Thrift (oz10342)

About this Plan

Thrift. Control line stunt model.

Quote: "Spanning just 48 inches and using a 0.19 - 25 cu in motor, this stunter offers maximum performance at minimum cost - cheap thrills in fact! Thrift, by Peter Miller.

The dictionary defines 'Thrift' as economy and as a flower; the model looks (to my eyes at least) beautiful, performs perfectly and is very economical, both in materials and fuel. To go into the design philosophy as our American friends call it, some time ago I compared the cost of one of my biplanes and a normal stunt model, and found that the cost differential was very marked. At about the same time the price of fuels had risen greatly so I began to think about a monoplane stunter that would give the performance of a .35 powered model at a reasonable price. A minimum reduction in size was called for to maintain the performance, so a Fox .25 was chosen as the power unit, as I knew that this motor was powerful enough to fly models intended for .29's while consuming far less fuel for its power.

The size of the model was set at 48 in span, with a wing area of 450 sq in, this was so that those of us who are unfortunate enough not to possess a .25 could use a .19 motor. I now started to think about using less wood in the construction; after all less wood means less weight and less money. All flying surfaces were built up from 1/4 in sheet strips of varying widths cut from sheet, but the biggest saving was made in the wing. I used the method of construction which has not been used in England very much, but was very popular in the States and is typified by Bill Werwage's Ares (oz4884) : cap strip ribs in which each rib is a 1/4 in wide curved strip on edge with the spar in the middle. This construction is light, cheap and surprisingly quick and easy to make while it also gives a perfectly smooth wing. The only disadvantage is that care must be taken when handling the wing as it is very easy to crack a rib or two.

It is almost impossible to save wood in the fuselage construction short of building it out of strip in the manner of a free flight job, but by using coloured tissue one saves money on paints and saves weight; one further economy was made by using 2 in diameter wheels as this size is available in the cheaper types. I have not done a real costing of the model but one saves roughly 25 per cent of the cost of an equivalent-sized, conventionally built model which in these days of rising prices, can't be bad!

Construction must start with the fuselage: cut out the 1/8 sheet sides and 1/16 ply doublers and glue these together, noting which is the port and starboard sides as they are different. The doublers must be accurately fitted to the side so that the spar holes are true, the trueness of the wing depends on this. Now cut out all the formers and bind or bolt the U/C to F-2 and glue this and F-1 to the bearers which are 3/8 in sq Ramin, which is far cheaper than the normal bearers and is just as strong; your local DIY shop should stock it. Next glue the sides to the bearer assembly, again making sure that it is really square. When dry, fit the remaining lower formers and glue the tail together..."

Thrift, Aeromodeller, August 1975.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction