7.7.3 Main Gear Doors

This entry is part 32 of 39 in the series 07 - Landing Gear

The main gear doors are supported at the bottom by a piece of 1/8″ aluminum that gets cut so that it has four “fingers”. The aluminum supplied with the kit wasn’t as big as I would have liked, so I bought a larger piece and cut it to the correct shape. Then it has to be bent to conform with the inside of the door. This is a bit of a trick since you can’t really see very well where to bend and it’s a somewhat complex bend. Lots of trial and error. And it’s almost impossible to get it in the exact position. If the aluminum isn’t perfectly flat against the door, once you tighten down on a screw, it will deform the door and it won’t align.

Malcolm give me a bit of advice: Once it’s as close as you can get it, cover the plate with duct tape, apply a glob of epoxy/cab-o-sil and then lay the door down. Once it cures, you have a small “pad” that conforms perfectly to the support plate.Then a quick cleanup of the pads and you’re all set.

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Then holes are drilled through the door and the plate.

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Next, Nutplates are mounted.

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I don’t have a jig that determines the location of the holes for the nutplate, so I temporarily mount it and use it as the drill guide.

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Here’s another view:     

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That takes care of where the door attaches at the bottom. The factory says to attach the top of the door after the bend. Here’s the diagram from the manual:

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But with the flexing of the gear leg, it seems that will cause cracks  to appear in the door where it has the 90 degree bend. So I beefed up the bend and put the mounting tab just before the bend.

This where I put the tab.

Another thing I did different is instead of using a piece of aluminum angle and screwing it to the door (which would leave a visible screw on the outside), I glassed a tab onto the inside of the door.

Here’s the tab on the gear leg.

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Another view of the inside of the door.

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When you’re done trimming and mounting the door, it looks like this from the back.
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This is the top of the door from the side.
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That big honkin’ gap is there because when the gear comes down, the door would hit the fuselage and prevent the gear from fully extending if it was any longer. I guess the theory is no one will notice it’s there when the gear is down and the only time the gear will be up is where it’s in flight. But I’d know it’s there.

A couple emails to Malcolm revealed that I COULD have saved the extra to use a small door to cover the opening. But I couldn’t do that because I used the “sneak up on it” approach when I located the final position of the cut.

So I covered the side of the fuselage next to the gear door and laid out a few layers of triax and BID (so it would match the curvature of the fuselage). Then I cut it to fill the opening. To accomplish this, I used the tape-it-to-the-outside-and-shine-a-light-from-the-inside method to locate where to cut.

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Then I cut and drilled a pair of hinges and did a dry fit. 
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Yep, it moves.
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I riveted the hinge to the mini-door and put nutplates on the side that would mount to the fuselage.

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 Next I beveled the edge and built a flange so it would fit with the door.

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Here’s how looks all installed and operational.

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