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Old 18-10-2012, 15:16   #1
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Importance of Hull Strength and Construction Quality

These features are often brought up in sailboat quality discussions, but how important is this, really (particulary in relationship to multihulls).

For example, I read a recent discussion comparing Catana's and Outremers, and a comment that Outrememer was "bulletproof" and that the Catana's, having composite construction, are not as strong.

But how important is this really to a Catamaran cruiser? Is there really a concern that a hull will simply fall apart at sea? Are the stresses really so severe that some well known and popular catamaran hulls will fail where others will not?

Is this a question of longevity? Of comfort and security at sea? Of maintenance and repair time/costs? Or is it just academic discussion that, in the end, really has no bearing on the seaworthiness or livability of a cruising catamaran?

Of course, not everyone on this board is a "cruiser", and sometimes people cross up design and performance issues between cats and mono's, but this is the "Multihull" category on the "Cruisers" forum. So my question is "What is the real relevance of this to a cruising catamaran?"
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Old 18-10-2012, 16:02   #2
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Re: Importance of hull strength and construction quality

Construction quality and scantlings are very important issues for catamarans especially. The two widely separated hulls are trying to tear apart from each other at times and the engineering and construction of the main beams and bulkheads tying them together are extremely critical. Much more so than on monohulls.

I know several different catamarans that had failures of bulkheads and main beams that caused the boats to start to fall apart at sea and rendered them inoperable until fixed. The fixes were expensive and necessary.

Very few (if any) of the known and popular catamarans have these issues because they are properly engineered and the quality is sufficient for the use they are put to (that is a key phrase). Any one-off issues are generally isolated to a bad boat and not the model in general. Of course, any boat can be used or driven in ways that were not envisaged in the design. A Gemini would probably fail in the Southern Ocean, for example.

Other than that, composite construction generally means less weight and that translates to sailing abilities, but not necessarily to safety or longevity outside of the beams and structural bulkheads. Other differences like gelcoat quality or deck stiffness, etc tend to be cosmetic and maintenance issues only.

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Old 18-10-2012, 16:06   #3
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Re: Importance of hull strength and construction quality

Your question asks seaworthiness as opposed to survivability. I interpret that as you have no plans to brave a hurricane at sea. That aside, in my opinion, it depends. If you plan on buying a new or almost new boat which was lightly used, I wouldn't give this a 2nd thought. If you plan on searching for bargains on older boats or one offs, then I suppose it's the number one issue to be considered.

I would imagine that any boat has been designed to take whatever the sea throws at her... when new, but today all boats are cored hulls and maintenance becomes an issue. I've seen boats with delamination issues although the boat appeared to be just fine.

If the hulls are good, no worries.
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Old 18-10-2012, 16:14   #4
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Re: Importance of hull strength and construction quality

The last thing a manufacturer wants is a reputation for hulls that fail. Over the years catamaran hulls as a whole have been getting better by knowing what and what not to do through better design software and knowledge of the causes of previous failures. It is not a perfect technology, but it has improved dramatically since recreational cruising cats have become popular.
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Old 18-10-2012, 16:31   #5
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Re: Importance of hull strength and construction quality

Build quality will tell more than about anything else. Most all boats made if made to specs are what they claim to be. It's not so much if they were designed strong enough but if the quality of the build will really yield what the naval architect designed. Build quality will for example mean you won't see delamination. It's is sign of a bad build more often than not. You'll find soft sports in the boat in the survey too.

Technology advances and the systems for building boats are better than ever. So age is a factor knowing nothing else. You need to check out specific boats over specific years. Some companies got a whole lot smarter and other were dumb and got dumber and went belly up.

Bottom line: No general rule of thumb. Each boat should be looked at as a lemon but it might be better after it's been completly thumped.
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Old 18-10-2012, 21:57   #6
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Re: Importance of hull strength and construction quality

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Originally Posted by ArtM View Post
These features are often brought up in sailboat quality discussions, but how important is this, really (particulary in relationship to multihulls).

...

But how important is this really to a Catamaran cruiser? Is there really a concern that a hull will simply fall apart at sea? ..

Way important. Catamarans, even in near coastal conditions (where most cruisers really sail...despite the much overused terms "Blue Water" or "offshore"), are much more heavily stressed than monohulls. I've never heard of a modern production build literally falling apart (in any conditions), but I have seen stress damage on charter and cruising cats.

Dramatic case in point: I know of one cat (an FP) in the charter fleet here in Belize which literally cartwheeled over the reef in a hurricane, lost its rig, took some damage, but was still seaworthy enough to motor it back in from outside the reef. It was repaired, re-rigged, and put back into charter service. I think this is a good example of the fact that most modern cruising cats (and monos for that matter) are over engineered. So, in my experience, I don't think this is a practical issue with any modern production builds.

If Minaret is on-line then he can chime in with a more detailed professional opinion.
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Old 19-10-2012, 01:20   #7
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Re: Importance of hull strength and construction quality

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Way important. Catamarans, even in near coastal conditions (where most cruisers really sail...despite the much overused terms "Blue Water" or "offshore"), are much more heavily stressed than monohulls. I've never heard of a modern production build literally falling apart (in any conditions), but I have seen stress damage on charter and cruising cats.

Dramatic case in point: I know of one cat (an FP) in the charter fleet here in Belize which literally cartwheeled over the reef in a hurricane, lost its rig, took some damage, but was still seaworthy enough to motor it back in from outside the reef. It was repaired, re-rigged, and put back into charter service. I think this is a good example of the fact that most modern cruising cats (and monos for that matter) are over engineered. So, in my experience, I don't think this is a practical issue with any modern production builds.

If Minaret is on-line then he can chime in with a more detailed professional opinion.

Thanks for the respect for my "professional opinion", but I have learned the hard way that it's not wanted here (the multihull forum). All I will say is that most of the really bad failures I have seen have been in larger cats, where the loads are much higher due to the greater aka length. Severe structural failures are much less common in smaller production cats. But most cats are designed with certain sea state parameters in mind, so using a cat as it was designed to be used is important if you want to avoid structural failure. I think the worst failure I have seen was in a 90' power cat actually, the design just couldn't handle the loads. Had to be totally rebuilt by us at great expense. I've never understood why some of the multi crowd get so upset at the concept that any cat hull could possibly fail, you'd think that discussing the reality of the situation to move things forward would be viewed as a positive. But say you've seen a broken cat and they'll call you a liar. All I ever want to do is hold the manufacturers feet to the fire by spreading the truth, in the interest of more quality construction. As it is they get away with too much, for many reasons. Cat construction requires more care and attention to detail, as well as more quality materials , not less. Some builders get this, some don't. And issues such as excentric loading of hulls are not discussed enough.


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Old 19-10-2012, 02:56   #8
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Re: Importance of hull strength and construction quality

>So my question is "What is the real relevance of this to a cruising catamaran?"


To me this is an academic question that might affect longevity, for example with regard to balsa cored hulls.

In most smaller standard cruising catmaarans (FP, Lagoon, Catana, you name it) I would not fear structural failures. I have only seen one Leopard with broken bulkheads, but I suspect it was just driven onto a reef.
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Old 19-10-2012, 04:12   #9
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Many of the links min Provides are more out that builders can do sloppy shoddy work, not sure it really points whether or not aboard design is not seaworthy just sometimes builders screw up. I've seen almost new monos w "keels a flopping"
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Old 19-10-2012, 06:30   #10
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Re: Importance of hull strength and construction quality

A Gemini would probably fail in the Southern Ocean, for example.

Mark[/QUOTE]

Can you elaborate a bit more on that please.

I have seen a video of the Gemini crossing the northern Atlantic with no failures,

The PO of mine sailed from California to Hawai, then Tahiti, Fiji, New Caladonia and across to Bundaberg and back to Fiji,

I sailed mine from Fiji down the Tasman almost to the Southern Ocean all with out damage,

I got washed up onto rocks while at anchor on Broughton Island punching big holes in the hulls,

The vessel is still structurally sound, My Gemini. 105 MC,

when its repaired, I will be sailing it out of Western Port Bay, straight into the Southern Ocean, Bass Straight and back up the Tasman,

Slap dash went around the world, Another Gemini. 105MC

I would be very interested in your opinion, regarding Gemini's and their tendency to failures..
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Old 19-10-2012, 06:51   #11
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Re: Importance of hull strength and construction quality

A Gemini would probably fail in the Southern Ocean, for example.

Mark[/QUOTE]


It's time for Gemini bashers to own up to their coments!!! I would like to know how you came to that conclusion. Have you ever heard of a Gemini coming apart? Are you aware Gemini hulls are built in a ONE piece construction, unlike most others which are built in three pieces? How often have you been on a Gemini? What gives you the expertise to decide a Gemini would fall apart?
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Old 19-10-2012, 06:53   #12
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Re: Importance of hull strength and construction quality

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Originally Posted by Tropic Cat View Post

If the hulls are good, no worries.
On a catamaran, the soundness of the main beams and structural bulkheads are of more importance than that of the hulls.

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Old 19-10-2012, 07:25   #13
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Re: Importance of hull strength and construction quality

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On a catamaran, the soundness of the main beams and structural bulkheads are of more importance than that of the hulls.

Mark
That doesnt explain why Gemini's are prone to failures,

Can you explain your opinion on the Gemini failures, and which ones you know off that have failed,

My hull is the 825th one to be built, The have built and sold nearly 1200 of them.

How many have failed to your knowledge,
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Old 19-10-2012, 07:59   #14
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Re: Importance of hull strength and construction quality

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Thanks for the respect for my "professional opinion", but I have learned the hard way that it's not wanted here (the multihull forum). ...

Thanks. I appreciate you posting.
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Old 19-10-2012, 08:12   #15
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Re: Importance of hull strength and construction quality

I don't know of any Gemini failures and did not mean to bash them (jeez are you guys sensitive - more so than the Hunter guys!). I like the Gemini and have never said anything bad about them, here or anywhere.

I just used the Gemini as an example of a boat that was not designed for use in the Southern Ocean - and I was thinking of that part of the ocean below Australia and New Zealand where all the race boats go. That is a vastly different ocean than the Northern Atlantic and South Pacific and "almost to the Southern Ocean". Our Manta is also unsuited for that, as are most (if not all) production boats. I specifically picked the Gemini as an example because it was the smallest production boat that came to mind at the time. I think you will find the designer of Gemini probably thinks the same way as I do.

The point I was trying to make to the OP was that while there were situations where the design of almost all productions boats will be exceeded, it takes an extreme example, LIKE A 34' GEMINI IN THE SCREAMING 50's AND 60's, to meet that situation.

Instead of getting all angry red eyed bull on me, please read back and point out where I said Geminis are prone to failure or bashed them in any way.

If you have big holes in your hulls, your boat is not structurally sound. And I apply that logic to all catamarans, not just Gemini's.

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