24-03: Wingtip Light Lenses

The flanges where the landing light lenses go were not great - they varied in thickness such that the lens material was above the surface of the wingtip in some places but below the surface in others. I decided i didn't like this and could achieve a better fit using the micro edge method. To start however, i had to fit the lenses into position. This was a lot of iterative cutting, trimming and sanding. There was no real knack to it, other than to go slowly. Every area you removed some material affected the other areas. But i eventually got them fitting ok. 

A note on the material for anyone following - these are not acrylic. They are "Butyrate" as far as i can work out. This means that acetone is a big no-no. It melts the plastic. Also, sharpies will seep into and stain the material - so don't mark anywhere that you won't remove. I found isopropyl alcohol was ok if only wiped quickly. If you rub too much, or leave it on the plastic, it also melts/clouds the plastic. So be careful! If you use any tape on the lenses - check the glue does not affect the plastic.

Normal tin snips worked the best for trimming.

It was a painfully slow, iterative process.

Eventually, i was able to get it all fitting nicely. Once this was done, i taped it in place and drilled for 2 cleco's where the attach screws will go. 

Here you an see how the flanges aren't great. 

Tape was used to mark the lens instead of a sharpie - as the sharpie stained.

Fixing the transition to the wingtip

As i did with the wingtip itself, the process started with sanding off the flange so there was a nice bevel to accept the micro against the lens material. I then covered the lens in electrical tape (i checked first that the glue didn't affect the lens material). The lens was then cleco'd in place. 

A micro mix was made up and applied in the same fashion as the wingtip / wing skins. I.e. applied toward the lens first to avoid air bubbles and voids, then in the opposite direction to be flush with the wingtip surface and to make a nice fair transition. I found by letting the mixture sit on the wing for about an hour or so, i could then scrape off some of the excess and it saved some sanding later. Be careful not to pull the mixture out of the seam against the lens though. 

Here i am using a flat Permagrit sanding bar to remove the flanges.

Here you can see the gap i created by sanding off the flanges. This will be filled with micro and make a perfect transition to the lenses.

This was the second lens - i found leaving it for an hour or so, then scraping off some micro saved a fair bit of sanding.

Sanding it all off again!

As per the process on the wingtip / wing skins, the micro was gently sanded off again until the tape showed and then the lens could be removed. The micro was faired into the wingtip surface. The lens was then placed back in position and a gap cut using the Japanese saw and the hacksaw blade. 

Pop!

Cutting a nice paint gap.

I am very happy with how fair these curves are now. Much better than before.

Now the shape of the wingtip is finalised, it is time to do the final surface finishing of the part.