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155. Getting Settled In

01/04/2015

Work continues on The Tank. As I’ve said before, it’s one of the most complex items to fit – it has to be made to match the rest of the airframe at the bottom, front and back, and the top is on show, so there’s no hiding place!

Ian Harris delivered the virtually complete tank, complete with filter and filler cap.

Ian Harris delivered the virtually complete tank, complete with filter and filler cap.

Yesterday I got both fuel taps piped up and the handle linkages connected to the cockpit. All of that was very straightforward, since most of it had been done already.

Today I had a bout of panic about the mountings. The tank has two channels at the bottom which are made of very thin steel. They are so thin we are convinced they will fracture from fatigue almost immediately, so I spent much of the morning dreaming up alternative ways of securing them to the fuselage. Then Rick came to give a hand and immediately spotted that this job would be done more than adequately by the side shields which are attached to the tank and also to the airframe!

Today we’ve mostly been working on the fit between the tank and the ply cover behind it. It’s a question of taking very, very careful measurements, and trimming back the ply very slowly, on the basis that it’s a lot easier to remove ply than to put it back afterwards! As usual with all the really tricky stuff, it’s Rick we rely on, and we do look as if we are making solid progress on that front. We hope to have it sorted tomorrow, so that we can move on to the front of the tank, where another problem has raised its head.

Fitting the ply cover to the tank. It's a tricky job, so we leave it to Rick

Fitting the ply cover to the tank. It’s a tricky job, so we leave it to Rick

The difficulty is that the plywood engine former (the more or less circular bit just behind the engine) was made from a drawing from a later model of Scout, and we hadn’t appreciated that it was made to fit a later model of cowling. The net result is that it’s about 5mm big all round, and reducing it in size in situ isn’t very straightforward. On the other hand, it does give us the opportunity to adjust it so that the cowling will match the exact shape of the tank which is pretty important visually.

But as I say, that’s a job for tomorrow. Sufficient unto the day…

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5 Comments
  1. Could your puzzlingly doubled tank back edge be related to your need for substantial structure to support the tank?

  2. I don’t think so. We’ve been puzzling over this whole business today and the drawing shows the plywood hoop at the back of the tank being a sliding fit with a strip of felt to seal the gap. There’s no question it makes a really nice flange without a sharp edge on it, and I’m beginning to think it was there because the makers knew how easy it was to form, and how much nicer it would be.

  3. I wonder. Felt can be an engineering material, even today and if the drawing shows flange resting on felt resting on ply hoop then in my utter ignorance of 1914 aviation technology I wonder if that is a bit more than just a gap seal. I have something in my mind about felt for anti vibration and abrasion protection, but I can’t work out where its come from. But you guys are far deeper students of this than I am, but I figure sometimes ignorant suggestions can lead to interesting insights just by considering why they are so wrong… Not often of course!

  4. The felt is under the edge of the tank, so it would only react downward loads, and the rubber between the underside of the tank and the longerons would undoubtedly do 99% of the work. We have got it sitting quite nicely on the rubber pads now, and have turned our attention to the forward loads, which will be reacted nicely by the front flange on the ply former in front. The two each side bolts through the longerons should restrain it in the upward direction, but we’ll leave them as loose as possible to limit the possibility of fatigue failure. We hope!

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