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02-05-2021, 10:27
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#16
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Registered User
Join Date: Apr 2021
Posts: 488
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Re: Beneteau 361 Grid/Matrix Separation
To be honest, I have no idea what happened. These are all guesses.
I went back and looked at the survey when we bought it. It included photos. No damage, no cracks, nothing. Surveyor reporter grid as ‘good condition’.
We could’ve hit a sandbar and not noticed it. The boatyard could’ve put the boat down hard on blocks and not said anything. The launch driver could’ve run it aground the many times it was towed to/from the Travelift. Who knows.
Looking at the paint, it matches the color of the paint in all the bilges and compartments, to include lazarettes, engine, etc. So it may not have been sinister.
I don’t know. I’m just grasping at straws here. Trying to make sense of this all.
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02-05-2021, 11:33
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#17
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Registered User
Join Date: Apr 2021
Posts: 488
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Re: Beneteau 361 Grid/Matrix Separation
Additionally, the keel bolts absolutely penetrate both the pan sections of the liner and the bonded flanges of the grid matrix, depending on bolt location.
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02-05-2021, 17:36
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#18
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Registered User
Join Date: Feb 2020
Location: Port adelaide south australia
Boat: Cheoy lee perry 48
Posts: 750
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Re: Beneteau 361 Grid/Matrix Separation
Have seen this type of separation of hull and liner a number of times, often where the chain plate part of the liner moulding separates from the hull ,a verry tight rig and a poorly supported lift or grounding will do it ,the keel bolts do not normally go through the grid but there should be cross floors side to side between every set of keel bolts, the only fix I know of is wot we used to do was to strip out the interior ,grind out and heavily reclglass the grid back to the hull ,not simple but the best fix ⚓️⛵️
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02-05-2021, 18:15
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#19
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CLOD
Join Date: Jul 2007
Location: being planted in Jacksonville Fl
Boat: none
Posts: 20,364
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Re: Beneteau 361 Grid/Matrix Separation
The picture means nothing to me other than cracked paint
__________________
Don't ask a bunch of unknown forum people if it is OK to do something on YOUR boat. It is your boat, do what you want!
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02-05-2021, 18:35
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#20
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Registered User
Join Date: Jun 2008
Boat: Tartan 40
Posts: 2,460
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by C420sailor
To be honest, I have no idea what happened. These are all guesses.
I went back and looked at the survey when we bought it. It included photos. No damage, no cracks, nothing. Surveyor reporter grid as ‘good condition’.
We could’ve hit a sandbar and not noticed it. The boatyard could’ve put the boat down hard on blocks and not said anything. The launch driver could’ve run it aground the many times it was towed to/from the Travelift. Who knows.
Looking at the paint, it matches the color of the paint in all the bilges and compartments, to include lazarettes, engine, etc. So it may not have been sinister.
I don’t know. I’m just grasping at straws here. Trying to make sense of this all.
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If those cracks really are a separated liner- it would take a grounding you would know about. And a really hard drop by the yard which would be tough with how slow a travelift moves. And usually boats are towed slowly in a yard so even it the boat hit a rock it should withstand this.
Bottom line either the boat was built really poorly or it had a heck of an accident somewhere
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02-05-2021, 18:55
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#21
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Registered User
Join Date: Mar 2013
Location: Slidell, LA
Boat: Beneteau First 375
Posts: 447
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Re: Beneteau 361 Grid/Matrix Separation
Really - just looking at the different colored glop in the bays in the original pics - how did that go unnoticed in the first place? How did the surveyor not comment on it?
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02-05-2021, 19:10
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#22
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Registered User
Join Date: Sep 2007
Boat: GibSea 472
Posts: 520
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Re: Beneteau 361 Grid/Matrix Separation
Thos grids are the fastest and cheapest to built a large volume production serie. But once cracked, by insignificant grounding or bad winter storage , you are in a very bad way.Re making a complete grid is not a trivial task.
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03-05-2021, 06:15
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#23
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Registered User
Join Date: Apr 2016
Posts: 164
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Re: Beneteau 361 Grid/Matrix Separation
Sure does sound like Expedition Evans all over again. Would be worth. watching some of their episodes to learn what the repair involves.
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03-05-2021, 17:42
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#24
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Registered User
Join Date: Oct 2015
Location: Newfoundland
Boat: Beneteau
Posts: 671
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by kenbo
There is absolutely no way that the through-hull fitting was holding the liner to the hull.
I am fairly certain that the keel bolts do not go through the liner/grid, only the hull. So removal of those two elements should have no bearing on the hull to grid separation.
If you have photo indication of no problem prior to the boatyard move then it may be that they either: 1) set her down too hard or 2) misplaced the keel blocking.
But none of that removes my suspicion as to why the bilge is partly painted in the damaged area. You may not have noticed the separation due to the way the boat was blocked, i.e. the keel could have been pushing the hull up to the grid and closing the gap and after the move the jack stands may be supporting the hull and the keel maybe be able to sink due to improper blocking, soft ground or soft wood.
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Actually in my boat the keel bolts go through matrix and the hull as it does in the other Beneteaus I've seen.
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03-05-2021, 17:50
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#25
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Registered User
Join Date: Jul 2016
Location: Atlantic Highlands, NJ
Boat: Swallowed the anchor
Posts: 976
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by nortonscove
Actually in my boat the keel bolts go through matrix and the hull as it does in the other Beneteaus I've seen.
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So are you saying that the keel bolt is holding the grid and hull together? If so that's terrible engineering.
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03-05-2021, 18:36
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#26
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Registered User
Join Date: Mar 2013
Location: Slidell, LA
Boat: Beneteau First 375
Posts: 447
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Re: Beneteau 361 Grid/Matrix Separation
Not like that in mine.
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04-05-2021, 04:11
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#27
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Registered User
Join Date: Jun 2008
Boat: Tartan 40
Posts: 2,460
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by kenbo
So are you saying that the keel bolt is holding the grid and hull together? If so that's terrible engineering.
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I suspect it’s not holding it together but rather in some models the hull laminate isn’t think enough so using the grid adds thickness to support keel bolts. It does seem like a more robust way to tie keel into the structural grid rather than relying on transfer from hull skin to glued on frames
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04-05-2021, 05:34
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#28
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Registered User
Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft 381 Catalina
Posts: 6,208
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by malbert73
I suspect it’s not holding it together but rather in some models the hull laminate isn’t think enough so using the grid adds thickness to support keel bolts. It does seem like a more robust way to tie keel into the structural grid rather than relying on transfer from hull skin to glued on frames
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I agree, bolting through both the hull and grid seems like it would do a better job of spreading the keel loads, particularly if the grid isn't heavily tabbed into the hull.
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04-05-2021, 06:28
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#29
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Registered User
Join Date: Feb 2016
Location: forest city
Boat: no boat any more
Posts: 2,510
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Re: Beneteau 361 Grid/Matrix Separation
99,9% this is from a hard grounding at speed!
__________________
...not all who wander are lost!
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04-05-2021, 10:01
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#30
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Registered User
Join Date: Oct 2015
Location: Newfoundland
Boat: Beneteau
Posts: 671
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Re: Beneteau 361 Grid/Matrix Separation
Quote:
Originally Posted by kenbo
So are you saying that the keel bolt is holding the grid and hull together? If so that's terrible engineering.
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First lets agree that the folks that engineered a boat that has been most of the way around probably know something about how it can be done. Secondly no one said that the keel bolts hold them together. The matrix is bonded to the hull. Both are then drilled and the keel fitted. The matrix is actually several times thicker than the hull as it is in traditional building techniques. You'll have a very difficult time finding any vessel where the outer skin whether steel, aluminum, wood or fibreglass that is in fact dimensionally thicker than the framework. The idea is that all of the loads are transferred to the matrix, again this is how boats are normally built.
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