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Old 09-17-2020, 08:18 AM
  #73  
JamesNoBrakes
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Originally Posted by Ace66 View Post
No, not all frost goes directly to the solid state:

Window frost

Window frost (also called fern frost or ice flowers) forms when a glass pane is exposed to very cold air on the outside and warmer, moderately moist air on the inside. If the pane is not a good insulator (for example, if it is a single pane window), water vapour condenses on the glass forming frost patterns. With very low temperatures outside, frost can appear on the bottom of the window even with double pane energy efficient windows because the air convection between two panes of glass ensures that the bottom part of the glazing unit is colder than the top part. On unheated motor vehicles the frost will usually form on the outside surface of the glass first. The glass surface influences the shape of crystals, so imperfections, scratches, or dust can modify the way ice nucleates. The patterns in window frost form a fractal with a fractal dimension greater than one but less than two. This is a consequence of the nucleation process being constrained to unfold in two dimensions, unlike a snowflake which is shaped by a similar process but forms in three dimensions and has a fractal dimension greater than two.[8]

Well then describe the adhering mechanism for two solids that come into contact. Also if all frost is the same then why use a different term for it?
It's the same as any other frost that forms when the temp is below zero, such as adhering to my windshield, the wing of an aircraft, etc. Small imperfections are like mountains and valleys on a microscopic level and the ice forms in those and creates a structure that is bounded by multiple anchor points, like a mountaineering cam. The same way the frost formed on that picture of the log that I took. I can "break" the crystals relatively easily, but they are adhering at the base and they do not brush off. The log is more of a macro scale. If what you claim is true, I'd have no use for a an ice-scraper most of the winter, since it remains below freezing and is clear most of the time. I'd be able to just "blow off" the ice crystals from my windshield, but we both know that's not real.

You have to realize the logic fail here. Ice, such as clear or rime ice is also a solid, so even though it's a liquid and then freezes, it too wouldn't have any adhering after forming, according to your theory, since both would then be "solids".

"Hoar frost occurs when a sub-zero surface comes into contact with moist air. The water vapour in the air turns directly into ice by sublimation, forming a white crystalline ice coating which can normally be brushed off."

https://www.skybrary.aero/index.php/Hoar_Frost
Hoarfrost, by multiple references, is the extent to which the frost grows in high humidity. Yes, it does go directly from a gas to a solid, but so does "normal frost" when the air temp is below zero, it's only the extent of the ice crystal propagation that is referred to as "hoarfrost". Again, if what you were claiming is true, there's be no way that hoarfrost can form on fences, signs, etc., because it would "fall off", since those are solids too.

WHAT?? Completely different mechanism. The cold fuel cools the warm air around the wing to the saturation point and water vapor condenses into water where it attaches to the surface which is below freezing so the condensed water then freezes into ice or frost adhering to the wing.
It still happens in cold temps when there's enough moisture in the air.

That's not hoarfrost. See above. The windshield radiates to cold space on a clear night thereby cooling it below ambient temperatures. The air immediately above the window is cooled, saturates, and water condenses onto the window where it then freezes, adhering to the windshield. Ambient air temperature can be above freezing.
100% wrong. It's below freezing the entire time, the water does not come out as liquid. Maybe you are referring to some warmer location where the air temp is above freezing and the cold surface causes the water to condense first. That's not what I'm talking about. I can take some pictures in a few months if it helps you.

So just to be clear, you are saying that the wing in the photos posted is unsafe and will not generate adequate lift?
Doesn't matter, the regulation is what it is. You can probably take off with a lot of ice adhering to the wing and leading edges in many situations. Doesn't change that it's illegal.
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