How Wide is Too Wide?

[nimblemotors]

As I plan to keep my boat anchored out almost exclusively, it is my view
that there isn't really much downside to making a larger boat.

At 18ft wide, there are not many haulout facility that handle it and I can beach it so plan to do that when needed. So why not 24ft, 30ft, or 32ft or 36ft wide?
(please ignore any structural issues)

I can understand it might make a tighter squeeze docking in some places.
Visiting the fuel dock seems the biggest concern.
The idea is my tender will actually contain the fuel tank, so even taking on fuel can be done anchored out.

Anything I might be missing?

[44'cruisingcat]

You really can't just ignore structural issues.... wider is heavier, so needs a bigger rig, which increases loads, which requires heavier construction which needs a bigger rig.... there's a practical limit.

The wider you go, the more bridgedeck clearance you need too.

[Kettlewell]

There are various reasons you have to go into docks when cruising. You might be limited in some places. I frequently jug fuel to the boat to avoid having to go into the fuel dock, but if you have big tanks that can be a slow process and inconvenient. How will you empty your holding tank? There are places where you are supposed to tie up to the dock in order to clear customs and immigration--theoretically, it is required in the USA, though they do sometimes let you slide. There are canals not much wider than that. There is a swing bridge on the Dismal Swamp Canal with 42 feet of horizontal clearance, and I think the lock width is 52 feet. And, there may be times when you just want to tie up in a marina for awhile, and you will be limited. A boat that wide takes up a lot of room in an anchorage. But, bottom line it is certainly doable if that's what you want.

[nimblemotors]

Originally Posted by 44'cruisingcat

You really can't just ignore structural issues.... wider is heavier, so needs a bigger rig, which increases loads, which requires heavier construction which needs a bigger rig.... there's a practical limit.

The wider you go, the more bridgedeck clearance you need too.

I am not ignoring the structural issues, it just isn't my question.

[Stumble]

So long as length increases with width proportionally, no there are no disadvantages. There is however a sweet spot for width relative to leingth on a catamaran. To narrow and it doesn't generate enough righting moment, to wide and it has a tendency to bury the bow and pitch pole. Getting it right is crucial to the design of a boat.

Wider boats are also heavier, though they can typically carry more sail. So depending on how this goes you may gain, or loose.

[mark_morwood]

Originally Posted by Kettlewell

There are various reasons you have to go into docks when cruising. You might be limited in some places. I frequently jug fuel to the boat to avoid having to go into the fuel dock, but if you have big tanks that can be a slow process and inconvenient. How will you empty your holding tank? There are places where you are supposed to tie up to the dock in order to clear customs and immigration--theoretically, it is required in the USA, though they do sometimes let you slide. ...

In our experience, all those docks are invariably face docks, so width is usually not an issue. Most marina slips on the other hand are almost always too narrow for even "reasonable" width cruising catamarans (say 20ft). That is unless there are no posts between neighboring slips and you can take two.

But as has been said, I think you will find that if you don't increase the length to match the width you will get bad behavior in offshore conditions. You really do not want to bury a bow and pitch pole.

Mark.

[belizesailor]

Beam does become an issue when you need to haul for a bottom job. At about 21ft beam I can just squeak my little cat into many travel lifts. Much wider than that and you've got to find other options.

Friends with much larger cats 65+ often have logistics issues when it comes to bottom jobs.

[Sand crab]

Some where around 30' things get really difficult ($$$$$). 300 ton travel lifts are about the only beasts that can handle this beam. Railways might do it but they may have other issues on tahat beam. However if you are staying around the major areas then it's no problem if your wallet can handle it. And FWIW there is no direct correlation between travelift tonnage and beam capacities due to the many manufacturers. If you have the means then do it.

[nimblemotors]

Originally Posted by Kettlewell

There are various reasons you have to go into docks when cruising. You might be limited in some places. I frequently jug fuel to the boat to avoid having to go into the fuel dock, but if you have big tanks that can be a slow process and inconvenient. How will you empty your holding tank? There are places where you are supposed to tie up to the dock in order to clear customs and immigration--theoretically, it is required in the USA, though they do sometimes let you slide. There are canals not much wider than that. There is a swing bridge on the Dismal Swamp Canal with 42 feet of horizontal clearance, and I think the lock width is 52 feet. And, there may be times when you just want to tie up in a marina for awhile, and you will be limited. A boat that wide takes up a lot of room in an anchorage. But, bottom line it is certainly doable if that's what you want.

Forgot about the holding tank. Exactly why I ask such questions! Thanks!
So I'm gonna need to incorporate a holding tank into the tender also,
that'll make it more complicated.

[Pelagic]

You can make it as wide as you like, provided it serves a purpose.
Docking is not a problem on T-Berths
Drydocking via synchro-lift, graving dock etc...
Superyacht of the Week: The 34 metre super catamaran Che - SuperYacht of the Week - SuperyachtTimes.com

[SVTatia]

How many hulls?

A wide monohull may pose some stability issues - once it goes beyond a certain angle, it will turn turtle and stay there, not unlike a multihull.

[boatman61]

When you need to arrange a pilot boat to enter port..

[SailFastTri]

Originally Posted by nimblemotors

As I plan to keep my boat anchored out almost exclusively, it is my view
that there isn't really much downside to making a larger boat.

At 18ft wide, there are not many haulout facility that handle it and I can beach it so plan to do that when needed. So why not 24ft, 30ft, or 32ft or 36ft wide?
(please ignore any structural issues)

I can understand it might make a tighter squeeze docking in some places.
Visiting the fuel dock seems the biggest concern.
The idea is my tender will actually contain the fuel tank, so even taking on fuel can be done anchored out.

Anything I might be missing?

I think you might be making this more of an issue than it really is. My trimaran has a 28 foot beam.

Hauling by crane is an option. Heavy cranes are common world-wide, and mobile cranes can be hired by the hour (or by "the lift") from the construction trades without paying boatyard premiums. Most multihulls have 4 lifting points built-in. If not, you can put straps around the outer hulls forward and aft of the bridgedeck and/or crossbeams. I carry load-rated polyester straps just in case the yard doesn't have them, for crane attachment.

As for approaching docks: All fuel docks are face-docks, so beam isn't a problem (certainly not 18'). Marinas want big, fat thir$ty powerboat$ to tie up to their fuel dock$, the bigger the better. Most pump-out facilities are located at the fuel docks. In some places I have seen floating rafts (about 30' long) for the pumpout facilities situated on a mooring in the harbor, and you just tie up alongside.

We never have had a problem yet with these things, and all my boats for the last 13 years have been 22' plus in beam.

[Kashmir cat]

Having a haul out facility nearby for routine maintenance and emergency repairs whether you are cruising or stuck in a marina is important. The narrower the beam the more choices you have especially when cruising outside the U.S. where facilities are few and far between. With our Prout's 20'10" beam, we can just squeeze into 50 ton Travelift.

[belizesailor]

Originally Posted by SailFastTri

...
Hauling by crane is an option. Heavy cranes are common world-wide, and mobile cranes can be hired by the hour (or by "the lift") from the construction trades without paying boatyard premiums. Most multihulls have 4 lifting points built-in. If not, you can put straps around the outer hulls forward and aft of the bridgedeck and/or crossbeams. I carry load-rated polyester straps just in case the yard doesn't have them, for crane attachment.
...

Sure you can lift anything but, should probably come up w a beam to budget ratio before building or buying. Have one friend w a large custom cat who drops about $30k per bottom job...much of that in crane rental...well beyond the typical cruising budget.