Build your first flying scale Jet - Chapter 3 - Blocks and sheeting

The trickiest part of the whole build is probably the hollow nose and tail sections, but if you work carefully and do things in the right order, it should be possible for anyone to make a neat job of it. It would be perfectly possible to avoid a lot of the work by just using sold blocks, sanded to shape on the outside, but the hollow parts looks so much better. A hollow nose also gives you somewhere handy to hide your noseweight!

So, the first stage is to roughly cut out the laminations from the 1/8” balsa, leaving plenty of wood spare around the outside. You will note that I used 2 laminations of 5 mm balsa instead of 3 laminations of 1/8”, for the simple reason that I found I had completely run out of 1/8” balsa! The cutting out would have been easier using the thinner balsa, so I was a tad cross with myself.

Next carefully cut out the inside shape of each lamination, but leave at least a 1/16” gap to the printed line. Work slowly with a sharp blade until the middle falls out. The top two pieces show this stage.

Now you can trim the inside shape back to the line a little at a time. The lower two pieces have been trimmed like this. There is not much danger of the balsa splitting because of the excess balsa around the outside.

When you have a set of three trimmed parts, they can be laminated together using aliphatic wood glue. Note the parts are stacked so the grain direction alternates between layers (two in my case, three in yours). Try to line up the inside apertures as well as possible, but don’t worry if there are steps. Place a weight on top of the laminated stack until the glue is dry.

The next stage is to smooth the inside opening using some emery paper wrapped round a piece of dowel (or in this case a pen). Make sure you do not make the aperture too big, or you could find things getting too thin when you shape the outside later.

Once you are happy with the inside, the outside shape can be trimmed and sanded to match the printed outline.

The two laminated blocks can now be glued to the front and rear formers of the fuselage.

When dry, the final shaping of the outside can begin. I did this entirely with emery boards, though if you are careful, you can do some rough carving first with a sharp knife. Take your time, and be especially careful as the lips become thinner and thinner. You should be aiming for the blocks to blend back seamlessly into the fuselage contours – check against the plan drawings as well.

The tail block in particular got very thin on mine. If bits of balsa start dropping out, stop!

To reinforce the thin edges after sanding, I wicked in thin cyano, which soaked into the grain, and effectively made a local area of balsa reinforced plastic composite. This is especially useful at the front, where the lip would be very vulnerable in a crash.

The next stage of construction is rather time consuming, though in my opinion very satisfying. We have a lot of pieces of soft 1/16” balsa to insert between the stringers. I covered the process in some detail in the Comper Swift article here, so will not be going into it in too much depth here. You do not have to fill in all the panels shown on the plan if you don’t want to, only the wing mounts are essential, but I think the improvement in appearance is worth the effort.

Here the first bay has been completely filled, and a start made on the next one. Note how the pieces are fitted slightly proud of the stringers, to allow for the curvature of the fuselage when they are sanded flush. Remember that the model will need noseweight anyway, so there is no weight penalty for this infilling at the front.

The Second bay now completed

Wing root pieces have been cut out from the sheets and inserted into the fuselage.

Infilling along the upper fuselage where the spine and cockpit will fit.

Final pieces in the area where the parachute housing will attach.

Sanding the filled areas to blend in with the stringers is a very satisfying job, though not to be rushed. Be especially careful at the extremities of the sheeted areas, that you do not dig into adjacent stringers with your emery board. Here is the final, smooth and streamlined fuselage.

Note extra shaping of the pieces that form the end of the trough.

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