Talk:Multihull

Multihull#Fundamental departure in concept needs different approach

Although much improved from before, a three months later self-review indicates that this section needs either expansion or a re-think, with possibly a different approach, to get the same points across. At the moment, it feels either incomplete or only teaches the concept to those that already know it.

--Slamlander (talk) 02:55, 13 March 2008 (UTC)

Needs a home

Western nautical traditions were built around moving large quantities of goods. Naturally, boats capable of carrying large payloads developed over the centuries, a job best handled by deep, wide hulls. On the far side of the Earth, across the southern Pacific, a different type of seafaring evolved. Cargos were very light - boats carried a few passengers and a minimal amount of gear. These sailors developed boats that were light and fast -- long thin hulls lashed together in numerous ways to achieve the stability needed to carry poweful sails. When recreational boating grew popular in the West, not surprisingly traditional boat forms were adapted to the use. Small and large, typical sailboats can trace their heritage back to fishing and cargo boats. The faster types might be derived from types such as pilot boats - themselves an evolution of western marine traditions. Racing rules through the late 19th and 20th centuries were almost universally based on the notion that a sailboat has one hull, all but preventing experimentation and development of multihull types.

In the past 40 years, the thinking has changed dramatically. Early pioneers such as James Wharram and Arthur Piver were inspired by the South Pacific multihulls and spent their lives (Wharram is still at it) adapting these types to the needs of modern recreational sailing. A sail on a modern multihull designed for cruising is a revelation to anyone who has spent time on a typical cruising monohull. The multihull hardly heels at all, the motion is much more agreeable to most, they stay upright and carry sail when the monohull is heeling hard and must reduce canvas, and they are just plain fast. But remarkable to anyone new to the type - at typical cruising speeds these boats don't feel that fast. The crew doesn't have to brace themselves and hang on, and they don't find themselves dodging sheets of water thrown up over the bows.

In racing, incredible speeds have been achieved by huge catamarans and trimarans. The round-the-world sailing record is currently held by Orange II, a catamaran that completed the journey in 50 days,16 hours, 20 minutes and 4 seconds at an average speed of 22. 20 knots. The course covered 21,600 miles. These are sustained speeds thought impossible for a sailboat a generation ago.

Monohulls will continue to excel at moving cargo, but to move people quickly and comfortably, multihulls have more than proven to have considerable advantages.

This is a good bit and I'm trying to find a place for it. I need the original author though.

BTW, I don't agree that monohulls will continue to excell at moving cargo. Their ballast makes them inefficient.

Slamlander (talk) 16:51, 10 January 2008 (UTC)

This is my piece -- not sure why the attribution was lost. --Woxbox. FYI -- Big monohull cargo ships do not carry ballast when loaded, and when as large as they are today, are quite efficient. —Preceding unsigned comment added by Woxbox (talk • contribs) 03:37, 21 July 2009 (UTC)

Needs much more on all types of Multihulls

This article is somewhat "small racing cat" biased. Nw that's ok since dubtless the early editors had that as experience, but surely it needs expansin into multihull commercial craft?

It's also rather light on trimarans.

Is a "Quadramaran" a raft? (tngue in cheek!)

Fiddle Faddle 17:16, 15 May 2006 (UTC)

This page clearly has some deficiencies. For example, it is internally self-contradictory. At the beginning it says that a multihull is a kind of sailing boat. Later, it mentions power multihulls. There are also some more debatable issues, such as the relative merits of monohulls and multihulls, and especially the relative space given to these two topics. Yet there's no indication here of any kind of discussion. Is/are there an/some active maintainer(s) of the page? Is discussion welcome?

Thanks, Dave Howorth. 2006-10-15

Definitely way too narrow in scope. After all, semi submersible drill rigs clearly are multi-hulled ships and the article correctly opens by defining multi hulls as being either ships or boats. The discussion on pro's & con's is good but needs to be supported by references instead of popular opinions. It also needs to embrace the notion of all types, not just sailing craft.

For example "It is a common concern that in the open ocean, multihull craft are unsafe in a heavy storm." This is certainly true of small sailing craft but completely the opposite is true for a semi-submersible or other SWATH vessels.

Possibly the bulk of this article could be moved under a Recreational Variants sub-heading with a seperate Commercial Variants heading? Jmvolc (talk) 16:40, 6 January 2008 (UTC)

I disagree with the scope critique. Working on it - Slamlander (talk) 16:24, 7 January 2008 (UTC)

A lot of Opinion and unsupported POV

Some writers hear have gotten into "selling" the multihull concept as an alterantive to monohull. An objective in Wikipedia is to present a nuetral POV (point of view).

Kevin Murray 23:19, 20 October 2006 (UTC)

Kevin: I'm still not done but would cast a sailor's eye view at what's there now? Slamlander (talk) 16:54, 10 January 2008 (UTC)

Hierarchy of terms

Craft include those that sail on water, these include marine vessels and hovercraft. Vessels displace water, and include ships, which are larger than boats. This article uses ship most frequently, even when discussing vessels that are clearly craft, E.g. proas. I plan to make the terminology more consistent, appropriate and general. User:HopsonRoad 23:15, 1 December 2015 (UTC)

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Types by size

• Beachable as in beachable catamaran
• Beachcats
• Dinghy-sized
• Beach as in beach catamarans

Dinghy-sized catamarans are sometimes referred to as "Beach Catamarans". These are some of the terms I've come across. The article should cover that. 213.149.61.151 (talk) 23:40, 21 February 2019 (UTC)

Thank you. We use reliable sources in our articles. Can you supply links to an article for each of the terms that you advocate for? Cheers, HopsonRoad (talk) 13:14, 22 February 2019 (UTC)

Comparison formulas

Multihull Rating Formulas https://www.sfbama.org/racing/multihull_ratings_general_form.htm used when multiple multihull classes race against each other to calculate combined result, similar to ORC racing. 213.149.61.151 (talk) 15:33, 23 February 2019 (UTC)

Hull speed

@Arrivisto: Thank you for your substantive efforts to improve this article and others, relating to sailing vessels. I do have a quibble with this edit, whereby you reverted one of mine.

If we look at the hull speed article, we find, "The concept of hull speed is not used in modern naval architecture, where considerations of speed-length ratio or Froude number are considered more helpful." That is why I preferred the words that I offered ("Their hulls displace less water and create smaller waves underway, requiring less propulsive energy for a given speed.") over the current wording ("thereby obviating the limitations of a monohulls "hull speed").

Adding to the confusion, as I see it, is the conflation of two solutions for vessel design: one promotes carrying capacity over speed (most monohull ships) while the other promotes speed at the expense of carrying capacity (most multihulls). It's just that naval architects choose a given hull configuration to achieve a desired balance between between speed and carrying capacity.

The Froude number, pertaining to ship hydrodynamics applies to multihulls, just as it does to monohulls, as long as neither one planes. Thus a monohull with a given beam (fine or wide) and length can be driven as readily as any given hull on a multihull of the same beam (fine or wide) and length.

Perhaps with this discussion, we can arrive at mutually agreeable text for the passage in question.

Cheers, HopsonRoad (talk) 19:43, 7 March 2019 (UTC)

I appreciate your comments, but I am sufficiently conversant with English to be able to convey complex ideas simply and succinctly! Perhaps naval architects scorn the straightforward self-explanatory term "hull speed"; but in general parlance it is still alive and well. I've recently bought another boat, a catamaran, and guess what? The surveyor's report referred to "hull speed", whereby the maximum hull speed in knots (were it a monohull) would be 1.34 x the square root of the LWL (in feet). The surveyor added that, "being a multihull, its sailing speed is perhaps twice that".

You wrote: "Multihulls are typically designed to favor speed over volume or payload, whereas displacement monohulls are typically designed to favor volume and payload over speed". This statement is neither supported by citation, nor true (and should be deleted). In reality, cruising multihulls are usually chosen over cruising monohulls because of their greater interior space, whereas monohulls may be chosen because there is more feedback and a " responsive feeling of sailing speed", even if they happen to be going slower than an equivalent catamaran!

It is also easy to overstate the multihull lack of "carrying capacity". Monohulls must have voluminous hulls as they have to be buoyant enough to support not only the boat's weight, but also the massive ballasted keel. Multihulls have no ballast, and so can get away with fine hulls. However, a monohull owner must resist the temptation to fill up its greater interior space with supplies and equipment, particularly as overloading would cause a multihull's fine hulls to sink lower than would a monohull. Arrivisto (talk) 16:40, 9 March 2019 (UTC)

Thank you for replying here, Arrivisto. I am confident in your ability to convey ideas. It appears that we are not always in agreement on which idea pertains. The words "were it a monohull" highlight the non-applicability of the term "hull speed" to vessels with narrow, long hulls; indeed, fine monohulls, like racing canoes, readily exceed the number that suggests a hull speed for them. A single scull has a waterline length of about 25 feet, which would give it a hull speed of about 6.75 knots, yet winning times over a 1.24-mile course are about 6.4 minutes and are closer to 10 knots without any wave to "climb over".

Your reply appears to apply to sailboats more than to vessels in general, most of which do not have a "massive ballasted keel" but rely on form stability. And I agree that sailing catamarans (not so much for trimarans) have volume (in their superstructures—not their hulls) and speed—as do high-speed ferries. However, my statement referred to vessels, in general. And it pertains better to ships than sailboats. And I have encountered references to support the speed, versus payload assertion. I'll look for it in the next 24 hours.

Sincerely, HopsonRoad (talk) 20:53, 9 March 2019 (UTC)

The following source describes naval architectural tradeoffs among payload, volume and speed in the context of Froude number:

• Papanikolaou, Apostolos (2014-09-16). Ship Design: Methodologies of Preliminary Design. Springer. ISBN 9789401787512.

The following source plots such tradeoffs:

• Parnell, Gregory S. (2016-10-25). Trade-off Analytics: Creating and Exploring the System Tradespace. John Wiley & Sons. ISBN 9781119238300.

I'm fine with omitting, for now, a discussion of such tradeoffs in this currently very flawed article. Sincerely, HopsonRoad (talk) 13:15, 10 March 2019 (UTC)

Some good points I'll take on board. Cheers! Arrivisto (talk) 20:42, 10 March 2019 (UTC)

"Figure 1"

Fig.1: Some examples of hull arrangements for multihull ships

I'm not sure about Figure 1 (in the "Types paragraph). Types 2,3, 4, 5, have no cited examples and I suspect are never seen. That leaves 1 (a standard catamaran), 7 (a standard trimaran), and 6 (the rare proa). Is this diagram useful? I doubt it! Arrivisto (talk) 18:20, 9 March 2019 (UTC)

I concur with you, Arrivisto! I found the illustration to be most peculiar, when I first opened this page. It would be wrong to call those layouts "ships", besides.

I doubt that there are such things as "quadramarans" or "pentamarans", either, despite the pentamaran article wherein this yacht concept and this ferry concept are discussed, which really have two sets of amas along their hull for stability and the M80 Stiletto, which really has a single hull with four channels down its underside.

I endorse ditching the image. Cheers, HopsonRoad (talk) 19:51, 9 March 2019 (UTC)

Cheers! In with the scalpel (sensitively, of course)! Arrivisto (talk) 17:53, 10 March 2019 (UTC)

I admit I've been pretty vicious, but a lot of the text had to go, although I've reused as much of the good stuff as I felt I could. Arrivisto (talk) 19:10, 10 March 2019 (UTC)

@Arrivisto: This article needed some serious pruning and revision. Thanks for your very effective efforts! Now, if we can find some references for the unsupported (although correct) passages. Cheers, HopsonRoad (talk) 12:12, 11 March 2019 (UTC)

Gondola?

@Arrivisto: As far as I can see, all references to a SWATH gondola use Dubrovsky's work as a citation and are written by non-native speakers. I did see an Australian article, describing an acoustic pod and calling it a "gondola", but the gondola wasn't a buoyant hull. If you can find native speakers, who use it in the context described, and its widespread use in the literature, then I'm fine with the term. This term isn't found in the SWATH article. If it's legitimate, then it should be introduced there, first. HopsonRoad (talk) 11:29, 26 March 2019 (UTC)

Au contraire; on page 323 of the article it says: "A Small Water-plane Area Twin-Hull Ship(SWATH) includes two submerged hulls (gondolas) and one or more water surface piercing parts (struts) on each gondola." QED? Arrivisto (talk) 13:19, 26 March 2019 (UTC)

@Arrivisto: I meant that it's not found in Small-waterplane-area twin hull. If the word is found in literature by native English speakers, then I'm fine. Cheers, HopsonRoad (talk) 13:36, 26 March 2019 (UTC)

Tandem Hull

Warren Mosler of Modern Monetary Theory notoriety invented a Tandem Cat multihull which has two pontoons up front and two pontoons at the back. He believes that this means that you never have a wave wetting the midpoint of the boat trying to break the boat in half. I think this design is notable because it is proven to be able to operate in very inclement weather. Also modern torpedoes are designed to break a ship's back, and warships designed along these lines would be immune to this.

https://www.maritimejournal.com/news101/vessel-build-and-maintenance/ship-and-boatbuilding/rough-sea-quad-hulled-cat https://www.youtube.com/watch?v=W97s3zbFKvc&feature=youtu.be&t=3050 Thuanjinkee (talk) 14:24, 3 November 2020 (UTC)