Build your first flying scale model - Chapter 10 - Assembly and painting

I usually like to assemble my models before painting, unless this would make the masking difficult. With this colour scheme there is no masking, so assembling first was the obvious route, avoiding the possibility of getting glue on the paint later on.



The Wing was first glued to the fuselage, checking that the leading edge is positioned as shown on the side view on the plan. I used balsa cement to attach the centre wing ribs to the upper keel. Some time should be spent making sure it is square to the fuselage when viewed from above. I found that the result was not particulary stiff, and you could still rock the wing slightly when viewed from the front, even after the glue was dry. The wing struts will stabilise things, but I found I also needed to insert a small balsa packing piece as shown here to get the wing dihedral looking symmetrical when viewed from the front.



Next, the tailplane was glued into position, making sure it was square to the fuselage, and that it looked correct relative to the wing when viewed from the front and rear. Before attaching the fin, I pricked a series of holes along the centreline of the tailplane with a pin. I do this to try and encourage some wood to wood contact when the glue is applied (balsa cement again). The glue should hopefully travel at least a little down the holes, and provide a key. Otherwise, all you have attached the fin to is the tissue. If using balsa cement, the base of the fin (which is end grain) needs to be pre-sealed with a thin coat of cement before the final joint is made.

You can also see here how I cut a little notch in the rear of the tailplane so the fin would sit snugly up to the tailpost.



Check all your rigging angles again viewing from the back



and the front. This photo shows how the down and right thrust I added has moved the nose botton away from the centre of the nose plug. This is quite normal, and nothing to be worried about.



Here is the finished airframe ready for painting.



I have often read that painting a free flight model will add a lot of weight and significantly degrade its flying performance. Thus I decided to do an experiment with this model to see just how much weight is added by an airbrushed coat of blue paint. The weight before of what you see here (to the nearest 0.5 gram) was 15.5 grams. This does not include the wheels, struts, prop etc.

So, what expensive top end equipment do I use to get my airbrushed finishes?



Here it is in all its glory. Go on, admit you are impressed. The diaphram compressor is about 20 years old, and was quite expensive at the time. A great investment though. There are plenty of reasonably priced compressors on the market now specifically aimed at airbrush users, so you should have no problem finding one to suit your budget.

There are, of course, alternative ways of powering your airbrush. The most expensive in the long term are the tins of compressed air you can buy at hobby shops. Other alternatives, if you have the room, are a tyre adaptor, or a large industrial compressed gas cylinder with a suitable regulator. I cannot give you much in the way of advice about the latter two possibilities, other than to say that with the tyre adaptor, the bigger the tyre you have it connected to, the more constant will be your air pressure, and the less often you will have to re-inflate it.



Here is my "well used" Badger 350 single action, external mix airbrush. It is over 7 years old, and I have been expecting it to pack up for the last two years, or at least have to buy it some new components. Anyway, it just keeps on working - probably mainly due the the simplicity of the design. It has the medium nozzle fitted, and it does everything I need. OK, it is not capable of the fine work you can do with an expensive double action airbrush, but I am happy to live with extra masking, if and when it is needed. A new Badger 350 currently costs about 35 in the UK, so is unlikely to break the bank.



My finish of choice is Humbrol enamel paint thinned with dope thinners. For the Swift, I mixed my own blue shade, which I have to say is not generally a good idea if you think about having to do repairs several years down the line. However, Humbrol Midnight blue is extremely dark - probably too dark for this model, so I added some French blue to lighten it a bit. This photo shows the neat paint poured into the glass airbrush jar.



The quantity of dope thinners you add is important. Here you can see the jar with the dope thinners added. I know I should really, but in practice I never measure quantities exactly. As a general rule I would estimate a ratio of somewhere around 4 parts paint to 3 parts thinners.

Although adding cellulose thinners to Enamel paint is not something Humbrol mention anywhere in their literature, you will find they mix very well. I think the dope thinner helps the paint to adhere better to the doped tissue surfaces, and the paint dries much quicker. I also think you get a smoother finish than when using enamel thinners.



Here is the first paint hitting the model. You cannot see if I am wearing a mask, which is probably just as well. At least I have some extraction from the booth in the corner, and a window wide open. You lot out there should definitely be wearing masks though!

You will soon find out if you got the thinners to paint ratio correct or not. Too little thinners and you will have trouble persuading the paint to come out of the airbrush. Plus, you may get severe orange peel, or little lumps of paint splattering on the model.

Too much thinners and you will find the paint has little covering power, and you may see little pinholes appearing - almost as if tiny spots of grease were on the model, and the paint was running away from them. Trying to cover them over with more paint (without adjusting the mix) will just make things worse, and the pin holes will become little craters.



Build up the paint layers gradually until you get the paint density you want. On this model, using the blue tissue has given a good base for the blue paint, and so reduces the amount needed to make the surface reasonably opaque.





Knowing when to stop can be tricky - the temptation is to keep on piling the paint on. This picture clearly shows the difference between the painted right wing and unpainted left one. I managed to stop myself before caking on too much paint. I still used about 2/3 of the jar though.



Here is the model fresh from the paint shop. The gloss finish may not be to everone's taste, as it does highlight all the lumps and bumps. It will however make the decals easier to apply than if a matt or satin finish had been used. There is always the opportunity to spray on a satin or matt varnish coat afterwards though if you really cannot live with it.

These last two photographs make the blue look lighter than it really is - my digital camera seems to have a problem with dark blue for some reason.



I weighed the painted fuselage, and guess what - the paint had only added 0.5 grams to the total. It now weighed just 16 grams. I have to confess I was rather surprised (and pleased) how little it had gone up.



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