Boot Cowl

[David47]

Phil, although unrelated to the seat pan question (sorry Brian) but do I see removable upper and lower boot cowl sections ?. Reason I ask is that I'm planning on doing the same thing, if possible. I'm a month or so off fitting up the cowl, but I was looking at splitting it horizontally as you appear to have done and then attaching screws into anchor nuts on a bonded in place backing strip. If removing the lower section, I guess you need to uncouple the cooling duct. Not sure what would be involved if removing the top section, or if that's even possible - haven't investigated that yet. Anyway, looks good and would allow great access to everything behind the firewall.

[jiott]

Just an FYI, to get access behind the firewall to the electronics bay, the top part of the boot cowl would need to be removable. That means you can't seal the windscreen-to-boot cowl with any kind of adhesive; you will need to make some kind of perfectly fitting rubber gasket to seal against rain, etc. Even a small leak here will drip directly down onto your expensive electronics. Some guys have done it so its not impossible; I also know some have installed a channel to direct the inevitable leaks off to the sides. All I'm trying to say here is that if you make a removable boot cowl you will need to have a plan up front to address water ingress.

My personal method was to permanently install the boot cowl and seal up the windscreen joint with silicone. The access to the electronics bay behind the panel was done by installing my wiring such that the whole instrument panel could be tilted 90 degrees into the cockpit by simple removing the 4 bolts at the bottom of the panel and the 2 small bolts holding the panel braces at the top and of course the glare shield. All this is quite easy to do.

[PapuaPilot]

David,

My cowling came as two pieces, top and bottom, and they went all the way back to the windshield and door frames. I assume yours is the same. I talked to John McBean about getting the current boot cowl (one piece), but that would have meant cutting the the back ends off of both the top and bottom anyways.

I figured I had nothing to loose in cutting the cowls vertically and making them into 5 pieces. That is what I did and it turned out very nice. After splitting the cowling I used some strips of aluminum to make the lip (I would suggest .032 - .040"). I made the lips so I could rivet them on the aft cowl pieces using 3/32" countersunk solid rivets and temporarily held them in place with clecos. Then I drilled through the front cowlings and lips to make the holes for the Dzus fasteners. I started with small holes and held everything in place with clecos. Then I enlarged the holes in the lip to hold the Dzus receptacles, and in the front cowling to hold the Dzus fasteners. I powder coated the sheet metal pieces to match the colors of my cowling and riveted them in place using a rivet squeezer.

The first picture shows how I used a Dremel tool with a 1/8" cutting bit which I used like a router. I used the pink foam to create a straight edge to follow with the Dremel and I home made guide.

I actually had the cowling in the wrong position when I made the cut. Pictures 2 thru 4 show the firewall & rubber edging behind the bump inside the top cowl. The last picture shows it in the correct position. The firewall should be ahead of the bump, so that the ram air pressure seats and seals it against the bump.

I am really happy with this setup. It gives me easy access to everything between the firewall and the instrument panel. The only thing I need to remove is the SCAT tubing on the lower side panels if I want to take these panels completely off. I can't begin to count how many times I have taken these off to work in this area. Almost everything for my avionics, electrical and other systems are located here.

The only negatives I can think of is the windshield cannot be sealed to keep out rain and the firewall will not be totally sealed from the cabin. I keep the plane in my hanger and bought the factory cover incase I ever have to leave it outside with the potential for rain.

[efwd]

I have made my boot cowl removable. something John M. suggested was that I liberally apply a wax (surfboard wax is what I am going to use) to the contact surfaces of the cowl. Then I will either use silicone DAP or a tar like weather seal at the windshield and firewall. Should I ever need to remove the cowl, it should just require cleaning off the sealer and reapply when reinstalling. If all the electrical stuff is operational I hope to not need to remove the cowl any more frequently than John... 10 years! He did an avionics remodel.
Eddie

[David47]

Phil and Jim,

Phil, thanks for the detailed description and excellent photos of what you've done. I really like the idea of having removable boot cowl panels, where it makes sense. In the current 7SS kit, the boot cowl comes as a single piece, seperate from the top and bottom halves of the engine cowl. I think I'll limit it to cutting the boot cowl horizontally and having the lower section removable, as you've done. The top section I'll leave permanently attached so the windshield can be sealed, and go with a hinging instrument panel per Jim's suggestion. But even just having that lower boot cowl section removable must give great access to much of the gear aft of the firewall so I can see why you did it.

Good thinking and thanks to you both.

[Av8r3400]

This is good information, so to ease future searching I moved it to its own thread instead of pulling away from the seat pan discussion.

[jrevens]

...My cowling came as two pieces, top and bottom, and they went all the way back to the windshield and door frames...

You did such nice work on your plane, Phil. The engine installation and baffleing look beautiful.

[ken nougaret]

I modified my 2 piece cowl to make it a 3 piece with removable boot cowl. I thought i had a good fit between the boot and windshield while i was building but once complete i had a bigger gap than i should. Still trying to come up with a good filler solution.

[HighWing]

I find this discussion fascinating. Having built two IVs, there is little I can offer except I do like very much my full access from engine compartment to the back of the panel and a thought on the windshield to cowl "seal". I put nothing on either of the airplanes. I did put a catch channel below the windshield to divert leaking water on the first one, but nothing on the current airplane as after 9 years of flying the first one it was never an issue. I think a lot of my interest in the discussion is a result of my experience helping with the Lancair IV. With no provision for a cowl aft of the firewall and the location of the seats over the wing spar carry-through, I retired my 65 year-old back from the project when all was complete except avionics and upholstery.

[jiott]

I'm kind of curious how those of you who choose not to seal up the windshield to cowl gap deal with washing your airplane and/or windshield without letting water drip down into the electronics area? I can understand never flying in the rain and using a cover when parked outdoors, but wonder about washing. Maybe you never use a hose to rinse it off?

[PapuaPilot]

When I wash my plane and windshield I put a strip of 2" blue masking tape across the bottom of the windshield. I didn't think about putting a channel on the inside, that's a good idea.

I normally clean the bugs off the windshield with a spray bottle and microfiber cloth.

Thank you John. I really enjoyed this part of the build. The baffles are done in white powder coating. The white makes it easy to see if anything is leaking or cracked.

[David47]

Just wondering out loud whether a "P" seal attached to the inner edge of the boot cowl that butts up against the windshield might work. You'd need to have a bit of pressure against the seal to compress it to form a water resistant seal. I haven't got to this point yet (couple of weeks off) so not too familiar with the geometry but would it be possible to put screws through the boot cowl and windshield into anchor nuts bonded to the inside surface of the windshield ?.

[southwind32]

Does velcro make a waterproof seam? Has anyone tried it? Just thinking out loud.
Brian

[efwd]

Velcro is not water proof. It will resist flow through it temporarily. In my experience, water weakens the bond between the two surfaces. I have lost stuff while SCUBA diving this way.
Eddie

[HighWing]

I'm kind of curious how those of you who choose not to seal up the windshield to cowl gap deal with washing your airplane and/or windshield without letting water drip down into the electronics area? I can understand never flying in the rain and using a cover when parked outdoors, but wonder about washing. Maybe you never use a hose to rinse it off?

This question resulted in me removing the cowl and evaluating what behind the panel is vulnerable to possible water drips. The only thing that extended forward of the windshield was the altitude encoder and only about 3/4" of one corner. This was evaluated only considering the exact area below the lip of the windshield. I had also recently washed the airplane to prepare it for our local hot rod and airplane show here. I carefully inspected anything in harms way for any evidence of water - lots of dust under there and found nothing. Because of many vulnerable areas wing roots, turtle deck, horizontal stabilizer root fairings, etc. I try to be prudent with the hose.

[jiott]

You are right Lowell, the water dripping problem depends a lot on your layout of the electronics bay. I was thinking mostly about my layout that has two shelves that extend under the drip line with things like xponder, engine instrument module, etc. mounted on them. If a person were planning to leave that area unsealed you could deliberately mount vulnerable items out of harms way.