Sail quantities at night

[Pelagic]

Originally Posted by carstenb

The worst night I had (my wife had one similar) was 6 squalls hitting us during my watch.
Once you've been through that, you decide that reefing down at dusk (when squalls become much, much harder to see) is prudent

But to each his/her own

Here in the Philippines just prior to Typhoon Season, we get a period of nightly thunderstorms and squalls

If sailing then, I am very much dependant on the Radar to track the squalls around us and reduce before we intersect with one

Being a big, heavy conservatively rigged boat with all furling, it is not a big deal to easily adjust in time.

And all from the safety of the cockpit

[Paul Elliott]

Originally Posted by barnakiel

I can see the process you are describing but I have not seen it develop squalls in tropical tradewind conditions.

I can confirm the nighttime tradewinds squalls pattern. I've made six San Francisco to Hawaii trips (and back to the mainland) between June and September from 2003 to 2014, and every time we saw the same pattern when in tropical waters. Mid-day the squall activity was minimal. There were occasional squalls, but generally not too strong. After sunset the cumulonimbus clouds would start building and as the night wore on the squalls became more powerful and more frequent. It was usually the worst just around sunrise, when the air was the coldest relative to the water.

When sailing under a squall we would often feel the air temperature drop significantly, and there was often rain. The wind in the strongest quadrant of the squall was usually about double the normal tradewinds speed. We would occasionally get stuck in the still air behind the squall where the windspeed would drop to practically zero.

Of course tradewinds squalls are local events, and sometimes they hit you, other times they miss you. At any time there can be big ones and little ones. But generally, the day/night pattern does hold.

Here's a nice squall near Hawaii, about to catch us just after sunrise:


When racing with a crew, we fly as much sail as we can handle, and take it down if it starts getting too exciting. Sometimes we don't get the spinnaker down in time and then things break.

When not racing we keep the main and genoa (and/or sometimes staysail) up, and reef as needed. My boat has roller-reefing headsails and a boom-furler, so it's easy enough for one person to do all the sail-handling. Sometimes we sail more reefed than necessary, just because we feel like relaxing.

[JPA Cate]

One time caught a squall in Fiji, fortunately in open water. It was down pole, gybe, up pole, etc. etc. till my final track on the GPS looked like this: _O_. It was a LOT of work, singlehanded (Jim's off watch.) But proof positive that the winds came full circle back to where they began when the squall first arrived. NB: this was a boat with large headsails and a small main, 4:1 aspect ratio. She didn't need reefing for the wind strengths encountered. It never occurred to me to seriously consider taking down the jib for the duration, at the time; it would, now. Also, now, I'd be using the radar to investigate the squall--sometimes you can dodge them without losing much.

Ann

[billknny]

The upward movement of the air is only what starts the process. Once the air is rising fast enough and high enough, you get large amounts of water and ice held up by the rapid rising air. As long as that happens, there are no significant effects at the surface.

Eventually, the water and ice become too heavy to hold up, and they come falling rapidly downward, pushing air ahead of them. That sudden downdraft (which might have originated at 50,000 feet, and hence is quite cold) is the start of the actual squall at the surface. If it is strong enough it can generate what a meteorologist would call a "microburst".

The strongest winds in the typical squall are just as the rain is starting, when the downdraft is at its most powerful. If you can see rain falling down to the surface as the squall approaches the worst of the wind is already past. Contrary to what you might think, if you see a very dark towering cloud without rain underneath it, THAT'S the one you most want to reef deeply before it dumps on you.

During the day you can tell the difference between the most dangerous squall that might be getting ready to fall on top of you, and one that is aging and mellowing. At night, navigation radar can not tell them apart--at least mine can not--and if it is dark enough eyeballs don't help either. You can see the towering cloud even on a moonless night, but figuring out if there is rain underneath is sometimes just not possible in the dark.

[barnakiel]

I think, at times, the reef/no reef choices may be dictated by how well your hull sails under-canvassed.

Our boat has a full length keel and light (moderate, by 21c standards) displacement. And she is narrow. Hence she hates not having enough sail and becomes way more uncomfortable then. Then again she will accelerate well and so we tend to bear off in a squall, if any.

So our natural choice is not to reef. Bear off and ride it. And forget it.

But as we reef less, we will also tend to notice the squalls less, and report lower than actual frequency of squalls.

I believe this may explain why I could be underestimating the need to reef for the night.

?

Maybe. Just thinking aloud.

Very nice thread. Educative.

Cheers,
b.

[bill martin]

Nice subject, discussion. More insights than ever before.

[zeehag]

i consider the potential for strong breezes, as there are specific areas in which strong breezes, aka gales, tend to occur at night, such as chubascos off so baja--these are real, and only occur between 0200 and 0600. speed of breezes gets to over 60 mph, a tad brisk for full sail, in my thinking. tehuanos and papagayos are also real, and occur more south of my location. i would reef at night for those as well.
btw my boat sails for **** undercanvassed. except in chubascos and storms...
much of my current sailing grounds lately have no such threat, so sailing at night under full sail is not discouraged unless you enjoy the sound of flogging sails.
i travel with more sail in darkness when i am out of the regions in which nocturnal gales happen.
building winds are easier to manage in darkness, as you adjust sail trim as needed. the chubascos give no advanced warning other than a poof of wind preceding em. we were able to use our chubasco well. 8.4 kts speed over ground under reefed mizzen and reefed genoa. . someone who tracked me told me i pulled 12.8, but had not adjusted for current, which was approx 4 kts southerly, in our favor.
i learned long ago predictions are only guidelines and nature heeds none of that.