[NYTOM]

Anybody out there have any tips on drilling drain holes for any rain water or other moisture that collects in the plane. I'm finally completing my first wing and realized there's no provisions for any drain holes. My old Ercoupe had drain holes everywhere and it was amazing how much water passed through that thing. I figure it's pretty much common sense where the waters going to collect but what size holes are you guys drilling. I might have to tie-down outside for a while waiting for a hanger rental so it's kind of important .

 

[AlexPeterson]

Great question

Tom, I don't recall putting any in the wings, it seems like those are ok. The various corner reliefs built into the ribs, etc., make for allowing water to drain. It is the fuselage and the rudder bottom that need drain holes for sure. Once the plane is complete, you can spray water on the belly, and based upon where it collects, you will know where to drill the hole(s). Seems like I had two, somewhere in the vicinity of the aft wing spar. The 7's and 9's would be quite different.

 

[NYTOM]

Thanks for the good advice

Tom, I don't recall putting any in the wings, it seems like those are ok. The various corner reliefs built into the ribs, etc., make for allowing water to drain.

After I read your response I went down and stared at my half skinned wing and imagined I was a splash of water trying to get out. Your absolutely right Alex, it doesn't seem like it's going to be a problem.
Hopefully I'll get to try your idea on my fuselage within the year.
Thanks for your help Alex.
PS Nice web site you have there.

 

[jsharkey]

Tom, I don't recall putting any in the wings, it seems like those are ok. The various corner reliefs built into the ribs, etc., make for allowing water to drain. It is the fuselage and the rudder bottom that need drain holes for sure. Once the plane is complete, you can spray water on the belly, and based upon where it collects, you will know where to drill the hole(s). Seems like I had two, somewhere in the vicinity of the aft wing spar. The 7's and 9's would be quite different.

Out of interest - how big a diameter were the holes?

Jim Sharkey
RV6 - Details!

 

[Vern]

Water Drains

You should consider a 1/8" drain hole in the airbox bottom, rudder bottom,and in front of each fuselage former. I've seen aircraft with 4-6" deep water in the rear fuselage (not RV's).

Most RV's are pampered and live in nice hangars, but being tied down on x-country or a heavy rain during flight could change things.

I saw a famous RV-6 abort takeoff and almost drown out the engine because of no airbox drain after a plane wash.

 

[AlexPeterson]

After I read your response I went down and stared at my half skinned wing and imagined I was a splash of water trying to get out. Your absolutely right Alex, it doesn't seem like it's going to be a problem.
Hopefully I'll get to try your idea on my fuselage within the year.
Thanks for your help Alex.
PS Nice web site you have there.

Tom - thanks.

Out of interest - how big a diameter were the holes?

Jim Sharkey
RV6 - Details!

Don't recall exactly - maybe 1/4" since that is the smallest my unibit can make.

 

[noelf]

I'm building a -6A and installed drain holes on the aft side of each bulkhead. Taildraggers may want these holes on the front side of the bulkheads. The hole size was smaller than a #40 drill bit...I think.

I positioned the drain holes on the center line (while the a/c was in the jig) so that at some future date, I could relocate the center line with little effort to validate any asymmetric issues/ concerns/screw-ups that I might come up with.

 

[Mel]

The hole size was smaller than a #40 drill bit...I think.

I would recommend that the holes be about 3/16" as a smaller hole can easily be clogged by trash. The drain holes in my -6 are 3/16".

 

[jsharkey]

I would recommend that the holes be about 3/16" as a smaller hole can easily be clogged by trash. The drain holes in my -6 are 3/16".

That sounds about right Mel,

Too small and even surface tension might stop all the water draining.

Where did you place them? Center line?

Jim

 

[Mel]

Where did you place them? Center line?
Jim

Centerline just forward of each bulkhead.

 

[roee]

Why forward of the bulkheads?

Centerline just forward of each bulkhead.

Mel, did you place them forward of the bulkheads because yours is a tail dragger? And for a tri-gear wouldn't the drain holes go just aft of each bulkhead? Seems like you'd want the drain holes at the lowest point of each bay at ground attitude (i.e. when the airplane is parked on the ramp). Right?

-Roee

 

[Mel]

Mel, did you place them forward of the bulkheads because yours is a tail dragger? And for a tri-gear wouldn't the drain holes go just aft of each bulkhead? Seems like you'd want the drain holes at the lowest point of each bay at ground attitude (i.e. when the airplane is parked on the ramp). Right?

-Roee

That's correct. It depends on how your airplane sits on the ground. Water generally flows downhill. Drain holes should be at the lowest point of any "compartment".

 

[USCANAM]

Drain Holes

Not having rain holes bothered me for quite a while, so I installed some just before painting the RV-9A.
I decided to just put them in the fuselage.
Looked at the plane while sitting level and decided what were the lowest points.
Put one in front of the main spar to collect any water that might be up front, and put one behind the main spar and the next bulkhead behind it.
Here's how we made them.
Drilled a 1/4" hole with unibit. Took Philips screwdriver with 1/4" shank, inserted about 1" into hole, and moved handle of screwdriver towards rear of plane. This will make the hole face towards the rear, and create a siphon effect.
One problem with the 2024 skin, is you might create a crack in the skin if you go too much. If this happens, simply take a rat tailed file, and file out the crack.
Hope this helps
Jack
RV9A
48 hours
Almost painted after a month of work!!

 

[rv7charlie]

1/8" hole with a piece of safety wire in it can keep the hole size small & keep dirt from clogging it up. A flat spiral inside the fuselage with a downward line through the hole, then another spiral outside to keep it in the hole. Vibration makes the wire move occasionally, clearing dirt out of the hole.

This tip came from an old A&P after I had a rather unpleasant experience in the Luscombe 8A I trained in. After a month of rain (plane tied down outside) I went out to practice touch & goes (student at the time). Water had accumulated in the belly & on each touchdown/liftoff would slosh back to the next bulkhead. The drain holes were clogged. After a couple of circuits with the trim changing each time, I realized that there was a problem (duh...) & landed using forward stick instead of back stick in the 'flair'.

Charlie