Building Cruising Catamaran: What is the ideal beam width on each hull?

[masindi]

Hi,

I am designing a 30ft coastal cruising catamaran in Jakarta, Indonesia and would like to know the ideal beam width for each hull that is suitable for simple and comfortable accommodation.

Based on Terho Halme's suggestions, the "length/beam ratio" of each hull should be between 9 and 12 for a comfortable cruiser. 8 would increase wave making and should be avoided. But if I aim for a ratio of 9, that means the beam width ends up only 3ft 3in wide (way too tight for accommodation, not to mention for retractable daggerboard).

Any suggestion for the ideal hull beam width for this 30ft cat?


Thank you!

Indi Soemardjan
Jakarta, Indonesia

[LookingForCruiser]

The beam of the hulls on my 30' Iroquois is 3'6". Yeah, they're narrow. I don't recall the Gemini's I've been on being any wider.

The centerboards on my Iroquois aren't in the middle of the hull, they're on the side and are angled inwards as they go down. So they are mostly out of the way.

[johnreggie]

Check out Woods Windsong catamaran . Mine is 30 ft. Hulls are deep v and widen to 5 feet max. Total beam is 18 feet. Draught 2ft 8 inches. fixed keels . Pylwood and fibreglass sheathing.

[masindi]

Thank you for the feedback, gentlemen

Woods Windsong dimension seems ideal but it's V hull creates hobby horsing I heard.

[johnreggie]

Hello, I appreciate your concern about hobby horsing using deep v hulls , and agree that my Woods Windsong tends to do this. I imagine a wider v may be better eg 50 or 60 degrees, and wider keel as well. This would mean more complex shaping with an angle or fold around half way up the hull's height., in other words a u shape rather than v. Keeping as much mass as possible near to the centre of length helps a lot, so I load up to suit, keeping only light stores at the ends of the boat .

[Cap10paul]

Masindi,
I had a 24' Hirondell with a 15' beam and hulls that were 4'. Daggers were outboard in the hulls and out of the way.
Now have a 1993 lagoon 42' with 20' beam and 6.5 inside hulls amidships. No discernible hobby horse unless too close hauled.