Displacement Question

[dragonfly203]

Hello wise people of the board,

I'm looking to replace a Catalina 36 for a vessel with a more modern, airy, seaworthy design. I've tried to follow Paulo's threads regarding the importance of displacement and keel weight, and frankly, I am confused. Are there standard equations that I can use to predict whether a boat is suitable for our needs? Some set minimum stardards? Our plan is to expand from our current sailing plan (Chesapeake Bay) up to New England and down to the Keys and/or maybe Carribean Islands.

I'm going to throw out 2 very different yachts and ask why one would be potentially better than the other, in terms of displacement and keel weight. From what I've read from Paulo and others, this is important. Both of these boats are in our "bin" for the boat show in October.

Jeanneau 409
displacement - 16,424 lbs
shoal keel -5,445 lbs

Hallbery-Rassy 372
displacement - 16,500 lbs
keel - 6,400 lbs

Appreciate your thought on this.

[cormeum]

Displacement and keel weight are only part of the picture. Beam and draft are also primary considerations in determining how a boat behaves in heavy weather. Additionally keel planform and hull shape etc.etc.etc.

You're looking at too few variables to get a good picture.

[sailingdog]

While displacement and ballast percentage are important, they are, as previously pointed out, just two of many factors that make a boat seaworthy. I'd point out that often the requirements for a seaworthy bluewater boat are different from that of a "airy modern coastal cruiser".

Most bluewater boats are going to have less spacious and less open cabin layouts that will seem less airy for safety reasons. Big, open wide airy layouts are dangerous on a bluewater passage, since the handholds can be far and few between and the distance you can get thrown is much larger, resulting in more serious injuries....

Going to the Keys or to the Caribbean does not require a bluewater boat for the most part. The passages are mostly shorter and can be done by a decent coastal cruiser most of the time.

I would point out that the best advice I've been given about boat buying is that the PRIMARY USE SHOULD BE PRIMARY. That means, if you're only going to have two people aboard most of the time, you shouldn't get a boat designed for carrying eight or nine people with four cabins, since they won't be used or needed most of the time and the boat will likely be too big to easily handle with just two aboard.

Likewise, if you're just coastal cruising and island hopping, there really is no need to get a full-bluewater boat.

Originally Posted by dragonfly203

Hello wise people of the board,

I'm looking to replace a Catalina 36 for a vessel with a more modern, airy, seaworthy design. I've tried to follow Paulo's threads regarding the importance of displacement and keel weight, and frankly, I am confused. Are there standard equations that I can use to predict whether a boat is suitable for our needs? Some set minimum stardards? Our plan is to expand from our current sailing plan (Chesapeake Bay) up to New England and down to the Keys and/or maybe Carribean Islands.

I'm going to throw out 2 very different yachts and ask why one would be potentially better than the other, in terms of displacement and keel weight. From what I've read from Paulo and others, this is important. Both of these boats are in our "bin" for the boat show in October.

Jeanneau 409
displacement - 16,424 lbs
shoal keel -5,445 lbs

Hallbery-Rassy 372
displacement - 16,500 lbs
keel - 6,400 lbs

Appreciate your thought on this.

[grmitche]

There used to be a rule of thumb that 35-40% plus would be a "stiff" boat - but that is when all boats had slack bilges. Nowadays most boats have a pretty sharp turn to the bilge and get much more initial stability from "form". As others have said - you can't just compare the weights of the keels.

Just knowing a bit about the brands, but not the specific boats - the Jeanneau is going to have more interior volume and those harder turns of the bilge, and therefore can get away with less keel weight - especially for a shoal keel. The jeanneau will likely have more immediate stability, while the HR will likely heel over a bit and then stiffen up.

Really 2 very different sorts of boats.

Also - keel shapes impact that % displacement dramatically - a bulb keel on a carbon or cast steel fin can be much less in absolute weight but provide similar righting moment to even a fin keel, much less a traditional keel.

Pick up Robert Perry's latest book - lot's of great info - and some pretty boats too.

[dragonfly203]

OK, so no easy answers, but I appreciate all of your comments. Will have to pick up the Robert Perry book. Saturday's trip from Annapolis to St. Mike's with 30 mph gusts made me long for a big, strong Island Packet! I was surprised to see cats in that weather, incredibly fast!

[PCP]

Originally Posted by dragonfly203

Hello wise people of the board,

I'm looking to replace a Catalina 36 for a vessel with a more modern, airy, seaworthy design. I've tried to follow Paulo's threads regarding the importance of displacement and keel weight, and frankly, I am confused. Are there standard equations that I can use to predict whether a boat is suitable for our needs? Some set minimum stardards? Our plan is to expand from our current sailing plan (Chesapeake Bay) up to New England and down to the Keys and/or maybe Carribean Islands.

I'm going to throw out 2 very different yachts and ask why one would be potentially better than the other, in terms of displacement and keel weight. From what I've read from Paulo and others, this is important. Both of these boats are in our "bin" for the boat show in October.

Jeanneau 409
displacement - 16,424 lbs
shoal keel -5,445 lbs

Hallbery-Rassy 372
displacement - 16,500 lbs
keel - 6,400 lbs

Appreciate your thought on this.

Sorry for any confusion

Take a look at the last post on the interesting sailboats thread. It talks about the 409.

From the two I would chose the Halberg Rassy, just because it is just such a beautiful boat and also because the boat has a better final stability, smaller inverted stability and a better AVS. I believe that in the positive part of the stability curve, till 90ş, both boats will have a similar stability.

If you want a more oceangoing boat, with a better overall stability look at a well equipped Hanse 400 (epoxy hull), a First 40, a Salona 41, a Dufour 40e or a Elan 410. These are (with the exception of the Hanse) what are normally called performance cruisers.

I know that you are not interested in racing or going fast, but these boats have to have a lot of stability that they need to carry their big sails. This means that these boats have a superior Ball/Displ and a better AVS than what we use to call pure cruisers. On two words, these boats are more stiff and have more stability than the ones we call cruising boats (big production boats).

Have one of these and sail conservatively (only using full sail with weak winds) or ask them to mount a smaller rig (the Dufour has one). The guys from Salona can even put more ballast on the boat, just to suit your needs.

Of course you can also have a Halberg-Rassy 40 or a Najad 405 and you will have all the seaworthiness you need for going offshore with a large security margin, but as you know this is a much more expensive option.

Regards

Paulo

[PCP]

Forgot about this one:

Moody Yachts

The moody 41 is made by Hanse. The boat has about the same overall stability of the Hanse 400 epoxy and it has a better interior, if you like classical interiors.

I liked the boat. I didn't like that there was no hull "window" but they have said that they could mount one. I wanted a not so simple rig, but that they could not change nor there was any option to upgrade it .

It has a simplified rig but it is a relatively fast boat (all the boat test I saw put that in evidence). It is more expensive than the Hanse or the other boats I have mentioned but it should not cost more than the Halberg-Rassy. Take a look at it on a boat show, perhaps you will find it interesting .

Regards

Paulo

[JiffyLube]

IMHO many different types of boats can go blue water sailing, as I think it really depends on the seamanship of the sailor.