The Vought XF5U-1
A model of the "Flying Pancake"
Picture
of the Vought XF5U-1 model. All photos ©
Giuseppe Ghisleri
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On this page a presentation is given of some data and a selection of photos of the model of the Vought XF5U-1.
The model is built by Giuseppe Ghisleri and he kindly supplied the photos and data shown on this
page.
If you want more information you can contact:
Giuseppe Ghisleri.
Building the XF5U-1 model
The XF5U-1 "Flying Pancake" model is made of what could be called "park-flyers" materials, Depron and blue foam.
The body is a multi rib and spar assembly which resembles closely to the real aircraft structure. The spars and ribs are cut from 3 mm thick Depron sheets, they are glued with depron-friendly cyanoacrilate and the assembly is covered with a single 3 mm Depron sheet on both the top and the bottom.
The "fuselage", i.e. the pilot's cockpit, is built the same way and has a hard wood dowel which takes the launching catapult's induced stresses.
The engine fairings and air intakes are from blue foam too. The tubes carrying the engines are hot wire cut from blue foam and covered with lightweight fiberglass ( 25 gr/sq m ).
The model is powered by two 1:2 reduced Speed 400 engines relying on a single battery pack of eight 1600 mA cells.
The "wing tips" are built with hollowed out blue foam as is the body leading edge, 2 pieces for each half span.
The elevons are all moving and are carried by a 5 mm dia. carbon tube. They are built from two 3 mm thick Depron sheets. The rudders are cut from 6 mm Depron sheet.
Launching the XF5U-1 model
To save weight the model doesn't have a landing gear. As there is no way to hold the model for the launch it was decided to construct a launching ramp using a bungee cord to power the model into the air.
The launching ramp was constructed from some wood strips and some 13 m of 10 mm dia. bungee chord.
The bungee chord is streched for 10-11 meters and gives a tension of some 8 kilos.
Take off is very simple: you press the release pedal and the model zooms away reaching a height of some 5-6 meters and a speed of some 50 km/h.
When the bungee chord releases the model, which it does on its own, just feed power and it flies away.
Flying the XF5U-1 model
Flying the first version of the XF5U-1 model:
The first flight was a little disappointing, not for the flying qualities of the XFU5-1, but for it's perfomance, which only allowed low speed cruising with a lazy climb.
On the second flight I decided to explore more of the models flying qualities and tried a tonneaux and it turned out to be one of the fastest a model of mine ever did.
The first flights were made over a field with almost fully grown soyabean plants of which the leafs offered a soft surface for an unwanted hard landing or even a crash.
Flying the second version of the XF5U-1 model:
The flying qualities were very good, no problem holding a steady path, easily controllable and predictable. To improve on the models performance it was decided to change to a direct-drive power train.
This was done by simply pressing two Gunther propellers on to the two engine shafts.
After these modifications confidence was high and the model was flown before a large audience.
The launch went fine, but when engine power was applied a few moments later, a noise was heard and a propeller flew away, leaving only one in place. The throttle was cut instantly but the model was already in a diving spiral from which it was impossible to recover.
The model crashed heavely. The cockpit was broken in three pieces and the engines nacelles were broken in half. All and all a very disappointing experience but the decision was taken to rebuild the model again as it still held some unfulfilled promisses.
Flying the third version of the XF5U-1 model:
Next to the necessary repairs two Speed 480 engines where installed along with normal propellers held in place by nuts.
After a while the model was again flown and finally showed how good it was.
Speed was good, two consecutive rolls could be executed from a straight flight. During a loop the model needs to pick up speed in a dive.
If the model doesn't get enough speed it rolls off over the top so nicely that it looks as if it was done intentionally.
The "wing" has a symmetrical profile so it flies inverted as good as upright, it needs only a fair amount of down elevon because the elevon needs to be trimmed up to fly level.
Landing the XF5U-1
When the throttle is eased back the controls become mushy and the model is not easy to control. While reducing the engine power gradually and pitching up however it is controllable with the rudders, which happen to be very powerful, and the model can almost be stopped in mid-air before it starts to fall down in a nose up attitude.
The landing is best accomplished by aligning the Pancake with the landing strip while reducing gradually power and giving a bit off up elevons, cutting the engines only when a few centimeters above the landing surface.
Of course it has to land on grass fields and if the grass is mowed the model will slip for a few meters and occasionally does a turn on it's underside stopping with the tail first.
There was a risk that the elevons could be easily damaged from tall grass or bad landings, but that fortunately never happened.
The model flew almost 40 times before it fell to earth for the last time caused by a radio glitch. It was damaged the same way as before. Although having had a lot of fun with it, it was decided (with a sorrow feeling) to start building some other strange flying machine.
