Bits and Pieces
By Ed Lubitz
With the help of some friends, Mark Taylor and I built a Silver Dart replica that we first displayed and flew in 2009 for the 100th anniversary of flight in Canada. The aircraft flew well enough and was stable in flight.
After four flights down the runway, we decided to ground the aircraft, because if we had an accident, we just didn’t think we had the enthusiasm to rebuild it. The aircraft, while easy enough to fly, was extremely awkward to handle on the ground. With its 49-foot wingspan, it had to be “danced” through the 40-foot door of our largest hangar.
Also the aircraft is a piece of history, and we felt it was unique enough that it should be on display, not tucked away in the back of our crowded hangar.
So this aircraft was donated to the National Air Force Museum of Canada in Trenton, Ontario, and is now on display there. Entrance is free, so if you’re in the area, please drop in and see firsthand what the first aircraft ever to fly in Canada looked like. You might note that our replica was registered as a two-place, basic ultralight and was flown in this category. If you wish to check out its new home, go to www.AirForceMuseum.ca and search for Silver Dart under Aircraft.
With the Silver Dart project completed. Mark and I began casting about for another project. The basic requirements were that it had to fit into the ultralight category and be an aircraft with some historical significance. Our approach in constructing the Dart was to build as accurate a replica as possible with concessions to modern materials. This time, we want an aircraft that will be more of a flying machine and less of a museum piece. With these criteria before us we started the search for the new machine.
The first candidate considered was the Demoiselle by Santos-Dumont. This is acknowledged to be the first ultralight aircraft, and plans are readily available (published in Popular Mechanics). However, by the time we got through updating the design, scaling it up to accommodate a normal-size pilot, the bamboo ribs were gone and the wingspan had nearly doubled from 18 feet to 32 feet. We felt we could stay with the bamboo fuselage structure, but other than that, it bore little resemblance to the original.
In the 1920s there was a worldwide movement to develop an efficient light aircraft. In Britain, there were a number of these aircraft; all were cursed with one major problem, lack of a decent engine.
One design in particular caught my attention – the English Electric Wren, a rather large monoplane that was very streamlined and efficient. The fuselage was airfoil shaped and the wheels were buried in the bottom. The wings were shoulder mounted, and a 3-hp motorcycle engine powered it. With only 4 hp, it was no homesick angel, but it did get up to 87 miles/gallon. With a bigger engine, it was a real possibility, but at about this time another British aircraft came to light – the Avro Baby.
The streamlined and efficient English Electric Wren. The pilot sits low and behind the engine. Pictured is the Shuttleworth Collection’s flying example in Britain. With the 3.75-hp (that’s right, less than 4 hp) engine running at full power, a bungee assists acceleration to takeoff speed.
This biplane first flew in 1919, was powered by a 35-hp inline water-cooled engine (we have a 40-hp Kohler), and is small enough to fit through our hangar door. The first couple of airframes built were single seat, but there was a two-seat version as well. I googled “Avro Baby” and turned up enough information to build a replica. Did I mention that it’s a biplane?
I contacted a chap in England who had scaled drawings of the original aircraft available for those that wanted to build a model. Since I planned to build a scale model of the aircraft, I obtained a copy of the drawings. I didn’t tell him until I had the drawings in hand that the scale I was planning to use was 1 to 1. He didn’t seem to mind.
The Avro Baby is a conventional biplane with a span of 25 feet and a rather roomy cockpit. Avro built her as a wire truss aircraft as was common in the World War I era. We have the expertise to build her this way, but we decided to build a wood-braced fuselage similar to the Pietenpol Air Camper while keeping the Avro Baby dimensions. We’ll be using wood, sticks, and gussets rather than bracing each bay with hard wire and turnbuckles.
The airfoil is the RAF 15 which is relatively thin but very efficient, requiring very little horsepower to move through the air. The tradeoff is that the stall speed will be a bit higher (32 mph). This same airfoil is used on the Tiger Moth.
The propeller is 90 inches in diameter with a pitch of 63 inches. We’ll be keeping this prop and gearing the Kohler to turn the same 1500 rpm as the original 180-pound Green, four-cylinder inline engine. The width of our modern V-twin is almost the same as the original Green. The Kohler engine’s center of gravity is further forward, so it appears that the prop will be in the same location as the original even though the modern engine is about 40 pounds lighter.
The outside dimensions of the original and the replica will be identical. We hope to have her flying in the spring. If you’re interested, drop me or Mark a note. My e-mail is email@example.com.Mark’s is firstname.lastname@example.org. We’d be happy to keep you up to date.
Light Flight, January 2011