Cabin top/doors – finally DONE! [320.0 hours]

I’ve been on a mission since April to get the fiberglass work on the Cabin Top and Doors behind me rather than in front of me. It’s been a bit of a marathon, the cabin top molding is not famous for its accuracy and everything has to be hand crafted to fit. Here’s the finished product:

I had planned to roll the thing in and out of the workshop to help with this work, but the weather’s been too cold to safely work with the plexi or cure fiberglass, so it’s all been done inside. I’ve had a pair of heaters going in the workshop 24/7 for the past month, and was finally able to turn them off last night. The shop vacuum copped a beating during this time, and I had to regularly clean out the filter.

Here’s all the steps I went through to get this job done. Skip to the end for the pictures.

1. Fit the rear windows

I used Lord Adhesive (available from Aerosport Products) for all windows. The forward surface of the rear windows needs to line up with the aft surface of the doors, which means spacing the windows up from the fuselage molding. I then built up the rear door pillar with a few layers of fiberglass cloth and flox until it matched. There is a flat spot on the left hand door pillar of all RV-10 cabin top moldings, this was the worst place and had to be built up about 5mm – too much for just micro/filler.

I used West Systems G/Flex with some microballoons to fill in any voids not filled with the Lord Adhesive, and trimmed any excess Lord Adhesive with a scalpel. I then taped and scuffed the window (and fuse), and applied 3 layers of fiberglass cloth on the outside. After sanding any high spots, and scuffing, I used regular West Systems epoxy with microballoons and Cabosil to fill and blend the outside surfaces into the cabin top.

2. Paint the inside door sills and cabin top pillars

The lower cabin top pillars had to be blended in, and painted, along with the door sills, to match the rest of the interior. This painting is best done before the front window is installed. Unfortunately, the inside of the cabin top and overhead is already finished, so I had to mask it all off with cardboard and tape. I didn’t want to have a yellow polyurethane primer leak splattered across the ceiling. This all took a fair bit of time, and I wound up spraying each side in sequence rather than together, because I didn’t trust myself leaning across wet paint to get to the other side.

The job took time but went OK, and you can’t tell where the paint transitioned into the existing painted part of the pillars.

3. Install the windscreen

Once again I used Lord Adhesive. It helps to have a second person helping, cleaning up any excess adhesive squeezed out on the inside using Q-tips and white spirit. I used a combination of clecos and weights to hold the plexi in position while the adhesive cured.

3.1 Extend/fill lower edge and prepare for fairing

I scuffed the upper forward fuselage area, acid etched it, and wiped some Alodine over it to prevent the oxide re-forming. I then filled the lower edge of the windscreen using Micro-balloons, with black dye to prevent it being seen from the inside. After the micro cured, I sanded it to align with the outer surface of the windscreen, taped off and scuffed the windscreen. All I used to figure the tape position was a cardboard cutout section with a 7 inch radius.

3.2 Construct the windscreen fairing

Once again using black dye. Preparation is the key to this layup, I cut all of the glass cloth strips, and allowed several hours to do this in one operation. It worked out quite well and a day later I sanded it into the correct shape, using a wooden block cut with a 7″ radius (using the band saw). I used a stick-on flexible perma-grit strip for this operation, which surprised me by staying in place. Gotta be very careful though, not to encroach onto the tape because the coarse perma-grit is a weapon.

After this I switched to 80 grit sandpaper, and finally 120 grit to carefully sand down to the top layer of tape. I used micro to fill low spots. It took a few iterations to get the entire fairing correct, and blend it into the fuselage at each side.

3.3 Glass in windscreen over the top

Fiberglass cloth across the top and down each side, once again fairing it with micro, matching it with the front edge of the door. To do this, I used packing tape on the door as a release agent, slathered micro through a section of the pillar, and closed the door onto it. The following day, a hard yank on the door would release it, and I can sand down any excess.

4 Door edges and cabin top alignment

Whenever I use packing tape as a release agent, I apply it over a layer of masking tape. It is easier to get off, and then any goo left behind simply comes off with the masking tape.

I worked sections of the doors at a time, applying micro to the pillar edges or anywhere that required building up, closing the door with packing tape in place, letting it cure, and then opening the door to release it. This is a good reason to leave the door windows out and fit them last – you’ve got the entire window opening to use rather than the door handle, and in some cases it requires quite a yank to release the door.

4.1 Door gaps, fairing across the top of the door

At this point, the doors closed properly but with basically no gap. Starting at the very top, I used a small piece of 120 grit sandpaper, and worked it from side to side through the gap, closing the door until it jammed, then lifting the door a fraction so I could keep sanding. I mostly sanded the cabin top – since it was micro and easy to sand, but also since the doors already had a nicely formed flat angle which I didn’t want to distort.

Once I could move the sandpaper side to side with the door closed and locked, I moved onto the front and back curves and did the same thing, working my way down each side in turn. Finally I sanded across the bottom and around the bottom corners, getting to the point where I could insert the 120 grit paper, and with a bit of friction still there, slide it all the way around the door.

I measured the 120 grit paper at about 0.01″ thickness. The gap will need to be wider prior to painting, but at this point I left it as is – as long as there is a gap the door is hanging freely, attached by the hinges and the door pins only. Setting up this gap allows the door to drop slightly, maybe a fraction of a mm. This required a bit more fairing work around the top of the doors, to match the door level with the cabin top.

4.2 Bottom of the doors

The bottom of the doors was a close match to the outside of the fuselage, aligned within perhaps 0.5mm across the entire length, but it is a simple matter to match it precisely. Once again, using packing tape as a release agent, I built up the door where required, and the surrounding fuselage area(s) where required, with a thin layer of micro, and then sanded it back to get an exact matchup. This introduces lots of pin-holes which of course have to be filled later.

4.3 Check the seal gap

Since the doors adjusted position a “bit” with the initial gap set, it’s important to go back and ensure that the “seal” gap for the McMaster seal is still correct – between 1/4″ and 5/16″ in my case. I made a few adjustments across the top on each side.

5 Fit the door windows

With the doors an exact match and a 0.01″ gap all the way around the doors, it was finally time to fit the door windows. These are the easiest windows to fit, you can take the doors off and use gravity to your advantage.

6 Optional – prime and fill pin-holes

I elected to spray on some primer and surfacer to seal everything up and fill almost all of the pin holes. I only sprayed two layers of surfacer, sanding most of it off each time. There are still some low spots, it’ll need more work prior to painting, but it’s good enough for now.

All of these operations took two months to complete, and it was with some relief that I took all the masking and protective film off, and wound up with a good result.

 

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    Fixing in rear window with Lord Adhesive
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    Window spaced up to align with door
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    Fiberglass cloth overlaid across window
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    Micro-balloons fairing filler
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    Priming the door sill
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    Topcoat on door sill
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    Topcoat on door sill
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    Front window ready for installation
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    Lord Adhesive applied to rear/top edge
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    Inside view of front window installation
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    Metal scuffed, etched and Alodined
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    Ready for window edge filler
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    Micro-balloons (with black dye) applied
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    Window edge filler sanded, window scuffed
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    Windscreen fairing - some assembly required
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    Completed windscreen fairing layup
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    f44q
    Fairing sanded to shape
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    Applied micro (with black dye)
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    Sides/Top glassed in, more filling/shaping
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    Fairing transition to match the door
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    Filling low spots
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    Sanding the door gap
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    Fairing door/fuse alignment
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    Fairing door/fuse alignment, some low spots left
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    Left side door/fuse alignment fairing
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    Fitting door windows
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    Fitting door windows
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    Glass cloth for door windows
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    Door windows glassed in
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    Preparing to spray primer and surfacer
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    f44ze
    Preparing to spray primer and surfacer
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    Light coat of polyurethane primer
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    First coat of surfacer
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    f44zi
    Filling pin holes
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    Tearing down after spraying
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    Removing window tape, protection
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    Cabin top and doors - finished!
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    f44zm
    Cabin top and doors - finished!
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    Door gap
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    Front view
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