P

PaulR

Well Known Member
Most if not all, of the airplanes I've ever flown have a small drain hole rearward (tricycle) of each bulkhead in the fuselage. I haven't seen anything in the plans about this though I may have missed it. I did a quick search and found a couple of threads that talk about it a little but nothing definitive.

So, I'm thinking just aft of the each bulkhead and probably also in the airbox. (carbed) Maybe an 1/8 or 3/16 hole to allow water to leave. What does everyone else do?
 
Draining water from wings

I haven't seen anything in the builders instructions about water drains either. And what about the wings? Are these self draining because of the dihederal angle. I know there are fuselage drains in my C-150 as PaulR has said, I also notice a few drain holes in the bottom wing skins near the aft spar.
 
In canada we require these holes in order to pass the final inspection. I drill a 1/8 hole in the low point of the fuselage in every second rib bay.
 
There is a small note in the plans about this. Just as you describe a #30 hole just aft of each fuse bulkhead.
 
TroyBranch said:
In canada we require these holes in order to pass the final inspection. I drill a 1/8 hole in the low point of the fuselage in every second rib bay.
Click to expand...

Troy has it right,

Plus... I always put a hole where the fuel pump resides so in case there is a leak the fuel has a path to drain overboard and not accumulate :eek:

Don't forget the rudder fairing and inlet airbox as well.
 
kevinh said:
There is a small note in the plans about this. Just as you describe a #30 hole just aft of each fuse bulkhead.
Click to expand...

There is???? I don't recall seeing this, but then again, I've parted company with the plans a while back once I got to FF stuff...this is a good topic and I'm very inrerested to know if there are any suggestions here...

Thanks...

Steve
 
1/8"???

Walt,
Is a no. 30 or 1/8" big enough? Seems like the surface tension on water might be to great to allow it to drain. Good idea about the boost pump. I wouldn't have thought about that location.
 
Paul, find some scrap aluminum and make a depression to hold water (actually it could be a can).

Fill it with a certain level of water. Maybe 1 inch. Drill a small hole (perhaps 1/16"). If it does not drain (surface tension/head issues) drill a larger hole.

Continue with less water depth until you determine what size hole is needed for the depth water you want to drain. Obviously the hole has to be larger for shallower water depths.

I will have to measure what I did but a wag is around 3/16" hole.
 
Last edited:
The only drainage holes I've seen on the plans for the RV-9A are on DWG 7, Note 3:

Add 1/4" dia. drainage hole to R-911 (Rudder Bottom) at low point when the airplane is in ground attitude.

I haven't drilled any other drainage holes in the fuselage. If there is direction in the plans to do that, I would like to see it.

It is things like this that would make having the plans in digital form so much better for searching... Imagine being able to "google" the preview plans and build instructions.
 
PaulR said:
Walt,
Is a no. 30 or 1/8" big enough? Seems like the surface tension on water might be to great to allow it to drain. Good idea about the boost pump. I wouldn't have thought about that location.
Click to expand...

I agree, #30 and 1/8" is too small in my real world experience. Just a little bit of dust collection compounds the problem of clean surface tension. I opened mine up to almost 3/16" after finding non-draining water.
 
PaulR said:
Walt,
Is a no. 30 or 1/8" big enough? Seems like the surface tension on water might be to great to allow it to drain. Good idea about the boost pump. I wouldn't have thought about that location.
Click to expand...

I usually use something along the lines of a #19 or #21
 
One technique to keep the hole clear is to use a piece of safety wire through the hole, with a loop on top & bottom. The loops can be bent over flat, but leaving play in the wire. The idea is that normal vibration will keep dust/dirt broken up so it can depart without plugging the hole.

I can testify that undetected water in the tailcone can be very---interesting.

Charlie
 
A hole for the boost pump was mentioned. Where have people put this hole?? Sounds like a good idea that I did not do.

My concern is that (RV7) my boost Pump is left side floor in cockpit and the exhaust is just forward of this area. How did people deal with this for safety?
 
Charlie above identifies a great option to keep drain holes clean w/ wire inputs! Man that is a great idea.
 
I'm sorry, but I don't recall any reference to any drain holes in the plans for the -7. When I'm out at the field next week, I'll check our club planes (Cessnas and Pipers), but I honestly don't recall seeing any drain holes in them, either.

I'm not saying it's a bad idea, I'd just like more than CW to go on before I start poking holes in my airframe.
 
Flying Scotsman said:
I'm sorry, but I don't recall any reference to any drain holes in the plans for the -7. When I'm out at the field next week, I'll check our club planes (Cessnas and Pipers), but I honestly don't recall seeing any drain holes in them, either.

I'm not saying it's a bad idea, I'd just like more than CW to go on before I start poking holes in my airframe.
Click to expand...

For the RV-7 emp, on DWG-7 there is a note for the rudder bottom cap: "Note: ADD 1/4 DIA DRAIN. HOLE TO R-911 AT LOW POINT WHEN AIRPLANE IS IN GROUND ATTITUDE"

But, I only have the full-size plans the for emp, and the preview plans are teeeeeeeny. :p So, I didn't look at the fuse/wings.
 
scard said:
I opened mine up to almost 3/16" after finding non-draining water.
Click to expand...

Of course that water will sit between the fuse skin and the bulkheads and promote corrosion almost immediately in bare Alclad un-primed aircraft. And in most cases the corrosion will initially go unnoticed. And when it IS noticed it will be virtually impossible to rectify.
 
In my -7A, I found the 1/8" holes were too small, so I increased up to 1/4" diameter. I drilled holes aft of the fuselage bulkheads after finding retained water aft of the baggage area bulkhead.

After sitting out overnight in a rain shower while traveling, I've found that water will find it's way to the center fuselage under the seats. Unfortunately, I can't always get it it into a hangar during rain storms. I'm still trying to figure out what path the water takes to get there. I've been reluctant to drill a drain hole directly under the seats, but I may have to to.

I'm sure if the water flows down the rudder and then all the way forward or somehow flows off of the canopy and fuselage down the sides past the wing root fairing. My wingroot seals are are tight and in good shape.

I've checked out Pipers and Cessnas and found drain holes aft of the fuselage bulkheads that are typically 1/8 - 3/16 diameter, but they were typically not flowing freely and needed to be cleaned out.

Mike
 
All this talk about actually getting water Inside the plane is a good reason to not put insulation in the floor. I did in the ten under the rear foot wells, baggage area and wish I hadn't, none in the nine. After it being out in rain on many trips I always make sure water did not get in. None ever has but I dred the day it does. The floor board area under the foot well will most likely never dry if it did get wet. The only use for my drain holes it to check to see the insulation is dry:rolleyes: I will open them to a #19 now though.
 
My -7 actually takes on a trickle of water while on the ground in a rain. It takes water at the overhead canopy latch. Any ideas?
 
scard said:
I agree, #30 and 1/8" is too small in my real world experience. Just a little bit of dust collection compounds the problem of clean surface tension. I opened mine up to almost 3/16" after finding non-draining water.
Click to expand...

Good idea - opened mine up a bit more today. Thanks Scott.
 
Cessna has a standard part that they use to provide for a bit of suction at the drain holes in the fuselage. The part number is S-349, Scoop-Drain, and it looks like a metal plug with one side of the lip cut off.

Any Cessna dealer, e.g. Yingling, should be able to get it for you.

I don't know offhand what hole size is used, but I can say that after 30 or 35 years of age, an airplane needs its tail cone washed out with soap and water from a hose, it's messy, and if these are plugged up, you'll have standing water there when you do it. Unplugging these is essential.

Dave
 
You must log in or register to reply here.