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Old 20-10-2012, 07:49   #31
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Re: Importance of hull strength and construction quality

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Originally Posted by colemj View Post
I

But I withdraw my example of the Gemini and replace it with the Manta. Will that make you all happy?

Mark
Yes, because

1) You clearly have extensive knowledge and expertise in Mantas.

and

2) Ironically, I know of two Mantas that started to break up in heavy seas, within a year or two of being built. Both needed extensive fibreglass repairs and reinforcement.
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Old 20-10-2012, 08:14   #32
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Re: Importance of hull strength and construction quality

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Originally Posted by neelie View Post
2) Ironically, I know of two Mantas that started to break up in heavy seas, within a year or two of being built. Both needed extensive fibreglass repairs and reinforcement.
And that reinforces the entire discussion here. Both of those boats did not have design issues, but the subcontractors used on those builds skipped a step involving tabbing bulkheads on one boat and fitting drain thruhulls on another and both got through production that way (these two boats were built while Manta was having financial and labor difficulties).

So it was a case of one-off quality lapse and not indicative of the design, make or model.

BTW, they both had problems on their initial delivery trips in rough weather, not within a couple of years.

Mark
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Old 20-10-2012, 11:07   #33
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Re: Importance of hull strength and construction quality

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Given that everything has design limitations (Boats and whatever), and that these are usually intentional to gain benefit elsewhere then I don't think the "answer" is simply making something stronger (as likely that means compromises elsewhere) - it's more about understanding the limitations of what you have, accepting them and then using accordingly. and the good news is that if you have a well known design and build (of anything) rather than version #1 then likely can find out a bit more than simply what the brochure says or the dream would like. If one wants to.

And for the sake of clarity, I am sure that most multihulls are not only capable of fulfilling there designed purposes (which for all practical purposes likely cover 99% of what any sane person would want to do recreationally - even if for that figure they may sometimes need at least some wit onboard). but are likely also fun as well. Albeit from the sounds of it, if someone wanted to navigate the Northwest passage in winter they will probably need a G#mini .

The problem with this theory is that as boaters, we don't always have control over the conditions we find ourselves in. You can find yourself suddenly doing something "outside the design parameters" fairly easily. And I think often the boats are not underbuilt strictly as a weight saving measure. It is more a question of economics for the builder. For instance, they could go to carbon fiber and epoxy vacuum bagged laminates and the problem would be solved. And of course some builders do just that. But then you are paying Gunboat prices, and that market is small. What they are doing is building cats in materials which are, IMHO, totally inappropriate for the loads which COULD be involved, because they know that the vast majority of boats will never be truly tested, and of the ones which are tested to failure, only a few will sue succesfully. All part of the overhead to them.
On another note, one of my dock neighbors who also has a large Nauticat has just sailed from Seattle to Scotland via the Northwest Passage. Our yard outfitted him.

Northwest Passage 2012 dot com: UPDATE - SV UPCHUCK departs Seattle for Scotland via NWP


http://www.nauticat.com/news_archive...rtwest_passage
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Old 21-10-2012, 02:31   #34
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Re: Importance of hull strength and construction quality

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Originally Posted by colemj View Post

BTW, they both had problems on their initial delivery trips in rough weather, not within a couple of years.

Mark

Ermmmm.... So that makes 3 then? So how many more are there?

I know the owner of one and it was NOT on a delivery trip.

That Manta have no "bad news" is because of the uber secretive Manta owners group. There are are many hidden secrets.

The point being, old bean, is that your taking cheap shots at Geminis is like someone living in a glass house throwing stones.

If you're going to make a point about poor design or shoddy build quality - stick to your area of expertise.

Sorry, to take you to task, but I'm tired of cheap shots from know-it-alls.
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Old 21-10-2012, 06:38   #35
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Re: Importance of hull strength and construction quality

Look, please read back in my posts and point out where I took a cheap shot at Gemini or said anything about them having poor design or shoddy build quality. Nowhere have I said anything even remotely approaching that.

And when the sensitivity started, I tried to reinforce the point that I have no qualms about Gemini, and that I picked them as an example that all production boats could be pressed into service beyond design and that I used Gemini in the extreme Southern ocean solely because they were the smallest boat that came to mind in one of the more unforgivable places I could imagine. Then I backed away from that example completely when the whining started.

Now you are banging on me about the whole thing still. Perhaps you do not have good reading comprehension skills. I am willing to accept that. Just read my posts again slowly, and do not be afraid to move your lips.

As for the Mantas, of the two I know, one was being delivered to a boat show and the other was being delivered to Texas (or somewhere on the Gulf). Perhaps the Texas boat was not a delivery, but it was very soon after being built. Both these boats were built during Manta's 4th incarnation as a company at a time when things were not going well on the build floor. They came off the production line together (Manta only had a maximum of 3 boats in build at any one time). If there are others, I do not know about them.

The Manta owners group is not secretive nor does it hide secrets or bad news. It is a yahoo group administered by an owner who is full time cruising and mostly out of internet connection. The group used to be open to all but quickly got overwhelmed by spam and people like you. This isn't an unusual way to run an owner's group - Catana, Southbound and many others are also closed groups.

Like all production boats, Mantas have had random issues. I would not say there are many hidden secrets (is that a cheap shot from a know-it-all?), and probably less problems than most production catamarans (perhaps you should stick to your area of expertise?). No one hides these or covers them up. If we did, why would I be volunteering the information I have? However, there were only 125 boats made, at least 2/3 of them were sold before the internet forums were invented (the last production run was 2007), and the main demographic market was retired couples going cruising. Even now on the second hand market, most of the boats are being cruised. Those facts severely limit the cyber footprint the boat makes. There is no conspiracy.

Mark
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Old 21-10-2012, 07:09   #36
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Re: Importance of hull strength and construction quality

Hey ColemJ,
Im with you mate, I wouldnt take my Gemini or any other yacht down into the deep Southern Ocean, 1000 miles south of here,

Thats not the Place for even big ships, Thats an Ocean you stay out of, Period,

Coming back across the Bight has me worried, Thats the return trip from the Kimberlys, and the top of the Southern Ocean,
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Old 21-10-2012, 07:13   #37
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Re: Importance of hull strength and construction quality

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Originally Posted by minaret View Post
The problem is that you can generally get away with some of that on a mono without it breaking, they are more forgiving. A cat is not at all forgiving of shoddy workmanship during construction.
I disagree. Both types of boats are unforgiving of shoddy workmanship in the critical areas, but forgiving in all others.

For example, a monohull build with a deck stepped mast could not get away with shoddy quality on the main bulkhead or post transferring the mast compression forces to the keel and hulls. Same with the keel attachment. However, they can easily get away with large voids in the deck layup and even some delamination in the hulls without serious safety issues.

Likewise, beyond the main beams and structural bulkheads of a catamaran, shoddy quality in deck layup and some delamination in the hulls can be accommodated without danger.

And all boats are equal when it comes to reliance on equipment installation, tankage, carpentry fit and finish, etc.

At most, perhaps, a catamaran has a few more of the critical areas than a monohull.

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Old 21-10-2012, 10:14   #38
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Re: Importance of hull strength and construction quality

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Originally Posted by neelie View Post
Ermmmm.... So that makes 3 then? So how many more are there?

I know the owner of one and it was NOT on a delivery trip.

That Manta have no "bad news" is because of the uber secretive Manta owners group. There are are many hidden secrets.

The point being, old bean, is that your taking cheap shots at Geminis is like someone living in a glass house throwing stones.

If you're going to make a point about poor design or shoddy build quality - stick to your area of expertise.

Sorry, to take you to task, but I'm tired of cheap shots from know-it-alls.
Please show details from this thread for everyones benefit where COLEMJ has engaged in the above behaviour..... YOU certainly have shown us that you fit the above description.

Bob
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Old 21-10-2012, 10:37   #39
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Re: Importance of hull strength and construction quality

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Originally Posted by colemj View Post
I disagree. Both types of boats are unforgiving of shoddy workmanship in the critical areas, but forgiving in all others.

For example, a monohull build with a deck stepped mast could not get away with shoddy quality on the main bulkhead or post transferring the mast compression forces to the keel and hulls. Same with the keel attachment. However, they can easily get away with large voids in the deck layup and even some delamination in the hulls without serious safety issues.

Likewise, beyond the main beams and structural bulkheads of a catamaran, shoddy quality in deck layup and some delamination in the hulls can be accommodated without danger.

And all boats are equal when it comes to reliance on equipment installation, tankage, carpentry fit and finish, etc.

At most, perhaps, a catamaran has a few more of the critical areas than a monohull.

Mark

I would agree with that-mostly. I would say quite a few more critical areas. As in, all the same areas as a mono, plus any and all structural beams and bulkheads. And, while these problems in a mono when found do need to be fixed, often in a multi they are found when the defect results in severe stress fracturing of structural members. One is fairly easy to fix, the other requires a rebuild. Cats are just much more complicated animals. A mono can overbuild everything because weight is not a concern, they've already bolted a big chunk of lead to it. Scantlings really only effect weight distribution, not total weight. Obviously the same is not true of a cat. Just simply more unforgiving to build. And if you think that major cat manufacturers are using good quality control, what's with all the lawsuits about osmotic blistering ABOVE the waterline? How many mono's have you seen that in?
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Old 21-10-2012, 10:47   #40
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Quote:
Originally Posted by minaret

I would agree with that-mostly. I would say quite a few more critical areas. As in, all the same areas as a mono, plus any and all structural beams and bulkheads. And, while these problems in a mono when found do need to be fixed, often in a multi they are found when the defect results in severe stress fracturing of structural members. One is fairly easy to fix, the other requires a rebuild. Cats are just much more complicated animals. A mono can overbuild everything because weight is not a concern, they've already bolted a big chunk of lead to it. Scantlings really only effect weight distribution, not total weight. Obviously the same is not true of a cat. Just simply more unforgiving to build. And if you think that major cat manufacturers are using good quality control, what's with all the lawsuits about osmotic blistering ABOVE the waterline? How many mono's have you seen that in?
The most blisters I've seen above the waterline would be on the Valiants, a well known solidly built monohull.
One diffrence between multi and mono is the multi doesn't have to deal with the stresses of the ballasted keel while heeled over. Definetly not unheard of to hear of a mono that's lost it's keel or has cracks between the keel and hull.
I'm sure also there are diffrent stresses involved since the monos go through the waves where the multis ride over.
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Old 21-10-2012, 10:59   #41
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Re: Importance of hull strength and construction quality

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The most blisters I've seen above the waterline would be on the Valiants, a well known solidly built monohull.
One diffrence between multi and mono is the multi doesn't have to deal with the stresses of the ballasted keel while heeled over. Definetly not unheard of to hear of a mono that's lost it's keel or has cracks between the keel and hull.
I'm sure also there are diffrent stresses involved since the monos go through the waves where the multis ride over.

I've never seen blisters above the waterline on a Valiant. They are notorious for osmotic blistering below the waterline, and sometimes as with all blistering it travels up to a foot above the waterline. I have read about cases where they blistered above the waterline, but not seen it personally. I have done blister jobs on many Valiants.
I don't know what French multi manufacterers are doing to cause this, don't even know how it's possible, because it shouldn't be. But I've seen and repaired a number of cases. With high moisture readings all the way up to the sheer.
While small cheap boats do occasionally lose a keel, I've never heard of it happening on a larger boat. Certainly you'd have to let the keel bolts go in an irresponsible manner. I've never seen fractures in an internally ballasted keel due to loading, obviously because it's so eaasy to overbuild them with no repercussions. And with an externally ballasted keel, cracking in the joint is not a structural problem. Obviously it's not good, because it can expose keel bolts to seawater, but as long as it's dealt with fairly early it's a very easy fix. These are all issues which have been dealt with for many many years and are well understood, with a long history of having been succesfully dealt with.
A multi "riding over the waves" is exactly the problem. All you need is one hull mostly out of the water and one mostly in it. This causes very high loads, even when it's just a little of one hull flying. The repeated load cycling causes delams and stress fractures. It's a no-brainer, I like a cat as much as the next guy, but building one for serious cruising is prohibitively expensive, at least for me. I will shut up and go away from the multi forum once again now, I've already said too much and don't want to go down this road yet again, believe what you will and be happy to spend away on your French cats...
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Old 21-10-2012, 11:28   #42
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Quote:
Originally Posted by minaret

I've never seen blisters above the waterline on a Valiant. They are notorious for osmotic blistering below the waterline, and sometimes as with all blistering it travels up to a foot above the waterline. I have read about cases where they blistered above the waterline, but not seen it personally. I have done blister jobs on many Valiants.
I don't know what French multi manufacterers are doing to cause this, don't even know how it's possible, because it shouldn't be. But I've seen and repaired a number of cases. With high moisture readings all the way up to the sheer.
While small cheap boats do occasionally lose a keel, I've never heard of it happening on a larger boat. Certainly you'd have to let the keel bolts go in an irresponsible manner. I've never seen fractures in an internally ballasted keel due to loading, obviously because it's so eaasy to overbuild them with no repercussions. And with an externally ballasted keel, cracking in the joint is not a structural problem. Obviously it's not good, because it can expose keel bolts to seawater, but as long as it's dealt with fairly early it's a very easy fix. These are all issues which have been dealt with for many many years and are well understood, with a long history of having been succesfully dealt with.
A multi "riding over the waves" is exactly the problem. All you need is one hull mostly out of the water and one mostly in it. This causes very high loads, even when it's just a little of one hull flying. The repeated load cycling causes delams and stress fractures. It's a no-brainer, I like a cat as much as the next guy, but building one for serious cruising is prohibitively expensive, at least for me. I will shut up and go away from the multi forum once again now, I've already said too much and don't want to go down this road yet again, believe what you will and be happy to spend away on your French cats...
Just google "Valiants blistering above the waterline" and you would be amazed at the stories. Something I thought was common knowledge.
My point of the stresses to keels was to show at least one area where cats have less stress loads than monos. I would agree that it takes a lot more skill and engineering to build a suitable performance cat for bluewater travel. Maybe that's why they are so much more expensive than monos. I for one do enjoy your posts in the multi forum. Not that I always agree with you but heck sometimes I don't agree with myself!
And no I do t own a French built cat!
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Old 21-10-2012, 11:28   #43
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Re: Importance of hull strength and construction quality

There are two ways to build anything: a) the right way (strong and seaworthy), and b) the wrong way (weak and not seaworthy). Why will anybody insist on building the wrong way?

Building things the right way is probably more expensive and not everybody can build them - it takes skills, materials and tooling. A crap boat can be built easily by any ignorant with a rusting hammer. Then it can be delivered to the market at comparatively lower price or/and sold with more profit.

If someone wants a convertible catamaran that can be easily converted into two monohulls then there is no importance.

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Old 21-10-2012, 16:04   #44
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Re: Importance of hull strength and construction quality

Valiants of a certain age are notorious for blistering all over - above and below. The problem was the resin used at the time. I wouldn't paint all Valiants with that brush because the problem was contained to specific years and it isn't fair to Valiants in general.

I have also seen Tayana's blistering all over deck and hull. But again, I have seen many more Tayana's without blisters of any kind, so it is unfair to call them blistering problems.

The widespread blistering catamaran problems are solely with Fountaine-Pajot and even there is isolated to specific models and years. Many other French catamaran companies have no endemic problems at all and I have never seen blistering on any FP catamaran earlier than the Lavezzi era (circa 2006?).

There is a third (and most common) way of building things - to a price and a design intent. These are neither weak and not seaworthy, nor built to tackle everything. Almost every single boat with any number of hulls is built this way.

Without a doubt, catamarans are attempting to rip themselves apart in moderate sea states and engineering and build quality is of utmost importance. However, the engineering stresses and solutions for this are very well known and failures in the main beams and structural bulkheads are exceedingly rare. Probably equally as rare as that for monohulls, and maybe even less. Many production monohulls experience broken bulkheads after being caught in bad conditions.

French catamarans are not in general structurally unsound and French catamaran engineers are some of the most highly experienced and respected ones in the industry. The Bay of Biscay is not a mill pond and the French lead the world in multihull insanity (sorry Aussies).

Production catamarans in general do not experience structural problems sailing in conditions any person of normal cruising desires finds themselves in. And they even suffer no damage in general when caught in raging conditions that sometimes happen. I define normal cruising as pretty much everywhere one finds cruising boats - and some of those places have good, strong weather to contend with. Repeated load cycling is readily handled through engineering design and build without resorting to expensive exotics. As someone else mentioned, you do not see catamaran hulks littering the beaches everywhere or boatyards filled with broken catamarans.

Note that I used the phrase "in general" - there can be, and are, single incidents of bad quality in every boat model from every builder regardless of the number of hulls. So one can easily find examples to make a point, but cannot find examples in general.

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Old 21-10-2012, 16:30   #45
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I agree, the majority of Valiants are quality products. There use of fire retardant resins will be remembered by many. I'm very surprised Minaret hasn't heard of the problems with the fire retardant resins on the Valiants. It's been we'll documented for years.
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