knock down

groundhogyh · Feb 17, 2008

Bruce,
I don't have any experience with (well, I did race and we occasionally diped the spreaders in the water) real knockdowns, but there is a calculation you can do to compare the tendency of different boats.

capsize ratio =beam/((disp/64.2)^.333)
ft and lbs.
2 is kind of the cutoff point. Below 2 being more stable, above 2 being less so.

But this brings up another question that has been in my mind. I've read sailing stories where boats have done a total 360.

When you are sailing in bad conditions, or even if you are down below, if a boat goes upside down, wouldn't it sink because the water would come in the companionway?

Unless you locked the hatch totally. And how do you lock it up once you are inside the cabin?

If the companionway was closed but not locked, wouldnt the great pressure of the water possibly slide open the hatch door?

rb

jbergman888 jbergman888@... wrote:
Any of you have any info on the vega's self righting ability??? not
that I ever want to find out first hand...

Thanks,

Bruce Bergman

Cygnet # 169
San Diego

capt_sail · Feb 17, 2008

Yes, boats have sunk due to downflooding well before reaching 180 degrees if the hatchboards are out... However, a boat that is buttoned up (as you should be when hove to or riding to a sea anchor , for example) can be knocked down or even do a 360 and only take on a relatively small quantity of water. Unsecured gear and stores flying about can do plenty of damage though, both to boat and occupants! Water pressure on the companionway hatch would press it down into the cabintop, not slide it, but a wave (or the impact of a boat sliding down a wave) could stove in a hatch. And our Vega hatches are far from overbuilt!

Bill
V 1390 Traveler

groundhogyh · Feb 17, 2008

I haven't seen this on boats, but do people add a way to lock the companionway from the inside? Like a latch or something?
rb

Bill Burke CaptSail@... wrote:
Yes, boats have sunk due to downflooding well before reaching 180 degrees if the hatchboards are out... However, a boat that is buttoned up (as you should be when hove to or riding to a sea anchor , for example) can be knocked down or even do a 360 and only take on a relatively small quantity of water. Unsecured gear and stores flying about can do plenty of damage though, both to boat and occupants! Water pressure on the companionway hatch would press it down into the cabintop, not slide it, but a wave (or the impact of a boat sliding down a wave) could stove in a hatch. And our Vega hatches are far from overbuilt!

Bill
V 1390 Traveler

capt_sail · Feb 17, 2008

I've had a number of boats set up this way, but not just for foul weather. A deadbolt or latch on the inside of the companionway hatch is also good security in port. Keeps the bad guys out when you're sleeping down below...
Bill

groundhogyh · Feb 17, 2008

Yes, the Vega is a 1.9.

Below are a few other examples.

If anyone is interested, I have an excel spreadsheet that I made up that does a number of performance calculations for sailboats. Just remember, I never intended for others to be using it. If you know Excel, you should be fine though.

Catalina 27 1.8
Cal 20 2.2
Contessa 26 1.7
C&C 25 2.2
Kirby 25 2.4
Ranger 26 2.2
Tanzer 26 2.1
Columbia 28 1.8
Pearson Triton 1.7

jbergman888 jbergman888@... wrote:
Have you done the calculations for the Vega???

papasbackhoeinc · Feb 18, 2008

A knock down comes in sight when you use the spinnaker. I have done a lot
of racing in the past on the IJsselmeer.

Of course we used the spinnaker when the wind was not too strong . As
far as I know there was never a knock down., but with the spinnaker the
heeling was very strong.

We were advised to keep the hatches well closed as well as the cockpit..

Now with my wife as the only company we prefer not to use the spinnaker
any more. The rolling jib has made things a lot easier.

Most of all we don't sail if force 7 or force 8 is being forecasted.

Regards,

Henk Jansen

Vega Le Cygne.

_____

Van: AlbinVega@yahoogroups.com [mailto:AlbinVega@yahoogroups.com] Namens
jbergman888
Verzonden: maandag 18 februari 2008 4:47
Aan: AlbinVega@yahoogroups.com
Onderwerp: [AlbinVega] Re: knock down

Have you done the calculations for the Vega???

capt_sail · Feb 18, 2008

There's a web calculator that runs the numbers for hundreds of different boats in their database at http://www.image-ination.com/sailcalc.html . It even allows you to print a bar graph comparing the characteristics of two different designs side by side.

Bill
V 1390 Traveler

wxt8981 · Feb 18, 2008

I had a knock down when flying the spinnaker. I had the spinnaker up all day not realizing how much more wind there was. I had to jibe, and that did it. The mast was in the water. I had the hatches closed, I was using a harness (which I always do when out in 'open' waters). The cockpit filled wirh water, but little water was inside the boat. The boat rightened
alone- the biggest problem was to get the spinnaker off the hull. I was lucky, the jibe brought me to calmer waters (the waves were about 8 to 10 feet when I broached the boat (during the jibe).
I don't want to experience a knock down again. And by the way- I wouldn't lock in any way the hatches from the inside: They may be the only escape should the boat sink!
Wilhelm, V-257Henk Jansen henk-jansen@... wrote: A knock down comes in sight when you use the spinnaker. I have done a lot
of racing in the past on the IJsselmeer.

Of course we used the spinnaker when the wind was not too strong . As
far as I know there was never a knock down., but with the spinnaker the
heeling was very strong.

We were advised to keep the hatches well closed as well as the cockpit..

Now with my wife as the only company we prefer not to use the spinnaker
any more. The rolling jib has made things a lot easier.

Most of all we don't sail if force 7 or force 8 is being forecasted.

Regards,

Henk Jansen

Vega Le Cygne.

_____