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If however you were getting freezing moisture on the outside.... best to stay out of icing conditions or get out ASAP. RV's and most other light piston singles are just not FIKI aircraft.- Unless you spend a bundle on electric hot edges, and or an alcohol prop and windshield system like Rocket Bob mentioned, and even then unless you hire a tanker with a water spray system to fly above and in front at several hundred K$ for all the test and paperwork you still won't be approved for flight into known icing. And don't forget your fuel tank vents or you will be landing with a collapsed fuel tank/ leading edge- just ask Bruce Bohannon what happened when he iced over the fuel tank vents on one of his time to climb or altitude record attempts. Canopy icing is the least of the icing problems. Lots of days it is best to stay home or get a motel. |
Heated Windshield
To expand on Carl's point, the amount of heat required to melt ice in a 150-200mph sub-freezing airstream is not trivial. In other words, it's not coming from any size or temperature of defrost fan inside the cockpit. Just look at the windshield protection on business jets or even light singles with FIKI certification.
Now, if you're looking for a defogger to keep the INSIDE of the windshield free of condensation on a cold day, I've found a couple of 80mm computer fans drawing warm air up from underneath the glareshield to perform quite well. |
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TBH, I haven't even done back of the napkin calculations or have any sort of FIKI experience so this is just a rough guess. I'm pretty far from this point in my build, but I figure even though I don't intend to ever encounter icing conditions, if it has any sort of benefit at all it may be worth it. *Depending on how hot the air is coming out |
Hot plates
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The heat gun in my shop draws way less than 20A. No way am I going near my canopy with it!
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q = m x C x DT
q = amount of heat energy gained or lost by substance m = mass of sample C = heat capacity (J oC-1 g-1 or J K-1 g-1) Tf = final temperature Ti = initial temperature You have to get Tf above 32 in order to thaw the windscreen. The colder it is outside Ti, the more amperage you need. The problem here is that you have a boatload (essentially endless supply) of freezing air and water hitting the windscreen so you are essentially trying to boil a gallon of water with matchsticks. Oh, and to top it off, all of that heat has to go through the plexi. I’d want to see some data on what that material does long term when exposed to a steep thermal gradient. The alcohol spray mentioned earlier would be far more practical IMHO. Yet again, you really need to research and understand what it is going to do to plexiglass. (With apologies to any real Mechanical Engineers) Don |
and...
...and your car windshield is GLASS, not plexiglass.
At one time I owned a C-421. It actually had an option for a heated windshield. That windshield was over $20k...and that was 20 years ago... The hot plate could probably be adapted for the RV, however, the best solution is NOT to be in icing conditions in an RV... |
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Cars don't encounter icing like airplanes, because they don't generally drive in visible moisture (clouds) in below freezing temperatures, or operate where supercooled droplets land on them and freeze on contact. The other factor, as you point out, is the speed of the airstream. The faster you go, the faster the air sucks away the available heat. To replicate what an airplane has to handle, imagine driving a car through freezing fog or an ice storm at well over 100mph! |
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In non-icing but high humidity scenarios this would have more effect than simply blowing inside air through the glare shield. |
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