Acrobit (oz14621)

About this Plan

Acrobit. Radio control sport aerobatic model. Wingspan 33 in, for .15 engines.

Direct submission to Outerzone.

Update 15/6/2023: Added article, thanks to RFJ.

Quote: "Full Size Free Plan. A 33 in span, easy-to-build aerobat for .15 engines and three-channel R/C. Acrobit, by J Farey.

This little sports model is ideal for those who seek airborne excitement at a minimum cost in time, effort and expense! Acrobit will fly fast or slow, can handle any type of weather from flat calm to very windy, and uses a .15 size engine so it's not too noisy and economical on fuel. But, best of all, it costs very little to build. So if you want a small, nimble aerobat that looks just that bit different I offer you Acrobit.

She's not hard to fly (Ray, my test pilot, says she flies "real smooth") and even I can handle her so she must be OK! Convinced? Then let's get building

Fuselage: Construction couldn't really be much easier and the result is a model that's both simple and very strong. Build as accurately as you can but don't be tempted to beef it up, it just doesn't need it - as the late Brian Peckham once said, light is right! We'll start with the fuselage. Cut two identical sides from medium 3/32 balsa sheet, taking care to make certain that the cut-outs in both for the wing are accurately positioned. Next fit the 1/32 ply doublers to the sides (arrows on the plan show the outline of these) and the 1/4 in square strips that run the full length of the fuselage from F1 back to the tail, chamfering a little as required. While that lot's drying, cut out the formers from 1/8- balsa or ply as indicated on the plan.

Now take the right-hand fuselage side and lay it flat on the building board. Glue formers F2 and F3 in place ensuring that they are at 90 degrees to the fuselage side and, when dry, glue the left-hand side in place. Make sure that everything is in line and pull in the sides at the tail adding former F4. Now add the 1/4 in ply former F1 epoxying it in place together with the 3/8 triangular braces behind it. Cut the 1/4 in ply engine mounting plate to suit your chosen power unit (the prototype has an OS 15) and epoxy in place, noting the required down- and side-thrust specified on the plan.

On a detail point, note the curve of the fuselage underside, especially at the rear end. Do please keep to this shape - it seems to assist the airflow around the rudder. Check again that all is nice and square (no banana fuselages, thank you!) and turn you attention to the flying surfaces.

Wing This is a standard white foam type covered with 1/32 obechi. It is dead easy to make yourself if you have a hot wire foam cutter, or could be made for you by any one of the numerous firms who produce foam wings commercially and advertise in the model press. The plan shows root and tip rib dimensions and these are all you need to plot the simple symmetrical section, constant-taper wing halves..."

Supplementary file notes

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