Windfoil Foil sizes ?

cgoudie1 · Posted: Mon Mar 30, 2020 6:29 am Post subject:

My common sense tells me air with water vapor in it is lighter than air
without water vapor in it. It told me that long before I became an
Engineer. A closed mind is a lot like eyes shut tight.

-Craig

p.s. we seem to have gone a little far afield of the OPs questions.

dllee · Joined: 03 Jul 2009 Posts: 5329 Location: East Bay

Yes, water is always lighter than air, every time, in every case.

westender · Joined: 02 Aug 2007 Posts: 1288 Location: Portland / Gorge

I appreciate cool dense air when I'm at full throttle on my sportbike. Cool

dllee · Joined: 03 Jul 2009 Posts: 5329 Location: East Bay

Difference between summer west winds and easterly morning winds. Whole difference in punch.

LUCARO · Joined: 07 Dec 1997 Posts: 661

cgoudie1 · Posted: Mon Mar 30, 2020 12:26 pm Post subject:

Here's a fun (though not very scientific since they aren't molar equivalents)
experiment. Cool down some
gaseous O2 until it becomes liquid. Fill a gallon container with that liquid.
The weight will be ~9.5 lbs. Now cool down water vapor until it is liquid.
Fill another gallon container, and find the weight to be ~8.3 lbs. This
isn't even a valid comparison since the 2 substances have very
different grams/liter, and the number of molecules is not the same in each
gallon of liquid, but yeh, LOX still heavier (slightly) than liquid water by
volume.

So here's the thing, if you get hit in the head by a gallon of LOX, it will be
slightly more painful than if you get hit in the head by a gallon of (liquid) water.

;*)

-Craig

p.s. there's always Heavy Water, and there might be some of that floating around in the air and the water where I sail (yuk yuk)

dllee · Joined: 03 Jul 2009 Posts: 5329 Location: East Bay

I am pretty sure the engineers definition is correct. How about 99.7 %?
But, we don't care about theory here.
We are talking about propelling a sail, NOT an exercise in mathematics and engineering.
As an "A" group student [academic] in school, I was taught all sorts of theory. Got A's in mechanical drawing for 4 years, never a B.
At around 10th grade, read the article about the development of the P-38 Lightning. My memory sucks now, I'm old.
Specifically, tested in the LOW altitude SoCal desert in winter '40, engineers decided it was NOT possible to land or takeoff from aircraft carriers due to length of runway and static LAND!
Guess they were wrong, as some pilot..I forgot his name, easily landed a P-38 on a medium carrier with a slight headwind and moving 15 knots.
Shocking news to the engineers... they thought in a vacuum!

dllee · Joined: 03 Jul 2009 Posts: 5329 Location: East Bay

Of course there is a NEED for engineers, mathematicians, and scientists.
Windsurf app.
Engineer, 185 lbs., sails a 6.2 WARP and 70cm Slab in 16-27 mph wind. Can jibe 99% and goes fairly fast.
One day, the wind and windswell both switch direction slightly to cause crosschop in both.
Everyone switches to smaller board and adjusts for changing wind.
Engineer complains the wind is fine, he can handle the chop....but he can't figure out why his sailing plain sucks!
His world in windspeed and windswell. His co
ntrolled enviorment.

dvCali · Joined: 23 Aug 2007 Posts: 1314

dllee · Joined: 03 Jul 2009 Posts: 5329 Location: East Bay

Another engineer.
We go out with 6 meter sail.
Wind drops 3 mph and sail is too small, but close.
Engineer stares at sail.
Artist lessens downhaul and outhaul, then planes again.
Engineer stares at sail and wonders why a badly tuned sail can plane, when his perfectly tuned sail just fast slog.