Motorcycle Dew...

[Jabba]

I got in a rare 337 miles yesterday...  I took my bestest riding buddy north from Greenwood, to South Bend to pick up a 2004 1100 Sabre with 8000 miles on it. (from my Brother-in-law).

When we left heading north at 7:00 AM, it was one of those wet mornings where the air is totally saturated with moisture.  You know the kind...

Well it never rained... and I never saw a car with it's wipers on.  Yet... my face shield was dripping wet, as was the bike, and even my clothes got pretty damp.

I call that phenomenon motorcycle dew.  Most of you have felt it... a sunny day... no clouds... yet you can FEEL the water hitting you in the face.  I have studied this a bit and thru my professional carrerr that makes me be familiar with psychrometrics (the study of water in air) I have decided that it's the pressure wave in front of a motorcycle rider that forces the moisture in the air to condense, the split second before it hits us.

Does anyone have any contradictory theories, as that's all mine is.  Or similar experiences?

Overall the 337 miles was uneventful, and we even snuck into Edwardsburg Michigan for lunch at Lunkers before heading back to the office.

Jabba

[Jess Tolbirt]

personally i think the moisture is floating in the air and with nothing to attach to its "just there" then when something hits it, it accumulates to that object....sometimes early in the morning the damp air will get into the blinker resovoir and cause my blinker fluid to get this moisture in it and make them not work until it all evaporates,,,especially on cold mornings,,,,

[Michael K (Az.)]

We call that the "Iced Tea Glass" syndrome!

[Jabba]

What I am talking about though... doesn't get on car windshields.  Only moorcyclists.

That I can tell.

Jabba

[sandy]

I've lived in AZ for over 37 years. Like I'm suppose to know something about water in the air. Some days we don't get into double digit humidity levels. I'd guess you're right about the headwave squeezing the water out of the air.

[alph]

i've often found it to be the drippings from the airconditioner on the car ahead of me....  haven't had to worry about that this year, too cold!!

just joking, yeah i know what you mean, i use to expierence that when i had a different job that i had to get up really early for.  it also accumulates on the mask of your full face helmet, really sucks!

[Cliff]

Actually it is the sudden decrease in pressure behind the front pressure wave that causes the water vapor in the air to condensate into fine water droplets (mist).  You will sometimes see this in the low pressure zone around aircraft wings when on final approach or takeoff.

[Jabba]

I hate to disagree with you Cliff... And I guess I am NOT really... but that goes against my learnings.  I have to think about it.

but psychrometrically... when you drop the pressure, the water boils at a lower temperature.  That's why water boils at 210F in the rockies, and 212 at the ocean.

Ever do the experiment ni high school where you put luke warm tap water in a beaker in a vacuum bell?  When they pump the air out of the bell, lowering it's pressure, the tepid water boils.  All the same principal.

I wonder why... there is visable water in the low pressure zone of an air wing?  I theorize that it's simply the delay of passing thru the high pressure that actually CAUSED the condensation.

Hrmmm...

I HATE  not KNOWING why about most anything.

Jabba

[Cliff]

Have you ever seen a "cloud chamber" in science class?  You pressurize a closed glass chamber and release the pressure suddenly... poof the chamber fills with water droplets that look like a fine mist.  You can see this effect in the wingtip vortices of aircraft also.  Any time humid air transitions suddenly form a higher to a lower pressure this will occur.  I can even do it with my mouth much to the amusement of my grandchildren.

[Jabba]

hrmm... when you release pressure suddenly... temperature drops.  That migh be it. 

We might be onto something Cliff.

Jabba

[Duey]

We did that on aircraft. 747 and etc. We pump it up to simulate flight at 30,000 feet. Then we simulate a major failure of cabin pressure. Dump the pressure very fast (like 15 seconds) and it would actually form clouds and rain inside the aircraft. The temperature would drop about 20 degrees at the same time. It was part of a system check.
ie. large drop in pressure can cause rain/moisture to appear.

[Big IV]

I know motorcycle dew well...

Don't have any scientific rationale.

[art]

where you riding behind an rv wiht a hole in it's holding tank? that is some kind of dew.maybe poop dew

[Cliff]

where you riding behind an rv wiht a hole in it's holding tank? that is some kind of dew.maybe poop dew

Ewwwww, now that is nasty dew, makes me want to go shower (after washing down the dragon first.)

[Jabba]

It's happened t o me a lot.  It's frequently high humidity here in indiana.

It happens at least a few times a year.  It was just strong on Friday.  Enough to form on the windshield of my helmet and drip off onto my passenger.

Jabba

[Daniel Meyer]

It's the same effect as airplanes get when high speed or a radical maneuver make serious pressure waves...squeezes the water out of the air ya know...