Tennis balls as plugs for exhaust

Salty

Salty

Touchdown! Greaser!
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Salty
So, I was talking to a guy about his plane, and when he opened his baggage door a bunch of tennis balls fell out. I asked if he was heading to the court, and he said 'nah, that's for the exhaust'. This was just a run of the mill GA aircraft. Never heard of this one.

I've seen it before on warbirds, and I think it makes sense there, if they are parked outside for long periods of time, but what says the crowd about this practice in general?

ac1645732522918570.jpg
 
Gives you something to chase when you forget to remove them and start the engine.
 
Never thought about plugging the exhaust. I use pipe cleaners to plug my vents to keep mud daubers out, but it would take an enormous dauber to nest in the exhaust pipe.
 
Don't see the point. Lots of moisture everywhere inside when you shut it down - I would rather let it out.
 
Half Fast said:
Never thought about plugging the exhaust. I use pipe cleaners to plug my vents to keep mud daubers out, but it would take an enormous dauber to nest in the exhaust pipe.
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https://en.wikipedia.org/wiki/Harry_J._Brooks
" He had also placed wooden toothpicks in the vent holes of the fuel cap to prevent moist air from entering and condensing overnight. On February 25, Brooks took off to complete the race, circled out over the Atlantic where his motor quit and he went down off Melbourne, Florida.[9] The wreckage of the Ford Flivver washed up, but Brooks' body was never found.[10]"
 
Capt. Geoffrey Thorpe said:
https://en.wikipedia.org/wiki/Harry_J._Brooks
" He had also placed wooden toothpicks in the vent holes of the fuel cap to prevent moist air from entering and condensing overnight. On February 25, Brooks took off to complete the race, circled out over the Atlantic where his motor quit and he went down off Melbourne, Florida.[9] The wreckage of the Ford Flivver washed up, but Brooks' body was never found.[10]"
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Yep.

Mine all have red “Remove Before Flight” streamers and pulling them is part of my pre-flight checklist.

And I use pipe cleaners because they don’t create an airtight seal.
 
You would really want your dog grabbing balls with lead oxide on them.
 
The guys with the short exhaust "stacks" plug them while they're still warm. Because, if they don't moist air will condense inside and the stacks will rust out up around the exhaust flange pretty quick. The old VW sand rails had a popular aftermarket 4-to-1 exhaust system, like a motorcycle exhaust. The muffler stuck straight up. You would always see those parked with an empty Foldger's coffee can over the top to keep the rain out.
 
wilkersk said:
The guys with the short exhaust "stacks" plug them while they're still warm. Because, if they don't moist air will condense inside and the stacks will rust out up around the exhaust flange pretty quick. The old VW sand rails had a popular aftermarket 4-to-1 exhaust system, like a motorcycle exhaust. The muffler stuck straight up. You would always see those parked with an empty Foldger's coffee can over the top to keep the rain out.
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That makes sense, but these were downward facing, something like this.

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Larry in TN said:
Am I the only one thinking, "We're not gonna fall for a banana in the tailpipe"?
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94033d498880f5fb5b1f63a993890b28.jpg
 
wilkersk said:
The guys with the short exhaust "stacks" plug them while they're still warm. Because, if they don't moist air will condense inside and the stacks will rust out up around the exhaust flange pretty quick.
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But there’s already moist air in the engine. Why entrap it?
 
I can see if they are pointed up or even horizontal, but pointing down, I don't get it. Parked outside, birds could nest in there, rain would blow in, etc. I guess bugs could get in, but I wouldn't think they would do much harm really, unless they could get into a valve....
 
Half Fast said:
But there’s already moist air in the engine. Why entrap it?
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Maybe I should'a prefaced that with "I was told..." Maybe you should do a scientific experiment that debunks this practice as an old wives tale.
 
wilkersk said:
Maybe I should'a prefaced that with "I was told..." Maybe you should do a scientific experiment that debunks this practice as an old wives tale.
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I don’t see the need.

Combustion of a hydrocarbon produces carbon dioxide and water. It’s therefore inevitable that the engine will have moisture inside the exhaust pathways at shutdown. If you trap it inside a hot engine and let the engine cool, it will condense.
 
I cover my fuel caps if I have to park outside traveling with an old tuna can :)

Had to park at a fancy FBO once due to Wx diversion, line boys looked at me as if I was quite the back-woodsman lol.
 
Regarding tennis balls, no comment about about the exhaust usage, but I will offer advice about tennis balls over the static pitot tube. There was a Saratoga that used one there for years. When I lost my usual cover, I decided to try it. After cutting a small slit, the fit was perfect for my blade pitot. I don’t remember how long that experiment lasted, but it resulted in water getting into those pressure lines and messing up my instruments. What I didn’t know, and should have realized, that rain could drip into the ball. Without putting a hole in the bottom of the ball to allow evacuation, this was a bad idea and a costly one.
 
Huckster79 said:
I cover my fuel caps if I have to park outside traveling with an old tuna can :)

Had to park at a fancy FBO once due to Wx diversion, line boys looked at me as if I was quite the back-woodsman lol.
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Are the cans meant to keep out water? If so, do they work?
Glad Press 'n' Seal plastic food wrap works too.
 
Domenick said:
Are the cans meant to keep out water? If so, do they work?
Glad Press 'n' Seal plastic food wrap works too.
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yes to keep water out, my 1947 Cessna 140 has vented caps. They fit perfect over them and a little electrical tape keeps em from blowing away in a breeze but doesn’t stick great to the wing either which is nice. I think if I forgot them they would blow off but even if they didn’t they aren’t sealing the caps…
 
Kenny Phillips said:
Not much at all, if the engine has been run for a while, actually,.
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Lots and lots if the engine has been run for a while.
If the engine is hot enough, the accumulated moisture in the oil will tend to be driven off, but the humidity in the crankcase and everywhere exposed to exhaust gasses will be well above the saturation point at the ambient temperature - and all that excess water is going to condense.

Engine exhaust is about 10-15% water vapor. At room temperature, air can hold only about 2-3% water.
 
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