About this Plan
Retro. Radio control sport electric model.
Quote: "Retro. Starting in electrics? Andrew Reid's shapley sportster will help.
Retro has been designed as a deliberate combination of the most attractive features of vintage models with the convenience of the latest electric-flight technology and compact radio systems. The slimmer fuselage and lack of elaborate drag producing undercarriage meet present day needs for efficient no nonsense flying from whatever flying site is available, but the elliptical wing planform is pure nostalgia for a more elegant age of model aircraft design.
Retro is intended for 540 size electric motors, using a belt-drive or gear-box to turn a large diameter propeller at lower revolutions than with a direct drive installation. Performance will depend upon the motor and reduction-drive setup but a good electric motor specially prepared for electric flight is recommended. The prototype uses a 'Superferrite' 540 motor in combination with an MFA Olympus belt-drive reduction unit, turning a cut down 10 x 6 propeller. Alternatively a 'traditional' 2.5 cc R/C diesel or glow motor could be used as a substitute power unit, with suitable modifications to the motor mountings.
The prototype weighs 3 lb 12 oz, complete with compact (not miniature) radio equipment and a 6-cell motor battery pack, giving a wing loading of about 17 oz/sq ft. Apart from the slight complication of the elliptical wing there is nothing in the construction of 'Retro' that will cause the average modeller any problems, but rigorous weight control should be maintained at all stages of construction.
Fuselage: Construction of the fuselage is quite straightforward, but it is advisable to check that the widths and details of formers F1 to F5 are suitable for the intended motor and R/C installation. Make any adjustments that may be required when tracing out the parts. Having prepared a kit of parts for the fuselage, the basic sides are assembled using PVA adhesive. Carefully mark out the former positions on each side paying particular attention to former F1, which establishes the thrust-line. Start final assembly by epoxying formers F3, F4 and F5 to one side. Note that floor-pan F4 is slightly tapered at its front end and do not apply any adhesive to this part of the former.
Check that the formers are square with the fuselage side and allow the epoxy resin to set. Fix the second side to formers F3, F4 and F5 in similar manner. Apply epoxy to formers F1 and F2 and insert these formers between the fuselage sides. at the same time drawing the sides together to form the nose taper. Bind the nose with tape or rubber bands to hold the assembly together until the epoxy has set, checking carefully that former F1 is in the correct position.
The fuselage is completed by drawing together at the rear end, and inserting the 3/16 sq cross-spacers. These may be suitably cut to produce a very slight 'waisting' of the rear fuselage in plan view. Add top and bottom sheeting after inserting the 1/2 in balsa infill beneath the front of F4..."
Retro, Radio Modeller, April 1991.
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Supplementary file notes
Article pages, thanks to RFJ.
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User commentsA great looking and atmospheric model but perhaps with some (easily solved) problems: The article mentions using a speed control rather than a flight switch because the sudden application of power will cause a tip stall - a statement that causes alarm bells to ring, considering the low power used here. Sure enough, looking at the plan reveals two reasons for this 1) The CG is shown too far aft, possible due to some confusion over MAC for the elliptical wing. I would suggest considering the most forward position shown as a realistic aft limit! 2) Building some washout into the wing is definitely recommended.
I seem to remember a VERY similar looking model published in RM around the same time but based exclusively on electrics removed from a buggy and an Olympus belt drive. I think its name was one of those electricity related puns but I can't remember specifically...
RMC - 18/10/2019
"I seem to remember a VERY similar looking model published in RM around the same time" - that would be the Buzz Cat by the same designer and published in December 1989 Radio Modeller.
RFJ - 19/10/2019
Buzz Cat! That's it! Thanks RFJ. Sadly December '89 is not in my collection of old RMs and I suspect it was a paid for plan rather than a free inclusion anyway but perhaps someone has it and it will appear on Outerzone eventually. That's the great thing about this site - despite the huge amount of content already found there are so many great designs still to look forward to!
RMC - 20/10/2019
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This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.
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