New Indoor Free Flight Model, the Manhattan


Just a few words here about my new free flight model for the Dome. This is a Manhattan duration class model called the “Tall Boy” which was published in the Aeromodeller Magazine of February 1979. Like many things, the Manhattan class was more popular in the ‘70s than it is today. In choosing to build this model, I was after something that would look good, give good duration flights and could survive the relatively turbulent conditions in the Dome. The lighter indoor free flight model classes, such as EZB, do seem to suffer from the air movement in the Dome – and F1D microfilm is just out of the question!
free-flight-meredith.jpg (76768 bytes)
meredith-free-flight2.jpg (73826 bytes) The rules for Manhattan are as follows: Max fuselage length 20ins without prop. The fuselage must be able to contain an imaginary 2ins x 2.5ins x 4ins box and must have a clear plastic windscreen of at least 2 sq ins.

The propeller must be fixed pitch and made of balsa sheet.

The model must take-off from a fixed 2 wheel undercarriage with wheels at least 1 ins in diameter.

The wing must be an unbraced monoplane directly mounted on the fuselage. Max span 20 ins, max chord 4ins.
Max tailplane dimensions are 12ins span by 3.5ins chord.

Tissue or condenser paper covering is required (Not plastic films)

Minimum weight without rubber motor 6 gram.

The current model is rather heavy at 9 gram without motor, but was strengthened compared with the published plan to ensure it survived the Dome environment, if not the flock of tiny RC models trying to avoid it! I’m planning a developed home brew design for next year, which should be lighter and perform better.

meredith-free-flight4.jpg (84438 bytes)

meredith-free-flight5.jpg (85398 bytes) Some notes on the technology:
Special selected “indoor” wood is used in special sizes, such as 3/64 square and 1/20 square. 1/16 square is like a tree trunk! The 1/40 sheet balsa prop blades are soak-formed on a specially carved jig to achieve the required blade twist distribution and camber. For strength, the fuselage of my model is covered in tissue, which was a big mistake as this is where much of the additional weight came from. The rest of the model is covered in super-light condenser tissue paper which is, or maybe was, used as the insulating layer between foil conductor layers in electrical capacitors.
The rubber strip for the 2 strand motor has to be specially cut using a specialist tool which will cut standard rubber motor strip down to any desired size to the nearest 0.001 ins. Fortunately, Tim Chant bought one of these in a moment of weakness, so I borrow his. This is really vital as standard 1/8ins (0.125ins) rubber is too powerful, but 0.110ins cut strip is too small. The ideal motor size for the Dome is probably 0.120ins and flights over the coming weeks will explore this. Hopefully flights of 5 mins should be possible.

Here’s hoping for a good winter’s indoor flying!

Video on Youtube

Meredith

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