Perhaps my "Sunderland" was not the first model have been built of this prototype, but as far as I am aware, it was in 1990 the first R/C model that have been flown.
After designing a number of non-scale floatplanes and a twin engined flying boat (2,6m span for '40' engines) and winning 10 waterplane championships, I wanted to build a successor for my smaller 1:10 scale B-17 Flying Fortress (1983-1988).
It had to be a model which could be entered for normal scale and water competitions, with models of these sizes and complexity it is not possible to build separate models for the land and water events (the more I do my own designs).
My choice eventually distilled into the British "Short Sunderland" 1:10 scale and, although not an amphibian, capable of being flown from water and- through use of the 'beaching gear" from land. The particular type selected was a late MK II with a lot of aerials and no top turret.
I used the Aviation News scale drawings as a basis for the design and by coincidence, I saw a very good full colour three side view of RB-U (W3986) in a Dutch book. For me this was a bonus as the camouflage scheme appealed more than the white and grey colours normally associated with the "Sunderland".
THE PROTOTYPE (pictures 000A till 000D).
The "Short Sunderland" is one of the most famous Flying Boats in the world and played such a vital part in the Battle of the Atlantic. The big plane was a military development of the famous pre-war C-class Empire flying boat.
In October 1934 the construction of the Sunderland "S2S" started and after a intensive choice of armament the in the beginning planned 37mm canons in the retractable bow turret were changed by a double Vickers 8mm machineguns.
In the same time the tail canons were changed for four machineguns in a FN13 turnable tail turret, and just these changes gave a shifting from the central of gravity backwards! To compensate this, the originally straight wings were sawn through and swept backwards for 4,5 degrees and the step also placed backwards.
This was the reason that the step became higher and the engines are not longer pointing straight forwards but outwards! So this is not on purpose designed so!
The Sunderland made its maiden flight in October 1937 and later the 950 HP engines were changed in 1010 HP Bristol Pegasus engines and given into service to the Coastal Command in 1938 as a MK I.
In june 14th 1946 the production of the last Sunderland (MK V) was ended.
The RB-U was part of the No 10 squadron of the the RAAF (Royal Australien Airforce) based at Pembroke Dock England. Damaged some U-boats in 1942 but crashed on the the 20th may 1943 near the Eddystone Lighthouse England, with the loss of all twelve crew members.
Drawings (pictures 000E+000F, 001+002+022)
At last, in autumn 1988, I succeeded in obtaining some black and White photos of this prototype from the Imperial War Museum in London, so I could start with the drawings. It meant a lot of hours working, because the fuselage was with his complicated forms very difficult and I had just 3 sections! And than I started building the Model.
The following spring, 1989, my wife Ria and I visited the Hendon museum in London, this for looking at the Sunderland MK V there.
At the museum we were accorded an appointment with Mr Cormack who was able to give me chapter and verse on the in-and outside of the aircraft.
Fuselage + Fin & Stabiliser (pictures 003 till 012)
The fuselage is built in two parts again with the formers being split into two halves. Formers are cut from 3mm plywood, and 3mm liteply or balsaply for the backward ones to save weight. On the building-bord was placed a strip of wallpaper (upside down) and drawn on it the centre line and cross-lines for positioning the lower half formers, which were jammed up side down on the building-bord. The tail had to be devisable because of the length, but was build on with provisions for the fuselage-joiners and bolts. (double former and sawn through later). Also provisions were build in for the wing- and beaching gear fixing and all formers connected with stringers. Now the framework looked like a wale skeleton and was planked with 3 mm en 2 mm balsa sheets. After drying the fuselage halve could be removed from the board and turned upright, supporting in foam blocks. Before the upper halve could be build on, I had to construct first the stabilizer and the fin.
Because of the amount of spraywater the tailplane receives during waterflying, the construction had to be fairly rugged. Construction for the stabilizer and fin is therefore in foam, planked with 1mm balsa. The rudders are fitted with pinhinges and a long 1,5mm piano wire in a plastic tube and have convex leading edges and are always removable.
As they were ready, on the rear the upper former-halves were glued and the stabilizer was glued in a saddle with the right incidence. Than the fin was glued in, and now I had to decide: Three servos in the tail + tailwheel servo at the rear, or all of them in the front?
In the tail could mean extra lead in the nose, a difference of 600 gram total. So I decided: all servos in the front of the nose! But in this way I had to solve the problem of a divisible closed loop linkage system in the tail for the inside controlled elevators and rudder. In the tail there are mounted three cranks with a permanent closed loop system (stranded controlline wire) to the rudders.
For the closed loop linkage system to the servos, ballinks with security forks from Graupner were bolted on the cranks. This system has proven itself up today in many flights and I have practised it also for my later 1/8th B-17.
Now the rear could could be planked, not frontwards because that had to become a hood, which is going over the Wings to the nose.
Now the rear fuselage could be separated from the front half, by loosening the 4x M4 socket bolts and saw through, between the 2 dual formers and through the flat brass tubes. In this way it will fit accurately!!
Wings (pictures 022 till 028)
These have a NACA 4415 profile from rootrib tot aileron, and further on progressing to a NACA 2415 profile section at the tip, so an aerodynamic wash out has been built in (a geometric wash out has always a resistance).
Wings I always build on raised supports (strips of cheap 12mm plywood), three ones: under mainspar, rear spar and Ribends. In these supports the wash out and dihedral already have been built in.
The framework was built quick, the more longer took the provisions. The ailerons are build in with the wings with pinhinges and a long 1,5mm piano wire in a plastic tube.
In the ribs there were glued, nearby the main-spar, 2 Brass flat tubes (from above and under) at 0⁰ level. Also 1 brass tube nearby the rear-spar. In the other Wing-halve too, but not glued yet here. The flat steel tongs were shoved in, both wing-halves put together, and these were checked for fitting together. When I was satisfied about this, and the flat brass tubes were at 0⁰ level, the tubes in the other wing-halve were glued too.
(In 2010 I have updated the plan to 4 sheets, and changed the Wing-joiners in a dural-tube and a carbon-tube!).
The wings are laying on the Fuselage Saddle, and over them there became a wooden hood as far as to the nose. (picture 049)
These had to be done before planking. Applied for example were: servo fittings, throttle linkages, wingjoiner-fixings, plywood strips for the fixings of the wing floats and scale exhausts, landing-lights, torpedo dropping system, flap linkage system (Fowler Flaps) and so on! In this phase the wings were putted on the fuselage, to position the self made wing-fixings with M6 steel-bolts.
Nacelles (pictures 024 + 027)
The construction of the nacelles is my own: the nacelle side walls are in one piece with some ribs and over these the nacelle formers and firewall were shoved and glued. Parts of the upperside must be removable for access to the fuel-tanks.
Fowler Flaps (pictures 025 till 029)
The construction of the originally Fowler Flaps can be made directly against the underside of the wing, placing clear folio between them, as a barrier. The flaps extend maximum 9 cm rearwards and 40 degrees downwards.
The system for these are build in before planking, tested and adjusted. It seems to be very simple, and afterwards it was, but before, puff, puff! It is functioning with a 10 kg servo to 2 large self made pertinax bell cranks from which are going out on one side 2 rods. One (outer) to the supported sliding rod ("ram").
On these rams the flap is hinged and supported and is moving for-and backwards. The other rods (inner) are directly connected to the flap-horn.
How do they work? The rods (outer) for the flap supporting and hinging "rams" (3mm piano wire) travel further than the flap tilting pushrods, although all are extending or retracting/ moving for or backwards, at the same time and direction. (see picture 025).
The wingpanel sheeting is commenced with the underside and the needles had to be pinned so that the wing could be replaced on the supports and weighted down. So later on also with the upperside, this will ensure the retention of a true straight wing. Than the nacelles could be planked, the apart planked ailerons cut out and convex leading edges glued to them.
Cowlings and Turrets (pictures 032 till 035, 045 + 046))
Cowlings were made from alum. stove pipe (Ǿ 150mm) with a, for the half, glued in 3mm plywood ring. To these the radial motordummies were glued and then over these rings a polyester GRP moulded nose ring. In the alum. pipe cooling gills were slotted and bent out a little bit. The plexiglass nose and tail turret are formed with plugs from 1mm clear pvc in the kitchen stove.
Cockpit Hood (picture 049)
This is removable from nose to wing trailing edge and has been build over bolted on wings to obtain a correct fitting, with a piece of clear film between them. The cockpit itself was made of a plywood framework with 1mm plywood strips cyanoed onto it, to form channels for gluing the clear pvc windshields.
Wing Floats (pictures 044 + 048)
Because of the water these are constructed from foam and planked with 1mm balsa. The struts are made from 3mm piano-wire glued into a alum. drip tube. Struts and floats are braced with stranded wire, one end being soldered to threaded rod with kwiklink. Floats are glass clothed with epoxy.
Beaching Gear (picture 047)
The Sunderland is a flying boat not an amphibian, so it doesn't have a real undercarriage for take-offs and landings from runways.
The prototype aircraft only has a beaching gear for services on a slipway! and this I have imitated. It can be given easily a wider track, otherwise it is to narrow for land take-offs. For water flying it is easily removable, it has to be pulled out of the steel pipes, which are going cross through the fuselage.
To manoeuvre on the water the rudder is mixed with the left and right engines which are mixed with each other via a third mixer.
The tailwheel is a part of the beaching gear, also scale and removable.
Finishing (pictures 036 till 053)
After a final sanding I glass clothed (25 gr/m2) with epoxy the underside of the fuselage from the nose to the second step, and also the wing floats. The rest of the model was covered with a lightweight tissue to keep the weight to an absolute minimum and 1x clear doped. Then panels were scratched in and 2x clear doped.
After sanding primer was sprayed on and rivets were brought on, and finally the model was sprayed with authentic colours (matt 2-component acryl), and weathered to give a believable finish.
Markings and codes were sprayed on, final details such as the aerials were applied, scale exhaust pipes were made of thin copper and brass tubing. Pilots and gunners were glued in at the same time with the turrets, and the cockpit frame was glazed.
The Sunderland was fitted with four Osmax 46 SF long stroke engines with self made silencers fitting in the cowls, props are Graupner 11x6. (Four-stroke 60/70 engines will not fit into the cowls, and that was a pity!). No side or down-thrust are fitted to the engines.
Synchronisation of the engine RPM is not critical in flying, but on the water when the model is on step, yes!
Don't never try with multi-engined models to get the the maximum out of the engines, but keep them running a little bit rich, and don't use to small fuel-tanks!
At last my Graupner MC 18 radio equipment was installed (in 1994 changed for MC 20) with total 13 servos,
2 PCM receivers, 4 switches and 5 batteries, 2 of them for the receivers, 2 for aileron/ flap powerboosters (in view of the long extension lead), and 1 for the landing lights.
With the 5 batteries and 5 servos in the nose the C of G came out right!
Elevators, rudders, tailwheel and also the ailerons are operated by closed loop linkage system, using stranded control line wire.
Fowler-flaps are actuated via M3 rod system to the bell cranks. (see back Fowler Flaps. and picture 025)
At the end of May 1990 the model was ready to fly, just a week before the Dutch 1990 Open Scale championships, every year at my home club Delta Oss.
See also chapter Technical Solutions for my Large Scale Models.
Maidenflight (pictures 054 till 060)
On the last Sunday of May 1990, the weather was beautiful and warm, and we could test-fly the model. My son and I assembled the model, checked everything of importance once again and photos were made. The engines were started and adjusted, some taxi trials carried out and the acceleration looked good, also because of the double wheels from the beaching gear.
Once fuelled up, we were ready for the ultimate test, will she fly or not, are the incidences right, how much run will she need to take off?
The model picked up speed quickly as the engines were opened slowly, a little up elevator and she raised her tail, and after a run of 50m and a little more up she rose majestically into the air. What a fantastic sight!
Height was gained and I was pleased that no trim what-so-ever was necessary! She flew with the characteristic nose down attitude so evocative of the real aeroplane, no doubt this was of 7 degrees wing incidence!
After flying some circuits I made some low fly-pasts just to experience the marvels of such a large aeroplane flying so beautifully and then thought about landing. With the the engines throttled back and 20 degrees fowler flaps the slow steady approach was followed by a smooth touchdown and roll out.
Once again I had that excellent and very proud feeling.
It was enjoying flying this model, so realistic and majestic! Made many flights and did win 10 International Contests.
In 1997 the Sunderland flew her last Contest, than I stopped competing Contests with the Sunderland, just Fun- and waterflying with her.
I was Water-flying with her, hit with the hull a rock below the water-surface, and she got a lot of water, but could save the model and repaired her.
During Fun-flying, I had to make an out-landing, but the damage was minor, but than I discovered than she had suffered a lot of that water in 2003.
Flying her further this way was irresponsible, it was too much work, so I did never overhaul her.
Up today, the model did not fly ever again!