Had the best sail in ages yesterday totally on the edge overpowered race in to the shore when the wind picked up then out with smaller gear and best jumps I've done for ages..buzzing..
Out today & crap..felt uncomfortable , hard work nothing felt right. New adjustable harness lines I haven't worked out yet and seem to slip..
It was about 8-15kts with sloppy chop left over from stronger wind + fairly onshore so had to work out to get some space..When I did get going I felt glued to the water and realised it was weed and had to jump off regularly to clear the fin.Grr.
It's not usually a problem there.
It's amazing how different two sessions can be..[}:)]
I suppose the crappy sails make you appreciate the good ones..

just be happy you got out 2 days ina row

Perhaps you were underpowered and underboarded today?

seanhogan said...


We're just so lucky over here I guess, finishing our third week of 15/20 knots every day !!!

Had a quiet winter but the summer breeze is back, been sailing every single day since the wind kicked back in

Mods!!! Ban this guy !!!!!!!

I'm glad it's not just me

Mr. No-one said...

Air density can have a big effect to, cooler dense air will have a lot more "push" to it than warm air even when the wind speed is the same. Ever noticed at dusk you can be comfortably powered even when there are no white caps, it's because the air is cooling and becoming more dense which is why the late session is often the best.
It's one of the reasons why one day can be magic and the next may look the same but just can't seem to get going.

I totally agree with this. I said it to someone the other day and they looked at me like i had two heads. In my limited experience i have found that what the bureau says is say 18 knots in winter on a freezing cold southerly has a lot more punch than these supposedly 18 knot "warm" NE seabreezes we have been getting. If the air is a higher density, ie when it is colder, it has to have more power to my way of thinking. Sort of like if you've got an adjustable spray nozzle on your hose. The same amount of water is going through the hose but get someone to spray you on jet then on spray and see which one hits you harder.

Mr. No-one said...

Air density can have a big effect to, cooler dense air will have a lot more "push" to it than warm air even when the wind speed is the same. Ever noticed at dusk you can be comfortably powered even when there are no white caps, it's because the air is cooling and becoming more dense which is why the late session is often the best.

So if the air has more 'push', why isn't it pushing the water over into whitecaps?

It's a common argument, one I see cropping up all the time. However when you crunch the numbers there really isn't much difference in density...

Also I fail to see how dense air can magically affect sails, more than the water surface or anemometers.

I sailor (not windsurfer) told me many years ago the thing he liked most about sailing was everytime he went out the conditions were different and that gave him a new challenge with each sail. Perfect powered up conditions are awesome but there not a prerequisite to enjoy windsurfing. A couple of friends cruising around on longboards in light conditions makes a good day too. The huge growth in SUP,s demonstrates you dont need to be planing to have fun.

joe windsurf said...

cammd - good point

AND i discovered that a board like the Fanatic Cats CAN plane in VERY light winds
asked on the Fanatic Forum about getting new models = nope

please remember - a "bad" day on the water is still better than a good day at work :-)

personally - there have not been any "bad" days - learn somethin new each time
even injuries and breakage have a message - remember - we DO go fast !!!

enjoy your summer mates - here in Canada snow has fallen and the winter tires are on
tommorow warm , n windy - so, hope for ONE more session :-)

Depends on whether you love your work!
Brr...
Ree wind density both sails were in the middle of the day so I suspect lack of wind + big leftover slop + lousy rigging and sailing as the cause..

Pel said...


Density of air has nothing to do with how the wind pushes on your sail. 18knots is 18 knots.

Yes 18knots is 18knots but density/weight does make a difference, would you rather get hit by a van carrying batteries or pillows at 18knots. They are traveling at the same speed, size but of different densities/weight. I know this is a huge a exaggeration, just trying to paint a picture, sorry Pel.

I've learnt a lot about air from windsurfing but the technical side of it mainly from hang gliding. Dense cool air is heavier than warm, if someone threw a water balloon and a less dense snowball of the same size at the same speed at an object the water balloon will have more pushing or kinetic force because it's heavier, same with air. Simply the heavier something is, the more it's going to push at a given speed.
When I fly it's a struggle to get of the ground on a hot day but no problem in winter, all because of air density, nothing to do with air or wind speed.
The less white cap effect may be from diminished light late afternoon or just surface texture changes.
I'm not saying it's the only reason why two days can be so different while looking the same, just one of them that some may have not considered before.

Pel said...
Density of air has nothing to do with how the wind pushes on your sail. 18knots is 18 knots.

Not true. Mr. No one is on the money with his batteries and pillows.
It's all about the transferring of energy from the air to the sail, and the energy in the air is given by E = 1/2 mv^2 i.e half mass times velocity squared.

The mass of the air is directly proportional to the air density.
Double the density is double the mass for the same bucketfull of air and therefore double the energy for the same velocity.
Obviously we're not talking in such big numbers with air density because it doesn't vary that much, but the effect is still there and probably noticeable to some.

A bigger factor is usually the smaller chop on the surface when the wind dies down because smacking through chop dissipates a lot of energy.
On glassy water, once you have kicked it up onto the plane you can keep it up with very little wind.

Mr. No-one said...

Air density can have a big effect to, cooler dense air will have a lot more "push" to it than warm air even when the wind speed is the same. Ever noticed at dusk you can be comfortably powered even when there are no white caps, it's because the air is cooling and becoming more dense which is why the late session is often the best.
It's one of the reasons why one day can be magic and the next may look the same but just can't seem to get going.

That is only correct when you are actually measuring the true wind speed, say via Doppler measurement with a laser or radar.

When you measure it indirectly by the force it creates, the measurement is similarly affected by the density of the air, just as it affects the sail and also water state.

For example if the using an anemometer with an impeller that reads 20knots in less dense air (hot air, high altitude or both) then it will under read and the true wind speed will be higher.

I.e. The indicated windspeed will only equal the true windspeed under a specific set of atmospheric conditions for example ISA is one standard (international Standard Atmosphere, 15C, 1013 millbars and zero water vapour)

terminal said...

Former PWA Race Director Alex Aguera explaining the difference in wind power with temperature.

The biggest thing for destroying the enjoyment of a session is variation in the wind. If its varying 15 to 35 knots (and usually gusty too), you are not going to have fun.
As long as I can choose a setup to cope (usually a bigger board with a sail set for maximum wind range) I can enjoy the session.

If you spend time slogging for a few minutes, then a few minutes overpowered, go into a gybe powered and when you try to exit there's nothing - its no fun.

It is fun using the apparent wind and the waves and coaxing the board to keep planing through the lulls and hanging on when overpowered and just about keeping the board under control and the fin holding at speed over chop. It just has to be within the range the sail (and my fitness) can handle.

So true..With the crappy session it was mainly 8-11kts with occasional 50m gusts of 15kts + and when I got going the chop was big enough to make it unpleasant with the board going slam slam slam..( not to mention the weed lodging on the fin and glueing me to the water.[}:)]).

I've been staring at that jumping elephant for too long now

nebbian said...

Mr. No-one said...

Air density can have a big effect to, cooler dense air will have a lot more "push" to it than warm air even when the wind speed is the same. Ever noticed at dusk you can be comfortably powered even when there are no white caps, it's because the air is cooling and becoming more dense which is why the late session is often the best.

So if the air has more 'push', why isn't it pushing the water over into whitecaps?

It's a common argument, one I see cropping up all the time. However when you crunch the numbers there really isn't much difference in density...

Also I fail to see how dense air can magically affect sails, more than the water surface or anemometers.

Thinking about this in more detail over the weekend, air density would have an effect when you add motion into the equation, i.e. it would affect the force created by the 'apparent wind'.

My maths is not good enough to work out all the numbers, but it probably has some effect when using the apparent wind, such as the kite surfers in the video posted often do as when they move the kite about, and we do when we are planing.

Apparently those cup type anonemeters are not affected by air density, but the ones with the impeller would be, and the usual method of looking at the trees, white caps, blowing sand etc are already 'calibrated' for density changes.

I did one calculation though comparing 35 degrees (very humid) and 5degrees (0 humity) at sea level and a true 20knots true came out about 18.5knots indicated, for a pressure based measurement. about 8% speed difference and thats for a huge variation in conditions.

And I agree with sboardcrazy it is a frustrating sport!

Dont often have ****ty sessions , pritty lucky with wind and swell and riding the right gear in light winds.

Sure you have better conditions IE windyer OR lighter with smooth waves and smaller and bigger swells on each given day etc

BUT i can say

I have been pulling up pritty bloody sore infact close to lame for a couple of days after the better full on wave sailing sessions .

To much travel and may be work or may be not enough electro lites / fluids through out the day. or is that enjoying the extra beer associated with the pleasure of a few after the joy

If the mind is not right the body has always got me through
If the body is not right then the mind will get you through

But if both the mind and body are fked well your better resting and waiting for the frothy conditions to return.

Must be getting old