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Permalink Reply by Bob Simmons on February 3, 2025 at 11:15pm

If you use ram air in the rain, you're almost guaranteed to get water. There are several ways to do this, though I haven't personally done them. The simplest is to not have a ram air inlet duct facing directly into the airflow where it will ingest water, such as facing down as opposed to forward. That also allows gravity to assist. Properly designed outlet ducts will actually suck air through the system, but I am no expert in designing those. I do know you don't need high airflow for electronics. If you want to get fancy, there are devices designed for this, such as a cyclonic separator. It spins the airflow to remove anything that isn't air. I have no idea where to get them or how much they cost, but you can actually make your own if you're so inclined. You can search for that stuff. Here's one link:

https://powderprocess.net/Equipments%20html/Cyclone_Design.html

You can actually use ram air to drive the separator if you want, called secondary airflow.

I wish I could provide more info, but I have no direct experience in this. I was hoping someone who did would chime in. I do know there are other forums centered on aircraft design that discuss airflow and ducting. One such forum is homebuiltairplanes.com. Maybe someone there could provide better info. Or maybe a Rotax forum?

From an electronics standpoint, I would probably also try a heatsink. Just make sure to properly secure it.

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Permalink Reply by Kurt Schaeffler on Thursday

Let it get wet

If my airplane engine, car engine, or boat engine... if it can't get wet, it is not worthy of carriyng myself or family.

All the electrical connections are sealed (the ones that need to be) all the components are sealed (that need to be).

I can and will continue to regularly wash my engine and cowling with a mild degreaser or soap and a garden hose. Car, boat, and aircraft, even lawn mower.

* I like Purple Power diluted concentrate in a spray bottle for all my equipment. Spray it on, let it dwell a few minutes, rinse it off (before it has a chance to dry). Allow it to air dry (or blow it off) then run the engine to get it up to temperature and allow the heat generated to help additional drying/evaporation. 

If it ever shows to be a problem, I want to know right away.

The last worry I want is a concern that my engine is going to sputter if a torrent of rain enters the cowling.

*Evinrude outboards (BRP, btw) recommends that their engine owners remove the cowling and rinse their engines with fresh water on a regular basis. Although, it seems that, very few actually perform this...

Cheers   

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Permalink Reply by Bob Simmons on Thursday

He's not talking about the engine, or an occasional wash. He's talking about electronics, and potentially a constant stream of moisture every time he flies. That's not a good thing for electronics, which I know from 48 years of working avionics systems. It would also be a potential corrosion hazard if it happened every flight, as opposed to an occasional wash. But hey, you do you.

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