Mirror Painter
Well-Known Member
I am a dinghy sailor. Sometimes I get it wrong and get wet. Are fast yachts like this impossible to capsize in normal conditions?
http://vimeo.com/3695120
http://vimeo.com/3695120
I have (another) stupid question- capsizing yacht?
- Thread starter Mirror Painter
- Start date
Kelpie
Well-Known Member
Pretty much. Unlike a dinghy, a keel boat is inherently self righting. Increased wind pressure will of course cause it to heel, but this reduces the power of the rig (assuming the wind is horizontal!) and simultaneously increases the righting moment of the keel, as it moves further from the centreline. Look up a 'GZ curve' for a typical yacht and you will find that when they reach about 80 degrees their keels exert a huge righting moment.
Wave action can capsize a yacht, but that isn't what most people would call 'normal conditions'...
Wave action can capsize a yacht, but that isn't what most people would call 'normal conditions'...
Mirror Painter
Well-Known Member
Thank you, makes sense.
DownWest
Well-Known Member
Also, in a dinghy, you are the ballast and the more the boat heels, the less effective your weight becomes as you approach the vertical and are over the centre of buoyancy.
Sailfree
Well-Known Member
Extreme conditions usually with a breaking wave can capsize a yacht but they quickly right themselves. Look up the Bavaria video clip of one entering a Spanish? Port with onshore wind/swell posted on here early this year.
We started learning to sail by racing a wayfarer and after 24yrs get it wrong less often now when we race! Got into some rough seas this summer on our big boat and boat tossed around sufficient to rip a heavy mirrored cupboard hatch off its hinges in the bay of biscay. While not a comfortable sail yacht did not feel out of control at all just rough seas.
With equivalent of the weight of 2 cars hanging some 2m below the yacht giving it stability I cannot imagine the sea that would cause a broach but happy not to put it to the test!
We started learning to sail by racing a wayfarer and after 24yrs get it wrong less often now when we race! Got into some rough seas this summer on our big boat and boat tossed around sufficient to rip a heavy mirrored cupboard hatch off its hinges in the bay of biscay. While not a comfortable sail yacht did not feel out of control at all just rough seas.
With equivalent of the weight of 2 cars hanging some 2m below the yacht giving it stability I cannot imagine the sea that would cause a broach but happy not to put it to the test!
woozy-UK
Well-Known Member
my intro 22 heels a lot and is designed to. the cabin entrance is high so that when water rushes in it doesnt go into the cabin. a previous owner has had it so far that the top of the mast was touching the water but it self righted
DJE
Well-Known Member
prv
Well-Known Member
Part of the answer is described by the "Gz Curve" for the type of boat you're interested in (of course, they may not exist for all boats, especially older ones).
Here's a few examples:
The horizontal axis is the number of degrees of heel (0 is upright, 90 is on her beam ends, 180 is upside down). As long as the curve is above the axis, the boat is trying to right itself - for any seagoing yacht this will be way, way past 90 degrees.
The curve below the horizontal axis describes the boat's stability upside-down - obviously we want this to be as small as possible so that it comes back upright fast. Nearly all boats do dip below the line (ie, in smooth water they would stay upside down and not self-right), but of course in conditions severe enough to turn them over, another wave will soon knock them out of that stable position and they'll come upright.
(The surprisingly stable Southerlies and LM27 on this graph achieve that due to a high wheelhouse, which adds a lot of righting moment provided it doesn't flood. Doesn't necessarily make them the ultimate ocean boats, hence why Gz is only part of the answer.)
Pete
Here's a few examples:
The horizontal axis is the number of degrees of heel (0 is upright, 90 is on her beam ends, 180 is upside down). As long as the curve is above the axis, the boat is trying to right itself - for any seagoing yacht this will be way, way past 90 degrees.
The curve below the horizontal axis describes the boat's stability upside-down - obviously we want this to be as small as possible so that it comes back upright fast. Nearly all boats do dip below the line (ie, in smooth water they would stay upside down and not self-right), but of course in conditions severe enough to turn them over, another wave will soon knock them out of that stable position and they'll come upright.
(The surprisingly stable Southerlies and LM27 on this graph achieve that due to a high wheelhouse, which adds a lot of righting moment provided it doesn't flood. Doesn't necessarily make them the ultimate ocean boats, hence why Gz is only part of the answer.)
Pete
Birdseye
Well-Known Member
No. Anything can be capsized but basically the resistance goes up with the cube of the lwl. In this issue, size matters.
Lots of other issues involved but size is the key one according to the USCG research project.
Sybarite
Well-Known Member
I passed a MacGreggor 65 going into Le Crouesty this summer. It's quite low in the water and it's only when you get quite close that you appreciate the length. I remember when they first came out they were about the price of a typical 40 footer. A friend of mine - a bank trader - seriously considered getting one with his bonus but I think it was the mooring costs which dissuaded him.
One made an attempt to beat the ferry time between Marseilles and Ajaccio in Corsica. Leaving during a good mistral, it hit top speeds of around 27knts. It failed in its attempt because of a lack of wind just before arriving.
MASH
N/A
I'm not sure I'd trust the data in a graph that had an axis labeled "righting leaver".
Mirror Painter
Well-Known Member
I always hesitate to end a thread with 'thanks for all the info' because it's not very interesting as a final post. But, ha ha, thanks for all the info which makes perfect sense. Thanks for the link to the video too, I foolishly showed it to my wife which has done nothing to assist my long term plan of one day having a sailing boat larger than a dinghy!
Cheers.
Cheers.
lpdsn
Well-Known Member
On that note, be careful with the charts. I knew someone who was planning a cross channel trip until his wife asked what all those Wk things on the chart were.
johnalison
Well-Known Member
That's better than a wife who assumes that you can sail anywhere with water shaded blue. Not that I know anyone like that, of course.
prv
Well-Known Member
