Spitfire IX (oz15973)

About this Plan

Spitfire IX. Radio control scale model WWII fighter. Wingspan 64-1/4 in, for 10 cc engine.

Direct submission to Outerzone.

Update 19/4/2025: Added article, thanks to RFJ.

Quote: "Build this 64-1/4 in span beauty for full-house and .61 motors. Spitfire, by Brian Taylor.

HAVING always been a Spitfire fan it was only natural that when I first started radio modelling, seven years ago, my ambition was to fly a radio controlled 'Spit'. To me, as to many others, it, is the most beautiful aircraft ever built. The fact that it has been modelled many times before to some extent lessened the appeal, but the ambition always stayed with me and I knew that sooner or later it would have to be fulfilled.

During my early days of radio modelling, a plan of a Spitfire was loaned to me and, for an American scale plan, it was fairly good. It did, however, in my opinion, fall down on several important points. The tailplane was huge - I think about twice the scale area! The vertical tail surface was also greatly enlarged and the general construction would, I estimate, have given one a model weighing about 10 lbs. Also, a snag from the practical point of view was that there was no provision for counteracting tip-stalling. So I put it aside and when the time came for me to get the Spitfire out of my system, I decided to start from scratch and see what sort of a job I could make of it.

Regarding this question of tip-stalling, I would like to dwell here somewhat, as I feel that it may be of more interest than a long list of instructions on how to stick this to that.

Before even considering the Spitfire I had learnt that it is advisable, on tapered wings, to incorporate a means to counteract tip-stall. Now, I have never quite been able to follow the theory behind the progressive thickening of section towards the tip that the stunt boys use, and have, in fact, seen models with this feature show, on occasion, what to me looked awfully like tip-stall tendency. I therefore favour washout and have found this to be foolproof. Most tapered-wing full-size aircraft have a decrease in section thickness towards the tip and so I think wash-out (if the full-size did not have it) is a less noticeable deviation from scale than the other method.

The first tapered wing aircraft with no washout I built was a Hellcat - and it lived up to its name. It was after attempting to fly this model that I decided that two months building for 3 seconds flying, was not the way to set about scale modelling. Of course, at the time, I could not be 100 per cent sure that it was tip-stall and, had I been using an early set of proportional I would probably have put it down to radio trouble causing a roll just after takeoff. However, I was using my F&M reeds, which had been completely reliable over a period of 4 years and, having since built six tapered wing scale models, all incorporating washout, I am now sure that the Hellcat suffered from a violent tip-stall just after take-off, a slightly cross-wind patch contributing to this.

Many of us saw or heard of the troubles that Dave Platt had with his first Dauntless, and I seem to remember reading that for his second and more successful model, he built in washout. Of course I'm not saying that it is impossible to do without it, but it certainly makes life easier.

The first scale model I built with washout was a 56 in span Hurricane for six channel reeds. Not knowing how to determine the correct amount of 'twist' to put in the wing I decided on 3° and found that this was too much. The model flew all right and, of course, would not tip-stall when flying normally. But, when inverted, washout becomes wash-in, and so, as the speed dropped off at the top of a loop, the model would often neatly roll out, converting the intended loop into an Immelman turn, and one could never be sure which way it was going to roll!

On the next model, a 69 in span Tony for full-house, based on an American plan, I built 2° wash-out into the wing. This was just right with no hint of the trouble I had with the Hurricane. Therefore 2° is the amount I have used ever since, and this is built into the Spitfire.

Knowing little about aerodynamics theory, when I came to the Spitfire I didn't know whether an elliptical wing would be better or worse as regards tip-stall than a straight taper, but have since read an article by one of the Boffins stating that elliptical wings have violent tip-stall characteristics.

This Spitfire was not intended as a competition model and is obviously not perfect in every detail, but I make no apologies for this. It was built as a practical every weekend all-weather flying scale model, and this it certainly is, having had now well in excess of 200 flights. If one agrees with Norman Butcher's categorisation of scale models (RM Dec 1969) and I think most of us would, then this model has to be classed as 'near-scale', because the tail area is slightly enlarged. I pondered on this point for several days and, finally, knowing that the model was not intended for judges' eyes, decided to play safe. The amount of the enlargement is indicated on the plan (the scale outline being shown) and I'm sure that it is not sufficient to spoil or affect the look of the aircraft. In fact I think it would take a real expert to say categorically that the tail is enlarged, without referring to a scale plan. Having flown the Spitfire this way, I can say now that I feel sure it would be perfectly flyable on true scale tail area.

Although not intended for competition, it was flown at the Westland's Scale Air Day. Two reasons for this; firstly, of my current models it was the one I most enjoyed flying and secondly, at Westland's as much importance is given to putting on a show for the spectators as to the competition, so I felt it would be nice to have a Spitfire present, this being one of the few aircraft that the general public can recognise. (Actually, I heard a small boy refer to it as a Hurricane once, but I don't think it's that far from scale!)

Incidentally, the Mk IX was chosen because it has a slightly longer nose than the earlier marks, but still retains the characteristic Spitfire shape as RJ Mitchell designed it. The later marks, although still nice-looking, gradually altered the appearance of the Spitfire, until it was really an entirely different aircraft.

CONSTRUCTION: Wing: Build the wing first, because you can't get very far with the fuselage until you have. Take your time cutting out the ribs, making sure they are really accurate with the jigging tabs on the ribs, as shown. This will ensure that the correct amount of wash-out is automatically built in. Build the two outboard panels complete with top leading edge sheeting before removing from the board. Set up the two panels (the tabs on the inboard rib will ensure that they are both at the same angle of incidence, so to speak, relative to the centre section); then fill in the centre section between the two panels. Don't cheat and build the ailerons flat on the board, because they twist slightly too, so use the tabs..."

Supplementary file notes

Article.

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