VEGA stability

[brockhaus77]

Hi all,

I've just read two articles in "SAIL" magazine (September and October 2004 issues) on
initial and ultimate stability of sailboats. Lots of complicated formulae to calculate things
like "vertical center of buoyancy", "vertical center of gravity", "metacentric height (GM)",
"righting arm (GZ)" and "Dellenbaugh angle" to determine initial stability/sail carrying
capacity, and lots more to calculate things like "angle of vanishing stability (AVS)" etc. that
determine ultimate stability (against capsizing). From a cursory glance at their examples, it
appears that the VEGA is not exactly in the range that they consider a "safe" off-shore
cruiser, but it's hard to figure out the numbers exactly since they require a lot of detail
knowledge about the VEGA (measurements). I'm wondering whether anybody on the list
has done such an analysis, or at least knows how to find all the necessary dimenstions etc.
to do one.

- Sebastian (VegaLyra 1060)

 

[wxt8981]

Hi Sebastian;
I have a "Measurement Certificate" from the Midget Ocean
Racing Club for my Vega.
It has lots and lots of numbers and formulars- don't know
if that's what you're looking for...
Wilhelm, V-257

 

[emmajen5]

Sebastian,

There's quite a bit of information on stability in the Vega Handbook
along with some interesting commentary by Per Brohol. The Handbook's
available in the files section of this group's web site in case you
don't already have it.

Garry
"Raven" Vega 2427

 

[robertgainer]

Sebastian,
There is a difference between the theory and truth of some things. The
numbers they are using are interesting and can be used to compare similar
boats. But they are not the end all and be all on the subject. The Vega is
from actual experience a great boat that has no problem with offshore
cruising. You need to be careful about how you interpret some of this
information.

I have done the numbers on other boats, but not the Vega. If you want to do
it you need a copy of the lines of the boat. You need to measure the area of
the midsection and calculate the center of buoyancy when the boat is heeled
and upright. It is easier to do if you have a planimeter or the software a
designer uses. Without this you need a lot of patience and time to do
everything by hand. If you know where on the net I can get a copy of the
lines I would be more then happy to run the numbers in some design software
called MaxSurf and let you know where the boat stands compared to others,
such as the Sea Sprite. I have done the numbers for that one; it was the
first boat I went Trans-Atlantic in. The Vega is the third one I went over
in. I run the Sailing and Boat-Building school for the Hudson Fisheries
Trust in Beacon New York and we have the software and hardware to do this.
Check us out at www.fisheriestrust.org . We are building an 18 foot 6 inch
Shad boat right now.
All the best,
Robert Gainer

 

[emmajen5]

The lines are in the Handbook. I think we would all be interested to
the see what you come up with.

Garry