MultiHull Motor Yachts over 100 feet.

Originally Posted by PsychicWarrior

Hmmm.. I have stated what I will, showed videos, facts and and numerous evidence.. against your caustic remarks and dubious opinion..

By so far you have not received any confirmation of your bias, quite the opposite. And I was just one opponent.

So all OUR "dubious opinions" stand against your expertise?

Facts and evidence you could not provide (of course not).

You are a impertinent amateur, and nothing else!

Go dream further, idiot.

[PsychicWarrior]

Apex you foul mouthed mentally deficient old chap.. try hurling your insults in the mirror as they would be much more fitting. For those who have contributed intelligently here, thank you.

[Stumble]

Just as an aside,

The around the world record is not even held by a power boat. Groupama 3 did it about 12 days faster than Earthrace. Though of course Groupama is a multi-hull too.

PW,

you have extrapolated from a very limited understanding of SWATH ships a whole mess of incorrect conclusions. So taking a look at the real technical notes for a moment:

SWATH ships, compared to traditional multi-hulls, are: (See British Columbia Ferry Corporation: Fast Ferries Technical Notes, available online)

1) More expensive to build
2) Require highly complexed control systems
3) have deeper drafts
4) Have higher maintenance requirements
5) Require 180% the power of a conventional multi-hull
6) Have a overall reduced spped compared to a conventional multi-hull

In exchange for this the vessel is more stable at all sea states than a traditional multi-hull


Now compare multi-hulls to mono-hulls for a moment and we find that multi-hulls are:

1) Faster for the same power due to reduced draft
2) Have higher initial stability
3) Typically lighter for the same surface area
4) More prone to pitch-poling as the forward amah digs into the water
5) Incabable of self righting in the event of being knocked passed 95%
6) Structually weaker due to the long leaver arms between the appendages


So yes, a large multi-hull can be made faster (though SWATH ships are pretty questionable), and in moderate conditions a Catamaran is more comfortable. However in extreme conditions a multi-hulls inability to be designed to self-right from a knock down makes them unsuited to service in the worlds worst sea conditions. Further the loading on the widly seperated hulls increases the possibility of the boat litterly breaking in half during heavy wave action.

Ad for the US Military's interest in SWATH ships.... Well they already have a few of them. However they are currently all relegated to research missions. Where their high stability makes them ideal for a number of missions related to sea state monitoring. They are not being bought for combat purposes at this time.


British Columbia Ferry Corporation: "Fast Ferries Technical Notes

[PsychicWarrior]

Stumble - thank you for that brilliant analysis. I ave been looking at this link http://www.******************/Bentley...nced_Hulls.htm and studying them. The knockdown feature is significant.. and one I had not thought of.. though of course its harder to knock down a multihull. Its hard for me to think pitch-poling is a possibility if its designed right.

The US NAvy has committed to SWATH for high speed transports and is building a number of them to do 30 + knots in rough sea conditions.

But my purpose is to create a motor yacht that can cruise at 22-26 knots without burning outrageous amounts of fuel and 16-18 knots very economically. As well, doing that speed in rough seas without too much rocking and rolling is a key component.

A full displacement monohull is out of the question therefore and semidisplacements can't handle the rough seas. Sure a floating ball is the best in rough seas as it cant be tipped.. whats the next best option?

Something tells me a multihull/SWATH could be designed to right itself if tipped in the case of a tidal/extreme rogue wave. Yet how often is that likely to happen? I am not sure a large (35-40mtr) yacht could right itself either?

Originally Posted by PsychicWarrior

Stumble - thank you for that brilliant analysis. I ave been looking at this link http://www.******************/Bentley...nced_Hulls.htm and studying them.

Congratulations! You have found the biggest scam in our business. That company never did a single boat, engine or what so ever.

The knockdown feature is significant.. and one I had not thought of.. though of course its harder to knock down a multihull. Its hard for me to think pitch-poling is a possibility if its designed right.

It is not that hard, when the conditions are right.

The US NAvy has committed to SWATH for high speed transports and is building a number of them to do 30 + knots in rough sea conditions.
What is rough?

But my purpose is to create a motor yacht that can cruise at 22-26 knots without burning outrageous amounts of fuel and 16-18 knots very economically. As well, doing that speed in rough seas without too much rocking and rolling is a key component.

Many others would like that too. Unfortunately, it is not possible.

A full displacement monohull is out of the question therefore and semidisplacements can't handle the rough seas. Sure a floating ball is the best in rough seas as it cant be tipped.. whats the next best option?

Something tells me a multihull/SWATH could be designed to right itself if tipped in the case of a tidal/extreme rogue wave. Yet how often is that likely to happen? I am not sure a large (35-40mtr) yacht could right itself either?

Why wouldn´t a 40 mtr yacht be self righting? It is not difficult to design them accordingly. And there are quite a few out there, which can stand being tripped.
The fact, that you like to have something, does not make it possible per se.

See my comments in red, above.

Regards
Richard