Originally Posted by KJB
Example: Boat A and B are the same model, but boat A has a draft
that is longer than boat B. Do both handle the open ocean equally well? I have come across this in my searches.
Lets assume that A is the standard model and
B is the shoal draft version.
Further assume that B has increased ballast to compensate for the decreased draft giving approximately the same stability curve and point of vanishing stability. Lets say ballast is increased 10% and center of mass is raised 5% towards metacenter. As a guess roll moment of inertia will be slightly increased so resistance to capsize
due to wave action will be also be slightly increased. This is all to the good in open ocean.
On the other hand the standard draft model will have a slight advantage sailing hard on the wind
. This will be an advantage if your destination
is upwind, you will be able to carry marginally less provisions, so the boat is marginally less loaded experiences marginally less fatigue and is marginally less likely to have a rigging
Then again you will not be spending most of your time in the open ocean, probably less than 20% of your time will be on passage
. Unless you are intending to go around non-stop or some other absurdity with your family
So the ability to claw
off a lee shore in heavy wind
and waves starts to look a little more important given that you will spent a fair amount of time in thin water.
On the other hand the shoal draft version with new sails
in good shape would probably do as well or slightly better upwind than the standard boat with older sails
In a completely rational world a shoal draft boat would be less likely to run aground. This is not that world. Charlie Wing in "the Liveaboard
Report" indicates that there was an inverse relationship between draft and the number of times a boat had been aground. My sense is that in mild or settled conditions when consequences wouldn't be as severe skippers of shoal draft boats got a little complacent about water depth
either sailing or anchoring
. My sense is that in heavy winds or in areas where the bottom is rockier rationality takes firmer hold and the shoal draft boat is less likely to run aground. My conclusions extrapolated from what Wing wrote.
My reccommendation is that a 40' or so boat with 5'-7.5' of draft is pretty reasonable. More than that I start to think it is a former racing
boat that may have a lot of characteristics that would be fine racing
but problematical cruising. That length boat with under 5' of draft I ask why? If it has a full keel
or a centerboard
then that about covers it. As an example the Bermuda
40 is almost 41' and draws 4.5'ish board up and it was designed for the Newport-Bermuda race
which crosses the Gulf stream
which can be very nasty during a blow. I think most people would agree that the Bermuda
40 is an acceptable blue water boat.
My feeling is that the moderate draft I mentioned above is a good compromise between upwind performance and general anchoring
friendliness. If you were going to the Bahamas
or were going to cruise
the canals of Europe
, then shoal draft would look more attractive.
As I use the terms capsize
means the boat rolls over approximately upside down, knock down means mast
in the water or just below, and founder means to sink, all distinct meanings.
For sailboats a capsize generally requires wave action to roll the boat over, exceptions would be the aforementioned J24 with a very limited range of stability or a vessel that is grossly overloaded or has it's stability compromised. An example of the second two is the recent capsize of a MacGregor
26 in San Diego
under mild conditions, the boat was overloaded though not grossly so and apparently had not taken on the required water ballast which is believed to have seriously compromised it's stability.