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Old 09-16-2020, 09:30 PM
  #71  
JamesNoBrakes
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Originally Posted by Ace66 View Post
No sir, not a myth - an actual meteorological term. And you are wrong, fog is water vapor that is condensing because the air is oversaturated. I've never seen fog on a surface. Did you perhaps mean to say....dew?


There's frost and then there's hoarfrost. By definition hoarfrost goes from the vapor state to the solid state. It can be brushed off the surface. Think about two pieces of lead at room temperature. Put them together - no adhesion. Heat one to the melting point and then touch the solid piece and then cool to room temp - it adheres. Think of dry snow falling on a wing cold soaked at -20degC. Are you telling me that snow will adhere?


"While hoarfrost forms directly on objects as ice crystals, rime forms when tiny, near-freezing water droplets, usually from thick fog and other clouds, attach to the surface of a below-freezing object and turn into ice immediately on contact."

https://www.accuweather.com/en/weath...hoarfrost/7092


Hoarfrost is described in many meteorological texts. Frost - AMS Glossary for an easy one.


Regardless, even if that frost did adhere to the wing like window frost, it would not affect the airflow. It's thin enough to see through it, it's on the aft portion of the wing, and it's far smoother than the screw heads, access panels, and other structure on the wing. But we continue to waste money and the environment on spraying clean wings because every uneducated idiot like this guy has a phone camera and the FSDO on speed dial.

Not sure why the "former bush pilot" comment was made. Dogma? Ok let's go - four years conducting aviation weather research including aircraft icing for a government lab funded by the FAA and years designing jets for Boeing as an aerospace engineer. Oh yea and I flew a 1941 warbird with a 65hp engine, no GPS, no electrical above the arctic circle - in the bush. Oh and I've flown a CRJ200 (supercritical wing) with the typical outer 4 wing panels having hoarfrost on them. If you want to pull out resumes and compare who's bigger, I'm game. But I'd rather argue physics. Crack a book sometime.
Regular frost also goes from the vapor state to the solid state. It's just the extent of the crystals and that hoarfrost only forms by deposition. You are trying to somehow claim that hoarfrost doesn't adhere because it uniquely goes from a gas to a solid? While the crystals can be broken quite easily, they are still attached at the base. See my comment at the end.

Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above freezing atmosphere coming in contact with a solid surface whose temperature is below freezing,[1][2] and resulting in a phase change from water vapor (a gas) to ice (a solid) as the water vapor reaches the freezing point. In temperate climates, it most commonly appears on surfaces near the ground as fragile white crystals; in cold climates, it occurs in a greater variety of forms.[3] The propagation of crystal formation occurs by the process of nucleation.

The ice crystals of frost form as the result of fractal process development. The depth of frost crystals varies depending on the amount of time they have been accumulating, and the concentration of the water vapor (humidity). Frost crystals may be invisible (black), clear (translucent), or white; if a mass of frost crystals scatters light in all directions, the coating of frost appears white.

Types of frost include crystalline frost (hoar frost or radiation frost) from deposition of water vapor from air of low humidity, white frost in humid conditions, window frost on glass surfaces, advection frost from cold wind over cold surfaces, black frost without visible ice at low temperatures and very low humidity, and rime under supercooled wet conditions.[3]
You are clearly cherry-picking what we are saying. No one is saying that hoarfrost is not a meteorological term or phenomenon, only that it's simply the extent to which the crystals grow based on higher humidity. It's still frost. You are attempting to make it out to be something it is not. It still adheres to surfaces just like any other frost...because it is frost.

The reference that we were asking for was the one that says it doesn't adhere to surfaces.

If you want to use the cold wing scenario, a cold-soaked fuel tank can make frost deposit directly on the fuel tank area even when there's no frost in the environment otherwise and the air temperature is well above freezing. It's the same mechanism. It adheres and no, it doesn't just brush off.

Due to the low sun and cold temps, hoarfrost often forms on our car windows in the winter time, even in the daytime, so we spend a few minutes scraping it off. Forms on the metal body as well. Sometimes it's damn near impossible to get off without heating the car from the inside to at least partially melt it. If it behaved as you claim, I could just blow it off with my breath.

The only situations I've observed in Alaska where ice does not adhere is dry snow when it's below freezing (I've seen this upset by various factors too, can't just assume it) and ice-fog under the same conditions. I've never seen a form of frost that can be brushed or polished off. I've seen plenty of people try...but it's still there after they attempt to brush/polish it. You seem to be implying the "polish smooth" thing about it...

My own pic:
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Last edited by JamesNoBrakes; 09-16-2020 at 09:59 PM.
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