power predictions method

[cjs]

Hallo

I will design an approximately 70 x 30 meters roro catamaran with wawe piercing hulls. Do You have any ideas if there is any appropriate resistance prediction methodes (semi empirical) for that kind of vessels. I guess that Holtrop and Mennens method not will do the work

brgds

C-J

 

[Tim B]

No, Holtrop and Mennon won't go anywhere near a catamaran, especially a wave piercer. AF Molland's work on Catamarans may be of more use, but I think fairly extensive tank testing would be highly advisable.

Tank testing will also give a good insight into the sea-keeping abilities, and (with the right model) sea-keeping in flooded conditions.

These vessels are quite hard to design, approach the problem carefully,

Tim B.

 

[french44]

test with michlet program i test it on big vessel (with bulb and trim wedge)and i have very good results on bare hull i compare with towing tank test and it'very good for 80% of hulls (include pods design hull)

french 44

 

[marshmat]

Michelet is a good option for resistance prediction in slim displacement hulls; it will also calculate interference drag in a multihull. Your individual hulls must have length/beam ratios of 6 or more to get good results from it, and should operate at a subcritical Froude number (full displacement hulls work best). It will not do any stability or trim calculations for you, but will give pretty good resistance and power curves. I agree with Tim that if you intend to actually build this vessel, you will need to do a lot of tank testing; I would include tank testing with appropriately scaled waves as well.

 

[cuongshipdesign]

hey, I may help you. I now own the Auto power software. But you must provide me more characteristic of the hull. The best way is to give me your lines plan.

My email is cuongshipdesign@yahoo.com
Best regard

 

[cjs]

That wolud be very nice, I email You the linedrawings in a couple of days.
Which file format do You want?

 

[PNACS]

Its pity that, we naval Architects are lagging behind latest scientific advancement. We are still dependent on empirical relations, statistical data from series of model tests in 1970s-80s. CFD methods are still in their transformation state to produce reliable results & common usage!