drain grommets

[Scott]

Hi All
What's the consensus on drain grommets in the wings...
one drain per bay?
inboard or outboard
there is no dihedral so depending on how the aircraft is sitting on the ground the lowest point could be inboard or outboard.

[Robert Lees]

Re: drain grommets

There is dihedral (1 degree) so IMHO one drain grommet per bay on the inboard side. One inboard and one outboard per bay would equally be good.

I prefer the Poly-Fiber aluminium grommets (even on a Ceconite covering). They are lower-profile and easier to cut/burn a neat 1/4" hole. Don't forget the doily!




My text: "To make a neat drain hole, roughly cut out the 1/4" inner fabric (I use a scalpel), and then burn the excess with a small-tipped soldering iron..then use the scalpel again to trim off the black built-up edge."

Rob

[3Dreaming]

Re: drain grommets

There is some dihedral, but not much. I always put them each bay and inboard. With Poly fiber I seem to remember that you can put a drain hole where ever you want as long as there is 2 layers of fabric. You don't have to put a actual grommet in place.

[Robert Lees]

Re: drain grommets

Tom is correct...I just like the grommet there for a neat(er) hole

[N95334]

Re: drain grommets

What about the bottom of the fuselage and the bottom of the tail feathers?
Use seaplane ones?

[3Dreaming]

Re: drain grommets

Tom is correct...I just like the grommet there for a neat(er) hole

I use them too. I have been using them since before Alexander Aeroplane company was bought out by Aircraft Spruce. I just thought I would mention in case he wanted to adda hole someplace where there wasn't a grommet, but had 2 layers of fabric.

[Robert Lees]

Re: drain grommets

What about the bottom of the fuselage and the bottom of the tail feathers?
Use seaplane ones?

No just use regular ones (unless yours is a seaplane!)

[PA1195]

Re: drain grommets

Drain grommets are great until they plug up with debris or become home to insects. Seaplane ones can be harder to inspect and keep open and bugs love to raise their young inside. Every plane that flies or is parked in rain needs drains in the low spots even those that are land only. Especially with wood parts inside.

I pay for double drains inboard and outboard in the wings and controls given the opportunity. The lower rudder and bottom tail are critical spots, plus at any low spot near cross tubing in the fuselage belly the fabric lays next to.

Gary

[N96337]

Re: drain grommets

I prefer seaplane grommets always. And....think about it....you've got dihedral, so you want the drain on the uphill side of the rib, which is outboard, so that any moisture will flow into the drain.
John

[N95334]

Re: drain grommets

N96337
I am with you somewhat. I think seaplane grommets are best under the fuselage bottom and bottom of tail feather and the bottom of the rudder.
But use the regular ones everywhere else. My reason is going through water or mud puddles the water will splash up into the holes if not covered as seaplane ones cover the holes.

[3Dreaming]

Re: drain grommets

I prefer seaplane grommets always. And....think about it....you've got dihedral, so you want the drain on the uphill side of the rib, which is outboard, so that any moisture will flow into the drain.
John

Outboard in relation to the rib, but inboard in relation to the bay.

[PA1195]

Re: drain grommets

luckily I've had seaplane grommets on most planes. They tend to get dislodged unless a small doily patch is placed over the edge when covering. Glue may not hold especially in the cold.

Every spring I take my air compressor to the plane and blow out the previous year's debris collection. That's easier than using an angled pick or pipe cleaner.

One Cub I bought used was a seaplane but had non-seaplane grommets. Water got in easier and when recovered there was lots of corrosion especially in the fuselage tail, stabilizer/elevators, and rudder.

I think it's important in rudders to have more than one drain location so there's some airflow through the structure. Water can condense in the upper part so air flow might help keep it dryer (?)

I also try to keep any low spots near metal tubing sprayed with a fabric compatible corrosion inhibitor through the grommets....like the rudder and tail parts.

Gary

[Scott]

Re: drain grommets

Thanks all

[astjp2]

Re: drain grommets

I used seaplane grommets everywhere, but I like the look....

[n6346m]

Re: drain grommets

I like seaplane grommets not only because they help keep the splash out of the belly but because I believe that due to their shape, they create a small amount of negative pressure and allow air to flow through easier.
When I recovered my Stinson floatplane I had to replace a lot of the formers and stringers of the lower "basket" because of corrosion. This time I wanted to make sure that the belly drained properly. When it came time to install the drain grommets I took a garden hose and filled up the fuselage with water (well not really full) and went around and poked holes wherever water had pooled. When I was done with that. I picked up the tail to a simulated seaplane position and went trough it again and made sure there was no more trapped water.
When I was looking for an airplane before I purchased my L-2, I looked at a real nice Aeronca L-3 in Cincinnati. It was very pretty with a nice fabric job and had obviously been hangared since its restoration. At the time I went to see the airplane it was in a dealer's tiedown area outside since he did not hangar space for it. After he took me for a demo flight, I removed my headset while taxiing back to the ramp and being in the back seat I could splashing noise behind me. It had rained the night before and after removing the rearmost inspection cover I found it full of water. There wasn't a single drain hole in the entire belly of that airplane. Needless to say, I passed on that airplane and that is a good thing because if I had bought that L-3 I would have never found my L-2 which I dearly love.