Sat Apr 24 2021

Rain gutter experiments

Using these test parts to make another attempt to control the exit path of water in the rain gutter. Formed an exit path with UHMW tape.

...then filed a slot to act as a discontinuity in the rain gutter strip before droplets can travel to the longerons.

Yeah, that didn't work *at all*. :-( Water did flow through the exit path, but once out of the channel, it just ran along the edge down to the end of the parts.

Let's try turning *this* tab down as a drip edge. Seeing that the bend is at an angle that leads forward, I'm concerned that water will want to follow this bend rather than running downhill to drip off the point.

...and that's exactly what happened.

Maybe if I bend that tab down more steeply?

No improvement. Here's a view from the underside.

Now, a different slot design where the bend of the drip edge should promote movement aft.

That's probably the best result so far. While testing this, I noticed that the little tip of the drip edge actually protrudes aft of the edge of the rain gutter strip a bit, so I trimmed it off.

If you look at the full size image (click on the small image to the left), you can see a gigantic drop stuck in the angle formed by the canopy skin and the drip edge. Definitely not ideal. Dang, once water latches on to a surface, it doesn't want to let go.

Variation on the theme: cut the drip edge square.

That seems worse...droplets now just stick to the underside of the canopy skin unil they get past the gap, then continue their happy path towards the longeron. Arg!

Maybe another geometry change for the end of the channel? Make it more of an abrupt exit. Surely that will help, right? Wrong. If anything that just made it worse.

After lunch I decided to take a different approach. Maybe I can make a wick from some glass fibers to wick the water out of the channel. I separated several bundles of fibers from a remnant of BID glass cloth.

...used some thread to tie the bundle at approximately the halfway point...

...fed that string through a piece of 1/4" diameter tubing. The bundle folded in half as I pulled it into the tubing.

Before pulling it totally inside, I trimmed the uneven ends square.

Hrm, I could tell that bundle wasn't thick wasn't going to stay put inside the tubing. So, I doubled it over once more and repeated the process.

Here's the fiberglass wick sticking out of the end of the tubing.

Since prior tests had consumed the length of my rain channel strip with varous notches and drip edges, etc. I cut a fresh piece and laid out UHMW tape for the forthcoming wick test.

Wick clamped in place...almost ready to test.

So, it appears I'm really good at finding things that don't work. This idea is proving to be as dumb as it sounds.

With the top strip off, I can see that it *is* actually wicking the water away...just very, very slowly. I'm going to think about this some more and work on it tomorrow.