The Silver Centenary
A One Off Australian Original
by Dieter Prussner
My first encounter with this unique and historic aeroplane came by pure chance in 2009 when visiting an open garden day at the late Dame Elisabeth Murdoch’s Cruden Farm property at Langwarrin.
I was attracted to the familiar sound of a Gipsy engine overhead, expecting to see a Tigermoth but instead saw an unfamiliar aircraft flying in the direction of Tyabb Airfield on the Mornington Peninsular. I managed to snap 2 photos before it disappeared behind the trees and later identified this machine from the prominent lettering SILVER CENTENARY under its wings. I contacted the Tyabb airfield administration and was informed that the aircraft was indeed stored there for a few more days before the owner was due to fly it back to Perth. Explaining my reasons of interest I was given permission to view and record the aircraft up close and also given the owner’s details in Western Australia. A phone call to Rod Edwards followed, and I explained that I was very keen to know more about his aircraft as I intended to build a 1/4 scale R/C model of his rare aeroplane. My enthusiasm must have been enough to persuade Rod to forward a lot of my requested documentation including the three view plans with construction details and photos during the coming months. In fact Rod and his wife Anita, eventually visited from WA to inspect the model in Melbourne prior to it being covered, or ragged as it is termed. I owe a great deal to Rod for his fantastic support throughout the entire period of this special project.
Original Aircraft Background
The original aircraft was designed and built by Rod’s great grandfather, Selby Ford during 1928-30. Selby was the engineer in charge of the Beverley power house in Western Australia. He knew very little about flight nor aerodynamics, but his interest was very keen, probably fired up by an earlier flight as a young passenger in 1919.
As there was plenty of down time at the powerhouse Selby decided that he would design and build his own aircraft by drawing chalk lines on the work shop floor and construct the aircraft over the top of the drawings. Unfortunately this hapless procedure became his ultimate downfall when trying to have the aircraft certified for its airworthy certificate as he had no plans or drawings.
One interesting design feature that certainly did nothing to hinder the performance of the real or model aircraft was the airfoil of the wing. Instead of incorporating a smooth rounded upper surface it had a rather short curved leading edge, then a long flat section with a more traditional tapering surface to the trailing edge. The lower wing surface was flat from L.E. to T.E. Both upper and lower flat surfaces are parallel, making the wings extremely simple and easy to build. Except for the straight wings and unusual tail feathers it somewhat resembled the Gipsy Moth which Selby hadn’t actually seen before. He managed to purchase a Gipsy motor from a crashed aircraft participant during the 1929 East West Air Races and mounted it in an upright position exposed to the air stream. Upon completion the aircraft was removed from the power house on the 1st of July 1930 and successfully test flown by a Captain Charles Nesbitt of the Western Air Services who afterwards commented on the surprisingly excellent handling characteristics of the Silver Centenary.
As Selby Ford was unable to have the aircraft certified the Silver Centenary was eventually loaned to the Beverley Air Museum, spending the next 40 years or so as its main attraction. Then in 2006-7 Selby’s great grandson, Rod and his friend Rob Felton, having acquire the Silver Centenary from the Beverley Air Museum, restored it to airworthy condition and produced the necessary plans and documentation for its eventual A.W.C. Two years later, in 2009, Rod and his team made the epic journey, flying the S.C. from Perth to Avalon for the International Air Show exhibiting it as a static display aircraft.
Much more information regarding this unique “one off” Aussie built aircraft can be found at:
The 1/4 Scale Model
As the plans were sent in PDF file format it didn’t take long to scale the model to its 1/4 size and have the plans printed. Construction of the model faithfully followed the original plans only substituting the hard wood main spars with spruce, and metal steel fittings with aluminium. Most of the airframe was constructed with balsa and some .5 and 1mm ply. My intent was to keep the all up weight as light as possible and rely on the final covering and rigging to provide the additional strength. This decision proved to be an asset when flying as it behaved very scale like and flew almost at scale speed as well.
The plan was placed on a flat particle board with waxed paper laid on top covering all glue points.
The 6.5mm sq. balsa longerons were cut to length and placed on the plan with dress making pins. Vertical and diagonal braces were carefully cut to size and glued in place with exterior grade PVA glue. After one side was completed the opposite side was built over the top of the first with small pieces of waxed paper placed where the glue points were located to avoid accidentally gluing the two sides together. When dry the two sides were positioned over the plan and joined with 6.5mm sq. balsa cross braces, held in place with pins as previously done. A set square ensured that the fuselage was aligned correctly. At this stage some of the control mechanisms, wing and tail joiners, as well as undercarriage and tail wheel parts needed to be made and put in position. To explain the making of each item would require a book so I’ll skip some of these tedious details as not to tire the reader. I’ll just mention that the two rudder pulleys were machined from Teflon. The elevator pull/pull mechanism was a combination of 4mm piano wire for a shaft with a Du-Bro nose wheel control horn secured on the servo side and the shaft mounted in small ball bearings at each end where it exited from the fuselage sides. The shaft protruded some12mm from each side to take a large control horn on each end. These external elevator control horns were fitted and secured after assembly.
The undercarriage and wing mount fittings were made from 10x10x1.6mm aluminium U channel (obtained from Bunnings) with lightening holes drilled along the length where possible without losing structural integrity. The centres of the alloy channels were filled with spruce and epoxied together to provide a wooden surface and extra purchase for mounting the undercarriage bolts.
The electric motor bulkhead was shaped from 6.5mm balsa and laminated with 1.5mm ply each side.
The fuselage sides were then covered with soft 1.5mm balsa sheeting with rear lightening holes cut out prior to gluing in place. The entire bottom of the fuselage was covered with 1mm ply, then 3mm formers. 2x5mm stringers were glued in place along the top of the fuselage to provide for the shape of the turtle deck which consists of 1.5mm soft balsa sheet for the rear section, glued into position and held in place with dress making pins. The forward decking was covered in .5mm ply from the back of the rear cockpit to the back of the scale motor, held in place with rubber bands and clothes pegs until the PVA had dried. The .5mm ply forward upper deck around the motor was then glued and held in place using clothes pegs, small clamps and rubber bands. The reason for using plywood in here was to provide a solid surface for the eventual miniature screws and bolts that would hold various pieces of alloy cowling in place. The cockpit openings were then traced using a pre-cut cardboard pattern and cut out with a sharp scalpel.
The Fin & Stabiliser
Building the fin was straight forward and also followed the original proportions and structure, substituting only hardwoods for 6.5mm medium balsa. Only the trailing edge of the fin was made from 6.5mm King William Pine to provide a firm post material for the Robart rudder hinges and allow the fin to be inserted and firmly located into the fuselage. The rudder is all balsa with 1mm ply lamination patches under the control horn mount. Rigging wire attachment points were reinforced with hard balsa gussets for added rigidity. A small plywood biscuit was glue into the underside of the leading edge to locate it on the fuselage.
The horizontal stabilizer is all balsa with two carbon fibre tubes epoxied into the fuselage and the stabilizer attached to the fuselage using two short 2.5mm wood dowels as joiners. Strength was not an issue, so all flying surfaces could be built light as the entire model is to be fully rigged later.
The four lower struts were sized and cut to length and were attached to the small 4mm plywood anchor points under the rear of the fuselage.
As mentioned the wings were simple and straight forward but the attachments, being scale like, were a fiddly job as were most other inter connecting fittings. When building antique scale aircraft there are very few ready made 1/4 scale fittings available, but some manufacturers are gradually adding more to their lists. One has to be resourceful and imaginative when replicating antique model aircraft parts. An engineering mind helps.
All ribs are identical so when cutting them by hand one only needs one template unless having the luxury of laser cutting available. I don’t mind doing the more laborious method as I find the process relaxing. There are 56 full ribs and 52 half (more like 1/8th) ribs made from 2.5mm medium balsa and are left as a solid rib except for a hole to allow threading of the servo wires in the lower wings. All 4 wings were built in the same fashion straight over the plan with grease proof paper in between. I started with the top wings as they were the easier pair to build. The original spars are solid but I decided to use 9x4mm spruce laid out horizontally top and bottom, flush with the ribs surfaces. Both bottom spars, the 12×6.5mm balsa L.E. and the 12×3.5mm slotted balsa T.E. are located then held in position with the usual pins and all ribs glued in place with PVA. The tips are formed from 6.5mm balsa. When done the top two spars are glued in place. Now 9mm blocks of balsa are glued as packing between the spars where the struts will be attached at a later stage. At this point the vertical 1.5mm balsa webbing is glued onto each side of the main spars between each rib for the entire span. This part was time consuming as there are some 224 pieced all up!
The next step involves gluing the half ribs in place. After completing the top wing panels both L.E. and the T.E. are carefully sanded to the finished shape prior to adding the cap strips on the top and bottom of all ribs. The final step is the addition of two 7.5mm brass tubes fitted and epoxied into the first three ribs to take the appropriate size carbon fibre rods as top wing joiners. I then added a 1mm plywood root rib in order to take a small screw eye to secure a light extension spring which is pulled through the centre of the fuel tank and holds the top wings together. This is probably not required as the final rigging alone achieves the same result. I just like to be on the safe side but it does help when going through the rigging process.
The bottom wings are almost a repeat of the top set except for the added walkway covering at the wing root and the ailerons which are cut away and finished after the wings are built. Also the bottom wing spars needed to be reinforced with spruce blocks at the root and the strut area in order to accommodate the scale like alloy brackets and rigging wires. HiTec H-81 M9 mini servos provide sufficient power and fit neatly in an upright position to allow smooth aileron control without any interference. They are easily accessible by removing a small 1mm cover held with four tiny wood screws.
The Fuel Tank
The sides consist of 1.5mm ply, were held apart with a 19x19mm square balsa L.E. and a 4.5x20mm T.E. As the tank is an integral part of the upper wing assembly the rigging it had to be strong and light.
The two 7.5mm brass wing connector tubes and all necessary blind nuts were epoxied into place prior to covering the whole tank with 1.5mm balsa. A final layer of alloy flashing covered the tank with an overlap on each side which was later bent over to give the tank a rounded edge and metallic look.
The tank is held in place with 4 cabane struts made from 15mm alloy model mast extrusion.
The Wing Struts
Two pieces of 30x8mm fine grain pine cover strips (from Bunnings) were cut to size, shaped to the required profile and varnished. Then a small piece of 20g mild steel sheet was used to make tabs which were slotted and epoxied into each end as anchor points to the wings. A thin brass shim material was cut and bent to shape, wrapped around and bolted to each end to resemble the real strut fittings. A pitot tube was constructed from alloy flashing for the brackets and 1mm alloy tubing, The air pipe is 1mm white styrene tubing.
The scale like undercarriage is constructed with 4mm piano wire cores and aluminium outer tubes. On the connecting ends, 1mm thick brass plate was used to fashion small tabs, a bolt hole drilled and finally soldered into pre cut slots on the end of the piano wire cores. A rotary tool with cut off disc was used to cut the piano wire slots.
Assembly of the undercarriage is completed with mini metal, also brass nuts and bolts which were obtained from a model railway supplier and attached to the appropriate alloy fittings under the fuselage. The wheels are Williams 5.6 Vintage wheels and the outer hub cover was cut and shaped from 22g aluminium sheet and held in place with five mini screws. All undercarriage fairings were shaped with balsa formers and epoxied to the piano wire rods, covered with thin cardboard and a layer of aluminium flashing finished the fairings. The original aircraft features a tail skid and this is the only break from total scale as I decided to substitute the skid with a wheel. So sorry Rod!!
The Scale Motor
One of the more challenging parts was making the De-Havilland Gipsy Mk II engine, as much of it is visible above the fuselage. The cylinders were constructed from paper rolled up around a plastic tube with the overlapping ends glued together. Then 1/32 balsa sheeting was used to cut out the many tapering cooling fins which were separated with thin pieces of cardboard and glued in place with CA. Other parts were made from scrap balsa and carved to shape. As I said, lots of fiddly bits. The exposed rocker arms and posts are made from balsa and ply with 1mm alloy tubing for all eight push rods. I happened to have a small box of suitable tiny coil springs and only needed to cut them to length to make the rocker springs. All parts are held together with thick cyano. The external motor cowling was cut from 22g. aluminium sheet and joined with 1mm alloy tubing cut into 2.5mm length, inserted into 1mm drilled holes and squeezed with a hand made riveting device, comprising of two centre punches and a small hammer. The result was reasonably pleasing and most effective.
The long exhaust pipe is made from white styrene tubing and the bent section from round balsa of the same diameter, with the balsa having tiny wedges cut out of one side and the remaining surfaces glued back together to gradually obtain the correct curvature in the S bend of the pipe. Small amounts of balsa micro filler and some sanding and a few coats of dope made a convincing result. The pipe is held in place with alloy brackets, mini bolts and nuts.
The Main Cowling
Added to the front of the fuselage was a laminated circular former made from 3mm balsa, laminated with 1mm ply at the front to hold the cowling screws. Then 22g alloy sheeting was cut with a pair of scissors and the five shapes were carefully formed by hand in such a way that no creases would form. Most of this process was reasonably straight forward and simple. Only the most forward cowl, being almost conical and the two halves joining at the top and bottom, was more complicated to get right. The port side panel included an air scoop for the motor and a cover for the carburettor that protrudes past the fuselage extremities. All cowling is fastened to the fuselage frame with tiny metal screws.
The Cockpit Area
The cockpit interiors are stained and doped in areas that are seen and feature the complete instrument panels but no seats or control stick etc. There is simply not enough space to get ones hands into these areas when handling batteries and radio gear. Just too many rigging wires and small cockpit openings. But a life like pilot, purchased from “Aces of Iron”, was installed later as it most closely resembled the real pilot.
The wind shields are made of thin acrylic sheet held in place with alloy brackets as per the original.
The cockpit’s padded edging was another teaser as one had to avoid being pricked by the dozens of pins holding the material prior to lacing it in place. It was also very time consuming. Holes were first drilled in the plywood edge, then a light tubular foam filling material was attached with a final soft blue/grey vinyl cover strip bent over the edge and held in place with pins. The lacing was made from 3mm leather straps material from Spotlight and stripped lengthwise with a steady hand and a sharp scalpel to achieve a width of 1.5mm which could then be threaded one hole at a time, withdrawing each pin as one progressed. It was a real thrill and relief to finally remove the last pin. Cyano was used for joining new pieces and tying off ends with many breaks due to the delicate nature of the thin leather.
Finishing & Flying
The motor cowling being all aluminium sheeting and fastened with mini steel metal screws allows ready access to the electric motor when needed. A good friend supplied the motor which was unbranded but was thoroughly tested and found to be of a rating more than sufficient to power this model. Rigging the model was an important step as it’s the integral part providing rigidity and correct wing alignment for a big model with a light wing loading. Uncovered 40kg metal fishing trace was used with aluminium swages connecting 1/4 scale Du-bro turn buckles and metal Kwick Links to the ends.
The model was finally covered in an aluminium Coverite 21st Century Fabric with an olive drab turtle deck covering. All necessary aluminium panels, undercarriage, fairings and struts were spray painted with etching primer and finished with Tamiya acrylic spray paints. The dummy motor was painted with Humbrol paints and the exhaust pipe with Tamiya Gunmetal spray paint.
R/C gear is a 2.4Ghz Futaba T7C Tx operating 4 channels. The original motor has been replaced by a Turnigy G60 outrunner 400kv electric motor and is powered by a Zippy 30C series 2450 6S Lipo and controlled by an 80 Amp ESC.
It drives an 18×6 inch cherry wood prop which was stripped back to bare wood, modified to give a more scale like appearance and features a specially hand made laminated wooden spinner with 8 tiny dome head nuts set into position. It looks great and I hope it never breaks! One can only wish.
The first flight, with heart in mouth, was recorded and can be watched on Youtube at the following link:
www.youtube.com/watch?v=uDExRyFZbSY, or simply type Silver Centenary aircraft into your search engine, turn the volume up and make sure you listen to the local’s commentary; it’s not only entertaining but tells you how the model impressed everyone on the day.
After comparing flying characteristics with Rod Edwards, it was interesting to note the similarities between the original and the model. It’s very forgiving in flight and one could almost claim it as stall and spin resistant. The CG needs to come forward a small amount as it’s a little tail heavy, as can be observed by its porpoising characteristics, but otherwise indicates all positives for future flights.
The Silver Centenary requires a relatively short take off run and in the air flies extremely slow probably due to all the parasitic drag. With each flight and fine tuning its CG, the model is becoming a joy to fly.
As a result of the successful outcome of the 1/4 scale Silver Centenary model I’ve decided to build a second version in 1:6 scale which fits assembled in the back of my van and can be taken to the flying field without the tedious rigging and de-rigging process which can waste valuable flying time.
Suddenly there are three Silver Centenary’s in the world.
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