Build your first flying scale model - Chapter 7 - Covering the fuselage

Even after a lifetime of building models, I somehow never really look forwards to the covering process. It still goes wrong for me sometimes, and I end up stripping a piece off to redo it. You can give yourself the best chance of a successful covering job by having as smooth an airframe as possible, with gussets strategically positioned in high risk wrinkle zones.

The type of tissue you use will also be important. Here is a selection from my stash:



The best you can get in my opinion is Esaki tissue (on the right of the picture), often called Japanese tissue. This is very light and has a smooth finish which seals well with just a thin coat of dope or Krylon. It is available in several colours and if you use the chalking technique (about which more later) this can be expanded to a much larger range of possible colours. I store my tissue rolled up in a cardboard tube. A good source for this tissue is Mike Woodhouse - his web site is www.freeflightsupplies.co.uk . Good value, high quality and post free if you buy a reasonable stock.

In the middle is a selection of SAMS “Super Lite” tissue, which comes in a huge range of colours. This would come under the rather broad description of “domestic tissue”. It is heavier than Esaki, but quite adequate for most models, where weight saving is not of ultimate importance. Click here for the relevant page on the SAMS Models web site. Easy Built Models sell something similar in the US - have a look here. You can also get lucky in card and gift wrap shops sometimes, picking up coloured tissue that can be used for models. Beware though that some may not be colour fast, and also may possess no wet strength (an important factor when you come to water-shrinking!) Hallmark produce some metallic tissue sheets that apparently work well for models.

On the left are some old sheets of a tissue which I used exclusively when I first started out – this was called Modelspan, and could be bought in both lightweight and heavyweight forms. It is a soft tissue, which is quite forgiving of double curves. Only drawback was that it has quite an open weave, so soaks up a fair amount of dope before you got a smooth non-porous surface.

Before commencing covering, we need to work out how we wish to finish the model. In this case I will be doing the all-blue scheme with silver trim and lettering. I see the following possibilities:

  • Cover the model with blue tissue, cut out lettering and trim from silver tissue and attach. If you cannot find silver tissue, spray some white tissue with silver paint (e.g. Design Master floral spray). Use glue stick to attach markings.

  • As above, but chalk the blue tissue with blue pastel chalk before you apply it to make it more opaque. Click here for an excellent tutorial on how to do this.

  • Paint the model overall blue after covering, then mask and spray all the silver markings.

  • Paint the model overall blue after covering and apply markings from cut-out pieces of silver decal sheet.

    I am going for the last mentioned method, as the markings are relatively large, and so fairly simple to cut out. You also avoid the risk of the masking tape pulling off the blue paint. Note that to get the decals to adhere properly, you will need a gloss finish on the model.

    The model will be covered with blue Esaki tissue to minimise the amount of paint needed later to provide a good coverage – it also shows up better on photographs, making it easier to see what is going on.

    One common question is which side of the tissue to put outwards - the rough or the shiny side? I do not think it really matters very much to be honest. I tend to cover rough side out (remember rough is only a relative term - perhaps matt would be a better description) because I think the paint keys slightly better than to the shiny side. For a doped coloured tissue finish, you may prefer to cover shiny side out.

    I am going to use the dope and thinners method to attach my tissue. Please do not think this is the only way to do it, it is just the method I am most comfortable with. A lot of people use glue sticks now, or thinned down PVA wood glue. I hope to add an appendix later detailing these alternative methods, but in the meantime, here is how I do it.





    The first step is to apply a generous coat of sanding sealer wherever you want the tissue to stick. So, the edges of the wings and tailplane, the fuselage longerons, all the sheeted areas, stringers and tailpost. Don’ forget the outermost wing ribs on the top, as we will be using two pieces of tissue on each wing uppersurfaces.

    Make sure you do this in a well ventilated area, as this stuff is really smelly. You may need to send the rest of the family out for the day......



    When it is dry, gently sand off any fuzz with a bit of wet and dry paper, or fine sandpaper.



    Now add a bead of full strength nitrate dope over the sanding sealer. Some people recommend two coats of sanding sealer plus dope, but it seems to stick fine for me with just the one.



    Let’s start with a fuselage side. If you place the tissue over the plan (or a copy of the plan if you do not want to damage it!) you can cut out a piece of tissue to fill the area between the two longerons. No need to get it exact – safer to leave excess all round. You should really use a brand new blade for cutting tissue, to avoid tears and rough edges.

    I need to bring up the subject of tissue grain at this point. Most tissue types (including Esaki) have a pronounced grain (similar to balsa), dictated by the distribution of fibres. Generally the tissue should be cut so that the grain runs along the longest dimension of the part you are going to cover. To determine the grain direction in a sheet, simply start a tear near a corner. The tear will run straight and true in the grain direction, but if you try to tear across the grain, you will get a ragged shape, and the tear will try to turn the corner to follow the grain direction. You will usually find the grain runs parallel to the longest side of the sheet of tissue.



    Position the tissue on the fuselage and using an old brush, apply a dab of dope thinners to the nose sheeting. You will have a few seconds before it sticks fast, so make sure the tissue lines up with the balsa frame.



    This close-up shows how I have cut a slit in the tissue to clear the wire undercarriage.



    Now work your way backwards down the fuselage, applying thinners as you go, smoothing the tissue outwards over the longerons.



    The slightly darker patches you can see on the tissue show where the thinners has been applied.



    If you get a crease, or it starts to go wrong, just lift it up and try again. If it has already grabbed and you want to reposition, apply more thinners which will soften the dope, and you can lift and reposition. It is normal for the tissue to look a bit loose at this stage – just make sure there are no major folds or creases.



    After the thinners have dried thoroughly (5 minutes at the most) you need to trim off the excess tissue. You can use a brand new scalpel blade as shown here, or sand off the edges with a small piece of wet and dry emery paper as shown below.



    The finer grit, the less risk of a ragged edge - 600 grit works fine. I usually use a combination of both techniques.



    After covering the other fuselage side, it is time to tackle the bottom. You can see that I did not try to match the shape at all at the back, but did cut the piece of tissue so it was a reasonable fit at the front. This was achieved by simple trial and error - cut, test fit, cut a bit more etc. You will also need to cut slits to clear the rear undercarriage wires. Once happy with the shape, start to apply this piece to the airframe from the rear, and attach it with thinners until you get to the cross piece where the nose stringers start.



    I thought there was a good chance that the lower stringer area could be covered with the same piece of tissue, without slitting it, if it was wetted first, so I had a go. If wrinkles did appear, then those sections could always be cut out later and replaced.

    Water was applied with a brush, then the tissue eased over the stringers and lower nose sheeting. It was smoothed out until it looked like this.



    Next, dope thinners were applied to the edges and all of the lower nose sheeting, through the damp tissue.



    Here is the same area after the tissue had dried out. Happily tight as a drum, and not a wrinkle in sight. The excess at the front was trimmed, then dampened again, smoothed around the front, and stuck to the nose former with more thinners.



    Here is the fuselage bottom after the edges behind the undercarriage had been trimmed (in this case using emery paper).



    The next stage is to work our way up the fuselage, adding strips of tissue between the stringers. Working up rather than down has the advantage of giving overlaps that face down, making the steps in the tissue less visible in normal viewing of the model.

    We are relying on the dope applied to the airframe to act as adhesive for the tissue, so we obviously have a bit of a problem on the top longeron, because this is now covered with tissue. Thus, before we add the next strip of tissue, we have to brush a bead of full strength nitrate dope along the longeron, on top of the tissue. If you get some dope on the tissue below the longeron, wipe it off quickly, as it can cause a wrinkle in the tissue as it dries and shrinks.



    A piece of tissue must now be cut which fits neatly on the bottom edge along the upper longeron. No need to worry too much about the top, as this will be trimmed afterwards. This photo shows my piece of tissue being test fitted. Getting the shape right is again just a case of trial and error. I find a steel rule helpful in trimming the tissue edges on a the cutting board with a scalpel blade.

    The tissue is attached with dope thinners, like the fuselage sides were, working from front to back.



    Behind the cockpit, I found I was able to use one piece of tissue to cover two bays - the triangular section, and the one above it, as shown here. Before adding this piece, it is of course necessary to apply the bead of dope over the tissue on the first stringer above the upper longeron.



    In front of the cockpit, you will need to add two separate strips of tissue to get up to the same height. This photo highlights the fact that when you overlap pieces of dark coloured tissue, you get an unsightly darker stripe. Using chalked tissue will reduce this effect considerably. If it bothers you, just try to keep the overlaps as small as possible (which means you have to be very exact in how you cut your tissue pieces). Because I will be painting the model, I can safely say it does not worry me at all.



    A small piece of tissue fills the gap to the centreline, leaving just one piece to go. The last piece is the only one that has to be trimmed accurately both sides. Remember to apply beads of dope either side before attaching using dope thinners.



    Behind the headrest, I found you could get away with one piece of tissue to fill the gap, spanning two bays.



    Here you see the final covered fuselage, awaiting water-shrinking using the high-tech apparatus illustrated. You can use any old household spray bottle, emptied of course and filled with water.



    Give it a good spray, and you will find the beads of water tend to sit on the surface without wetting it. Like this in fact.



    Wipe over the tissue with your finger to spread the water out and it will wet the surface properly, as shown here. Now just leave it to dry in its own time.

    It is quite possible to take a more sophisticated approach to water-shrinking than demonstrated here. For instance, if you get hold of an old perfume atomiser and fill it with water, this will allow you to coat your model with a fine layer of (delicately scented) water droplets. For a gentler shrink, you can spray the droplets into the air, then waft the model parts through the mist. This could be a good technique if you are building a more delicate model than this one.



    Here is the finished result, which thankfully shows no wrinkles.



    I was a bit worried about this area, with the undercarriage binding, but I seem to have got away with it.



    View of the rear decking, again showing everthing nice and smooth.

    The next step will be to cover the flying surfaces.



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