Match-drilling Elevator Stiffeners

Mon 3rd Dec 2hr 30min

Match-drilled stiffeners to left Elevator skin

With the experience of the right elevator, this was no problem. There are two wrinkles: Firstly, all but one of the stiffeners are left-handed (the flange with the holes is to the left of the vertical web when looking forward). This means that when you install them in the top skin, the reverse is true and the flange extends across the skin to the right of the the vertical web. The end effect is that the webs of the top and bottom stiffeners do not interfere with each other because they are separated by the width of the flanges. Secondly, the only exception to this rule is E-908 - R which closes off the edge of the elevator in the recess where it abutts the trim tab. In this case the two webs will lie cheek by cheek with two pop-rivets through the two of them.

The second issue is simpler still. It is that the 5 long E908-L stiffeners go in the full width section of the elevator and the shorter E-909 stiffeners go in the narrower section forward of the trim tab.

The E-616PP trim cover plate is itself a stiffener and is match-drilled in place at this stage also.

Elevation

Sunday 25th Nov 7 hrs 45 min

Cut and edge-prepped 16 E908 stiffeners for the right Elevator. Match drilled stiffeners to E901-R skin. Dimpled Stiffeners.

Building the elevators, particularly the right elevator, is like a lot like building the rudder. Much of the time today was spent marking out and cutting the stiffeners and then preparing the edges after match-drilling. This time I didn't have to worry about the length of the stiffeners as they are all the same.

The main difference is that the skin is pre-bent so that it wants to stay closed. This makes it quite awkward to gain access to the inside, particularly if you are working alone. I am quite sure that Dorothy (my wife) would be happy to help out if asked but she was away visiting her mother as she does on most Sundays and in any case, I don't want to call on help too often so that I have lots of 'credit' left for the times when I can't do without a second pair of hands.

So I rigged the set-up you see pictured here (actually this is the left elevator). I used the wooden cradle from the horizontal stabilisers, clamped one trailing edge to the bench and placed one of my lengths of teak seating rail running between the two cradle blocks. The spring tension in the skin kept the length of teak fairly securely in place. I was working on my sacrificial slab of chipboard again as I needed to drill into the surface. The piece of scrap timber you see under the drill is placed so that the far edge just overlaps the trailing edge where it is 'indented' to allow space for the trim tab. It is screwed down into the chipboard to hold that section of the trailing edge firmly.

The tension in the skin is such that it bends up between the clamped trailing edge and the leading edge so it was important to work systematically from the trailing edge forwards and from left to right ensuring that the stiffeners hold the skin perfectly flat.

I kept the blue vinyl in place for this operation as there is a lot of potential for scratches from the stiffners whose edges have still not been polished.

Dimling the stiffeners was done with the pneumatic squeezer.