With Chip's encouragement, I repost this, which I consider one the RAS
Top 10 Postings (note that it's written by Chip, not me):

==============
Subject: Relief Bags
From: (JNBearden)
Newsgroups: rec.aviation.soaring

In article , Mike Lindsay
writes:

I'm having my own plane
configured to have the relief tube exit through the gear door.

This is what an old friend of mine did, he said you have to be very
careful because it will cause corrosion in the u/c.

There should be no problem so long as you put the exit end of the tubing
on the lower aft corner of a gear door. This is the technique Karl
Striedieck wrote about in his excellent article, entitled "To Pee or Not
To Pee" in Soaring magazine.

The idea of getting the dump tube away from the fuselage actually goes
back at least 15 years (probably much more than that). The first time I
saw it was (as I recall) on Kai Gertsen's 301 Libelle in the early 80s
at Elmira. I radioed to tell him his wheel was down while on course at
the Nationals and wondered why he ignored me! Kai attached the tubing
directly to the landing gear which, on the Libelle, got the exit port
well below the fuselage.

Six years ago, after I heard all the horror stories about urine
accumulating in the bilges, etc., and while contemplating the difficulty
of getting a tube installed in the fuselage skin aft of the wheel well
in the diminutive fuselage of my new ASW-24, I installed the same thing
as Kai, but put the dump tube on the gear door, thinking I wouldn't have
to extend the gear all the way. In fact, I found that in the '24, I only
had to lower the gear slightly to flip the doors open 90 degrees, so the
corner of the door is perpendicular to and farthest away from the
fuselage. Karl--who with a few other ridge pilots had made the external
catheter socially acceptable in today's cockpits--then took things a
step further and performed some experiments with colored water on his
ASW-20--the '20s having been notorious for sucking urine into the low
pressure area at the base of the vertical fin and corroding the lower
rudder bearing--and demonstrated conclusively that this method avoided
the problems of the typical exit on the bottom of the fuselage. The rest
is history.

Another method I've heard of (on a '20) is an extendable tube which the
pilot pushes out into the airstream perpendicular to the fuselage
through a small hole drilled in the belly near the seat back rest. This
gets the exit even farther away from the fuselage and might be the best
method of all.

I much prefer the external catheter/dump tube method because it's easier
than using bags (no hands required for peeing), especially for ridge and
gaggle flying (from experience, though, pilots below you don't always
react well to seeing your wheel come down in a gaggle).

Plus I hate the idea of littering the countryside with non-biodegradable
plastic bags. To say that a few more bags won't make much difference in
the general clutter seems like saying that it's OK to steal a little
money from a fairly well to do pilot because he won't be able to tell
the difference. When a method works better AND avoids the litter
problem, I can't see why anyone wouldn't go to the little bit of trouble
to install the system on his own sailplane.

No problems with skin irritation so far as I know. The slight bit of
negative pressure at the exit port seems to collapse the catheter and
empty it pretty well.

Known problems: If it's below freezing, use a "T" and another length of
tubing to blow out the dump line (don't confuse it with your water
bottle tube!). You haven't experienced everything flying has to offer
until you've looked down to see a rapidly expanding catheter "water
balloon" about to blow off your male appendage at 15,000 feet in the
wave. Fortunately in my case the blockage melted quickly, releasing the
"tension", as I was fast running out of ideas (and bladder control) on
how to defuse the situation. The other problem also relates to urine
which remains in the low point of the tubing under the seat, which can
back flow either when the nose goes down on final approach (from
experience, bad if you've already unhooked) or in the trailer after the
flight.

Solutions include not unhooking until after you've landed (from
experience, don't roll to a stop right next to the spectators),
installing a small valve in the line close to the catheter fitting,
removing the catheter but leaving it attached to the tube and tying a
knot in it (from experience, this can be fun on fast final glides!), and
using air or water to blow/flush out the tube after landing (from
experience, make sure your crew is not washing the dirt off the
belly as you do this!)

Other issues for the senstive male: Can't recall whether Karl's article
mentioned it or not but sorry, guys, size DOES matter. Unlike condoms,
external catheters come in different sizes. If you were too embarrassed
to buy condoms when you were younger, this won't be any easier. Not to
worry, the literature for the product says that if it's too big (the
catheter, that is), just squeeze the excess together so the adhesive
sticks to itself and forms a fold. Still, too big is too big; buy a few
and find out what size you need. Surgical supply houses sell them,
sometimes at wildly different prices though even then the cost is
minimal ($1.25 to $2.50 each). Sometimes you can get a quantity
discount so maybe several pilots can pool their purchases (and the
bravest one can go buy them). Don't know for sure what the shelf life is
but I've used some which were several years old without problems (it's
not like you carry one around in your wallet in case you get lucky with
a friend's ASW-27). Also, I find it easier to put the thing on before
launch. From experience, just make sure no spectators or crew persons of
the opposite sex wander up to your cockpit as you're finishing up the
"assembly" process or you're likely to get some strange looks.

Chip Bearden
ASW-24 "JB"
=========================

Back to me: At the 2004 SSA convention, Dick Johnson said a flying with
a slight slip while using a relief system will ensure the liquid is
blown away from the tail boom in all but the poorest installations.
--
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Eric Greenwell
Washington State
USA