About Yacht Design

[topi]

Hi everyone,

I've been actively looking for my next boat around half a year now, and the more I learn about boats, the more questions I seem to be having.

I thought I understood everything about yacht design, like sacrificing the height of the rig to bring the center of weight down, but then again there are some things that do not seem to make sense.

Can anyone explain me about such strange occurrences like differences in ballast in different versions of a design? I'm particularly looking at the specs of a Van De Stadt 34 steel boat. Look at these values:

Displacement (steel) 5.40 t

Displacement (aluminium) 4.50 t

Displacement (wood) 4.50 t

Ballast (steel) 1.80 t

Ballast (aluminium) 2.00 t

Ballast (wood) 2.00 t

Why does the steel version have less ballast? I would automatically think that having a bigger displacement would also require a heavier ballast. I've tried to look for boats that have ballast nearly 50% of the displacement, because that would mean that these designs are less likely to heel under heavy winds. Last week I took a Jeanneau Melody 34 for a test sail, and it was much faster in upwind performance than the VdS 34 even though the Melody has more than 6t of displacement. The keel was 3 tons! So maybe she is able to carry more sail area in comparison.

Although I am mainly looking to buy a ocean-capable yacht for cruising the world (circumnavigation), I am hard-pressed to give up on good sailing properties! I'm especially fond of the upwind performance of my Finn Express 83, which I can point at 35 degrees True wind and she still does 5 knots.

topi

[MMNETSEA]

"Although I am mainly looking to buy a ocean-capable yacht for cruising the world (circumnavigation), I am hard-pressed to give up on good sailing properties! I'm especially fond of the upwind performance of my Finn Express 83."

The reason to circumnavigate is an objective not understood by many realtime cruisers - we will run a topic and pole on the subject a little later.

I suppose the answer to you question is "that one cannot have their cake and eat it"

IE, A cruising boat that provides comfort, space , easy to maintain a course, is not like a go fast design that requires constant attention. Steel boats need less ballast, because the lower part of the hull and keel already provide ballast.

[JeanneP]

I'm not sure I understand your goal here. Are you saying you don't want the boat to be easy to heel? In my opinion, heeling is what you want the boat to do to protect the rig from failure in violent gusts, among other things. This is coming from somebody who really dislikes heeling, but who put our mast in the water more than once in my novice sailing days.

Our Jeanneau Sun Fizz's displacement was 7.3 t, keel weight 3 t. She was one of the first "racer cruisers" and certainly wasn't for everyone as a cruising boat. She was a quick and lively boat that sailed very well. We were not racers, but cruising we consistently outperformed other cruising boats of the same size. For example, from Ecuador to Easter Island, we arrived after 19 days, our friends in a heavier, but same size, boat took 23 days to make the same trip.

Because we seemed to want to go places that weren't downwind, we sometimes beat ourselves and our boat up a bit more than the average cruising sailor. I don't think that we could have done some of those trips had we had the conventional heavy-displacement full-keel boat. When we weren't going to weather in 35+ knot winds I think she was as comfortable as a heavier boat which, I understand, is the average cruiser's reason for getting one of those "oyster crushers". I would comment, though, that had we wanted to do high latitude sailing I believe that we would have had a heavier boat.

Just one opinion among many, though.