The past few weeks I spent, for a change, not in the workshop but on holiday. This doesn’t mean the project has come to a halt, though. While enjoying a cold beer under the Sicilian sun, I worked on the design of the fuel tank. I fully modelled the tank in CAD and placed it in the fuselage. The insights gained were quite diverse. The tank volume is about 220 litres at best. The 235 litres stated in the documentation were slightly overestimated. Fuel is drawn through a siphon pipe from a sealed compartment at the rear of the tank, which is continuously supplied with fuel via check valves. The purpose of the trumpet-shaped pipes on the upper check valves remains a mystery.
The fuel outlet is located at the front and leads into the landing gear bay. The reason for this was the engine start-up procedure. The engines had to be primed with gasoline before switching to jet fuel via a valve in the landing gear compartment.
A fuel volume of 220 litres for four jet engines is quite tight. An increase in the tank size would be desirable. Such a modification is also noted in the documentation as a development suggestion. My own attempts on the CAD to maximise the volume resulted in around 300 litres. Additionally, I’m considering building the tank out of composite instead of welding it from aluminium. However, this will first require a complete redesign and recalculation of the mounting to the fuselage.