Fat or thin ?

[Sixpence]

No I'm not going on a diet /forums/images/graemlins/blush.gif
I'm curious , I've been on a nice slim yacht and enjoyed it immensely , but I've also been on a less than slim one and can't help thinking that the less slim one had more room . Obviously I'm talking about beam , but is there any real difference between a wide beam and a narrow beam . Do they really handle that much differently ? and if so why ? and the dreaded question , which one is better ?

 

[fireball]

Wide Beam - flat underside means more wetted area and your foils will be at the surface sooner when you heal. Superb for downwind sailing - surfing down the waves (hence the open 60 design) but not so good at the upwind stuff ..

 

[Sixpence]

Thanks for that , sounds like wide is better in most ways then

 

[ean_p]

Mmmmm me thinks that most wisemen say that unless racing or wanting extra accomodation then in most case's all other things been equal a slim boat is a better boat !

 

[tangofour]

[ QUOTE ]
Mmmmm me thinks that most wisemen say that unless racing or wanting extra accomodation then in most case's all other things been equal a slim boat is a better boat !

[/ QUOTE ]

Hmmmm, so how do you explain the 'ultimate racers' that are Americas cup boats. long and slender, as opposed to the 'ultimate racers', flat bottomed skiffs, that the open 60's represent.

It really all depends on the type of sailing you do!

 

[Salty John]

As in all things, moderation is the key. A beam of no more than one third the length was long considered the best ratio for seaworthyness.
Beam gives accomodation, speed down wind and some resistance to heeling. It can also be difficult upwind because the bow is too fat and, combined with shallow draught, can give a tendency towards excessive weather helm when heeled.
But also, a beamy boat provides greater reserve buoyancy in the ends. But it can also have a scary amount of inverted stability so that it can be slow to right itself if capsized, the main problem with catamarans.
Moderation is the key.

 

[heerenleed]

let me put it this way

Wehave friends that own an X (X-yachts of Denmark). It is one of the better versions of the Wider variety (though not extreme) . We own a Nicholson, one of the better version of the narrower variety (though not extreme).
When we were considering a trip to the English East Coast together and told them that it would not be fun for them, because they would always arrive way ahead of us they said: Of course, we will get there much quicker than you. But when we arrive, we will be exhausted. When you arrive, you will go straight to the pub to celebrate as you won't have suffered at all.

This is it. Apart from the difference in quality bewteen high volume "low" priced boats and low volume high priced boats (the latter mostly being the better) it is the sea kindliness which is usually: the narrower the better". As for speed: the wider boats are, as stated by others, mostly much faster downwind. Upwind it's the narrower boats you want.

So... It all depends on what you want. Want to race: wider boat. If you want to cross in comfort in less favourable conditions: narrower boat.

cheers

 

[LadyInBed]

I like my beam, but it is a bit of a problem having to take four or five steps to get from port to starboard side /forums/images/graemlins/ooo.gif

 

[flaming]

Re: let me put it this way

I think a lot of opinion here is equating wide with light and narrow with heavy.

This is not necessarily the case in modern yachts. The modern cruising "fat" yachts are in fact quite heavy, so lose a lot of the good performance downwind that their wide shape should bring. I'd be supprised if a modern benjenbav of the "cruising" variety - eg oceanis - would be significantly faster downwind than the likes of a Nicholson.

 

[Noddy]

[ QUOTE ]
But it can also have a scary amount of inverted stability so that it can be slow to right itself if capsized, the main problem with catamarans.


[/ QUOTE ]
Obviously Multihulls offer the best of both worlds. Fast and wide with a comfortable ride (like my women! /forums/images/graemlins/laugh.gif)

The above qoute is unduly negative: Along with the 'scary inverted stability' comes equally scary upright stability.

I know this is a tired debate but I felt the need to add a bit of balance. (balance is not required on a multihull as they are very stable /forums/images/graemlins/laugh.gif)

 

[Salty John]

I like catamarans and would have no hesitation in owning one myself. However, there is no getting away from the fact that they are as stable inverted as they are right side up!

 

[FullCircle]

I contest that assertion.
In fact they are more stable inverted, as the mast and rigging will resist any attempts to right the vessel, and the same mast/rigging will contribute to inversion whilst waggling about in the air.

 

[Danny Jo]

[ QUOTE ]
A beam of no more than one third the length was long considered the best ratio for seaworthyness.

[/ QUOTE ] Yes, and note also the unpleasant tendency of broader boats to slam in head seas, shaking the very teeth out of the skulls of their crews.

The downside is the need for a longer boat to get the same accommodation. Freestyle, at 38 foot with a length to beam ratio of 3.3, has less accommodation that many modern 32 footers, but gets charged more in marinas. Is this fair?

 

[jamesjermain]

While not disagreeing with what you say, you don't right a catamaran by pulling from the side. You take a line from the forward cross beam over th hull to the stern and pull her up bow over stern. You may even be lucky and retain the rig.

I was glad to discover that the RNLI know this trick and have used it successfully (not on my boat, I hasten to add).

 

[douglas_family]

[ QUOTE ]
I like catamarans and would have no hesitation in owning one myself. However, there is no getting away from the fact that they are as stable inverted as they are right side up!

[/ QUOTE ]

They are at there most stable upside down and mono hulls are at there most stable on the sea bed neither is desirable or particularly likely with a well designed boat and a bit of seamanship.

 

[FullCircle]

JJ, I bow to your knowledge of righting. /forums/images/graemlins/grin.gif
As a recent ex-virgin to the catermeringue experience, I took a lesson in Greece on a Dart 16, and successfully raced it in the resort regatta, just 2 weeks ago. I have a certificate to prove it too. The righting rope on that came from just behind the mast, and was thrown over the leeward hull, and tugged on by the ex occupants. The 10 knots of wind I did this in meant that a 'real' capsize was difficult to organise. Bit trickier on one with a bit of accomodation I guess.

 

[alec]

One thing worth mentioning is that water is not keen on being disturbed, and will get upset and slow you down. Narrow boats push less water about than the wider bodied yachts and therefore have less resistance. But narrow boats tend to have bigger underwater areas pro rata to the wide boys.

Unfortunately, narrow boats are tender and will heel quicker which my wife hates.

The modern trend is obviously to go wide and high ( power boats ) as we are charged by the metre for mooring. Not such a bad thing if you don't do a lot of sailing or motoring.

Viva la difference !

 

[pyrojames]

The amount of water being pushed about is proportional to the displacement of the boat. The shape (wide versus narrow) has little to do with it. In general terms, narrow tends t be heavier for a given LOA, so the reverse of what you have said is true.

 

[fireball]

[ QUOTE ]
In general terms, narrow tends t be heavier for a given LOA

[/ QUOTE ] Eh?

 

[Twister_Ken]

Yup, coz narrow boats (not narrowboats) pack more lead in the keel to provide a righting moment that on fat boats is provide by hull form.