Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 14-03-2019, 18:36   #1
MTF
Registered User

Join Date: Feb 2014
Posts: 3
Flex in Lagoon 380 hull below waterline

Hi
Thanks for the great information on this forum so far.

I had a 2007 Lagoon 380 hauled for a pre-purchase survey and the surveyor found issues. Specifically, flexing in hull skin below waterline which he thought may be delamination. A composites worker at the yard also thought delamination was also present in the hull. I could depress the glass easily with my hand and it flexed about 5-7mm with a slight crunching noise till it hit what we thought was another layer behind it. I cancelled the deal due to high estimated costs of repair.

See attached vid of flexing.

The owners and broker were shocked and rehauled the boat a day later, ground an affected area and found no issue. They stated it’s thin glass between the bulkheads.

I know Lagoons are built to a price point but I’ve not seen solid glass below the waterline flex so much and so easily. Is this normal in an L380 or does it look like it’s suffered damage, had a poor repair or manufacturing defect?
__________________

MTF is offline   Reply With Quote
Old 14-03-2019, 18:58   #2
MTF
Registered User

Join Date: Feb 2014
Posts: 3
Re: Flex in Lagoon 380 hull below waterline

https://youtu.be/HEv07qssvzo

Video of the hull flexing
__________________

MTF is offline   Reply With Quote
Old 14-03-2019, 19:38   #3
Senior Cruiser
 
atoll's Avatar

Cruisers Forum Supporter

Join Date: Mar 2010
Location: gettin naughty on the beach in cornwall
Boat: 63 custom alloy sloop,macwester26,prout snowgoose 37 elite catamaran!
Posts: 9,867
Images: 75
Re: Flex in Lagoon 380 hull below waterline

sounds like a core failure ie balsa turned to mush due to water damage
__________________
my catamaran building project updates http://www.cruisersforum.com/forums/...36#post2502136
atoll is offline   Reply With Quote
Old 14-03-2019, 19:44   #4
Registered User
 
admiralslater's Avatar

Join Date: Sep 2014
Location: Toronto summer rest somewhere else
Boat: Outremer 45/pdq36
Posts: 969
Re: Flex in Lagoon 380 hull below waterline

Be very wary pf this boat. We built our pdq36 with a light laminate on the core because we where saving weight but there is no way even after 15 years that I can depress the skin by hand
__________________
“Growing older but not up”
admiralslater is offline   Reply With Quote
Old 14-03-2019, 21:40   #5
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 3,575
Re: Flex in Lagoon 380 hull below waterline

I found areas of the hull (uncored) in a Lagoon 450 that were only 3mm thick.
Water was leaching right throught the hull. The white areas of the thermal image below show some of the thin spots. This shot is around the drive leg with the cover plate removed.

The other two shots show my awl bent and hooked inside the hull (where I poked it through) and placed a piece of black tape on the outside. The third shot shows the thickness as indicated between the black tape and the hook.
Attached Thumbnails
Click image for larger version

Name:	Picture 105.jpg
Views:	125
Size:	76.0 KB
ID:	188037   Click image for larger version

Name:	Picture 106.jpg
Views:	122
Size:	83.3 KB
ID:	188038  

Attached Images
 
__________________
That hysterical laughter you hear as you sail a way in your "new" boat ..... is the seller.
boatpoker is online now   Reply With Quote
Old 15-03-2019, 05:25   #6
MTF
Registered User

Join Date: Feb 2014
Posts: 3
Re: Flex in Lagoon 380 hull below waterline

Hi Atoll, I thought these boats were solid glass below the waterline and balsa core above?

Thanks Admiralslater, yes it does seem very thin doesn’t it? Would it help to thicken and reclassify the thin areas and wood this fix the issue?

Boatpoker that’s good to know and the moisture meter reading on the hull suggested water was getting inside as you noticed on the thin sections you investigated on the 450
MTF is offline   Reply With Quote
Old 15-03-2019, 05:35   #7
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 23,377
Flex in Lagoon 380 hull below waterline

First boat we were going to buy you could flex the hull exactly like that.
In that case it was due to two things, the shape of the hull was flat there and not rounded like an egg, and the laminate was thin.
An egg of course gets most of its strength from its shape, not the thickness of the shell.
It took both to be able to flex the hull, if the hull had a rounded shape you couldn’t flex it, and if the hull had been thicker you couldn’t have flexed it.

In this case it was a known issue I found out through the users group, the fix was to cut the floor out of the head and glass in a stringer, which of course reinforced the thin hull.
This was a Mono, so it’s not a Cat thing.

I think it’s entirely possible that what you found is “normal” and other than a flatter spot in a thin hull you wouldn’t have found it.

A lot of modern boats don’t have “excess” glass, but don’t seem to be breaking up, so there must be enough.
a64pilot is offline   Reply With Quote
Old 15-03-2019, 13:49   #8
Registered User

Join Date: Feb 2019
Posts: 3
Re: Flex in Lagoon 380 hull below waterline

When i bought my ‘05 380 the surveyor tapped all over the bottom with a hammer and got nothing but a nice “ring”. The boats in general are solid, sounds like this on has problems.
tdotson is offline   Reply With Quote
Old 16-03-2019, 02:23   #9
Registered User

Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,537
Re: Flex in Lagoon 380 hull below waterline

That area is uncored solid glass in a 380.

The 380 hulls are thin and it is possible to depress the skin by hand in some areas between bulkheads. Same for the uncored areas of other cats I have owned.

Now who knows how much thickness is required? Most folks in the forum have ideas & anecdotes to share (like myself) but very few have the qualifications to give a definite answer.
My take: I doubt there is any cat model that has done more circumnavigations than the 380 and we haven't heard they break up frequently. So maybe its strong enough.
rabbi is online now   Reply With Quote
Old 17-03-2019, 06:37   #10
Registered User

Join Date: Jul 2009
Location: Hillsborough, N.C. (Boat located: Tortola, BVI)
Boat: Lagoon 42
Posts: 157
Re: Flex in Lagoon 380 hull below waterline

This may be a serious issue, but in my search for a catamaran I was advised by a couple of brokers and one well-regarded surveyor that it should be far from a deal breaker, if the boat is solid in all other respects.

We often think brokers tell us what we want to hear to make a sale; however, I thought both were being forthright about the issue. It first came up in looking at a 2009 Leopard 40. The second time was a 2010 FP Lipari 41. Both boats had flex similar to that shown in MTF's video. I also saw it on a Lagoon 420. Each broker gave similar explanations and insisted it's not "that uncommon". I got the same general explanation and opinion that it was normally a minor issue from a well-regarded, Florida-based surveyor who had no connection with either broker. I also got a couple of opinions that differed.

What I did learn is that many boats do have areas of flex in their hulls, it was demonstrated to me several times on cats and monos alike. The owner (for 30 years) of the boatyard I used for over 15 years, thought it to be more than a minor issue and something that definitely needed attention, but again seldom a deal breaker. He said he had seen it often over the years in both high-end and production boats. He said a proper repair was generally straight forward. Of course, he does own a boatyard, what else would he say?

The hull flex issue, be it minor or not, was one of several things that eliminated both boats early on in my search. My wife and I ended up buying a 2019 Lagoon 42 and our boat doesn't appear to have areas of flex in the hull.
Jim Woodall is offline   Reply With Quote
Old 17-03-2019, 07:52   #11
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 3,575
Re: Flex in Lagoon 380 hull below waterline

Quote:
Originally Posted by rabbi View Post
That area is uncored solid glass in a 380.

The 380 hulls are thin and it is possible to depress the skin by hand in some areas between bulkheads. Same for the uncored areas of other cats I have owned.

Now who knows how much thickness is required? Most folks in the forum have ideas & anecdotes to share (like myself) but very few have the qualifications to give a definite answer.
My take: I doubt there is any cat model that has done more circumnavigations than the 380 and we haven't heard they break up frequently. So maybe its strong enough.
I think it's a matter of degree. Having a large enough flexible area adjacent to a tabbed (rigid) bulkhead could result in hinge fractures over time. I've seen a few of those. I surveyed a Hanse 35 that was so flexible in the aft quarter below the waterline that I could depress it one half inch by hand with only moderate pressure. I did not buy the brokers .... "It's fiberglass, it's supposed to be flexible" .
I would not have bought that boat.
__________________
That hysterical laughter you hear as you sail a way in your "new" boat ..... is the seller.
boatpoker is online now   Reply With Quote
Old 17-03-2019, 13:29   #12
Registered User

Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,537
Re: Flex in Lagoon 380 hull below waterline

Quote:
Originally Posted by Jim Woodall View Post
My wife and I ended up buying a 2019 Lagoon 42 and our boat doesn't appear to have areas of flex in the hull.
If I'm not mistaken the Lagoon 42 has balsa cored hull below the waterline. Flex in a cored hull is a different story than flex in uncored solid skin.
rabbi is online now   Reply With Quote
Old 17-03-2019, 15:24   #13
Registered User

Join Date: Mar 2014
Location: Caribbean
Boat: Lagoon 450
Posts: 808
Re: Flex in Lagoon 380 hull below waterline

Quote:
Originally Posted by rabbi View Post
If I'm not mistaken the Lagoon 42 has balsa cored hull below the waterline. Flex in a cored hull is a different story than flex in uncored solid skin.

Lagoon 42 Spec sheet:


"Balsa core hull, solid laminate under the waterline."


https://api.cata-lagoon.com//images/...il-2018-gb.pdf
Bean Counter is offline   Reply With Quote
Old 17-03-2019, 15:32   #14
Registered User

Join Date: Mar 2014
Location: Caribbean
Boat: Lagoon 450
Posts: 808
Re: Flex in Lagoon 380 hull below waterline

to the OP, did you go around the other hull and see if that one pressed in as well at the same spot?
Bean Counter is offline   Reply With Quote
Old 17-03-2019, 18:04   #15
Registered User

Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,537
Re: Flex in Lagoon 380 hull below waterline

Quote:
Originally Posted by Bean Counter View Post
Lagoon 42 Spec sheet:


"Balsa core hull, solid laminate under the waterline."


https://api.cata-lagoon.com//images/...il-2018-gb.pdf
Thank you , I stand corrected!

I thought all recent designs like 40 and 42 were balsa below waterline.
__________________

rabbi is online now   Reply With Quote
Reply

Tags
hull, lagoon, lagoon 380, water

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Flex Shot vs Flex Seal vs Mighty Sealer? Paradise1 Product or Service Reviews & Evaluations 19 25-01-2017 16:40
Admiral 40 Balsa Below Waterline laser Construction, Maintenance & Refit 28 08-06-2010 16:01
Head/Holding tank below waterline - options? Beausoleil Plumbing Systems and Fixtures 13 15-10-2008 17:59
AC discharge thru-hull: below waterline, or piss off my neighbours? Geoff S. Plumbing Systems and Fixtures 16 24-04-2008 07:24



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 15:42.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.