A

alcladrv

Well Known Member
I've been flying my -7A for 4 years and kept it in a hangar until the the last 8 months. After moving to a new location in TN where hangars aren't available, I've kept it tied down on the ramp.

Today, I removed the seats and forward floor pans that cover the spars and sticks. Inside was puddled water between all of the ribs under the seats. After soaking it up and mopping it out, it amounted to over 32 ounces (1 quart) of water.

The bottom of the cabin is a continuous sheet of aluminum. The plans didn't specify any drain holes.

Anybody with a similar experience? Where did you drill drain holes?
 
No holes, sealed the outside.

alcladrv said:
The bottom of the cabin is a continuous sheet of aluminum. The plans didn't specify any drain holes.

Anybody with a similar experience? Where did you drill drain holes?
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The water enters the area between the wing and the fuselage through the wing root fairings, then seeps under the fuselage side skins where the bottom skin meets the outside skin(s).

When I was finishing up my fuselage, another builder tipped me off to this. We laid a bead of sealant from the forward edge to the rear at the bottom of the fuselage side skins to prevent water from entering under the fuselage side skins.

It is also possible water enters around your canopy, especially if you have a slider. The only prevention is a cover. :(

YMMV
 
N131RV said:
The water enters the area between the wing and the fuselage through the wing root fairings, then seeps under the fuselage side skins where the bottom skin meets the outside skin(s).

When I was finishing up my fuselage, another builder tipped me off to this. We laid a bead of sealant from the forward edge to the rear at the bottom of the fuselage side skins to prevent water from entering under the fuselage side skins.

It is also possible water enters around your canopy, especially if you have a slider. The only prevention is a cover. :(

YMMV
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Doing what you can to prevent water from entering is a good thing. But if there's any possibility that water will still get in (and there always is that possibility), then shouldn't you make provisions for drainage?
 
drain holes

Where did you drill drain holes?[/QUOTE]

Before adding holes in production aircraft, I look up negligible damage limits. Typical for this type and size aircraft you could expect to see a half inch hole a minimum of one ince away from any structure or fastener.

Andrew
 
That's a lot of water

I have been flying my RV-6A slider for five years and I've never experienced that problem. I do keep the plane in a hangar and when I travel I always put on my good custom cover from Bruce's Custom Covers. You may be using a cover but if not I would do that right away, for rain protection, sun protection and to discourage acts by others that are not in your airplane's best interest. If you are using a cover then you have to wonder when it came in - removing the seat pans is something I do once a year - did it come in during flight or sitting on the ramp. Most of the fuselage penetrations are at the wing roots and seepage under the wing root closure strip while the plane is sitting out in heavy rain is a good possibility and the canopy cover will not help that problem.

Bob Axsom
 
awm said:
Where did you drill drain holes?
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Before adding holes in production aircraft, I look up negligible damage limits. Typical for this type and size aircraft you could expect to see a half inch hole a minimum of one ince away from any structure or fastener.

Andrew[/QUOTE]




BEFORE you drill any holes, take a look at a Piper and see the size that they drilled. For location, set a bearing in the location that would hold water and watch where it finds the lowest spot. Respect edge distance when you go to drill.
My 6A has a drain hole at every bulkhead.
 
Need Holes

gasman said:
Respect edge distance when you go to drill.
My 6A has a drain hole at every bulkhead.
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Two reasons for drain holes. First to drain out water that gets in (and it will get in), and second to drain leaked fuel or other fluids. At the big aircraft company we put drain holes in every bay (except the fuel cells). Some bays drain to other bays that then drain overboard.

I put a 1/8" drain hole forward of each bulkhead. My RV-6A sits 3 degrees nose high therefore the water/fuel will drain. I drilled the holes just forward of the the bulkhead flange if it was forward of the bukhead plane.
 
Thanks for your responses.

My -7A is always parked outside with a cover that reaches from just behind the firewall to an inch or so aft of the "doghouse" on my slider. During a downpour at Oshkosh, it proved to be very water repellent and none got in the cabin.

During flights in rain, water will occasionally drip from the canopy latch. More will enter through the doghouse, which I've learned catch by hanging a folded-up water absorbent cloth on the support rod that makes a good coat hanger on the aft baggage wall.

The water low point is right under the seats. I did a little experiment with an 1/8" hole in a likely location in the wing root. While some water will drain through it. There was still a fair amount of water remaining when the surface tension of the water took over and no more drained out.

I'm reluctant to drill too many holes inline with the engine exhaust. Do you notice any entry of oily exhaust residue?

Mike
 
One way to determine where to drill is to spray water on the underside, and see where it tends to finally drip to the ground. I have a 6A, and I drilled two holes. 7A's sit much differently on the ground, so I can't suggest where the hole(s) might need to be.

I agree with Joe (131RV) that a bead of sealant along the fuse sides to bottom skins is a good idea. But, I still would drill some holes, 1/4" diameter should be enough. In a driving rain, you would be surprised how many places it can find its way into the fuse. In fact, the way the 7A's sit, it might be a down hill run from the tail to mid-fuse?
 
alcladrv said:
Thanks for your responses.

My -7A is always parked outside with a cover that reaches from just behind the firewall to an inch or so aft of the "doghouse" on my slider. During a downpour at Oshkosh, it proved to be very water repellent and none got in the cabin.
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My Bruce cover has been great for the OSH downpours. One othe place to drill a hole is in the bottom of the rudder. Two years ago at OSH my rudder had a quart of water in it. Not a good thing to have that much mass in the bottom of the rudder.
 
Part of the final inspection here in Canada is to make sure there are adequate
drain holes in the fuselage. Some are drilled in the belly between bulk heads and some bulk heads are drilled to allow the water to run down and out the tail.
 
before drilling

BEFORE you drill any holes, take a look at a Piper and see the size that they drilled.

Thanks gasman
Andrew
 
Not too big, not too small......

Not sure of the "proper" size for drain holes, but if you drill them too small, the water won't drip out due to the normal surface tension of the water. My GUESS is that 1/8" would be the smallest, and IMHO a little larger would be better.

$0.02 and YMMV
 
alcladrv said:
I'm reluctant to drill too many holes inline with the engine exhaust. Do you notice any entry of oily exhaust residue?
Click to expand...

To prevent air pressure from forcing its way into the drain holes perhaps you could consider glueing/riveting something like a seaplane drain grommet at those locations. It would create create a low pressure area at the drain hole to suck water out and prevent water/exhaust entry.
 
Where to put drain holes

Asked Vans the same question, and they said to drill them where the water is standing. Each plane will sit differently depending on the ramp slope where you are parked.
 
I learned to fly in a ramp-dog Luscombe. During my training, we had several weeks of rainy weather with no flying. With clear weather, my1st flight for T&G practice resulted in an unexpected number of turns on the trim handle when setting up for landing. The next circuit was even more strange, with almost no nose-up trim needed for landing trim. The next lift off & crosswind turn & I knew something was really wrong; even the tower called to ask if I had a problem. I had to maintain forward pressure on the stick to keep from pitching up, even on final. After getting it back on the ground, I found that water had been trapped under the seat area, and on each climbout it was sloshing over the bulkheads further back in the tail. The Luscombe had ~1/8" drains at each bulkhead, but they were clogged with debris. I cleared the holes with a small screwdriver & the plane must have peed for 20 minutes.

Friends in aviation maintenance later recommended a loop of safety wire in each hole, set up so that it's free to dance slightly with vibration but can't come out either the top or bottom.

I know that most RVers wouldn't let their interiors get that dirty, but with no drain holes water in the fuselage flight could be pretty dangerous.

Charlie
 
I used to fly a spam can with 1/8" drain holes in the baggage area.

At first you'd think that was great. But after a few months of dust, maybe an old insect carcass, spiderweb, or a combination of them would wash into the hole and block it.

After a rain, I frequently had to push a toothpick or something into the hole to clear it enough to drain.

I sure wished those holes were large enough to drain on their own..
 
Same thing hapened to my Spam

I had a 172 that built up several gallons of water in the tail behind each bulkhead. It had 1/8" drain holes that had gotten clogged up with dirt and algae. I had to poke a wire in each hole for it to drain. I hate to think if anyone had flown it like that.
 
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