Relief tubes in sailplanes
I have a couple thousand hours in sailplanes and use a relief tube on every flight. I fly a lot in regional and natinal competitions where our flights are from three to five hours long. What we have learned from long hours in the cockpit is that continuous hydration and relief are necessary to keep your electrolytes in balance, and that failure to do so can have an negative effect on the way you feel and think at the end of a flight. And that's not a good time to be making bad decisions. A relief system is seen as a matter of safety.
A problem with using a relief system in a sailplane is that modern high-performance gliders require one hand on the stick at all times to keep it going where you want. So, the relief system of choice is a completely hands-off device consisting of an external male catheter like one of these:
http://www.mentorcorp.com/bladder-control/incontinence-male/MEC-ClearAdv.htm. The catheter usually is connected with a barbed tubing connector to a length of latex surgical tubing that comes up through the floor pan just aft of the stick. Below the floor pan, the tubing usually runs aft to an exit in the gear well just behind the cockpit. You get in, unzip, hook up, and fly the whole flight "read to go".
However, the external catheter probably isn't necessary in an RV, especially with an autopilot. I think a modest sized open-mouthed vessel of some sort with a tubing outlet that you can leave hooked up to the relief tube would be better. Perhaps a plastic funnel like this would work:
http://www.usplastic.com/catalog/pr...splastic&category_name=25425&product_id=18470 The funnel could be rinsed with fresh water after use, and capped off with its lid. I think that would keep things clean and odor free in the cockpit.
An important variable is how and where the relief tube exits the fuselage. Many pilots have had the experience of finding rust in the tail wheel and/or lower rudder hinge from a relief tube opening that exited flush with the outside of the fuselage. Some experimentation was done with dyed water that showed it was necessary to locate the relief tube exit point well away from the fuselage to prevent the stream of fluid from attaching to the fuselage and wetting everything downstream of that point. One effective method that has been widely adopted is to attach the relief tube to the rear lower corner of one gear door, which puts it four to five inched away from the fuselage when the doors are open. You have to lower the gear when using the relief system, but this keeps fluid off of the fuselage. Another scheme I have heard of, but never seen, is a lance made from tubing that can be lowered into the air stream through a hole in the bottom of the fuselage for use, and retracted after.
I haven't given a lot of thought yet to locating a relief tube exit on an RV-7, and I'm several months away from having a fuselage to work with myself. I don't think you would want to run the tube forward to go down the gear leg, and I think you need to keep the tubing run short and route it so that it will drain empty after each use. Perhaps a lance made from a piece of stainless tubing would be a workable solution for an RV. Ideally, you need a way to close off the exit port when not in use. Perhaps a ball valve could be used on the exit port. You would extract the lance and close the ball valve when not in use.
In short, I think I would try a Clean Funnel, a length of latex surgical tubing, and a stainless steel tubing lance long enough that it could be inserted through a hole in the bottom of the fuselage and extended into the air stream. The tubing would, of course, have to be strong enough to withstand aerodynamic loads at cruise speeds.
). A bulkhead fitting and a turkey baster...LOL! The funniest part is that this is a serious conversation.
