john_morris_uk
Well-Known Member
That's about our limits when sailing for fun.
To the OP: there's no easy answer as its not just wind, its swell and waves and size of boat and which direction you are going in!
What conditions are you happy to go out in?
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That's about our limits when sailing for fun.
To the OP: there's no easy answer as its not just wind, its swell and waves and size of boat and which direction you are going in!
JumbleDuck
Well-Known Member
It's more dense, all right, but not much more dense, and the density variation due to temperature changes is similar to those due to pressure changes - 10% or so for each. Significant for the bulk movement of air and the establishment of weather systems but not, I suggest, for the effects on yachts' sails.
prv
Well-Known Member
If the theory is about flax sails holding more wind in damp weather, then asking a modern Working Boat sailor is unlikely to help - I can't imagine any of them are still using natural fibre sailcloth.
Pete
John.edwards
Well-Known Member
here in Adelaide our winter sailing gives us 10 - 14 C after a cold start with clear skies. Summer can be 46C so our problem is covering up. in season I always wear long pants, long sleeves (cotton shirts) and hat and sunscreen. Our weather for sailing depends on sea state. Happy in 25-30 knots with flattening seas, but in 2metres plus, even 15 knots is a chore. sailing from Hobart once we had the wind gear blow off the mast - last reading before gear disappeared was 68 knots. we were triple reefed and storm jibbed in a 52 foot reischel pugh. sea was about 2 metres so we kept sailing. steady wind would have been about 45knots
snowleopard
Well-Known Member
I'd go further and say it isn't about the wind at all but the seas it kicks up. I've had a tolerable afternoon beating up the Solent into a wind averaging 45 kts and gusting to 55. It's just a question of reducing canvas to suit. The waves were only about 3 ft and though the boat staggered a bit in the gusts she was quite comfortable. South of the IOW on a day like that would have been pretty grim.
snooks
Well-Known Member
A f5 on a warm summers day is quite different to a f5 in the middle of winter, and it's not just the temperature drop.
Warm air is less dense, but it also has a lot to do with the amount of moisture in the air too. Wiki facts: http://www.wikipedia.org/wiki/Density_of_air
John.edwards
Well-Known Member
JumbleDuck
Well-Known Member
Mainly psychological. Which is not at all to say that the effect is unreal, of course. Mainly I think it's because we tend to underestimate wind speed on nice days or in nice weather. The sun goes behind a cloud, we cool down slightly and suddenly realise how strong the wind is.
For the relatively small variations involved, air density is inversely proportional to temperature. Since normal temperature changes by at most 10% (273K - 300K), density only changes by about the same amount too. Damper air is less dense than dry air, because the molecular mass of water molecules (18) is less than that of the oxygen (32) and nitrogen (28) molecules it displaces. It's a tiny effect, though. Even at 30C the saturation pressure (and therefore partial pressure) of water is only 0.042 bar. That means that saturated air at 30C is about 2.6% less dense than dry air at the same temperature. On a winter's day at 5C, the difference is only 0.5%.
Comparing a winter day (5C, 980mb, saturated) with a summer day (25C, 1020mb, dry) the density will be 7% higher in winter due to the temperature change, 4% lower due to the pressure change and 0.5% lower due to the humidity change, giving a grand total effect of a 2.2% density increase.
Vara
Well-Known Member
4/5 with no rain suits me, but I take care to avoid wind over tide if at all possible. Cold isn't a problem, got gloves and a wooly hat.
Mantra...I do this for pleasure.
Mantra...I do this for pleasure.
jdc
Well-Known Member
Well as JumbleDuck said already there is a variation in density, and you're right that this effect is a bit enhanced by cold air being drier, but they are simply not effects which I'm sensitive enough to really notice - and I have some experience (including a F7-8 in a snow-storm in the arctic last year). The magnitude is only about equivalent to a 5% change in wind speed, from 28 to 29.4 for instance, and this is swamped by random gusts and fluctuations anyway.
What one does really notice are down-drafts; these have a disproprtionate effect because heeling doesn't reduce the force, conversly it increases it to start with, and so one can get knocked flat. And down-drafts do happen in cold places, for instance off glaciers or snow covered mountains. I suspect that it is these which have given rise to the cold = stronger association (and it can happen in home waters - the most I've ever been heeled by such a down-draft was in the lee of Dodman in a NW 5-6).
Back to the OP's question, there are two aspects:
What do I enjoy? (feel comfortable as in warm, cheerful, this is fun...); and
When am I genuinely worried that we might come to grief?
So was a snow-storm in a near gale fun? - No way! Was I really worried we'd sink because of it? Again, no way.
Boats are almost without exception much stronger than their crews and very very few ever come to grief by being overwhelmed by wind and waves; not even in hurricane force winds in the soutern ocean. So be confident in yours.
But those which do get in trouble are usually (not always, sometimes it's just bad luck) in trouble becuase the crew make mistakes or can't take it any more or have not done the required maintenence or preparation and so have got themselves into a situation with no viable exit. While experience should help avoid this happening, actually your own stamina and common sense are probably even more important!
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jdc
Well-Known Member
I think the point about Falmouth working boats is that they go out pretty much every day through the winter as there is a local rule which allows trawling through the winter in the Carrick roads, but only under sail. Ie it's their experience in winter rather than sail materials which they could offer opinions about.
Whatever, they are a cheering sight when one is down there in mid winter doing some maintenence job on the hard.
Amulet
Well-Known Member
There isn't an answer to this. It depends on where you are, the strength of your crew and boat, and the direction of the wind and tide and the nature of the harbour entrance you are contemplating (and the viability of your plan B if all goes wrong). I can imagine that in piddly wee bit of water like the Solent you can contemplate sailing with fairly vigorous winds. I remember sailing inside Mull and Skye for three weeks with every forecast including a number 7. I wouldn't venture out into the North Sea from my Orwell base into that lot, and my limited experience of the English Channel is that outside of the Solent it can give you a pretty busy sail in a force 5 - in my small boat - and make you wish you hadn't gone out there. I wouldn't contemplate going North from the Orwell with forecast over a 3-4 from the East, but have done it forecast 6 perhaps 7 from the West. I never really believe my wind instrument, but the most I've ever seen it read while under sail is 45 knots, which is a lot for a tiddly wee boat like mine, but we were in sheltered waters and having fun.
john_morris_uk
Well-Known Member
I agree with that - except one could also add the temperature makes a difference and whether the sun is out makes a real difference.
Nighttime freezing cold beating in midwinter your limits for enjoyment are a lot less than beating into trade winds in 30 degrees with the next island in sight!
Nothing to do with density of the air. The physics have been investigated about that before. It's all about air on human skin I suspect!
Seajet
...
PRV Pete,
I crewed on a Falmouth Working Boat while racing - my idea of racing, trimming the sails every few seconds while passing around pasties & beers ! - and those guys know their stuff re sending down topmasts in winter, it's a local byelaw that oyster dredging can only be done under sail.
I expect there'll soon be a new byelaw that career conservationists can only be shot when under sail, judging by the interference they've tried at places like St Mawes !
One can go on about classroom physics but the fact is the winter air seems to have a denser charge - think why harrier aircraft and some fast cars use water cooling to cool the air into the engine and make it denser - I wouldn't mind betting that this re boat rigs will be proved right some time in the future; either way I agree with the very experienced professionals reducing their rigs in winter.
I crewed on a Falmouth Working Boat while racing - my idea of racing, trimming the sails every few seconds while passing around pasties & beers ! - and those guys know their stuff re sending down topmasts in winter, it's a local byelaw that oyster dredging can only be done under sail.
I expect there'll soon be a new byelaw that career conservationists can only be shot when under sail, judging by the interference they've tried at places like St Mawes !
One can go on about classroom physics but the fact is the winter air seems to have a denser charge - think why harrier aircraft and some fast cars use water cooling to cool the air into the engine and make it denser - I wouldn't mind betting that this re boat rigs will be proved right some time in the future; either way I agree with the very experienced professionals reducing their rigs in winter.
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Ripster
Well-Known Member
As a relative newby sailors (ex moboers) we now go out and can cope with far worse conditions than previously - a lot of this is because you have to as you can't run away at 30kns like before. Our present sail boat (AWB with deep fin keel) is far more planted than our previous MOBO FB planer and is far more comfortable in bigger waves and higher winds if you keep the sails up and the power on. Take the sails down though, and you roll about all over the place. As mainly coastal sailors, we will set out in anything up to F6 if its off shore, allowing for gusts going to 7. If the forecast is a 7+ then unless we really have to, we stay put. We don't mind waves, we can put up with some wind - but again like others, heavy rain is terrible - good gear or not. Our ideal day is sunny and bright - F3-4.
Seajet
...
Ripster,
welcome.
I've found there's a lot to be said for ' keeping the power on ' to allow manouvering, it's easy when frightened to reduce sail too much then be a sitting duck to get clobbered by wind & waves !
welcome.
I've found there's a lot to be said for ' keeping the power on ' to allow manouvering, it's easy when frightened to reduce sail too much then be a sitting duck to get clobbered by wind & waves !
AntarcticPilot
Well-Known Member
It depends a lot on which way you're going in a sailing vessel. A comfortable fast ride with the wind on the aft quarter becomes a hard, bouncy ride in the exact same conditions close-hauled!
Most sailing boats will in fact be perfectly safe in conditions that their crew find hard to endure.
Most sailing boats will in fact be perfectly safe in conditions that their crew find hard to endure.
alant
Well-Known Member
I come from the Mobo side of the world where little to no wind and dead flat water is best.. I am happy going out when swell is up to about 0.5m at about 5s interval, preferably without too much chop and up to 10kn wind for a reasonable ride.. Personally I would go out in rougher that that but any more and it becomes uncomfortable with lots of slamming at speed or pitching and rolling when going slowly which means the people with me tend to be unhappy..
So I am wondering if things are different in sail boats being displacement hulls with huge keels for stability.. Obviously you want a fair amount of wind but what about water conditions.. At what point does it start to become unsettling for the crew that haven't spent much time on the water? Do you pitch and roll as badly as a similar sized Mobo?
Sorry if its a daft question, I have no idea how sail boats react in the water..
Anything over top end of F4 on an Ebb Tide, anywhere near the Needles, can be 'exciting'.
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Bobc
Well-Known Member
I come from the Mobo side of the world where little to no wind and dead flat water is best.. I am happy going out when swell is up to about 0.5m at about 5s interval, preferably without too much chop and up to 10kn wind for a reasonable ride.. Personally I would go out in rougher that that but any more and it becomes uncomfortable with lots of slamming at speed or pitching and rolling when going slowly which means the people with me tend to be unhappy..
So I am wondering if things are different in sail boats being displacement hulls with huge keels for stability.. Obviously you want a fair amount of wind but what about water conditions.. At what point does it start to become unsettling for the crew that haven't spent much time on the water? Do you pitch and roll as badly as a similar sized Mobo?
Sorry if its a daft question, I have no idea how sail boats react in the water..
Not a daft question at all.
First thing to say is that, much like with MOBOs, a lot depends on the size and weight of the boat.
Flat water is easiest and most comfortable, and 30kts in flat water is fast and fun.
What starts to make things uncomfortable and wet are the waves, however it can also be what makes it fun and enjoyable. Its not so much the height of waves that makes it uncomfortable, but the wave interval. 10m waves when offshore are fine (assuming you're in the right kind of boat), but 2m waves certain parts of the English Channel can be orrible.
Generally speaking, I'll go out in up to a F6/F7, but my ideal conditions are F3/F4 with 0.5-1m waves with a reasonable wave interval.
Ripster
Well-Known Member
Yes, its one of the early mistakes we used to make, taking the sails down in a lumpy Sea and turning the engine on if conditions started to become more - err.. exciting with gusts and spray. Now, unless its flat calm with no wind, we try to keep some cloth up at all times, even if its just half a Jib. We were caught in a coastal squall the other week, visibility down to couple hundred yards, waves washing over the boat, rain blinding us and the spray hood working hard, but with only a heavily reefed main up, she ploughed on and got us back safely. We find that if we can maintain 5kns or more, the passage is far smoother. The crew were the weakest bit!!
