Crack in pilot side window. Repairs?

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GimpyPilot
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Crack in pilot side window. Repairs?

Post by GimpyPilot »

Hi,

I've got a crack running from the corner of the small window opening downward to about an inch above the corner of the main window, on the pilots side. I am going to carefully stop drill the crack, however I'd like to find a way to bette repair the crack itself, if anyone has any suggestions for doing so.

I understand that the later airframes do not include the small window openings. Now I understand why.

Thanks,
-Michael

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Re: Crack in pilot side window. Repairs?

Post by Bigphoto »

Sorry to hear and you are correct I do not have any window openings in mine serial number 105. Maybe she's not happy hearing you say you might sell her if you find a Glassair?

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Re: Crack in pilot side window. Repairs?

Post by N645XL »

Sounds like a temper tantrum to me. 😬

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Re: Crack in pilot side window. Repairs?

Post by Amello »

I use a soldering iron. Grind the tip like a needle. Insert. Pick melted plastic off hole. Fill with clear caulk.

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Re: Crack in pilot side window. Repairs?

Post by Amello »

I use a soldering iron. Grind the tip like a needle. Insert. Pick melted plastic off hole. Fill with clear caulk.

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Re: Crack in pilot side window. Repairs?

Post by GimpyPilot »

So, here's a quick update...

In devising an appropriate repair method that will last as long as the airframe does, we took apart the pocket window. Having made some precise measurements which were necessary to cut the plexiglass (acrylic) doublers which will be bonded to the cracked area of the window, we have realized that the root cause of the failure is in fact a manufacturing error. The hole spacing in the hinge is very slightly different than the hole spacing in the factory pleixglass. (ie: The hinge spacing is metric and the window spacing is standard or vice-versa), so the plexiglass is constantly stressed accordingly, and eventually cracks with flex and movement created by use and vibration.) We have adjusted the holes in the starboard side hinge so that the window on that side does not also crack. For the port side, we have machined a pair of .08 acrylic doublers which completely "sandwich" and reinforce the cracked area under the pocket window. They will be bonded to the interior and exterior of existing window using a UV cured epoxy, yielding a very strong bond, and optically appropriate results. We've also machined a 2024 aluminum doubler for the hinge itself, to reinforce the holes and backspace the window closure as needed.

If your aircraft has the pocket windows and your windows have not yet cracked, I highly recommend that you modify the holes on the hinges such that they are properly aligned with the holes in your windows, to alleviate stresses on the plexiglass.

Here are couple of photos to demonstrate what is going on. Notice that the forward portion of the doublers are extended to provide rigidity which will support the area where the cracking originated. Aluminum hinge doubler not pictured. I'll post photos of the completed repair next week.

Image

Image

Image

-Michael
Last edited by GimpyPilot on Mon Aug 26, 2019 2:34 pm, edited 1 time in total.

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Re: Crack in pilot side window. Repairs?

Post by Bigphoto »

Interesting that when the factory originally drilled the holes that they didn't use the hinge as a template to ensure they would line up and not put stress on the plexiglass? Guess that's why I'm not handy with tools and pay someone to add/subtract/modify things to my airplane LoL...

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Re: Crack in pilot side window. Repairs?

Post by GimpyPilot »

Here is the completed repair:

Image

Unfortunately the plastics shop that did the UV bonding refused to let me supervise the setup and somehow managed create some small cracks in the doublers. They also enlarged the holes very slightly, probably because they didn't get everything precisely aligned. In any case, the doublers are very well bonded, and the affected area of the window is now three layers thick, and will not crack further. The optical quality is excellent, save some very small bubbles around the cracks themselves. This artifact was not unexpended, because the cracked surfaces of the window could not be precisely aligned such that the bonding surface would be perfectly flat. Fortunately the repair is not in the line of sight for flying or general observation.

We chose not to drill the additional forward hole as the structural rigidity is now considerable. We also decided to forego the aluminum hinge doubler. Obviously we had to use slightly longer screws to affix the hinge.

I do have the Solidworks CAD files for the plexiglass doublers and the hinge doubler, should anyone wish to implement a similar repair, including bevels, backspaces, and hardware countersinks. (Files can be exported as .STL or .DXF as needed.) Total cost was less than $125.00, including materials and the bonding work. I am quite satisfied with the result. If I were to do this over again, I would likely insist on supervision of the bonding work to avoid the implementation artifacts.

-Michael

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Re: Crack in pilot side window. Repairs?

Post by XL2driver »

Great detailed info, thanks for sharing all that!
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