Coachman (oz14560)

About this Plan

Coachman. Radio control sport trainer model. Wingspan 53 in, wing area 490 sq in, for .20 to .30 engines.

Quote: "Although my preference is for the larger training model in the 75-85 inch bracket, I still believe that the smaller model, as long as it is not too heavy or too fast and has the correct airfoil section, has a place in the scheme of things.

Cost will be the deciding factor for a first model I suspect, and it may be cheaper to build from a plan than to buy a kit, especially if the plan is free!

If you are a beginner it would be advisable to get someone with modelling experience to help with the building. My advice would be to join the local model club and buy all of your material from the same shop so that they get to know you. Tell them that you are new to the hobby and ask them for advice on building, if and when you require it - but choose a time when the shop will not be crowded!

I had been flying my 'Royal Coachman' for a few months when it was accepted by our Editor for publication as a plan feature. He later suggested that, should I ever design a smaller version suitable as a free pull-out plan, he might be interested. Being a failed stockmarket investor of many years standing and in need of yet more gambling money before the market collapsed again, I went to work immediately.

Royal Coachman was reduced to 70% and 'Coachman,' presented here, was the result which I hope will give you many hours of enjoyable flying.

I don't like a training model which dashes around the sky like a demented bee with its stinger on fire frightening other flyers and the trainee alike. I much prefer something a bit more gentle and sedate. To this end, I designed in plenty of drag in the form of a thickish wing section and a fuselage which is a little wider than normal for a model of this size. In order to slow it down even further, the ailerons may be drooped to the position provided by template 'A' (see plan). When you have progressed to flying solo and wish to do some aerobatics, the ailerons are repositioned to the angle provided by template 'B'.

For those building the three channel version, the ailerons are permanently glued in place using template 'A' to get the angle correct.

Horse power: My first model used an OS.30 engine of pre-Schneurle design, circa 1977, but almost unused. In order to check out the performance using a modern economy engine I later fitted an MDS.25 which has performed very well. Engines in the .20 to .30 range will suit, with a .25 being ideal for training. Using this engine the flying qualities are nice and gentle on half power and at full chat, most of the basic aerobatics are possible. Fitting a .30 engine turns the plane into a hot potato! A .25 four stroke would be great too!

Shotgun or glue-gun: The fuselage sides are cut from medium weight 3/32 sheet balsa suitably joined to obtain the required size. 1/32 ply doublers are then contact-glued to the front and tail end inside faces, ensuring that you make one left and one right side. Next, glue on the 3/16 sq longerons and vertical spacers together with the servo rail chassis and the 1/2 sq beech wood undercarriage blocks, using epoxy glue. Positions for the formers and vertical spacers may be accurately marked on each fuselage side by laying them carefully on the plan, inside face up. Using the double indicators marked on the plan (outside the fuselage outline) as guides, draw the positions on the fuselage sides.

When making the formers, mark a vertical centre line on the forward face of F2 and the rear face of F3. Using epoxy glue, fix formers F2 and F3 onto the inside of one fuselage side using a set square to keep them perpendicular. When the formers are glued in, keep the side flat on your building board and glue the other side to it. Stand the set square on the board, just touching the first fuselage side at the tailplane seat. Now align the other side so that its tailplane seat just touches the square. This will give you a nice true fuselage, as long as the formers have been made square!

Epoxy the ply undercarriage plate to the beech blocks. Using aliphatic glue, secure the bottom sheeting between F1 and F3. Draw a straight line on your building board 40 in long and set the fuselage upright so that the centre lines previously marked on F1 and F3 are aligned with it. Secure the structure with whatever means you have. Pull the tail end sides together with a suitable spacer in between and set the spacer's centre line over that marked on your board. Carefully fit the 3/16 balsa spacers along the top without moving the fuselage..."

Coachman, RCM&E, November 1996.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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