Questions About the Wider Beams on Newer Boats

[Rohan]

A question for everyone.

One thing I've noticed while looking at cruising boats for purchase is that the average beam width of monohulls seem to get progressively wider and wider as you go from from the 1960s to today. Some of the newest boats, like the Beneteau Sense, look absurdly wide. In the 48' range, there seems to be about 3 feet average increase in beam over the past 50 years.

Yet, I've looked into it, and performance doesn't seem to have suffered. All other things being equal, aren't narrow beams faster? So how have modern gotten around this? Is there are new design technique I'm unaware of? Or do they make up for it by decreasing weight or increasing sail area?

Also, how much of a difference does a wider beam really make toward increasing stability and reducing rolling? Thanks.

[Hydra]

In fact, beam is related to initial stability, that gives sail-carrying power: in *normal* sailing conditions, a wide-beamed yacht needs less ballast in the keel than a narrow-beamed one with the same sail area. But a wide hull has more wetted area and more resistance at low speed than a narrow one. Then, an architect aims for a compromise.

The extreme solution for increasing beam without adding wetted area is a multihull.

In fact, the main reason for increasing beam in cruising yachts is just to have more internal space.

The trend is the same for warships: the old DDG 963 (Spruance class) had a waterline length/beam ratio of 9.6 when the present DDG51 (Arleigh Burke class) is 7.9.

But this increased initial stability sometimes increases rolling when the ship's natural roll period is closer to the more frequent wave periods. A well-known case is USS Midway, which rolled so much after being widened at the waterline that she couldn't operate planes safely anymore and was decommissioned.

Alain

[barnakiel]

Plenty of beam well aft can make a boat sail very fast and stable downwind. Downwind is also what most sailors like to do. If you are one of them, you may like beamy boats. Some modern cruising boats take it from modern racers.

Entry is narrow when the max beam is well aft, hence upwind performance is also good.

Initial stability is good - these boats tend to be initially stiffer than narrow boats. I like this characteristic very much.

I think the new design is great for marina queens (cockpit size), charter boats (interior volume, cockpit access from stern) and for boats that will sail on predominantly downwind passages (speed and stability off the wind) (e.g. coconut milk run).

This much said, they may be less than optimal for sailing in other set of conditions, on other routes.

b.

[goboatingnow]

Originally Posted by barnakiel

Plenty of beam well aft can make a boat sail very fast and stable downwind. Downwind is also what most sailors like to do. If you are one of them, you may like beamy boats. Some modern cruising boats take it from modern racers.

Entry is narrow when the max beam is well aft, hence upwind performance is also good.

Initial stability is good - these boats tend to be initially stiffer than narrow boats. I like this characteristic very much.

I think the new design is great for marina queens (cockpit size), charter boats (interior volume, cockpit access from stern) and for boats that will sail on predominantly downwind passages (speed and stability off the wind) (e.g. coconut milk run).

This much said, they may be less than optimal for sailing in other set of conditions, on other routes.

b.

Yet they are common in high latitude Northern European sailing ( and in NZ etc) . Were there a demand for a narrow beam, older style yacht , it would get produced. The fact is the modern form factor represents a better compromise in the minds and experience of such sailors.

" Optimum" , is very much a fickle fashion item. Today boats are much more widely available , then years gone by, yet the owner is often not going to be a DIY yacht minder, so boats have to be stronger, need less maintenance, and be able to take care of its less skilled occupants .

Dave

[Amnesia II]

From what I've seen most racing yachts these days are very broad and carry that right to the stern.
My own boat is beamy with huge cockpit and access at rear for swimming...ideal for us old codgers.
Initial stiffness was demonstrated in a 40 knot overnight gale mexico to Galapagos.....never put the rail down at all, doing 10kts with 3 reefs, broad reaching....excellent!

[barnakiel]

99% of Northern European Yachting is done in the summer. Most any boat will do. If they were to build boats for Northern European winters, them boats would look different. Proof: look at some possibly stronger built boats from Scandinavian, Dutch and UK boatyards. (Regina, Malo, Rustler, Contest, etc.)

These possibly stronger and definitely narrower boats tend to sail slower off the wind, roll, have smaller cockpits, less interior volume and poorer swimming platforms. Not what you want in the Med, or when on a long downwind adventure in predominantly tropical conditions.

Horses for the courses.

My only objection to many of the beamy sort of boats is that they are too fragile - they are sort of like racers only lacking racers' structural and mechanical strength. Not to say they need this much strength, but it is nice to know your boat can take a knock or two.

b.

[goboatingnow]

Originally Posted by barnakiel

99% of Northern European Yachting is done in the summer. Most any boat will do. If they were to build boats for Northern European winters, them boats would look different. Proof: look at some possibly stronger built boats from Scandinavian, Dutch and UK boatyards. (Regina, Malo, Rustler, Contest, etc.)

These possibly stronger and definitely narrower boats tend to sail slower off the wind, roll, have smaller cockpits, less interior volume and poorer swimming platforms. Not what you want in the Med, or when on a long downwind adventure in predominantly tropical conditions.

Horses for the courses.

My only objection to many of the beamy sort of boats is that they are too fragile - they are sort of like racers only lacking racers' structural and mechanical strength. Not to say they need this much strength, but it is nice to know your boat can take a knock or two.

b.

That's ok then , our summer just experienced a series of offshore gales upto f9, no problem for these summer boats.

In winter nothing really sails here

Dave

[builder dan]

Having sailed a lot in a narrow yacht I thought they were the only way to go until I sailed a long passage on a mates wider beamed boat,I loved the way it sailed upright and just as fast as the one I was used to.It seemed a lot less tender and at the end of the passage I felt a lot less knocked around,they are great.

[Andrew B.]

So can one now presume that the typical 3:1 ratio was just a fad that one
can now ignore when selecting a seaworthy sailboat ?

Are there any compromises one needs to be overly concerned about with a wider beam boat ?

[minaret]

Originally Posted by Andrew B.

So can one now presume that the typical 3:1 ratio was just a fad that one
can now ignore when selecting a seaworthy sailboat ?

Are there any compromises one needs to be overly concerned about with a wider beam boat ?

Righting moment. Initial stability provided by high beam seems great when upright, but when the boat turns turtle and won't right itself due to that high initial stability, you may not like it so much. This is one reason these boats are often referred to as coastal cruisers, or not "blue water" boats. They do great in benign conditions.

[valhalla360]

Length to beam ratio makes a big difference if you are talking about a high performance cat where it may be upwards of 20-1 vs the typical mono 3-1 or 4-1. The small change in monos makes negligible difference in hull speed and what is lost is made up for with other advantages such as less wetted surface and the ability to stay upright and carry larger sails (dragging the rail thru the water doesn't help performance).

If you are a racer, performance counts. If you are a cruiser, performance is nice to have but 90% of the time you are anchored or docked, so it becomes the primary design concern once you have a reasonable boat under sail.

For an afternoon sail, putting the rail under is exhilerating. Day after day of clinging to life at 30 degrees, is tiring.

[neilpride]

Originally Posted by Andrew B.

So can one now presume that the typical 3:1 ratio was just a fad that one
can now ignore when selecting a seaworthy sailboat ?

Are there any compromises one needs to be overly concerned about with a wider beam boat ?

Wider beamy boats have a better initial stability compared to narrow hulls, if the limit is broken the roll is far worse than in a narrow boat, dont know exactly what size we talking about, 13 ft , 15? 16? all in the transom or aft of the boat?

I like the new wider transom designs out there, more room inside, bigger cockpits, 2 wheels , fast downwind etc... but there is a limit or we can got some problems, wider mean less ballast and light construction in some designs, anyone remember the firsts Vendee globe RWT capsizes??

2 picture is a Pogo 40 doing a roll over test and the other is a Beneteau Sense, i see some similarities in the hull form...
Anyway i like the concept, the boats are stiffer in the gusts, more room inside, faster downwind,,,
Cons?? at the moment nothing, as far i know......

[barnakiel]

Originally Posted by Andrew B.

So can one now presume that the typical 3:1 ratio was just a fad that one can now ignore when selecting a seaworthy sailboat ?

Are there any compromises one needs to be overly concerned about with a wider beam boat ?

My opinion:

I am not sure this is about seaworthiness.

Not all boats are designed to cross oceans in predominantly rough conditions. A charter boat or a weekend queen does not call for the level of seaworthiness or structural strength designed into boats that will sail the Southern Ocean.

I also strongly believe that pure seaworthiness should be well proportioned to well thought out crew comfort. Many s.c. seaworthy boats are very uncomfortable on some points of sail or/and at anchor. A well rested crew will be better able to sail their boat longer, safer - adding to the seaworthiness of the whole 'boat+crew' system.

I think the a/m typical ratio was a result of common sense and design methods/traditions as they were (you will notice some historical US boats were actually beamier). I believe this ratio still broadly and generally holds: benneteau sense shows ratio 3.5 - roughly same with a HR 55. And one ratio is just that and we must look at all other ratios and then also at how the final product of all these ratios sails.

As for concerns, in any marina that charges by LOA x beam, a narrowboat is a winwin ;-)

Seriously though: if you want to make many offshore passages or some adventures in less than perfect weather, then you may want to look INSIDE the boat and decide for yourself if the extra space below has been organized in a way that will allow for safe living and moving in rough conditions. I have sailed and been onboard too many beamy boats that were great in port but became extremely uncomfortable (IMHO edging on dangerous) on the passage - with too few handholds spaced too far apart, flat and glossy floors, glass panels in the galley area and sharp edges everywhere...

So you must think about how you are going to use the boat and then see if she offers the features that are most desirable for this kind of use.

b.

[Rohan]

Originally Posted by minaret

Righting moment. Initial stability provided by high beam seems great when upright, but when the boat turns turtle and won't right itself due to that high initial stability, you may not like it so much. This is one reason these boats are often referred to as coastal cruisers, or not "blue water" boats. They do great in benign conditions.

I would have to disagree if you are saying that necessarily makes them coastal crusiers. Compare this to cruising catamarans - they don't flip over very often, but once they do, they won't right themselves without the help of a crane. Yet they are fine as Water boats">blue water boats.

[Suijin]

Don't forget what has made wider beams possible is changes in materials and technology. In the same way that the fin keel brought performance gains over full keels due to less wetted surface, today's boats are lighter, with even less wetted surface because they displace less water. That in turn allows for a wider boat, which is generally an advantage in terms of performance as it allows the boat to carry more sail in moderate winds. Technically, the perfect hull cross-section is a perfect circle is it is the mathematical route to the least wetted surface possible. Modern boats ride higher, so less of the circle is in the water, but you need to carry that radius up the topsides to ensure low wetted surface as the boat heels, resulting in much wider beams.

A month ago I spent a few weeks at the Brewer yard in Westbrook CT. The 40' IRC beast "Catapult" was in her cradle at the yard. Freakishly low wetted surface and she rides like a cork. That boat is insane. Here is a shot of her at work, and you can see how the wider beam gives her stability and keeps her waterline length long, and how the flared topsides become wetted surface as the boat heels:



The downside to this approach is that these boats are generally supremely uncomfortable going to weather, compared to heavier displacement boats with deeper forefoots. Put in your mouth guard when you're close hauled in a seaway.