achimha wrote:
No, it actually tells us that flying (for whatever period) does nothing because the water in the crankcase comes from the combustion process and after every flight, there will be more water in the oil than before the engine was turned on.
Exactly. It is what you do after the engine is turned off that counts. De-hydrator, heater, both? In Norway, in winter time we typically stick the electric heater in, and let it stay until the next flight. In the summer I guess a de-hydrator would be better, but a lot more work.
It is what you do after the engine is turned off that counts
There isn’t much you can do before the engine is turned off 
Peter wrote:
There isn’t much you can do before the engine is turned off
Before it’s turned on, or after it’s turned off… 
There is a difference there when you add time into the equation. If you don’t, it wouldn’t make much sense either way I guess. Well, anyway, the point is as Achima wrote, to remove the surplus water the engine produces when running – also when it has stopped running.
Rust, or oxydisation, requires three things – always:
Remove any one of them, and voila – no rust.
When it’s running, the metal is protected by heat ,oil and lack of oxygen. The combustion uses oxygen, leaving very little left to enter the crankcase, but produces tons of water that do, mostly in the form of steam. When it’s turned off, it cools down. Water condenses and oil drips off, exposing bare metal. The cooling process sucks fresh air into the engine. So, very fast you have all three components, and then it starts to rust immediately, even though it takes some time for a human eye to see it. To stop that process, you have to remove one of the three components again. Obviously, water is normally easiest to remove, either by heating the engine above ambient, or by using a de-hydrator system of some kind. This is also a (yet another) major benefit of two stroke outboard marine engines vs four strokes. A two stroke doesn’t accumulate water in the crankcase like a four stroke do. A two stroke engine typically have a oil fogging system. A push of a button, and the engine is soaked in oil fog for longer stays, like during the winter. Completely rust free, even though it operates in the worst thinkable environment for rust (salt water).
Well, to be pedantic you can have oxidation without oxygen :-) Fluorine for instance is a stronger oxidiser than oxygen, and some really nasty things like chlorine trifluoride will set asbestos on fire…
One thing I keep reading about is that changing the oil, prior to a period of non use, is a good idea.
It cannot make any sense because, in a stationary engine, all you are doing is draining out what was in the sump and replacing the sump contents with fresh oil.
Unless you run the engine afterwards, at least for a few mins, the fresh oil isn’t going to be anywhere useful.
Here’s my just finished effort. Single pipe which will go into the oil filler. RH in the box is 10%. I bought a solar air pump that has battery backup where any overvoltage from the panel charges the batteries. Ideal for continued pumping for a few hours of darkness. However the bloody thing doesn’t have automatic switch-over to battery power making them useless. Nonetheless I think even 8 hrs a day in winter and 18 hrs a day in summer should go a long way to keeping things dry in there. At very least I’ll have some more peace of mind if I can’t get to fly for a couple of weeks, or there is extended mx.
That’s neat.
You can use a couple of diodes to power the motor from either source
or just forget the diodes (wire them across) and then the panel will charge the battery as well. Solar panels (the ones I have played with, for e.g. cars whose central locking systems flatten the battery in a week or so) don’t leak backwards.
It already has a little box of electronics to switch between panel mode and battery. I assume some of it is the charging circuit too. Bit beyond my rudimentary electronics skills to figure out what does what. The two big black switches are the master on/off and the day/night mode selector (ie panel or battery)
The only time you need any “electronics” is when the solar panel is big enough (in relation to the battery) to overcharge it.
The solar panel you have would barely charge a smartphone if it was running at the time
Admittedly there is a case for “electronics” when one is trying hard to extract the maximum amount of power from a solar panel. Standard electrical theory says that this occurs when the loading on the panel is such that its output voltage drops to 50% of the no-load voltage. It is the same rule with e.g. starter motors, if you want max power transfer. I don’t know the no-load voltage of your panel (it depends on how many cells and how they are wired but let’s say it is 30V, and your battery is 6V. If you just wire the panel straight to the battery, it will definitely charge it, but you won’t be getting max power transfer, because that would need a 15V battery. However the panel output will vary dramatically with the light intensity, over say a 100:1 range from direct sunlight to a cloudy day, so the whole thing is going to be really vague… In applications where power transfer is to be optimised, you have a switching power supply which emulates a dynamic load and it uses the hill climbing technique to continually optimise the power transfer into the load. One can even make it work when the panel output is say 3V and it will up-convert that to charge a 6V battery (although to be fair if a 20V panel is outputting only 3V, the available power is going to be miniscule). Your little board may be doing some or all of that. But you don’t need this; just a bare solar panel will work fine. It is the same scenario with electric fences for cattle, etc.
I made my last flight yesterday – 5 circuits, landings reasonable, including PFL and flapless. Now we are under lockdown in UK, and while I can reach the aircraft without interacting with anyone, I don’t think I’ll be doing that. So I added a bottle of Camguard before the flight, and secured the aeroplane carefully with tie downs before leaving her. She has a new, substantial, fuselage cover, new annual, and all the equipment (that usually works) was A-OK.
What other precautions against what might be long lay up do people advise? My engineer, who is on site, says he will inhibit the cylinders if I ask. (PA-28-161, O-320 with about 900 engine hours, parked outside on grass).
It won’t just be the aeroplane that will be rusty after a long break, either!
