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Subject: Re: [LML] [LNC2] Wing Tank Drains
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-6651594@logan.com>
Date: Tue, 24 Dec 2013 08:56:39 -0500
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Message-Id: <457E4F17-6460-455B-9E95-EFFF3B45A255@earthlink.net>
References: <list-6651594@logan.com>
To: "Lancair Mailing List" <lml@lancaironline.net>

The approach taken by some is to simply arrange for the fuel pickup to =
be higher in the tank than the sump drain.

This does lead to a question I hadn't thought about:   If the sump drain =
is under water when it freezes, how do you get the water/ice out of your =
tanks, short of bringing the whole airplane into a warm hangar?

On Dec 24, 2013, at 7:45 AM, John Cooper wrote:

When building my 235 wing tanks, I was concerned that the drain valve =
wasn't located at the lowest part of the tank, possibly allowing water =
to accumulate next to the BL-51(?) rib. Here is what the instruction =
manual showed:

<Wing Tank Drain.jpg>

I chose to mount the flush drain exactly in the lowest portion of the =
bottom wing skin where there was no foam core. I drilled a hole at the =
lowest point then used structural adhesive to glue the aluminum hard =
point onto the outside of the bottom wing skin so that the drain holes =
in the quick-drain were peeking just above the interior of the tank =
sealant. Afterwords, I fiberglassed over the hard point, which I had =
previously rounded and beveled. When it came time to finish the =
aircraft, I used micro to build up an aerodynamic "blister" to cover the =
hard point and quick drain. I probably lost a couple of Potential Knots =
of airspeed by sticking the drain out into the wind, but I won't have to =
worry so much about un-drainable water in the wing tanks.

Speaking of water, we had a recent weather change here in NC from 40-ish =
to warm and humid and rainy. The entire aircraft was sweating in the =
hangar - not just the engine but the fiberglass airframe as well. I'd =
never seen anything like that and I have to assume that under such =
conditions, moisture could also build up inside the fuel tanks. It's =
something to think about. Here's what my "blister" looks like, and you =
can actually see the condensation in the photo:

<Transformed_Lancair lower cowling - wing sumps 005.JPG>