Manoeuvrability catamaran

[sizzurp]

I'm designing a workboat for the northsea. Dimensions: LOA 17 m, BOA 6.5 m, speed of more than 20 knots.

I would like to hear your thoughts about the manoeuvrability (at low speeds) of a catamaran versus a monohull.

[Alik]

At low speeds cats have excellent maueverability due to bigger distance between engines, and ability to reverse the engines. They just need different driving technique compared with monos.

At high speeds - yes, cats have bigger turning radius.

[sizzurp]

Thank you Alik.

I know cats are generally harder to maneuver in high wind speeds because of the smaller underwater ship.
But why do they have a larger turning circle? They drift more?

[Typhoon]

They have a larger turning circle at speed because they have more lateral resistance than say a planing monohull.
If you put small permanent skegs on the hulls near the shafts, cats gain a lot more manouvreability.
But as said above, low speeds, cats win, especially if you put the rudders nice and close to the props as well.

Regards, Andrew.

[Alik]

Originally Posted by sizzurp

Thank you Alik.

I know cats are generally harder to maneuver in high wind speeds because of the smaller underwater ship.
But why do they have a larger turning circle? They drift more?

I never experienced problems with manoeuvring in wind, though I admit that there is some effect.

Lager turning circle is due to group of factors: higher inertia, higher hydrodynamic damping of turning motion, etc. Actually cats possess about double hydrodynamic damping compared with monohull craft.

Recently I have presented a paper on catamaran design at CPBS, there is some data on turning diameter of catamarans.

[sizzurp]

Thank you for the explanation!

Can i find your paper somewhere on the internet? Sounds really interesting.
(Sorry, don't know what CPBS is)