Flexi Foil. Radio control sport model. Uses a 'hang-glider' style wing.
Quote: "Flex-wing fun with S Salmon's 30-35 powered pilot pleaser.
THE DESIGN OF THIS MODEL stemmed from a desire to have a fuselage that would take a variety of different wings and rotors. The Flexi-wing has proved so successful that other wing types have been for the time being shelved. That is not to say she 'flew off the board' - initial flights were a series of loops which had to be tamed by copious amounts of down thrust.
Once trimmed she has proven very easy to fly, with a very good slow flight capability. In fact she does not like flying fast, the wing starts to 'flap', which tells you when to slow up. She can climb very steeply under power, the glide is similar, but with a nice low rate of sink. Even when abused she does not drop a wing but 'rocks' and is fully controllable. Another major advantage is that the model is very cheap to construct, especially the wing!
Construction. The fuselage and tail surfaces are very basic and therefore need little explanation. In fact if you have spare components left over from previous models these might be pressed into service. The fuselage shown with its light ply sides and nylon covered is very robust -as any one who has witnessed my landings will know. The tailplane is also 'banded on' for resistance to damage.
The wing is simple to make and cover but must be made accurately because minor differences in covering area, either side of the keel, or differences in the angles of leading edge to keel, will lead to large amounts of rudder trim being needed. The original framework was made of scrap alloy tube, scrounged from a local microlight manufacturer and as such is ideal.
If you use this material make sure you check the bolts regularly and if possible plug tube with dowel (otherwise the vibrating tubes lead to some very interesting glitches). A second wing has been built with 10mm dowel reinforced with brass tube at fastening positions.
Wing covering is any available thin polythene. The prototype used dustbin liners, which has caused many rude remarks as this item is more commonly used to carry models home. I have since used a polythene sheet used for masking in spray shops and a clear light reinforced polythene available in garden centres. It is important to use light polythene as this takes shape easily. The covering is held on by waterproof Sellotape such as is used to repairing greenhouses. The bracing wire is used to keep the wing level as wing tilt produces a turn, this can be helpful when trimming if the wing is not assembled accurately..."
Flexi Foil, RCM&E, October 1988.
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