Mounting Windows

[spinningwrench]

Today I created a CAD drawing of the left hand pilot window for my Patrol. This allowed me to machine a solid aluminum trim bezel piece for mounting to the outside of the window frame. Normally people are using another interior trim piece for mounting the Plexiglass window to the outside bezel. I am wondering why this is necessary as it seems that the Plexiglass could simply be sandwiched between the window frame and the aluminum trim piece. Any thoughts?

[jaredyates]

I had the same feeling, and just sandwiched the plastic between an outer aluminum frame and the steel frame. It has been working great, but I'm also using pretty thin polycarbonate. I could imagine that if someone were using something more like 1/8 inch, it may cause the window to protrude more into the air stream.

[robcaldwell]

I created a trim bezel to hold my rear windows in place. Except I didn't have CAD and a machine to mill my pieces. I used poster board and a band saw.

[spinningwrench]

I am planning on using .093” Plexiglass for the side windows and the bezel was .025” aluminum as called for. This would make the window bezel protrude a bit but not by much. Debating between screws and pop rivets.

[jaredyates]

I used all-aluminum large head pops. Less tension required to break the stem, and easy to drill when the window needs to be changed.

[Bcone1381]

I've posted this photo before I think and provides how the thickness of the window + Bezel might appear. It's an experimental Cub Crafters product.

Your Bezel gives more support. The subject aircraft has a square tube frame, and uses an adhesive (It might be 3m VHB tape) to attach the plexiglass to the frame. The "frame" is painted on. The certified CC products do not use this installation.

On the interior of your application, a crevice would be created between the top of the round tube and the plexiglass that would catch dirt, breadcrumbs and dead insects. I wonder if there is a way to cover the crevice that might be incorporated into the design?

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[spinningwrench]

The Cub Crafters approach does look very clean. I think I will go with the pop rivets for a bit more security. I would imagine one could run a bead of silicone into the crevice but I don't think it is necessary. I will mount the bezel to the window frame today and get an idea of how the general fit up will look.

[svyolo]

I saw several companies that did windows similar to CC at SNF. Most of them had a single pop rivet in each corner of the window as a safety.

[stinger]

I mounted my window in the sandwich fashion .020 aluminum over plexiglass straight to frame. Window and frame are recessed behind front windscreen fairing with small outward bend deflecting air flow . Stinger

[spinningwrench]

I made a drill jig today to allow drilling the window frames exactly in the middle for securing the plexiglass window and aluminum bezel with 1/8" pop rivets. The jig guarantees that the rivets are exactly in the center of the frame and there is no "winding" to the thin aluminum as it wraps around the perimeter of the steel frame. It worked well, the aluminum is flat.
Drill Jig Assembly.jpgIMG_1312.jpg

[rodsmith]

Great solution. I learn so much from other builders.

[coosbo]

I’m trying to decide if I should drill through the plexiglass, or the interior trim pieces when using the angle trim pieces that come with the kit. “The Bearhawk Book” and Eric Newtons manual show drilling through the acrylic but not into the door frame. But then in the kit builder manual it says in all caps (so I assume it’s important) to NOT drill through the acrylic and to fasten the trim pieces to the frame. Perhaps I’m misunderstanding the kit builders manual and it’s referring to the rear windows or something other than the pilot/copilot windows. But assuming both are acceptable methods, could anyone say why I might want to use one over the other?

[spinningwrench]

I am just mounting my Pilot side windows directly to the window frame with a pop rivet through the outside Aluminum bezel and into the steel frame. I don’t really see a purpose to the trim pieces. Jared Yates confirmed that he did it that way as well. You do want to drill a hole in the plastic larger than the fastener. Eric Newton I believe went oversize an 1/8”. The rear windows simply float in the D frames. Use Acrylic for side windows as it is fuel resistant. Use Polycarbonite for the skylight as it is tougher.

[Mark Goldberg]

Spinningwrench's comments are correct. Bob intends for builders to sandwich in the side Plexiglas between the inner and outer "trim" pieces for the pilot & co pilot side windows. And drill the trim pieces to the window frame. Anywhere you do drill a hole in the Plexiglas like the aft part of the windshield on the sides - make the hole bigger than the screw or bolt and use a piece of rubber or nylon line. To allow the uneven expansion and contraction of the steel/plexi. Mark

[Bcone1381]

Drilling Plexi is worth a thread of its own. There is a free pdf available on line titled "Acrylic Sheet Fabrication Manual" by Plexiglas. Its easy to find, 36 pages long. Info on drilling and cutting acrylic is logical and authoritative just a few pages of the manual. You might use it rather than trusting truth and opinion we find on line. Using it one can learn how to drill a hole that is polished inside if you follow there advice and that may avoid future cracking.

Also, the expansion difference between AL and Plexi is easy to find online. If I recall correctly, I calculated about .060 difference for the length out our side windows. Thats 1/16th inch expansion/contraction from 50 degrees to a Michigan winter and a AZ summer.

I followed all the advice given in the manual. I cut and drilled all my windows after practice on scrap and had no fatalities/errors. That is unusual for me. Buy the drill bits they recommend....I used Spruce as my supplier, used a toilet wax ring for my drilling wax and snuck up slowly on the final size hole.

[svyolo]

That is a good resource. I just printed a pdf.