Fred₂O

Door window crazed like crazy. How to replace?

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@hmasing what size drill did you use for the window mounting holes?  I've read that oversized is good, some say 3/16", but I've also read 1/4".    Do those holes require a 100-degree countersink?   I haven't ordered plastic drill bits yet.

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On 3/27/2019 at 2:37 PM, SheryLoewen said:

 DRILLING TIP

 

NOTE: Windshields installed with flush screws through dimpled holes in the skin need special attention. When drilling the Plexiglas being held in place, the windshield will be resting against the dimpled upset-holding it slightly out of position. To compensate for this, the pilot holes #40 should be drilled  to the outside edge of the existing holes.

They will lineup after the hole is drilled full size and countersink!

This prevents puckering of the metal on the finished job.

Shery/Paul thanks so much.  This is extremely important to know!

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On 9/3/2018 at 3:56 PM, cliffy said:

Yes OK for owner maintenance, must be signed off correctly , by the owner doing the work, with name , pilot lic. number, date, hours and what was done and reference the proper section of 43.13 that lists what an owner can do.  You technically need the maintenance manual at hand while you do the work. Plexi drill bits can be bought or made by grinding the leading edge of the cutting point paralleled to the length of the drill so it doesn't dig into the plexi.  

Again, technically, if you use a thicker plexi for replacement you "technically" are making a change to the type design of the airplane that goes into a "minor alteration" of the airplane and that needs a real A&P for sign off-"TECHNICALLY"

 Any band saw blade used in cutting plexi should have a very fine tooth spacing. A wood cutting blade may/will crack and break the plexi. 

@cliffy  a search through the Mooney M20 maint. manual PDF for the words "window"and "windshield" turned up nothing about window replacement.  This weekend I'm going to replace the door window.  The old one is soooo bad it must be the '67 original.

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On 3/27/2019 at 2:37 PM, SheryLoewen said:

 DRILLING TIP

 

NOTE: Windshields installed with flush screws through dimpled holes in the skin need special attention. When drilling the Plexiglas being held in place, the windshield will be resting against the dimpled upset-holding it slightly out of position. To compensate for this, the pilot holes #40 should be drilled  to the outside edge of the existing holes.

They will lineup after the hole is drilled full size and countersink!

This prevents puckering of the metal on the finished job.

Your recommendation worked out great!     I noticed after removing the old window that if you lay one on top of the other, they appear do be different sizes relative to each other depending upon which one is on top.   This means that using one to mark the hole locations in the other is not really possible.  Your technique eliminated that problem while accounting for the curvature issue.  I really appreciate your advice.

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The end result - before and after photo.   There is a new window in the door, it is just so clear compared to the old one that it seems invisible :)

door_window_before_after.jpg

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Great details, Fred!

Thanks for sharing them.  

The old window appears to have changed colors a bit... comparing to the edges.

nice pic.

Best regards,

-a-

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8 hours ago, carusoam said:

Great details, Fred!

Thanks for sharing them.  

The old window appears to have changed colors a bit... comparing to the edges.

nice pic.

Best regards,

-a-

Yes, the part that was exposed to the sun is badly crazed, while the edge is not nearly so.   The edge was inflexibly clamped, while the center probably experienced a lot of vibrational motion.    So, I leave it to you to say if it was UV exposure that weakened the material, vibration, or both that led to the changes in optical properties of the acrylic.

Mixing and applying that polysulphide sealant reminded me of that old Cheech & Chong comedy routine featuring the two Russians: "Look Like Dog $#!%?".  "Da.  Smell bad too."   We had a fun weekend.

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16 hours ago, Fred₂O said:

The end result - before and after photo.   There is a new window in the door, it is just so clear compared to the old one that it seems invisible :)

door_window_before_after.jpg

The only drawback is you will now need to use foggles when you ant to practice IMC flying.  :D

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