Benataeu grid construction - Page 4 - SailNet Community
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post #31 of 40 Old 02-22-2019
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Re: Benataeu grid construction

"the iron keel rusting under water because, likely, nobody bothered repairing the glass."
Is the OP talking about an encapsulated keel, where damage would indicate a grounding? Or, is the OP just mistaken about "glass" with this being a typical faired--not encapsulated--Beneteau iron keel?

If it is just rusting because the fairing and coating was neglected, that's routine maintenance. To be expected unless you find a boat with a more expensive lead keel.

But if that's an encapsulated keel that indicates damage from a grounding, there's more reason to question what might have happened to the hull.

The liner and hull are "just" glued together. Like the tail and wings on combat aircraft and even some commercial jetliners. But even there...there was the tragic instance of the tail breaking off an Airbus after takeoff at JFK some years ago. Apparently the glue job wasn't strong enough, they hit turbulence from the flight before them, the plane broke.

Absent any sign of a grounding, this could easily just be the tabbing and gelcoat showing their age, and not a structural problem. But that's a decision for a competent engineer to make, hands-on. Old boats often show cosmetic cracking. I haven't heard of any Beneteau grids coming off their hulls.
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post #32 of 40 Old 02-22-2019
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Re: Benataeu grid construction

Mark
Yes I do consider these boats 'relatively' modern. By the mid to late 80's fibreglass boats had a pretty long history, thousands were built without the problems being discussed.
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post #33 of 40 Old 02-22-2019 Thread Starter
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Correct me if I'm wrong .. but if there was a hard grounding say.. 10 years ago.. and the keel was damaged and water got in.. and that never got repaired... wouldn't it be a serious issue?
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Re: Benataeu grid construction

I would like to retract my negative statements regarding build quality of these 80's Beneteaus. After re-reading the posts, this doesn't seem to be a very common problem.
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post #35 of 40 Old 02-23-2019
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Re: Benataeu grid construction

Quote:
Originally Posted by hellosailor View Post
"the iron keel rusting under water because, likely, nobody bothered repairing the glass."
Is the OP talking about an encapsulated keel, where damage would indicate a grounding? Or, is the OP just mistaken about "glass" with this being a typical faired--not encapsulated--Beneteau iron keel?

If it is just rusting because the fairing and coating was neglected, that's routine maintenance. To be expected unless you find a boat with a more expensive lead keel.

But if that's an encapsulated keel that indicates damage from a grounding, there's more reason to question what might have happened to the hull.....
The Iron Keels on the 1980's era Firsts were not encapsulated but treated and sealed castings bolted onto the keelson with Dacrotized bolts. Over time (on the average these keels are now 34 years old or so) the finish does break down and need replacement and the keels do develop rust spots. Rust invariably looks worse than the "damage" it reveals in that the volume of the "rust" that develops is about 600% of the volume of the iron that has been oxidized (or rusted). The fix is relatively simple, involving grinding or sand-blasting the keel surface down to clean iron, surfacing with a protective primer coating such as Petit RustLok, fairing with a decent fairing compound such as Petit's EZ-Fair, where necessary, and finally repainting with bottom paint primer and then paint.

The more salient question will be the integrity of the keel-hull joint and a clue to what's happened to the yacht vis-a-vis groundings disclosed by any damages to the bottom leading edge of the keel--hopefully none! One can evaluate the keel-hull joint by pulling one of the forward keel bolts while the boat is in or out of the water. (Freeing the bolts may take a bit of doing as they are torqued to an average of 150 lbs-ft.) If the bolts come out clean and dry, regardless of the condition of the exposed heads (they are, after all, in the bilge) the joint is good and can be left alone, even if one sees a bit of a "smile" along the leading edge of the joint. One merely has to re-torque the bolts, or replace them (preferred), in a star pattern and fair the edge of the joint with a flexible caulking compound that can be painted such as LifeCaulk. If a bolt comes out "wet" or there is evidence of damages to the bolt or moisture in the bolt hole, the keel should be dropped the interfaces between the keel and hull cleaned and smoothed, new caulking applied (keeping it away from the bolt holes so it doesn't squeeze into the thread channels as the keel and hull are rejoined) and, preferably new bolts installed and torqued. On this, the caulk should not be an adhesive such a 5200 or its weaker sister 4200 as some day, someone somewhere may want to remove the keel again and doing so with that stuff as a caulking compound makes separating the two a near impossibility with damages to one or the other. The preferred bolts are available from Beneteau though they may have to be shipped in (to the USA) and are, frankly, not inexpensive (but worth the expense IMHO!).

FWIW...

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post #36 of 40 Old 02-23-2019
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Re: Benataeu grid construction

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Originally Posted by newbie3 View Post
I suppose more specifically, I'm trying to find out if there's anything worth investigating that can put some doubt on the results. Or are these results concrete?

Is this a sign that the stringers and framing are destroyed? Or could they be intact and the bones are still solid?

Any chance what the surveyor found as delamination is only cosmetic? Or is there no doubt that this sailboat is no longer fit for use?
The grid IS the bones of that boat.

Why did you employ a surveyor if you are not going to listen to their recommendations?

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
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post #37 of 40 Old 02-23-2019 Thread Starter
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Re: Benataeu grid construction

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The grid IS the bones of that boat.

Why did you employ a surveyor if you are not going to listen to their recommendations?
My original post was me asking if there's any reason to get a second opinion and if there's anyone here familiar with the manufacturing of this boat.

At best, some former Beneteau engineer bumped in to this thread and confirmed or disputed the significance of the delamination at these specific points marked in the photos. That's is why I attached the photos.. I didn't really expect anyone to visually find anything new but consider where the marks were located.

I've learned a bit here so that will help me as I keep searching. Probably help others too

I'm actually planning on returning to that Beneteau this weekend. I'm hoping the survey chalk marks are still there and I can go tap/sound them for myself... Use that as an example to learn what delamination sounds like and maybe save money next time by finding problems in advance of survey. I'll post a video of the sounding if anyone is interested like I am.

There are helpful posts here but I don't understand why some are bothered by me asking questions or trying to learn.
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post #38 of 40 Old 02-24-2019
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Re: Benataeu grid construction

Tapping on the sides of the grid/ribs will tell you nothing. If you really want to see what's going on, slide the tip of an inspection scope into the channel of the rib through the limber holes and you can see whether the grid has become detached for the hull.
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post #39 of 40 Old 02-24-2019
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Re: Benataeu grid construction

A borescope could be a tedious and ambiguous process, but it certainly beats tapping.
Probably ultrasound is the definitive way to tell what is or isn't bonded in the hull. Economically unfeasible at this time, I expect. Although I'd note that GE(?) came out with a $10,000 portable ultrasound machine that looks like a fat cell phone, a year or three ago. Maybe that will trickle down into the marine market one of these days.
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post #40 of 40 Old 02-25-2019
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Re: Benataeu grid construction

I had a bene 365 that hit the bottom hard.

There were some cracks in the grid starting at the bottom and going up.

What happens when a boat with a fin keel hits hard is that the aft most location of where the keel is attached to the boat is driven up.

Some amount of flexibility is possible but if driven up too high something like the grid will crack. Check in that location specifically.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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