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Rupert View Drop Down
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Topic: Wiki Sail by GRF
    Posted: 17 Apr 13 at 4:16pm
Originally posted by fab100

Now I want to know what happens if someone loads the air with bubbles - cos, we are told, they make stuff lighter

  


Helium bubbles?
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fab100 View Drop Down
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 13 at 4:16pm
Originally posted by Peaky

Graeme knows this, he just likes to use this Wiki page as a means of theorising about what happens on the moons of Jupiter, whilst travelling at the speed of light.

... and running an Infinite Improbability Drive at full throttle


Edited by fab100 - 17 Apr 13 at 4:17pm
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Post Options Post Options   Quote RS400atC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 13 at 5:39pm
Unfortunatley the New Scientist blurb misses a couple of points.
1) air with suspended droplets of water will be more dense, e.g. fog or cloud.
2) what we call 'damp air' generally means air with a high relative humidity.
100% relative humidity is a water vapour content which increases rapidly with temperature.
'Dry' air at say 20degC and 50% humidity actually contains (roughly)the same amount of water as 'wet' air at 10degC and 100% relative humidity.

I believe the perceived variation in 'wind force' for the same wind speed is largely about turbulence.
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Post Options Post Options   Quote Noah Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 9:55am
Originally posted by transient

Originally posted by iGRF

nowhere near as much moisture in it, so any given windspeed felt less.


I may be missing an "in" joke here, if I am just ignore me. LOL

Molecules are measured in moles or more precisely millimoles. Water molecules weigh less than oxygen or nitrogen molecules. A given volume of air can only contain so many molecules. If air molecules are replaced by water molecules = moist air less dense than dry air.


I once had a race scuppered by a fish.


OK, for the benefit of a bear with very little brain, how the hell can one water molecule (H2O, or - worse - H5O2 (which is wot I seem to remember a science teacher telling me many, many aeons ago)) weigh LESS than one Oxygen molecule (O2)?

My head hurts!
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:03am
I don't care what the google scientologists reel out here.

Air with moisture in it feels heavier than air without moisture in it

Cold Air feels heavier than warm air.

Cold Air with moisture in it feels heavier than Cold Air without moisture even more so if it is actually raining.

Warm Air with moisture in if feels heavier than warm air without moisture in it.

Facts, pure anecdotal facts derived from holding sails in ones bare hands in those circumstances.

Resulting in sail size choice accordingly. (Bigger sails in warm less moist air, smaller sails in cold.

What you lot feel may of course, like the way you speak, be different because it is conducted by and large through your arse..
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Post Options Post Options   Quote alstorer Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:10am
Originally posted by Noah

OK, for the benefit of a bear with very little brain, how the hell can one water molecule (H2O, or - worse - H5O2 (which is wot I seem to remember a science teacher telling me many, many aeons ago)) weigh LESS than one Oxygen molecule (O2)?

My head hurts!
Molecules are weighed in atmoic mass units. H2O is the correct formula. This consists of two hydrogen atoms, each of 1amu, and one oxygen, which weighs 16amu, for a total of 18amu. If you're good at maths, you'll have already spotted than an O2 molecule, consisting of two 16AMU oxygen atoms, must weigh 32amu.
 
At a given temperature and pressure and pressure, a certain volume of gas will always contain the same number of molecules. The usual volume chemists would use for an example is the "molar volume", that is, the volume of 1 mole (nothing to do with furry burrowing creatures), which at 1 atm and 0°C is approximately 22.4 litres. This volume of water vapour would weigh 18 grams. The same volume of oxygen would weigh 32 grams.
 
Clear as mud?
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Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:11am
Originally posted by Noah

Originally posted by transient

Originally posted by iGRF

nowhere near as much moisture in it, so any given windspeed felt less.


I may be missing an "in" joke here, if I am just ignore me. LOL

Molecules are measured in moles or more precisely millimoles. Water molecules weigh less than oxygen or nitrogen molecules. A given volume of air can only contain so many molecules. If air molecules are replaced by water molecules = moist air less dense than dry air.


I once had a race scuppered by a fish.


OK, for the benefit of a bear with very little brain, how the hell can one water molecule (H2O, or - worse - H5O2 (which is wot I seem to remember a science teacher telling me many, many aeons ago)) weigh LESS than one Oxygen molecule (O2)?

My head hurts!

....IT JUST DOES, OK LOL

edited (just saw als post)

well explained that man Smile



Edited by transient - 18 Apr 13 at 10:13am
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Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:23am
Originally posted by iGRF

I don't care what the google scientologists reel out here.

Air with moisture in it feels heavier than air without moisture in it

Cold Air feels heavier than warm air.

Cold Air with moisture in it feels heavier than Cold Air without moisture even more so if it is actually raining.

Warm Air with moisture in if feels heavier than warm air without moisture in it.

Facts, pure anecdotal facts derived from holding sails in ones bare hands in those circumstances.

Resulting in sail size choice accordingly. (Bigger sails in warm less moist air, smaller sails in cold.

What you lot feel may of course, like the way you speak, be different because it is conducted by and large through your arse..

Me thinks (and I am guessing) that you rightly noticed an increased difference BUT you then attributed  it to  high humidity when in actual fact it was because of low humidity......Several people I know have made the same assumptions because it seems intuitively correct

Unless you checked at the time with a hygrometer how would you know the humidity?
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Post Options Post Options   Quote pondmonkey Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:29am
Originally posted by iGRF

I don't care what the google scientologists reel out here.

Air with moisture in it feels heavier than air without moisture in it

Cold Air feels heavier than warm air.

Cold Air with moisture in it feels heavier than Cold Air without moisture even more so if it is actually raining.

Warm Air with moisture in if feels heavier than warm air without moisture in it.

Facts, pure anecdotal facts derived from holding sails in ones bare hands in those circumstances.

Resulting in sail size choice accordingly. (Bigger sails in warm less moist air, smaller sails in cold.

What you lot feel may of course, like the way you speak, be different because it is conducted by and large through your arse..

or is that in warm climates you tend sail towards the lower wind range of any given sail choice as you rightly fear the dunking less when hanging on in the gusts; whereas in cold frosty conditions, we sail far more conservatively- selecting a higher volume, lower sail area combo than you would otherwise on a 23º day in a consistent thermal breeze at the seaside?
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Post Options Post Options   Quote maxibuddah Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 13 at 10:31am
There's some very clever people on here, or they know where to look on Google. I know what jimbo means though, is about risk versus warmth.
Everything I say is my opinion, honest
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