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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


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Editorial status: In magazine.

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  • Answered by Anonymous
  • on 2009-06-12 10:36:18

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Actually dry air is by volume 78% Nitrogen (N2, atomic weight 2*14=28), 21% Oxygen (O2, atomic weight 2*16=32) and some traces of other gases (mainly Co2).So dry air could be considered a gas of molecules each of which has, in average, an atomic weight of .28.5Humidity, H2O, has an atomic weight of 18. To me that means that humid air is less dense than dry air.Leodp

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

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  • Answered by Anonymous
  • on 2009-06-12 20:56:16

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Sail fabric is already non-porous.

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

sssss
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  • Answered by Marc
  • on 2009-06-12 23:44:28

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The first two posters are correct. Water vapor (18 g/mole) displaces dry air (28.966 g/mole) and so moist air weighs less than dry air. Meteorologists use the term #39;virtual temperature#39; (Tv) - the temperature which dry air must have at the given barometric pressure p in order to have the same density of moist air at the same pressure p.Tv = T (1+r/e)/(1+r)where T is the temperature (in Kelvin) r is the mixing ratio (grams of water vapor per gram of dry air), and e is the ratio 18/28.966. Tv is always greater than T.

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

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Not exactly an answer, but years ago I worked in Sri-lanka and made friends with a local fisherman who used to take me out on his boat (a tree trunk with an out-rigger and a course woven sail). They used to splash water on the sail. when I asked why, the answer was basically that the water caused the weave in the sail to swell making the sail more impervious to the wind, thus making the boat go faster

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

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  • Answered by Yggdrasil
  • on 2009-06-15 09:15:09

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Golf ball - yes, less lift because damp air is less dense.... shorter shot. Excellent! (thnx Francis)Guess my NS subscription was worth it...

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

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  • Answered by Yggdrasil
  • on 2009-06-15 21:13:28

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Ooops - for non-golfers, quot;taking and extra clubquot; means, in my example, that from 100 meters, I would take an quot;extra clubquot;, or one that I would normally hit 110 meters, on a humid day.(The air being humid and thinner, the (a) ball spin does not hold the ball in the air so long, the (b) ball falls shorter than its normal 110 meters, (c) right beside at the flag at 100 meters, and (d) I#39;m soon doing my quot;birdie dancequot;, which (e) I refuse to explain.)

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

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In answer to Mike Stovold’s question.The sail produces it’s driving force (lift) because of it’s aerofoil shape.Lift = Dynamic Pressure x Coefficient of Lift x Sail Surface Area (q x CL x S)Dynamic Pressure (q) = ½ rho x Velocity squaredWhere rho is the Air DensityHumid air contains water vapour.The density of a gas is proportional to it’s molecular weight.Air is a mixture of gases, Nitrogen 80% approximately, molecular weight = 28, Oxygen 20% approximately, molecular weight = 32 giving a mean of 29.Water, molecular weight = 18, is less dense as a vapour than air. So humid air is less dense than dry airSo, when applied to the lift formula L = ½ rho x V squared x S x CL it can be seen that less lift is produced in higher humidity conditions.Simon Walker.

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

sssss
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  • Answered by Anonymous
  • on 2009-06-22 03:42:23

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Military parachutists have told me that in humid air, they fall to earth noticeably slower.

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

Report abuse

Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

sssss
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There are 24 answer(s) for this question. View answers | Submit an answer
  • Answered by Anonymous
  • on 2009-06-22 13:28:14

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A yacht’s sail is designed to take energy out of a passing mass of air (wind) by deflecting the air mass and by slowing it down. If the air is more dense, it carries more energy for the same wind speed.It turns out, perhaps counter-intuitively, that the relative humidity of air has very little effect on it’s density.However atmospheric pressure does have a considerable effect. For instance, in a deep low in the Caribbean hurricane season, for instance, you might get 810mb and 30degC; this has an air density of 0.92 kg/m3. But in a Winter high off Scandinavia, you might get 1005mb and 6degC; this has an air density of 1.31kg/m3.The Caribbean wind can only carry 2/3rds of the energy of the Scandinavian wind (for the same wind speed).The sailors are right, some Force 4’s pack more punch than others.

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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Does the wind exert more force on a yacht's sail if the air is humid?

I have been told that the wind has more force on a yacht's sail in conditions of high humidity, such as in the tropics, because the higher water content of the air increases its mass, and therefore the force, on the sail at any given wind speed.

Is this true? If so, is there an equation I can use to calculate the increased force?

Mike Stovold, London, UK

(Image: johnnyberg, stock.xchng)


 media

Editorial status: In magazine.

sssss
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  • Answered by slysci5
  • on 2009-06-23 23:13:56

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perhaps everyone has ignored one crucial factor here. humidity is produced when the area is warm. if the surface air temperature is warmer then more evaporation would take place and there would be increased humidity. so far this has been pointed out many times. but everyone fails to note that the majority of the drag comes from the boats contact with the ocean. warmer water is less dense and less quot;wetquot; so it does not cause as much drag. temperature goes up choeisve froce goes down , not sure what adhesive does but id b suprised if it went up. soo if the less dense saturated air gave 10% less lift, but the drag is reduced by gt;10% wouldnt the overal effect be to go faster? also does humid air contain water vapours( H2O) or hydrated forms of the gaseous molcules??? please correct me if im wrong

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Last edited on: 2010-03-10 15:02:18

Categories: Weather , Technology.

Tags: wind, force, humidity, sail, yacht.

 

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