Remaking left landing light cover - Part 2
TLDR
- Finished mkaing the new left landing light cover
Details
I finally finished making the replacement landing light cover for the left wing. It’s a lot of work, mainly trying to match the holes through the skin, plastic cover, the doubler’s rivnut. There are 20+ holes and each hole took a super significant time to position and adjust. It’s definitely a patience game.
Forming the plastic
So last week I failed to form the cover using 1/16 thickness cover. It was too hard, and my oven’s temperature was too high so the entire thing melted and deformed.
The new material I bought is 12 X 12 0.04” Plexigalss. I bought 5 of them from amazon in case I run into another experiment failures.
The size is perfect. I didn’t even need to cut it at all, the entire thing can be inserted into the wing skin to match drill holes. Of course I still needed to cut it later, but being able to first drill holes and cut later made the whole process safer. I didn’t have to worry about cutting off too much material.
First attempt
I used duct tap to wrap the palstic around my aluminum forming block. And I used heatgun insetad of oven this time to warm up the material for bending. But maybe it’s because of the thinner thickness, it still deformed quickly. As I blew hot air, I could feel the cover became soft and started to bend at places I didn’t actually want to bend. Basically the entire bending was uncontrolled even though I wrapped it around the block.
Second atempt
I took a new plastic cover, and this time I didn’t wrap it on the block.
I just held it in my hand and started to blow hot air. Within a minute I started to feel the plastic getting softer and starting to bend more. I immediately pushed the cover to the forming block, and just used my hand to hold it.
This time it worked way better than the first time. I got a reasonably shaped cover bend.
Match drilling
I then started to match drill holes on the cover. This was a slow and careful process. I first drilled the bottom row, then clecoed them as I made progress.
After drilling all holes, I enlarged them all to 9mm so theyy can fit a rivnut, which was already installed on the doubler.
Combining the cover and doubler
The KAI suggests to use flush rivet to permanently bind the doubler and cover together. I did that. This is the most challenging part of the process.
Because when the doubler is clecoed on the skin, it’s clear where holes line up between skin, cover and doubler. But the moment I take the doubler out for drilling, the relative position between the cover and doubler cannot be determined. I tried to use a pen to mark position, but it’s just not accurate enough. Missing even 0.5mm alignment will block the rivnuts from taking screws. So I spent a huge amount of time trying to make perfect alignments between the 2 parts.
The solution I ended up using: first drill 8-9 holes on the doubler itself. The holes are drilled at the position where I want to install flush rivets. Then I put everything on the wing using temporary screws. Once everything is lined up, I then used a pick with 90 degree tip to press on the center of the drilled holes to leave a mark on the cover. Then I would take the whole thing off and drillecd holes on the cover.
I did this 8-9 times, counterssunk the holes, then installed the flush rivets to finally hold everything together.
enlarging the holes
After all the work, there were enough misalignment that several holes on the wing were unable to push through screws.
I drilled those holes to 4mm to provide a little more wiggle room for the screws, then started to final install screws.
After another long night, I was able to finally install all screws.
