Back in February 2020 we designed a foamboard motor frame for the Blade Inductrix 200 quad with the ability to fly various paper model fuselages including two science fiction models and a harrier jet fuselage. And, at just 13.5g (without motors, board and switch) the foamboard frame is not only ultra light-weight but also torsionally rigid with a natural density that eliminates any vibration – making the foamboard frame very stable in flight.
This first design is based around a ’90 degree interlocking’ system where the motor mounts are secured in the centre of a right angle to provide the best possible rigidity.
However, during the two years development of the paper Harrier fuselage, the overall weight had to be reduced by the removal of the landing gear. This meant that the motor frame required further modification to allow the sides of the motor frame to double as landing skids making this particular frame design unsuitable for our scifi fuselage designs. Furthermore, the 90 degree interlocking frame is limited to a total flying weight below 200g to enable a five minute flight time (the Harrier’s flying weight is around 195g including a protective coat of clear enamel sprayed onto the Harrier’s fuselage). As soon as the Harrier project was completed (September 2022) we concentrated on designing our first scifi model (the Space 1999 Eagle) and it soon became apparent that the flying weight would exceed 200g. As a result, we have designed a new prototype foamboard motor frame that successfully exceeds the 200g weight limit with a five minute flight time.
This design is based on the usual ‘X’ type quad design with interlocking frame parts consisting of vertical supports on the underside of the motor mounts to provide rigidity in the absence of an interlocking 90 degree construction format. At 10.8g (without the inductrix components) this motor frame is nearly 3g lighter than the Harrier’s ’90 degree interlocking’ frame and also has a more efficient thrust output enabling the new motor frame to carry even more weight and still fly for the standard five minutes. As previously mentioned, our first science fiction model for the new motor frame, is the ‘Eagle transporter’ from ‘Space: 1999’. Below is the prototype 22 inch (1/48 scale) paper Eagle which has a total flying weight of 206g (including an 80g battery) while still flying for over five minutes.
This model is over 10g heavier than the Harrier, and although the flight handling is still good, it is not as precise as the Harrier – so a few grams will have to be taken off and hopefully we can reduce the total flying weight to around 200g – in our experience even 5g of extra weight makes a noticable difference to the flight handling. After removing a few parts we tested the Eagle at 202g and this is indeed the magic number for the flying weight – enabling the Eagle to handle in small spaces just as precisely as the Harrier even though it is still actually 7g heavier. The Eagle is relatively easy to build as all of the ‘tubular framework’ is made from flat 160 gsm card – no requirement to roll any paper – you just need a sharp scalpel to cut out the holes in the framework. The Eagle’s fuselage is constructed from 75 gsm paper (not 80 gsm as with the Harrier – as this too saves 3g to 4g in weight), 160 gsm card and 5mm foamboard. Without the motor frame this Prototype Eagle fuselage weighs in at 56g (the Harrier’s fuselage net weight is only 41.5g!) which demonstrates the improved efficiency of the new motor frame.
The Eagle has a split top card framework (which is not load bearing) to allow for battery fitment. This centre section is magnetically attached on the underside of each end using tiny magnets which contact staples fixed into card sections of the underside foamboard spine – the part that is load bearing. In order to Keep the weight down the motor frame is also a ‘stressed’ member taking most of the weight so the Eagle will not fold in half while in the air. At present the engines, cockpit, side blade guards and landing gear are removable. The engine bells are made from six parts printed on 75 gsm paper and then sprayed using plastikoat brilliant silver metallic spray paint before being glued to the rear engine plate.
This prototype Eagle is still being flight tested and it also requires a few ‘tweeks’, including, increasing the rigidity of the top spine framework, making the four leg pods removable (and also making them mount a little more level too) and hopefully some weight reduction before we are happy to make it available for download. The finished version has been designed and will be assembled and flight tested soon. Pics of the final version will be posted when complete.
Papermodels4rc would like to mention that this design is only available due to the immeasurably creative genius of people like Brian Johnson, Nick Allder, Martin Bower and the rest of the FX team of Space 1999, and of course, also with thanks to one of the greatest visionaries of science fiction – Gerry Anderson.
