 3 capacitors, and a diode across the motor terminals. The BEC function of my speed controller was disabled and an 110mAh NiMh receiver battery installed behind the cockpit canopy.

The receiver aerial had originally been routed through the fuselage. It was now re-routed out through the wing to keep it away from the motor and speed controller – and its weight also helped balance the weight of the epoxy repairs in the other wing! I wired both wing servos and the aerial through a de-shelled 9-way computer D plug so that the wing could be conveniently removed, taking great care to ensure that the effective aerial length was not altered.

The rebuild took a long time. Here's the repaired airframe, before painting.

I felt that I had now done everything I could to minimise the chance of a repeat of the disaster. Since the model had flown well (apart from the landing!), it was now time to paint it.

Finishing
I applied a dope and lightweight tissue covering to the fuselage. This added only 12g. The foam motor pod also had tissue applied, but with dilute PVA to avoid melting the foam. Once dried

The servos and receiver aerial are routed through the wing. For convenience, a single 9-way computer 'D' connector was used to connect the fuselage-to-wing wiring.

out, this was lightly sanded and a covering of dope applied. Several coats of dope were also applied to the tissued area of the wing. The whole model was then painted with Tamiya acrylic colour, which added about 10g.

Markings were also painted on, using enamel. Lastly, I added panel lines using the method described by Chris Golds in his excellent April EFI article. I was very pleased with the model’s finished appearance. It certainly looked a lot better than at the conclusion of its first flight!

Finally, the model was fully repaired and painted. Painting really brought it to life.

Testing!
I was very disappointed to discover that the weight of the model had crept up to 1,204g - and elated to find that the TMR revealed that the initial static thrust was 480g, and averaged 445g over the first minute. This gave an average T/W ratio of 37%.

Also the mystery of the hot blade had been solved: the steel was getting very hot due to the current flowing. Realising that the steel blade was a material with an electrical high resistance, I replaced the it with thick copper wire and re-tested it – no more heat and even more thrust – over 500g initially!!! This result showed that Kyosho’s claim of 400g thrust for their fan unit was justified, if it was efficiently installed.

I then checked every possible detail of the whole model and completed all necessary measurements and photographs. I also decided that on all subsequent flights, the transmitter aerial will never be pointed at the model and that any sign of a malfunction, however slight, will be designated reason enough for an immediate landing.

The sort-of-Salamander, and the sketch from which it was built. Very few people recognise the model’s origins.

More flying
The model was tested again on a windy 22 April. Prior to flying, I decided that I would not point the transmitter aerial at the model, even if it was close by, and that I would immediately land at any sign of a malfunction, however slight.

In spite of the weight increase, the performance was at least as good as before. The model seemed relatively unaffected by the wind, probably due to its relatively high wing loading. Climb rate and level flight speed were good. It was able to loop from level flight and it had a good rate of roll. However, the flaps, although they gave no trim change when deployed did not seem very effective. By comparison with the T-33, I estimate top speed in level flight is about 50% greater, speed in a dive about double. The flight time was 6 1/2 minutes, about half of which was ambling around at low power for photos.

Conclusion
This was an enjoyable and satisfying project and my aim of producing a capable model using the parts from the T-33 was satisfied. I am looking forward to flying the model a lot more. The project taught me a lot about EDF and probably even more about persistence! Grateful thanks are due to Chris Golds for sharing his knowledge both through his writings and via his telephone.