More on the fuselage

Skipping ahead a bit, we are well into 2003 now. I have been too busy to take lots of photos but the following should give you some idea of progress. Completion of the fuselage has been the main job. My metalworking skills and general aircraft construction knowledge are improving all the time and it’s becoming much easier as I go. Completion of the fuselage will see an end to the metalwork, but there’s a lot more to do. More on that later.

After much effort in making the formers and a struggle to bend the skin around them, the turtledeck is ready for riveting. There are many parts to make and their assembly takes time. Taking photos was not a priority, sorry, so there’s only one photo. The aft fuselage is built like the harbour bridge. This is one strong little machine.

Construction of the forward fuselage starts by making a seemingly endless number of parts from angle material. Here they are ready for primer after alodyne treatment.

The two sides of the forward fuselage are made from .032 sheet material and all the parts just completed. Everything is A OK, precise to 0.5mm.

There is no jig. Just set it all up as well as you can and drill the holes. I spent far too long measuring and squaring up. In the end, as long as the layout of the bottom and side skins is square, it has to fit.

I could do most of the work on the fuselage by rolling it from side to side. Here I have clamped the splice plates to join the fore and aft longerons for drilling. Precision in making these parts really paid off here. Tight fit and not much room for error.

The main spars overlap in the centre and are housed within a tunnel box across the width of the fuselage. The tunnel skins are dimpled and angle material countersunk for flush rivets in this section.

Here is the spar box fitted into the fuselage. It is attached by four sturdy vertical angles either side (only one visible here). The lower skin and stainless steel firewall are fitted. The whole thing is becoming stronger and heavier and it’s quite an effort to flip it over by myself now.

There is an assembly beneath the seat that strengthens the area and provides support for the control column and elevator idler. I found it easier to make the entire thing on the bench and fit the completed assembly to the fuselage.

The elevator is connected by way of a steel pushrod tube. There is an idler to transfer the movement from under the seat to a higher level. Both tubes move fore and aft without significant vertical movement. There is a bit of work to drill and fit the sintered bronze bushings so everything moves freely but without any play. The same sorts of bushings are used throughout the control system

I had an early set of axles which had to be replaced but, rather than replace them, I had a new set welded up from a different design based on experience and tips from other builders. This gives me a more robust fitting in my opinion and a larger jacking point for the inevitable flat tyre.

The gear legs are solid rods of titanium which makes the undercarriage extremely simple. Drilling it is another matter. The bit heats up very fast and can grab in the work. I had to take it slowly, working up from 3/16 to 1/4, 2mm depth at a time, and cool with a fan between cuts. A few hours later I was done and only three more holes to do, and two more for the tailwheel rod!

Asuza drum brakes are specified so I used them. Here you can see the drum, backplate, actuating arm, cable and cable guide after fitting to the gear leg. Disc brakes would be better but would add complexity and expense. I like the simplicity of a handbrake. If the landing is long or fast I will have to go around rather than rely on the brakes. I always do that though, don’t you …

The workshop has become too small and I want to rig the whole machine inside, so out comes a partition wall. the Sonex is much more valuable than the wall at this stage. Soon comes the exciting part, assembling the whole machine and drilling the wings to the fuselage The next page in Lynn Jarvis’s Sonex project is the stage where it all comes together.

Lynn Jarvis’s Sonex project

| 1. Introduction | 2. Sonex specifications | 3. Building the Sonex |