Home > Filtered Air Box, Firewall Forward > More Filtered Airbox Work – 8 hrs

More Filtered Airbox Work – 8 hrs

Sunday April 28, 2013

I worked mostly on the filtered air box this weekend but I also made a small doubler plate for the front left engine baffle section because I realized the gap to the engine there is too large to seal with RTV. I used a piece of scrape aluminum from the baffle trimmings and painted it red like the rest of the baffles. It is riveted on in this picture with the four unpainted rivets in the lower right corner.

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So then on to the airbox again. I made the six aluminum retainers for the filter, aligned them to be flush with the filter cutout, drilled, dimpled and installed nut plates. This photo shows you how they fit with the filter.

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I went out to Corona on Saturday to take my biennial flight review (I passed) and I stopped at ACS to pick up a few things including a 2 x 2 foot sheet of .032 alclad aluminum 2024-T3. From that stock I made a doubler plate for the .062 thick top mount for the FAB. You can see it on the left in this picture after I scuffed up the surfaces of the plates for bonding.

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I want a uniform thin layer of ProSeal between these two plates so I made some small shims out of .016 thick aluminum stock and epoxied them down to the .062 thick plate as a first step for bonding. I allowed the epoxy to cure about 5 hours and removed all the excess with MEK and fine sand paper. Then I mixed up a batch of ProSeal and spread it out thin over the plates (but not on the shims). I put the two plates together and aligned them with clecos, then I removed the clecos and stacked a piece of plywood on top and added several gallon paint cans to press it down. After about 10 minutes I removed the paint cans and plywood and found that the two plates had shifted relative to each other. The ProSeal is like a lubricant and it allowed the top plate to flow because the table is not perfectly level. It was clear I need a way to maintain plate alignment while this cures.

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I drilled holes in the plywood to allow clecos to pass through with clearance around each one and I drilled six holes in the table top so the cleco tips would not touch the table either. Now the clecos align the two plates in plane and the plywood just presses down on the plates for uniform pressure. You can see I put wax paper on each side of the plates stack to keep it from sticking to the table and the plywood.

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Here you can see four gallon paint cans and a 10 lb bag of cat litter on top squishing it all down to apply pressure while this cures. It will take a couple of days to set up so I won’t find out until at least Tuesday if this was a success.

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I also drilled the airbox top cover flange to the fiberglass shell this weekend – except for the part in front of the upward bend that is. The plans say to wait on that part until the vertical alignment of the top plate is set with the cowl opening. The bare fiberglass shell is kinda ugly so I sanded it and sprayed on a coat of white primer. An hour later I found a bazillion pin holes so I put on an additional coat of UV smooth prime because it fills the pin holes better than Stewart Systems primer.

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I also carved the airbox foam block enough to fit it into the front air intake opening. This is in preparation for carving out a hole and laying up a fiberglass tunnel to the air box. I have to wait until the air box is assembled and back on the engine and aligned before I bond this plug in place and start carving.

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This photo shows the approximate line around the intake scoop that I am considering cutting to make the scoop removable for easier cowling installation. The line will be at the top of the tape leaving just enough room for a ring of screws (probably six).

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