Skip to content

49. Bits & Pieces

09/03/2013

In the interim before our next assault on the fuselage, there have been a few bits and pieces to catch up on.

Fuselage fittings

Those fittings – the ones where the wings attach to the fuselage – have required some final fettling, including remaking by Rick of a couple of parts that seem to be the wrong size, and manufacture of some more washers for brazing onto the fittings, owing to the fact that I’d miscalculated when we had them waterjet cut. There’s a total of 244 of the little beggars in 8 different sizes, all brazed onto the fittings to thicken things up a bit where the rigging wires attach. Anyway, they are finally ready for welding, and Alan will be onto that sometime today.

Tailskid

I’ve also had a go at fastening the metal fittings to the tailskid with copper nails. This was technology borrowed from traditional boat building, and consists of a copper nail driven through the joint with a conical washer (called a rove) popped on the other end. You use a drift with a hole in the middle to flatten the rove onto the nail, then trim the end of the nail and peen the end flat. You get the idea here. Originally the front and rear halves of the fuselage longerons were joined with copper nails, but now we have glues which are far superior, so this is probably the only place they’ll be used.

We bought the nails from Jackson Marine who specialise in traditional boatbuilding materials. The process is very simple; the most complex part is getting the right size of hole, since the copper nails are very soft, and you can’t just hammer them through wood as you wood with conventional nails. Otherwise they are very straightforward to fit, and the end result looks suitably authentic.

Tailpost assembly

Tailskid assembly with the rudder hinges reamed and fitting nicely, and the tailskid rivetted to the fulcrum fitting.

 

Close up of the rivets in the tailskid fulcrum.

Tanks

We are also starting to look at construction of the fuel tanks. The Scout B had the petrol tank on top of the fuselage close behind the engine, with the oil tank behind the pilot. They quickly found that when the aircraft was on the ground, the slope of the fuselage meant that there wasn’t enough head to get the oil up to the engine, and so it was moved just in front of the instrument panel, and the space behind the pilot became a cupboard.

In fact, later drawings show an enormous variety of different arrangements of petrol and oil tanks, and I’m not sure how many were actually built. Anyway, we have the correct drawing for the oil tank, which is built out of brass sheet, about 0.5mm thick.

Oil tank

It’s mounted on top of the fuselage longerons, so it has a flat bottom, and a curved top to match the outer shape of the fuselage. Parts are joined by riveting, and so the most complicated bits are the ends, which are roughly the shape of a segment of orange, and have to be slightly dished, with a flange all round. You can get the general idea from this picture.

The oil tank made of brass, with about 300 rivets holding it together!

The oil tank made of brass, with about 300 rivets holding it together!

In order to make the ends, we think we’re going to use a basic ‘hydroforming’ method. There’s a good video of the method here. Once the pieces are made, they all need to be riveted. So far, we’ve just used ‘pop’ rivets which are dead easy. These will need to be solid rivets, but they too are available, as is a setting tool like this.

Typical hand rivet setting tool

Typical hand rivet setting tool

We also need to find a filler cap, but that’s straightforward enough from vintage car specialists, and the outlet which is cone-shaped. That will take a bit of thinking about since it too will need to be flanged so that it can be riveted to the tank bottom, but is not impossible.

Petrol tank

The petrol tank is bigger and made from tinplate. We don’t have the original drawing, but we reckon that the later one is pretty accurate, apart from the fact that it’s made out of three different thicknesses, whereas the parts list only shows a single thickness, so that’s what we’ll use. There’s an arrangement drawing which appears to show simpler internal baffle plates, so we reckon we’ll go down that route too.

The underside of the petrol tank. The two channels are for fixing it to the fuselage longerons, and you can see the horizontal lines of rivet heads that mark where the internal baffle plates are. It's sat on the front end for the picture, which as you can see is wider than the back, and you can see the cone for the petrol outlet that will have to be made up.

The underside of the petrol tank. The two channels are for fixing it to the fuselage longerons, and you can see the horizontal lines of rivet heads that mark where the internal baffle plates are. It’s sat on the front end for the picture, which as you can see is wider than the back, and you can see the cone for the petrol outlet that will have to be made up.

Whichever drawing we use, it’s more complicated than the oil tank because the front is wider than the back, because the back slopes to match the cabane struts, and because there are internal baffles to stiffen it up and to try to stop the petrol slopping about too much. It’s going to be a considerable test of our metalbashing skills, and – as you can see from the picture – we’re going to be very expert at setting rivets by the time we’re done – there are over 500 to be done…

We’d looked at buying tinplate, but have decided that we’re going to be better off using ordinary steel sheet, making the parts, and getting them tinned afterwards.

Finally, once the riveting is done, both tanks will need to have solder applied to the joints to seal them.

Advertisements

From → Building, Technical

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: