Fitting flush windows

[Clarence]

Has anyone ever machined new side windows so they will fit flush with the fuselage skins?

Clarence

 

[N601RX]

I would think it would be very difficult due to the compound curve in the window.

[Steve Dawson]

Just a thought but maybe with a router, turn it upside down, raise the router bit to the right hieght, then make a guide to guide the side of the window along. Give me a call if you need a hand. I have a router also

[5854Q]

Just a thought..... the sharp inside corner formed by the router bit may be a stress inducer & therefore promote an increased risk of cracks there.

[1970m20e]

I recently replaced all side windows in my M20E and there is slightl bulging in the skins anyways from bolt to bolt in the window mounting that it would probably be a wash and a waste of time.  Plus you have no options for a mistake.  If you machine it wrong, it would look worse in my opinion because the window would have gaps or tight spots where you made a mistake.  I think your best bet is to keep it simple and cheaper and keep your windows flush the regular method. 

[Ned Gravel]

Clarence:

The comment from 5854Q got me thinking of how the section handles induced forces and, as a result, stresses.

A modification of the section along the edge of the glass, may, in fact, be a stress inducer and the little lip it produces (what you are actually looking for) will distribute stresses unevenly over that section of the glass.  It may not cause any problems later on and I do not have the tools to do the numbers, but the distribution of stresses during and after installation, if there are any, will be uneven.  If any forces are imparted to the glass, the focus points (the inside edges of the lip) might experience more stresses than local areas surrounding them - making them somewhat weaker than these other adjoining areas.

In the end, the differential may not be enough to worry about, and the actuall stresses induced may be too small to cause any problem, but the engineering consideration is an interesting one.

 

[Clarence]

Hi Ned,

 

I finished machining steps in all of the windows, the front curve on the pilot side was the most difficult to do.  Compared to the rest of the process the steps were easy and added only a little extra work.

The windows are all re-installed with new PRC sealant, the results are very pleasing.  I'll show you next week when you're out.

I'll post some pictures of the process when I'm back next week.

 

[Ned Gravel]

Clarence:

I guess it got done when I wasn't looking.    I hope to see the results next week when I am back. 

I will be looking for something similar when you do my 201 windshield in a couple of years. 

 

 

[DaV8or]

Quote: Clarence

I finished machining steps in all of the windows, the front curve on the pilot side was the most difficult to do.  Compared to the rest of the process the steps were easy and added only a little extra work.

[Clarence]

Dave,

I bought a narrow kerf 60 tooth carbide blade for my table saw.   Fastened a plywood top on the table with a pine 2X2 over the saw blade to act as the fence.

First I trimmed the windows so that all over lapped the fuselage skins by the same amount (7/8")  Then marked the outline of the skin on the masked surfaces of the window.

Once all the edges are equal I wound the saw blade up 7/8" with about .045" of the blade kerf outside of the 2x2 fence, the rest cut a pocket into the 2x2.

After practicing on all of the old windows I took my new 1/4" thick ones to the saw and like a hot knife in butter cut the step in the plastic.  The windows were then installed with new screws and PRC sealant and are completely flsh with the skins with a tiny line of black sealant all the way around.

If I were to do it again I would machine the step first and then drill the mounting holes afterward.  I made the mistake of doing the holes first.  Liberal amounts of Johnsons paste floor wax makes all sawing and drilling operations alot easier. Sharp tools are the other important item.

The most challenging part of the process was the very curved forward edges of the pilot's window and door window. These took some real nerve and a steady hand!

I will post some pictures next week when I'm back home.

 

[Bacachero]

Great Project

Anxious to see those pictures!

Cheers!