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Permalink Reply by Matt Pope on Wednesday

This seems to be a common problem on the pilot's side door, so unfortunately I doubt you'll find one. AC 43.13-1B has instructions for fixing cracks, section 4 - 3.40

I fixed mine by drilling a 1/8" stop hole at the end of the crack, which I filled with a slice of 1/8" acrylic dowel I bought on Amazon. I glued it with Weld On 3. Just make sure you get the sides of the crack lined up perfectly before the adhesive sets, and if it ends up uneven, don't try to sand/polish it flat or the optics will be slightly wonky around it (ask me how I know...). 

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Permalink Reply by Thomas Heiting on Thursday

Thanks Matt for the info !

Zenith could have definitely increased the structural integrity of the door in their design specs.

You are correct that it is a problem in the bubble door design.

If you have any photos of your repair please send them.

Thanks again for the help!

Tom

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Permalink Reply by Matt Pope on Thursday

You can see I filled and glued the previous owner's unsuccessful stop holes, too. The white scuffs are where I got carried away with the cutoff wheel while trimming off the acrylic dowel (lesson learned) but I decided it's better to live with the scuffs than to polish them out and have worse optical warping. 

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Permalink Reply by Thomas Heiting on Thursday

Thanks Matt

Interesting that my door cracked in the same area!

Dremel cut off wheel or reciprocating saw ?

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Permalink Reply by Thomas Heiting yesterday

Hi Matt,

Final questions before I quit bothering you:

Door removed and flat on work surface?

Glue on inside, outside or both?

How to clean up drips or runs?

Thanks much !!

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Permalink Reply by Matt Pope yesterday

Hi Thomas, I'm happy to help where I can.

Yeah, mine was hinged such that two lengths of hinge were butted together there, and they weren't perfectly aligned with each other so the door frame flexed there a bit every time the door opened or closed, so I'm not surprised it cracked. Maybe take a close look at your hinge line and see if it's straight. 

I used a Dremel cutoff wheel to trim the dowel after it was glued in, then sanded it down, but I scuffed the window with the Dremel, so if I had to do it again I might try cutting a slice off the dowel that's the correct thickness beforehand, then glue it in after polishing the faces. I'm not sure which way would get a better result, but if you're going to glue it in before cutting, maybe use a hacksaw blade and cut it by hand with the window protected by tape or something. If you're doing that with a straight blade, it'll be easier to cut off the excess dowel on the outside of the door, rather than the inside where the curve of the window will be in the way. 

I removed the door and lay it flat - I can't remember which side was up. Make sure it's well supported all around so there's no stress on the crack and the edges sit together naturally, the way they should. 

The Weld On 3 comes with a steel needle to squirt it through, and its viscosity is low enough that it wicks into the crack pretty well. I think I only applied it from one side, but it's been a few years and I can't remember exactly what I did. I may have put tape over the surrounding area to protect it from runs, but maybe not - I don't recall it being a problem. After it cured, I cut the dowel close to flush, sanded it flush with maybe 400 grit sandpaper, sanded the area with increasingly fine sandpaper up to 2000 or 3000 grit, then polished it.

The better you line up the sides of the crack before gluing, and the less sanding you have to do afterwards, the less the optics will be affected. 

Good luck!

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