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Old 10-03-2016, 02:08   #1
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Lagoon Hull - Deck movement

Just for info I noticed a leak in the aft bathroom on our L450. I traced this to the hull flexing at the stays and could feel it moving against the deck by about 2-3mm. I don't think that this is a structural issue? However with time the sealant gave way and let water in.

The screw/bolt in the picture is about 10mm long and I don't think serves any useful purpose.

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Old 10-03-2016, 02:36   #2
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Re: Lagoon Hull - Deck movement

Not sure if I'm looking at the right bolt. But on our 380 that screw is one of the fixings for the deck/hull join that continue the full length of the hull. Most (though not all) are hidden under the teak toe rail.

We have had to re-seal a few, but in our case more towards the bow.


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Old 10-03-2016, 02:44   #3
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Re: Lagoon Hull - Deck movement

Quote:
Originally Posted by DavefromNZ View Post
Just for info I noticed a leak in the aft bathroom on our L450. I traced this to the hull flexing at the stays and could feel it moving against the deck by about 2-3mm. I don't think that this is a structural issue? However with time the sealant gave way and let water in.

The screw/bolt in the picture is about 10mm long and I don't think serves any useful purpose.

Attachment 120332


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bolt is next to shroud attachment. Possible that loosened as too much force applied to shrouds - not following reefing guidelines ?
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Old 10-03-2016, 08:48   #4
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Re: Lagoon Hull - Deck movement

Hey Dave,

here is a picture from inside
Maybe this helps

one of the pictures i took 2 weeks ago
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Old 10-03-2016, 09:43   #5
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Re: Lagoon Hull - Deck movement

Quote:
Originally Posted by DavefromNZ View Post
The screw/bolt in the picture is about 10mm long and I don't think serves any useful purpose.
It is as the other poster put, one of the many screws that holds the top sides to the hull. So it does serve a purpose.

Suggest taking it out, re-sealing.

If the problem persists you could glass over it from the inside, or counter sink the screw more and then gel coat over it from the outside.

Hope that helps
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Old 10-03-2016, 11:09   #6
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Lagoon Hull - Deck movement

Thanks everyone for advice. The screw is actually a stubby bolt as it has a flat and not pointy end.

At this stage I have just put new sealant on. However I guess the strength comes from the hull and deck being glassed together? 4 years old so maybe Lagoon will pay for under warrantee. Both port and starboard sides move.

Thanks for photo Darksyde. Do you have any from under the deck before attached as from inside it feels like it has a beam running forward/aft at this location.

Has any other L450 or Lagoon owner sat with your fingers on the hull/deck joint at the shrouds when sailing to see if there is movement?


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Old 14-03-2016, 10:20   #7
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Re: Lagoon Hull - Deck movement

Had same issue in 2011 L450 about 12 months ago on port side. Sealant had perished. Re-sealed it. No water ingress since. I will check for deck movement next time we are out in a big wind. There are no stress cracks. Some around the spinnaker sheet block fitting, but thats all.
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Old 12-07-2016, 03:47   #8
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Lagoon Hull - Deck movement

An update. Lagoon acknowledged the problem and have paid for most of the work. The more I ask around I find it is relatively common and also on Beneteau and Jeanneau yachts.



The fix was not too difficult. We could take out the cabinets in 5 minutes from the aft bathrooms for internal access. The toe rails came off fairly easily - drill out the plugs, two screws and one bolt each. We added a lot more bolts under the toe rails and used strong and slightly flexible bond. Pictures attached.
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Old 12-07-2016, 06:15   #9
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Re: Lagoon Hull - Deck movement

How is the hull to deck joined, is it bonded with Plexus?
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Old 12-07-2016, 07:24   #10
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Re: Lagoon Hull - Deck movement

I'm going to assume 5200?
How did you notice the movement? Did the bond from the sealant get sheared?
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Old 12-07-2016, 21:27   #11
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Re: Lagoon Hull - Deck movement

Quote:
Originally Posted by DavefromNZ View Post
An update. Lagoon acknowledged the problem and have paid for most of the work. The more I ask around I find it is relatively common and also on Beneteau and Jeanneau yachts.



The fix was not too difficult. We could take out the cabinets in 5 minutes from the aft bathrooms for internal access. The toe rails came off fairly easily - drill out the plugs, two screws and one bolt each. We added a lot more bolts under the toe rails and used strong and slightly flexible bond. Pictures attached.
Dave,
You mentioned that Beneteau, Lagoons mother organization was having similar issues with hull to deck joints opening up. I'm not aware of this but it is a very serious issue on a boat if the hull to deck joint is compromised. By the way, according to Beneteau's website they have never had a failure in their hull to deck joints so maybe it's something that has just been effecting Lagoon yachts. Good on you for finding it and having it repaired. R
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Old 13-07-2016, 03:51   #12
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Re: Lagoon Hull - Deck movement

Hi, they used FIX15. They assured me it was a good product to use. It is a sealant/adhesive.

Two independent local boat builders said they had fixed a number of Beneteau and Jeanneau yachts. I don't think you would call it a failure but certainly there were gaps that needed sealing. I mentioned it to my neighbour who has a Lagoon 380 and he pointed to where his leaked close to the stern.


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Old 13-07-2016, 08:19   #13
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Re: Lagoon Hull - Deck movement

Dave, good info. I don't know enough about the engineering in multihull designs to comment on them but if you loose the integrity of the hull to deck joint in a mono hull it's not good news as that keeps the whole boat in one piece. Obviously in mild conditions it would not be a problem but if you were in storm conditions you might have the boat coming apart. Hull to deck joints used to be built with sealant and thru bolted but in these days of modern high production boats they tell us that the sealant/glue is more than sufficient to bond the hull and deck. Your evidence would suggest otherwise. You did the right thing to add thru bolts, probably should have been built that way in the first place. Thanks for the feedback. R
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Old 13-07-2016, 09:21   #14
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Re: Lagoon Hull - Deck movement

Dave,
We had a similar issue with our L450 a couple of years ago. We were told that the main structural support is from the bonding compound applied between the hull and deck join, not the bolts. After a couple of leak repair attempts we found that there was a small area of missed bonding compound (I don't recall what was used) at the leak location (same spot as yours). We had the join slightly separated and filled with compound and then re-bolted and have not had the problem since.


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Old 13-07-2016, 09:49   #15
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Re: Lagoon Hull - Deck movement

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Originally Posted by DavefromNZ View Post
Hi, they used FIX15. They assured me it was a good product to use. It is a sealant/adhesive.

Two independent local boat builders said they had fixed a number of Beneteau and Jeanneau yachts. I don't think you would call it a failure but certainly there were gaps that needed sealing. I mentioned it to my neighbour who has a Lagoon 380 and he pointed to where his leaked close to the stern.


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A couple months back, I was approached by a Broker / Beneteau dealer to gauge my interest in a 2015 Sense 55 that was available and that had this issue. He stated that Beneteau had it repaired by factory techs and that all was well. Sounds as if this might not have been an isolated incident.
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