SPEEDBIRD CONCORDE ONE

Jeff Barringer builds an electric powered Concorde from the Tony Nijhuis plan.

Having built the Tony Nijhuis Mosquito and Gnat recently, and being well-pleased with the results, I decided that I’d like to have a go at his Concorde.

Powered by no fewer than four 50mm Electric Ducted Fans (EDFs) the model has a wingspan of 32 inches (815 mm) and is 69.7 inches (1770mm) long. Tony’s plan packs are of excellent quality and the laser-cutting is very accurate, so I had no problem in deciding to go that route. My only problem was finding a suitable scale subject...

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Jeff's model recreates G-BOAC, the flagship Concorde of British Airways.

A very good friend was a 747 captain with British Airways, and he was offered an air experience trip in Concorde, back in the day when that was encouraged. On November 5th, 1983 they left London Heathrow and, clearing the English Coast, First Officer Chris Norris gave up his seat to my friend Ian, with the simple instruction to take her through Mach 2. Ian reports that she handled perfectly and reaching Mach 2 and into super-cruise was something of a non-event - but what a fantastic experience!

I decided that I’d like to build a model Concorde and base my rendition on the one flown by Ian. And so, I enquired of her registration and was told she was G-BOAC – the British Airways flagship.

Golf Alpha Charley in 1980s colours it was then. No more excuses...

STARTING THE BUILD
The build instructions are in pictorial form on the Nijhuis website and are in logical order and easy to follow. But there is little text so I will run through the procedure and mention a few points as I go. The build starts by creating an egg crate wing framework, starting with that iconic leading-edge planform.

Upper wing skinning comes next and rather than go 1/16" sheet by sheet, I created a single sheet and then cut out the planform shape, plus an overlap. This meant that I had full control over the sheet-to-sheet joins. Before sheeting it is important to sand the ribs to suit the curvature, especially on the leading edge.

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Sheeting the upper wing surfaces over the egg box framework.

I began sheeting close to the fuselage using slow set cyano and gradually worked my way outwards, leaving extension stubs at the front for the eventual leading edge join to the fuselage. It is especially important to keep the wing flat and level during this process, so I weighed down the wing as I went.

Once the two wings are created the fuselage formers are added. Each is a very precise fit into the existing framework and the structure at the end of this is remarkably rigid when you consider the minimal amount of material used so far.

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Fitting the fuselage formers.

The fuselage stringers are added next. I found it easier to extend seven of the 5mm square balsa lengths to be 1010mm long, using splices, before fitting them to the framework. The underneath stringer should not be glued in at this time as you will want to remove it later to make the bottom sheeting easier. Applying the stringers should be done carefully, keeping the model in alignment as you go. A banana-shaped fuselage created at this stage cannot easily be corrected!

ELECTRICS
The next step, before bottom sheeting, is to sort out the electrics. The model is, of course, an elevon machine, so I began by setting up servos to suit. There is an option to use two elevon servos per side, or alternatively connect inboard to outboard elevons across the motors using a torque rod. I went for the two servos option, the inboard 6g and the outboard 9g.

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All wiring neatly in place.

To carry the servo leads into the main fuselage slots are made in the framework and, at the same time, a rudder servo is installed. This is not specifically mentioned in the instructions, but I mounted mine on a well-braced piece of fibreglass board a couple of inches forward of the rudder hinge line.

The power connections for the motors are added at this stage. I opted to mount the ESCs within the fuselage because conventional wisdom has it that the two leads on the power side of the ESC should not be extended, while the three ‘phase’ leads on the motor side of the ESC may be.

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Adding the bottom sheeting, evenly weighed down while the glue sets.

Since building I have been informed by Tony Nijhuis that this is no longer the case, so I would recommend to another builder that they follow his practice of fitting the ESCs in the nacelles, both for cooling and for accessibility.

Once completed all the wiring was tested and the ESCs mounted before the bottom sheeting was added. Another innovation worth mentioning is the throttle arrangement. Conventionally, if one has multiple ESCs on a model then only the BEC from one ESC is used; the rest are nulled by removing the power connector at the receiver connection. But, if I have four BECs, I like to use them all in case one or more fails.

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Throttle ESC mixer using Schottky diodes mounted on Veroboard.

The circuit illustrated uses simple Schottky diodes to mix the BEC voltages without any danger of one failing short-circuit and pulling the others down. I have been using this technique for many years, both for multiple BECs and also for connecting a reserve battery into the receiver as a standby and it has stood the test of time. Highly recommended.

FORWARD FUSELAGE
With power and servo connections installed the bottom sheeting can be added and then the wing sanded to the classic Concorde shape.

As you may have noticed there is a fair amount of forward thinking to do during building and this is very much the case for the forward fuselage. This structure carries the retractable front undercarriage, steering servo and nose retraction servo, as well as undercarriage doors should you wish to fit them.

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Nose-leg bay door former.

The open framework is constructed quite easily but before sheeting I fitted undercarriage bearers, undercarriage doors and mounting points for the two servos. I also added a plate to carry the outer sleeve for the nose retraction cable and doubled the underside gear door framework to be removed later.

Sheeting of the forward fuselage can now begin, but it is important to make sure that you make a good key between F4 and F5 because you will have to hold the two fuselage parts together during sanding after the fuselage sheeting is complete.

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Pre-bending the fuselage sheeting.

Ah, yes, the sheeting! I found this quite challenging, mainly because of the compound curves at front and rear. I prepared the balsa sheeting by pre-bending using steam from a kettle and then housing them overnight within a cardboard tube, as shown. In order to squirt the glue inside the sheeting during assembly I extended the spout on the gluepot using a piece of brass tubing.

For the gentle taper at the rear, beyond F11, I cut ‘V’ slits into the balsa sheet so that it could conform to F12 and left the residue length of sheet in place down past F13. When sanding be very careful not to create ‘starved horses’, which can be caused if the glue used is much harder than the balsa.

The underside sheeting is added next, which is fairly straightforward if the instructions are followed. The fully assembled fuselage is long and quite unwieldy, so I decided to sort out the front end before joining the two parts.

DROOP SNOOT
As instructed, I cut out and trimmed the two plastic nose components - normal and the iconic ‘droop snoot’. I then fitted the ‘normal’ nose. The ‘droop-snoot’ servo is fitted, along with a snake outer to the centre of the nose. In operation, the inner wire has to bend significantly on nose droop, so I used 0.9 mm piano wire and an elongated slot in the nose moulding, which worked fine.

Having made up the nose from the plastic parts supplied and reinforced it with fibreglass tape, I added the bulkhead carrying the servo horn for the droop. I made up the hinging mechanism using a standard Kavan hinge. I carefully removed the hinge pin so that I was able to disassemble the nose at will. The ‘droop’ servo was connected to a separate channel from that of the gear, but is driven from the gear switch, allowing me to slow down the droop and rise of the nose to aid realism.

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Droop activation rod.

The front undercarriage is quite challenging and needed a considerable amount of thought due to the fact that I was not using the recommended units and the space inside the forward fuselage is quite restricted. I fitted the undercarriage unit and the steering servo and had to mount the droop snoop servo forward of these. Eventually I had the retraction working and also the steering.

By using a separate channel, I was able to centre and turn off the steering servo whenever gear up was selected, as well as allocate a separate trim for the nosewheel, independent of the rudder trim.

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A closer look at the finished drooped nose.

By far the most challenging, however, were the gear doors. These are not shown on Tony’s plan, but I thought I’d have a go. First, I made up a double framework for the underside, as mentioned above. I cut out the sheeted framework and used this as a mould for a couple of glass fibre doors, which I reinforced with carbon fibre rod (see pic).

As far as door activation was concerned, after a good deal of research and thought I came up with a viable method of using the oleo to open and close the doors as required. This involved a great deal of fiddling and some carefully bent lightweight piano-wire, but eventually a usable solution emerged. If you are interested, then you will find a video here: youtu.be/AndJPGHom-A

ENGINE NACELLES
Once the droop snoot and the front undercarriage were sorted it was time to turn to the nacelles, which are assembled directly onto the underside of the wings. As the inside of the nacelles would be visible through the cheat holes in the underside, I elected to glass and paint the insides of mine and the underside of the fuselage before fitting and testing the motors, and then finally fitting the under sheeting.

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Building up the nacelles.

At the same time, I glassed the fuselage underside in order to provide extra strength around the hatchway and undercarriage retraction bays. The pinkness evident on the picture is caused by mixing a very small amount of red acrylic paint to the laminating resin as a tell-tale to show thickness and coverage.

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Glassing the underside using 18g cloth.

I was then able to cut the hatchway for the battery compartment. My attention next turned to the main undercarriage, which was not the recommended one, so some fettling had to take place, but no major problems.

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The hollow tail cone is added near the end of the build.

CONTROL SURFACES
The elevons were each made as one piece per side and then the individual control surfaces were cut out in order to ensure that they matched. The outboard elevon on each side is driven on the plan by a short rod running inside an outer, but I had to hand some very thin fibreglass which I felt would do the job as well, using slots cut into the mating ends of the elevons.

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Fabricating the elevons.

Having built the servos into the wing at the outset it was then only a matter of making up pushrods for the surfaces.

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Rudder linkage is short and direct.

BODY JOIN
Up until now the front and rear fuselage halves had been worked upon separately, but the time came to glue them together. In order to do this and maintain an accurate airframe I used a laser to throw a line down the centre of the fuselage top while the glue dried. After this it was a matter of sanding and filling to create a smooth finish for covering.

COVERING
As is my normal custom with sheeted structures, I used glass cloth and resin to cover the Concorde. Everyone has their own method for glassing, so I won’t go further than saying I used 18g cloth and laminating resin, followed by primer and then the topcoat.

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In flight she looks most realistic.

The livery represented is the ‘Negus & Negus’ scheme, which the BA fleet wore until around 1984, when they went over to the ‘Landor’ scheme. Mine was part airbrushed and part waterslide using transfers created in Word and then laser printed.

FLYING SPEEDBIRD ONE
Lockdown has caused significant difficulties in test flying the Concorde. But at the time of writing, I have managed to achieve a few flights with the Speedbird.

The first attempt cannot count as a flight as she failed to achieve flying speed from a grass field, even though the grass was short, the field smooth and I managed to achieve a nose-up attitude of at least 20 degrees. I put that down to drag caused by the tiny wheels and probably not enough oomph in the battery.

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Landing approach with the nose drooped.

For the next flight I managed to get permission to fly off a hard runway at an airfield. Letting the speed build and gently easing in elevator, she came off cleanly and climbed out strongly. Not having flown a fast jet before, I was taken by surprise by the amount of airspace she needed in a turn, although I have to confess, I was reluctant to pull too much back elevator in the turns for fear of stalling. Those of you who have flown fast jets will be quite used to the required flying technique, but it was all new to me.

I found the model made very rapid progress and Tony Nijhuis’ deflections for aileron and elevator were dead right, as was the C of G. The wind on the day was slightly gusty and slightly across the runway, but this didn’t seem to bother my Concorde. Of course, she looked superb in the sky and I was more than a little relieved after a safe, if rapid, landing.

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Jeff has had lots of positive comments about the appearance of his Concorde.

The second flight was to capture on camera those iconic Concorde landings and so I enlisted the help of my good friend, Tony King. For this flight I left the landing gear down and flew circuits and approaches, holding about one third throttle on finals and then shoving in a burst of power to aid the flare. This proved successful and we managed to bag some superb pictures of typical Concorde landings. Unfortunately, because we left the gear down, there was not a single decent shot of the bird without the undercarriage showing.

Tony again did the honours for the third flight and by this time I was becoming more familiar with the handling. Still really quick, I found rudder helped to bring her around in turns and also back elevator prevented height loss. Under Tony’s direction we bagged some good shots with the aircraft clean. After a three-minute flight the battery meter showed 29% remaining, which will allow for a go-around should it be necessary.

It now remains for me to put more time into learning to fly this lovely bird, hopefully graduating into a fully-fledged Jet Jockey.

SUMMARY
Well, what a build!

The TN Concorde is definitely not for first timers but would be very satisfying for those with a few models under their belt. As mentioned, the instructions on Tony's website www.tonynijhuisdesigns.co.uk/mini-jet-concorde-32.html are pictorial, supported by some text, but are still very adequate. The finished weight of my model was 1.83 kg and the addition of a 4S 4000 LiPo at 400gm brought it right into line with Tony’s published weight of 2.2 kg, as is the C of G.

Since building, I’ve had lots of positive comments about the appearance of my Concorde, but in reality, she’s such an iconic aircraft and Tony’s model is such a good representation it would be hard to come up with anything other than a devastatingly attractive machine.

DATAFILE
Name: Concorde
Model type: EDF jet
Designed by: Tony Nijhuis
Wingspan: 32” (815mm)
Fuselage length: 69.7” (1770mm)
Wing loading: 19 oz/sq.ft. (5.9 kg/sq.m)
Power 4x 50mm fan units, 850g thrust each
Control movements: Elevator 15mm, Aileron 8mm, Rudder 20mm

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