A new tutorial on the technique I use to finish a wooden fuselage. This step occurs after construction and before painting. I will illustrate it here from the fuselage of my Potez 58. This one is covered with 0.6 and 0.4 mm aircraft plywood. To add to the difficulty, you need access to the so-called “technical” areas (servos, batteries, controls etc…) and so there are 3 hatches under the fuselage that should be as little visible as possible, since we have a scale model here.
You will find below the whole procedure step by step. If you prefer, you can download a PDF version of this technique.
Applying the putty
A fuselage when covered with wood (balsa and plywood) will be made of smooth or jointed planks. The first step will be to use a putty to seal and plug all these joints. Personally, I use Hobbico’s filler. It’s a light product that can be sanded easily after drying.
To apply it, I use a plastic card, like a credit card, to fill in the holes and junctions while smoothing roughly to remove the excess putty. You can see on the pictures below, the putty on the front of the fuselage after application and before sanding.
The next step is sanding. Nothing complicated, it can be sanded very easily with sandpaper of different grains. OUTSIDE the sanding so as not to irritate Mrs …. It must not rain.
As Pascal would say on his site “lecoinmaquette” that I highly recommend (see links), you have to look with your fingers. That is to say that you have to touch and touch the holes, the junctions and if you still feel differences in level, edges, then you have to apply a new coat, sand again until everything looks the same to the touch. Here is the result on the fuselage of the Potez 58.
Covering the fuselage
The marouflage will consist in wrapping the object and thus completely covering the parts of the aircraft that will have to be painted with a coating (in this case a light fiberglass in the case of Potez 58).
To begin with, the fuselage must be dusted. This is important for good adhesion. Personally, I use a cloth and I wash with water and let it dry.
I use the technique developed and tested by Pascal (Allalou) on his website lecoinmaquette (see links).
In this case, I will use 25g fiberglass glued twith nitrocellulose dope. You have to work outside, because it’s going to sniff strong and it’s not great to breathe it. I start by applying a layer of nitrocellulose coating.
You need gloves, a brush, acetone, and a glass container (like a glass yoghurt pot) to put the necessary amount in the container. Avoid dipping the brush directly into the pot of dope, because doing so will dirty the clean cellulose dope. This is why it is better to use a glass container. Also, prepare another glass container to put acetone in it to rinse your brushes. Don’t forget to have a suitable outfit, cloths and if you can’t work outside, it is essential to have a gas mask, like those used by car painters.
Everything is ready outside, you can see on the next picture, the gloves, the brush, the glass jars, the fuselage and of course the coating.
A coat of cellulose dope is brushed on the entire fuselage and the technical hatches below. It is left to dry. It is very fast (less than 30 minutes).
Once dry, lightly sand to remove all the wood fibers that can be felt on the surface. We cut the fiber coupons that will be placed on the fuselage. Be careful, the fiber is very fragile, so I used masking tape to put it on the cut area to prevent the fibers from being removed.
The cellulose dope is applied starting from the center. Don’t forget to cut the place for control cables.
The advantage of the cellulose dope is its fast drying capacity. After 30 minutes, excess fiber can be removed. To do this, a sanding block is used on the edges. It is fast and effective.
A light sanding is carried out. As Allalou would say, one looks with the fingers to remove imperfections not visible to the eye.
Afterwards, I applied a coat of G4 varnish to fill all the pores.
In total, this step has increased the weight of the fuselage by 32 g, which is still reasonable.
The fuselage is now ready for the painting work which will be the subject of a future tutorial.
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What is G4 varnish?
The G4 varnish is a single-component polyurethane resin protection particularly used in the nautical environment. This primer varnish forms a protective layer against moisture infiltration.