SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Heavy winds?

6K views 34 replies 18 participants last post by  Faster 
#1 ·
I was out the other day with a cold North wind on the bay. There was only a few white caps so I believe the wind was around 12 knts at most. I like to get the boat moving between 3.5 to 2.5 knts. I am trolling. Almost all summer there in these conditions I would use small jib and main. Yesterday with this setup I was doing almost 5. So I reefer and that only slowed me down to 4-4.5. Finally decided to drop main. Now I was sailing at 3-3.5 knts. Are cold winds heavier then warm winds making your boat sail faster. Also i was sailing across channel so current would be a very small factor.
 
#2 ·
No, if that were the case the wind would have "felt" stronger to you and to the waves as well. However I have noticed that the bottom stays cleaner in the winter; less growth and some of the summer slime just falls off.

I'm not saying cold dry air is not heavier than warm humid air, I'm saying that if the impact on the waves is the same, the impact on your sails is the same.
 
#5 ·
Actually cold air IS denser than warm air.. We notice it here in winter where you reef earlier than in summer, and have definitely noticed that sailing in 20+ knots in the trades seems less powered up than 20+ knots at home. The heavier air packs a bigger 'wallop' at the same velocities...

 
#6 ·
If you have reduced sail to the smallest set up you can, and you still want to reduce sped, you will have to resort to other tactics.
For example, if sailing close hauled, pinch up into the wind higher and she will loose speed.
Down wind, sheet in the sails or the opposite of what you should be doing. Beam reaching ease until you are spilling some. All of this after you have reduced sail area.
Wind speed is wind speed no matter how heavy or cold. Hey, I am not a weather man, just my thoughts.

Whhhattttt????
I guess I have to edit my post, Faster has charts to prove it :) :eek:)
 
#7 ·
Here on western LI Sound, late fall and winter sailing gives us a
definite edge as there is not the chop that is generated by the weekend summer powerboat traffic, but points made (all good) in above posts would be hard to explain almost doubling boat speed**
unless maybe a combination. Including possibly setting traveler in
different position as well as outhaul and halyard settings.
**except clean vs fouled bottom could definitely make the difference.
 
#8 ·
...., but points made (all good) in above posts would be hard to explain almost doubling boat speed.....
Agree... truly doubling boat speed on that factor alone is unlikely.. but lapworth's data is a bit subjective and there will be plenty of other variables at play.

The point was that indeed, the 'force' from a given windspeed can be noticeably stronger in cold air than warm.
 
#16 ·
Imagine extremes to make the comparison between light and heavy air understandable. First think of a sail in space. Space is not 100% empty, it has just very, very little particles. Probably you are not gonna see anything hapening to your sail if these particles are moving at 12 knots? Now imagine using a sail in water with a 12 knot current. Water here represents very very heavy air. Probably your sail rips to pieces pretty soon.

So i dont know for certain how to explain scientifically why i think your airpressure difference thingy is wrong, but it really seems wrong to me :)
 
#13 ·
check pressure density altitude and the temp relationship and the lift you get under the wing? Is a sail a wing on its side? Yes you are at the same alt unless the lake level is lower but small drops will not mean much. Alt may only come into play if you sail a lake at high alt vs ocean sea level Regards , Lou
 
#14 ·
As other have said, the cooler drier air of winter is noticably denser than the warmer damper air of summer. So a cooler wind of any given velocity will definitely result in more force on your sails than the same velocity breeze in summer. This is most notable during a winter sail when a small numerical windspeed change results in a much bigger apparent wind shift and more heeling. Sails that I can carry in summer into the mid-20 knot range, barely make it to 20 knots in winter.

Jeff
 
#15 ·
A few years ago on new years, sons and I went out sailing in about 15 knots, put up the 135 I had at the time as we did in the summer, needed a reef pretty dang quick! So yes as others have said, winter colder temps one does not need as much SA up to hit the same speed, heeling etc. I'm 3-5 knots of wind slower in the winter vs summer temps, ie over 60 vs under say 50-60. Closer to freezing, even less yet.

marty
 
#17 ·
Btw, i am pretty new to sailing and have a question:

-How do you decide when you need to reef your sail, where is the limit ?

I have just recently gotten myself a boat and have sailed it from guatemala to cozumel this far. On the road i got into some pretty winds a few times. The first time as i was going sharp into the wind, it got really strong, it scared me and i took the sail down just(didnt yet know how to reef so took it down completely) Probably the boat bouncing like an idiot, sprays of water reaching into the cockpit and me getting seasick helped create my fear more than any objective observations. :p

A few days later i had a wonderfull SE wind when going from san pedro, belize to cozumel on a beam reach. I made 8,5 knots while my hullspeed is 7 knots. I figured that must be ok because there is supposed to be a 2 knot current helping me and i kept the sails up. But stil l must admit i hade some slight doubts if this was being a good thing for my boat and sails. So where should i draw the line ?
 
#18 ·
The thread is off the point. The OP judged the wind speed only by sea state. He did not measure true wind speed.

OBVIOUSLY cold air is more dense. Airplanes in the desert commonly take off lighter because they don't have the lift. But the point is if you measure the wind speed by its effect on the sea state, that has already been taken into account. It will push the waves in the same manner it will push your boat.

Simple, no aerodynamic hand waving required.
 
#19 ·
Simple, no aerodynamic hand waving required.
True. That, and climate change...:laugher

Just kidding. I agree with the science. It is enlightening to hear some that have actually been able to percieve the difference. If I was guessing, I would have assumed that small differences in wind velocity would have a much larger impact than air density. Good to learn new things!
 
#20 ·
So basically, if i am sailing downwind and am drinking an ice cold beer, the wind blowing over it to my sails, my boat will go faster? Yet another reason to drink ice cold beer. Thank you Faster. Btw, if I put a fan behind my beer, will I go even faster (no pun intended Faster).

Brian
 
#23 ·
So basically, if i am sailing downwind and am drinking an ice cold beer, the wind blowing over it to my sails, my boat will go faster? Yet another reason to drink ice cold beer. Thank you Faster. Btw, if I put a fan behind my beer, will I go even faster (no pun intended Faster).

Brian
Problem is, Brian, the waste heat from your BBQs will undo all the good that cold beer did, esp considering the beer probably didn't last more than a few boatlengths!!
:p:p;):):)
 
  • Like
Reactions: T37Chef
#21 ·
CD,

That option only works if you are ugly! But being as you are the "BEST LOOKING MALE MOD" that drinking a cold beer with the wind behind does the opposite effect! Now if you were drinking a hot buttered rum, it might work!

Marty
 
#22 ·
I figure it's just more of those nitrogen and oxygen molecules hitting your dacron. I noticed it in frostbite racing on those cold days back in the frozen northeast.

Okay, another question. Since colder is more dense, we heel more. But if we're up at say 12,000 feet on some mountain lake, are there just fewer molecules to start with? So would we heel less in 30 knots on top of Mount Everest than at sea level, given the same air temperature?

Are we faster in fresh water because it's less dense than salt and fewer molecules for the hull to have to push around? Or is it because we sink down more than in salt? Is cold water slower than warm water to sail through?

I'm just full of questions. I never think of this out sailing, only at desks with keyboards..
 
#24 · (Edited)
If you would like some fun try to find an eb6 Pressure density calculator. IMHO You would be at your fastest in cold air, at sea level. in warm salt water. Slow Just the other way around High alt, cold fresh water lake, with a hot wind. Factor in the waves a small shallow body of water means smaller waves this adds speed if the surface turbulance is just right. How much is for an expert looking for a speed record . Most likely on a kite board? Since the Kites are behind. far beyond me. Regards, Lou
 
#27 ·
I had to get some numbers. I would not stand behind this "science", but I had to get this out of my system. I used this site Air Density Calculator to figure out air densities. I used this site Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Force to calculate lift of a wing. I used 1.5 for Cl for a sail.

So the jib on my Sabre 28 would theoretically have 10% more lift in 45 degree 40% relative humidity air than it would have in 85 degree 60% humidity air. That was fun.
 
#29 ·
Alright, would my little home weather station (or your mast top anemometer) read higher wind speeds on a colder day? But a little dandelion poof blowing in that same wind would be going the same 12 kts regardless of temperature?
 
#30 ·
The change in density produces more force for the same velocity... the anemometer speed is based on the velocity...I doubt it's affected by density changes.
 
#32 ·
I was out the other day with a cold North wind on the bay. There was only a few white caps so I believe the wind was around 12 knts at most. I like to get the boat moving between 3.5 to 2.5 knts. I am trolling. Almost all summer there in these conditions I would use small jib and main. Yesterday with this setup I was doing almost 5. So I reefer and that only slowed me down to 4-4.5. Finally decided to drop main. Now I was sailing at 3-3.5 knts. Are cold winds heavier then warm winds making your boat sail faster. Also i was sailing across channel so current would be a very small factor.
To answer your question, air density at 80 degrees is 0.070 lbs./cubic ft. while at 30 deg. it's 0.081lbs. But since the major driving force was the Bernoulli effect, I think that the cold air gives a different perception, imho.
Dick
 
#33 ·
This is way out of my limit . Bernoulli did most of his work of I think in fluid dynamics. Fluid that you can not compress. Air can compress more than fluid. Some fluid can because it has gases inside. I fly, I sail I fit pipe with fluids and gases and changing of state from gases to fluid super heat and so on. This could be the point when we need to ask the PE to explain. I will just have to take his word he will pull out a lot of math with letters an such, I will stay with my first and the majority. Cold air has more lift and power. Any PE want to jump in this? Regards ,Lou
 
#34 ·
My question about the anemometer - mine is three little cups on short plastic arms, all of which rotate about an axle. When the wind is making the whole mess rotate, it's more or less "filling" one of those cups at any time, but the other two are heading (backwards) back into the wind. Maybe nice weather stations take temperature into account when converting shaft rpm into wind speed?

Air feels a whole lot heavier when riding a motorcycle without a windshield. 23 degrees is the coldest I've ridden any real distance. Noticeably different lean-forward angle compared to 95 degrees. Not that I care at 23 degrees. I'm just cussing and hanging on for dear life.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top