Lagoon bulkheads

[redneckrob]

Originally Posted by motion30

But most certainly not a sign of structural integrity either

Curious what your naval engineering background is and what in that background would lead you to believe that noise from rubbing nonstructural finishing panels is related to structural integrity any more than how the boat smells or what color it is? Have you decided flexing is per se bad? Don't ever fly a commercial airliner then, most larger aircraft wings routinely flex more than 10', including composite wings. Some other reason, or just an uninformed gut feel from someone with no actual knowledge of the underlying concepts?

[smj]

Originally Posted by redneckrob

Curious what your naval engineering background is and what in that background would lead you to believe that noise from rubbing nonstructural finishing panels is related to structural integrity any more than how the boat smells or what color it is? Have you decided flexing is per se bad? Don't ever fly a commercial airliner then, most larger aircraft wings routinely flex more than 10', including composite wings. Some other reason, or just an uninformed gut feel from someone with no actual knowledge of the underlying concepts?

I would say the vast majority if not all of the creaking and groaning furniture is non structural on most Lagoons. But would you rather have a boat that is silent while underway or one that makes noise?

[motion30]

Originally Posted by redneckrob

Curious what your naval engineering background is and what in that background would lead you to believe that noise from rubbing nonstructural finishing panels is related to structural integrity any more than how the boat smells or what color it is? Have you decided flexing is per se bad? Don't ever fly a commercial airliner then, most larger aircraft wings routinely flex more than 10', including composite wings. Some other reason, or just an uninformed gut feel from someone with no actual knowledge of the underlying concepts?

You're right I do not have a naval engineering background but in fact I do have an engine clearing background and have lonely worked on but race boats, That are much more highly stressed than a spleasure boat. Those interior panels do not move on the road as they are fastened to structural members. Any continued flexing to a certain degree will eventually lead to failure even in fiberglass. You can sail around in denial if you wish. But I find your comments interesting Considering lagoon is the only manufacturer I know of that has these exaggerated Movements of their interior panels especially given the history of bulkhead failures of on these boats

[sagablu]

Some of you guys needs to separated by a large bulkhead, preferably a big squeaky one. All are entitled to an opinion without backlash however well or poorly founded it may be. However I personally, know nothing of the magical art of boat building. Peace out

[Sand crab]

The Nahoa crew is on Vancouver Island now. They were seen in the most recent O'Kelleys vid right at the end. Not sure who is fixing the boat if it is being fixed. That is a really nice tri the O'Kelley's looked at BTW.

https://www.youtube.com/watch?v=fEEigG7Y2ng

[smj]

Originally Posted by Sand crab

The Nahoa crew is on Vancouver Island now. They were seen in the most recent O'Kelleys vid right at the end. Not sure who is fixing the boat if it is being fixed. That is a really nice tri the O'Kelley's looked at BTW.

Saw that, absolutely beautiful tri. In your backyard? Maybe your next boat? [emoji16]

[Sand crab]

I'm back east for about another year, family stuff gets in the way sometimes. I agree that it is a really nice tri. I wonder what the asking price is.

[Firemandivi]

I have been a long time viewer of Nahoa well before they had kids. In their previous video Ben says I believe a couple of times that they don't know what the issue truly is and will have it inspected when they reach the Seychells. I hope its nothing serious and can be easily repaired. I know in previous videos he has gone through the boat looking for issues and from what I remember there was no previous issue with the bulk heads and that is from them sailing for a number of years.



As for the person claiming to be an engineer are you sure you can spot not just a flaw in that boat but a true design flaw from a video? I've been a civil engineer for over 20 years and there is no way I or 99% of the PE's I know would say something like that. Calling yourself a PE and saying there is a design flaw means a lot more then you may think. As a PE you are held to a different standard then the general public. But then again this is a forum and people love to hide behind their screens and type what they want with no repercussions. Its one of the reasons I'm not that active on forums anymore. But if someone claiming to be a PE makes a statement about a design flaw for an entire line of boats from watching a video, well I have to say something.

[Joli]

Boats have to move somewhat or they break. Are these boats moving to much? Only way to know is have it inspected. Hard to tell much from a 10 minute video.

[Uncle Bob]

Originally Posted by redneckrob

Curious what your naval engineering background is and what in that background would lead you to believe that noise from rubbing nonstructural finishing panels is related to structural integrity any more than how the boat smells or what color it is? Have you decided flexing is per se bad? Don't ever fly a commercial airliner then, most larger aircraft wings routinely flex more than 10', including composite wings. Some other reason, or just an uninformed gut feel from someone with no actual knowledge of the underlying concepts?

And in a balls to the wall aborted take off the fuselage flexes damn near as much.

[wingssail]

Originally Posted by Joli

Boats have to move somewhat or they break. Are these boats moving to much? Only way to know is have it inspected. Hard to tell much from a 10 minute video.

The interesting thing about that is if the overall structure is moving then the bits attached to it are going to move, often relative to each other.

If that is part of the design then those attached bits should not be affixed to each other or they will soon become un-attached, as was obvious in the video.

It's all conjecture but it seems to me that the hull/deck, cabin etc structure is flexing on this Lagoon, and probably others, and not only can the cabinetry break free of the structure but structural bulkheads could also become unattached.

By the way, my boat, and undoubtably yours, does not significantly move or flex even in very heavy seas. The engineering problem is much more difficult in a catamaran.

[ozsailer]

Originally Posted by danno7

As an engineer, I realize the source of the problem with the 450 is a design defect in bulkhead support. They did not include enough tabbing, straps, layers, and other issues.

It is quite common for a manufacturer to use the same materials, parts, or design processes for several models. The bulkhead design of the 450 could be similar in all Lagoon models of the same year of build, size range and using the same build processes. Agree, the video of the 410 is only a sample of one, and I have nothing more to go by than that video. But Parley Revival was only a sample of one until Colin exposed it worldwide as a problem. There is also a video of a Lagoon 500 with door gaps exposing too much movement.

It is proven to me that Lagoon had a serious design flaw in their build process. It is highly likely that only certain models or years of production had a problem, and the model of the 410 you had is for a year they were built correctly?

For me, I do not want the risk of purchasing a boat that could have this issue. Let me purchase it for half the price they are typically asking, fix the problem correctly (like Colin did), and the Lagoon would be a fabulous boat.

Danno, unfortunately and disappointingly for me I have to agree that the issue with the L450 is most definitely a design issue. The response from Lagoon IMO was less than satisfactory. I can confirm that while many of the construction methods are the same there was some difference between the earlier models. My bulkheads were tabbed in but as with all boats there were things done that had me scratching my head going saying "why the hell would they do that". You may not be aware that over 1000 Lagoon 38 were made and only in recent years ceased production. I am unaware of any of the 38s having any bulkhead issues (to date),
I note your comment regarding if there is an issue in one model it is likely in all models. I disagree with this as many of the different models are made in different factories. Remember the Fountain Pajot Mahe 36, or the 40 foot Lavezzi, Both models renowned for issues with Osmosis which was ultimately traced to faulty chemicals. Yet the Osmossis was not an issue for other models.
As with any model of boat, one has to do their own investigations to determine the history of the company and build quality and check hearsay against fact. Remember all the whoha against Hunter yachts for having no backstay and the doomsayers stating the mast would fail. I stand corrected if I am wrong but I have not heard of a single case of a Hunter mast failing due to not having a backstay. (Yes I know i am on a tangent here)

Ozsailer

[smj]

Originally Posted by wingssail

The interesting thing about that is if the overall structure is moving then the bits attached to it are going to move, often relative to each other.



If that is part of the design then those attached bits should not be affixed to each other or they will soon become un-attached, as was obvious in the video.



It's all conjecture but it seems to me that the hull/deck, cabin etc structure is flexing on this Lagoon, and probably others, and not only can the cabinetry break free of the structure but structural bulkheads could also become unattached.



By the way, my boat, and undoubtably yours, does not significantly move or flex even in very heavy seas. The engineering problem is much more difficult in a catamaran.

Our catamaran doesn’t significantly move or flex in a heavy sea. It also hasn’t suffered from loosing a keel nor a grid de bonding as some monohulls have. Guess there’s problems in all types of designs?

[redneckrob]

Originally Posted by motion30

You're right I do not have a naval engineering background but in fact I do have an engine clearing background and have lonely worked on but race boats, That are much more highly stressed than a spleasure boat. Those interior panels do not move on the road as they are fastened to structural members. Any continued flexing to a certain degree will eventually lead to failure even in fiberglass. You can sail around in denial if you wish. But I find your comments interesting Considering lagoon is the only manufacturer I know of that has these exaggerated Movements of their interior panels especially given the history of bulkhead failures of on these boats

I flew a helicopter (As-365) with elastomer blade hub that flexed to its full extent every blade revolution, 360 revolutions per minute. And that wasn't even a part we ever really had to change out! Fiberglass can be designed to flex many thousands of time with no ill in thousands of applications from aircraft to fishing rods. That's not denial, that's just facts. And every catamaran flexes significantly, bar none. If they didn't they would actually fail, its a pretty fundamental misunderstanding of structural engineering to believe it seeks to eliminate flexing or that flexing in any way is per se undesirable. Some manufacturers do a better job of ensuing the furnishings don't rub than others. That has nothing to do with safety or structural integrity. I am curious about the hundreds or is it dozens, or is even one death attributed to Lagoon structural failures of the thousands of Lagoons that have sailed around the world?

[Jim Cate]

thousands of Lagoons that have sailed around the world?

Awww, come on Rob! While I agree that designed flexing is common, this statement is pretty hard to stomach. I simply do not think that thousands of Lagoons have circumnavigated... that is patently ridiculous. Thousands of Lagoons have been built and sailed somewhere. A small number of them have sailed across oceans, and likely a smaller yet number of those have circumnavigated... I'd believe maybe ten or so... maybe!

Jim