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post #21 of 40 Old 02-21-2019
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Re: Benataeu grid construction

My final comment. I have cobbled up a quick/dirty sketch (hopefully attached) to illustrate the fabrication of the hull grid assembly. The points in all of the photos where there is supposedly "delamination" or cracking are at points where the gel-coat on the tabbing tape intersects the vertical sides of the grid. In some places one might be able to see "glass" where the gel-coat has cracked away. That does not detract from the structural integrity of the assembly, merely the cosmetics. The boat is now 30+ years old and the hulls do flex whereas gel-coat is notoriously brittle and easily cracked (hence an entire industry has evolved for their repair).

As for rust on the iron keel, that is another non-issue issue and easily treated.

FWIW we have owned a First 42 for 17+ years and at one point several years ago, I penned an article on the boats for a popular sailing magazine. For that I did extensive research on the boats and their construction over an extended period including an extensive personal interview with the designer, Germán Frers, who declared that the First 42 was still one of his favorite designs and detailed the extensive efforts for high strength/quality in the build of the 1980's era Firsts by Beneteau, including the personal involvement of Madam Annette Bénéteau Roux in their quality assurance. But hey, what do I know. I'm only a simple professional structural engineer with 40+ years of experience.

That's all folks...
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F42 Grid Sketch.jpg  

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post #22 of 40 Old 02-21-2019
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Re: Benataeu grid construction

OK, so this is clearer to me now. Those are definitely not gelcoat cracks. However, they also seem nothing to be concerned about.

From the drawing, it is clear that the stringer flange is glass tabbed to the hull and that tabbing extends to the edge of the stringer. The OP's two drawings show that this wasn't too neatly done, contained CSM and not all edged taping, and parts of it were laid against and up the stringer itself. Since I doubt the stringer was prepared for tabbing like the flange and hull, it is expected that the part of the tabbing laid against the stringer would eventually part from it a bit.

So it is not just gelcoat, there are fibers in that crack, and they have separated, but they appear inconsequential because they were never meant to be part of the bonding tabbing at all. Just a bit of layup overlay on an unprepared surface. This would have nothing to do with quality assurance, and similar examples are found on pretty much every boat.

In the one picture, it looks like the crack formed where the flange was cut away a bit to install a pass-through for hoses. It looks like someone just globbed a bunch of CSM in the cutaway after installing the pass-through. This shouldn't be of concern.

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post #23 of 40 Old 02-21-2019
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Re: Benataeu grid construction

Liner bond failure is a scary thing and happens right from the factory more often than any manufacturer wants to admit.

Take a look at one case I investigated.

Liner/Hull Bonding Failure

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post #24 of 40 Old 02-22-2019
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Re: Benataeu grid construction

boatpoker, that link is to a file on your computer and goes nowhere for us. You would need to attach it, or provide a web URL.

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Re: Benataeu grid construction

Quote:
Originally Posted by colemj View Post
boatpoker, that link is to a file on your computer and goes nowhere for us. You would need to attach it, or provide a web URL.

Mark
Sorry .... Try this one

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Re: Benataeu grid construction

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Originally Posted by boatpoker View Post
Sorry .... Try this one
Wally--

You do not say what make of boat you were inspecting in your reports although whether you feel doing so might be problematic would be understandable. N'any case, I do not dispute in any respect the possibility of an inner liner coming detached from a hull or the possibility of not having been properly adhered to a outer hull to begin with (as illustrated in your second report). However, these possibilities are/were not the original subject of this thread which was engendered by apparent cracking in the surfaces some of the vertical elements of the transverse "ribs" formed by the "grid" hull liner of a mid-80's First 38, which was all I addressed in my comments.

In the course of the thread, someone made reference to the loss of the Cheeky Rafiki, a 2006 Beneteau First 40.7. That event and the foregoing discussion had little in common. That yacht had suffered several hard groundings while racing, at least one of which necessitated extensive repairs although in the event, the keel was not dropped as it should have been, so the actual extent of damages and the required repairs could not be fully assessed. The yacht had also suffered several "soft" groundings, ex post facto, that while not consequential in and of themselves may have exacerbated the deterioration of the grid liner and hull connections occasioned by the earlier hard groundings. Coincidentally, as reported in yachting World's 2015 article on the event and subsequent trials, several sister-ships of the yacht were found to have similar though less severe damages/separations between the outer hull and the "grid" liners although, again, caused by hard groundings. Considering the "prying" action of the forward end of a keel on a hull as it is rotated downward in a hard grounding, placing the hull and liner in direct tension across the bond, it is understandable that some of the bonding might separate adjacent to and just forward of the keel. Whether one can design and build a yacht to withstand such unintended abuse is not in question. Whether one can do so within the economic constraints of affordable production yachts is another question entirely but best answered by keeping the yachts off the hard spots, no?

N'any case, as it has been said: "It ain't the open ocean that kills boats, it's the hard stuff around the edges."

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Re: Benataeu grid construction

The hull grid separation is something I came in very familiar with since I've seen it on multiple boats for sale. I've talked to quite a lot of surveyors about it over the years and they insist to stay away from any signs of it. But I've never really understood how a grid works, how it's attached, and how it fails.. so this thread has been pretty insightful.

I've always wondered how many sailboats are out on the water right now that have hull grid separation to some degree and people still sail without knowing it.

Attached is a photo I took of a different sailboat with a grid that failed. You can see up the thru hull where the grid liner separated and moved away from the hull.
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Re: Benataeu grid construction

I find it pretty surprising that these relatively modern boats are having this problem; it doesn't say much for the production standards.
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Re: Benataeu grid construction

You consider 35yrs old "relatively modern"?

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Re: Benataeu grid construction

The problem with the boat in the surveyor report appears to be one where that boat construction relied on a complete and separate interior pan bonded to the actual hull with some type of glue as the only bonding component. No aspect of the main hull is accessible below the pan, so separation isn't noticeable and repair impossible.

The problem the OP has presented appears to be a system of stringers formed separately from the main hull, then attached to the hull with glass tabbing and probably also glue (according to reports from others familiar with the construction). Much of the main hull is accessible around the stringers, and any issues are readily visible and could be repaired.

These seem like two different construction techniques that are being conflated. The first looks to be problematic, but the second doesn't seem too different than glassing and bonding bulkheads, individual stringers, and other structural parts to the main hull - which would be considered "traditional" techniques.

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