Skip to content

52. Concentration

01/04/2013

The plan this week is to complete the assembly of the main fuselage frame. Yes, I know it looked pretty nearly there last time, but you’d be amazed (or bored to tears, depending on your interest in this sort of thing) to know just how much time it takes to drill a hole in exactly the right place, for example.

And the first couple of days this week have involved the most important holes in the entire aircraft. If anyone comes to any one of us in years to come and mentions CB or DB, expect to see our faces take on an unnatural pallor, and be prepared for a long explanation.

CB and DB are the locations of the fittings where the lower wings attach to the fuselage. Immediately you can see that they are therefore pretty important. They also the point at which the flying wires attach to the fuselage, which makes them very highly stressed, and in the case of CB, it’s where the undercarriage legs are attached, so they take all the landing loads as well!

So. We have supercritical fittings that need to be bolted extremely accurately to two vertical members, a horizontal crossmember, a longeron, a matching internal bracket, and the fitting at the end of the wing which has to fit absolutely exactly, both for angle and distance from the other one. Oh – and the two horizontal crossmembers need to be exactly aligned because they are connected by the flying control mechanism. Various bits of it need to be riveted, other bits need to be welded, and some parts are brazed. Finally, because the bottom longerons are curved, there are no right angles anywhere. No pressure then…

This is the CB fitting. You can see the socket underneath for the undercarriage leg, the lug at the top sticking out at an angle for the main flying wires, and the holes for the internal bracing wires. You can see the curved longeron that makes the measurements so difficult, and the two vertical timbers that it has to be so carefully aligned with. And the parts sticking out horizontally have to fir the ends of the wing spars absolutely exactly...

This is the CB fitting. You can see the socket underneath for the undercarriage leg, the lug at the top sticking out at an angle for the main flying wires, and the holes for the internal bracing wires. You can see the curved longeron that makes the measurements so difficult, and the two vertical timbers that it has to be so carefully aligned with. And the parts sticking out horizontally have to fir the ends of the wing spars absolutely exactly…

As always, we leave all the tricky bits to Rick, and as always, Rick comes up trumps. We’d done preliminary measurements on our last visit, and he took them away and got the welding done by Alan Hazeldine and the brazing with the help of Peter Crownshaw, and by the Sunday afternoon, we had checked, double checked, triple checked, gone for a cup of tea to cool down, built a jig to assist with the drilling, and actually got the holes drilled. Result.

Meanwhile, I spent time on loads of little aluminium corner brackets on the rear fuselage. They are unbelievably simple, and unbelievably time-consuming and difficult to get really accurate. Thankfully, they are mostly needed to hold the thing together while you assemble the aircraft, and don’t do much work in flight.

Theo? Well, if you’ve been reading earlier episodes of this blog, you won’t be surprised to learn that Theo got on with yet more splicing, though he is finally getting to the end of this mammoth task, and will be completely fazed when we need him to do anything else.

Advertisements

From → Building, Technical

Leave a Comment

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: