Saturday, December 11, 2010

It all hinges on.... hinges.

It's hard to say which of the flight controls is the most critical, but a strong contender in any debate on the topic would have quite a crowd lined up in support of the ailerons. While the RV-12 doesn't officially have ailerons, the hybrid aileron/flap surfaces (known as flaperons) that it does have would carry the same weight of argument. As with any of the movable surfaces, the flaperons would be useless if they were unable to perform the critical function of, well, moving. To that end, at some point I was going to have to construct the hinge braces that will provide the pivot point for that movement. That point was today.

With surprisingly mild temperatures in the low 40's accompanied by low-ish clouds and generally unattractive flying weather, I thought it would be a good day to spend some time in the hangar. We have a cataclysmic forecast for tonight, too, so that was added impetus to get some work done in relative comfort.

First step: make sure we all agree on which holes should be countersunk. This looked to be another double flush operation since the countersinking was done on both sides of the parts.

The "ham in the sandwich" is a thick piece of aluminum that supports the bearing that will be the hinge point. It's a tight fit, so Van's suggests using a 7/16" socket on one side and a 9/16" socket on the other to force the bearing into the hole.

Once it's in there, it ain't coming back out.

I've seen people have a lot of problems building up these sandwiched hinge braces. They get unsightly gaps between the side pieces after they squeeze the rivets in. The plans suggest finding a way to hold the ends together while riveting. I just stuck the ends back into the vise.

They also mis-use the word "random" again in their effort to instruct the builder to spread out the order in which the rivets are squeezed. Between that and the vise, it all turned out just fine.

The hinge braces get set aside while the rear stub spars get prepared to host them. A pair of doublers that I've taken to calling "the tuning forks" are retrieved from the parts shelf.

3.2 miles of the obnoxious blue plastic is stripped from the spars.

Starting at the easy end, a flange strip is clecoed in at the wing tip.

The a hinge brace is clecoed in at the end of the spars.

I was getting pretty cold, having over-estimated the ambient temperature that I would find at the hangar and failing to dress suitably. Rather than proceed with the riveting required to finish up the page (and section 14, for that matter) while distracted by being cold, I decided I'd call it a day.

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