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Old 24-05-2019, 10:37   #1
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New Beneteau's - How is the decks secured to the hull?

So my dock neighbor just got a brand new Bene Oceanis 38 - Delivered in Feb 2019.

What I find incredibly interesting about the new boat beyond the hard chines is how they've secured the deck to the hull.

They have teak toe rails, but it appears that the deck joint has a white polysulfide(i assume) caulk line. This caulk line runs from bow to stern, down the stern sides and down towards the water(below) the drop down swim platform.

Is this common of NEW builders to use a caulking joint on the external side - exposed to the elements for creating a watertight seal?

What is holding the deck/hull together? I am assuming they have some sort of bolts bedded in the laminate but I was also thinking maybe they used something like 5200?

Would make me feel quite nervous having that caulking joint being so exposed and also not having any bolts through the joint.
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Old 24-05-2019, 11:08   #2
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Re: New Beneteau's - How is the decks secured to the hull?

It is my understanding that there are screws, or bolts (I am not sure), through the toe rails joining the deck with the hull.

On my ex-Lagoon 450, there were using screws by the side stays. Due to the hull flexing and mast pumping, the screws sheared and I got leaks. I replaced the screws in the area with larger bolts, SS backing plates (inside and out) and layers of fiberglass cloth on the inside. Not a fun job but needed to be done. This may not be the case for monohulls as they do not flex as much.
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Old 24-05-2019, 11:20   #3
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Re: New Beneteau's - How is the decks secured to the hull?

SCREWS???? WTF? You mean self tapping screws? Thatís so bad itís almost criminal. Thatís not how you build an oceangoing boat!
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Old 24-05-2019, 11:34   #4
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Re: New Beneteau's - How is the decks secured to the hull?

“Our hull to deck joint with wide return flange is one of the strongest in the industry. It is chemically bonded (polyurethane mastic) with mechanical shear fasteners (screws and nuts/bolts) - 100%reliability with no recorded failure in millions of miles of tough ocean conditions.”
https://www.murrayyachtsales.com/wp-...etter-Boat.pdf

However:

"Hull-deck joint screwed, bonded and trimmed with 1 toerail”
https://www.beneteau.com/sites/defau...S_light_en.pdf
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Old 24-05-2019, 12:21   #5
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Re: New Beneteau's - How is the decks secured to the hull?

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SCREWS???? WTF? You mean self tapping screws? Thatís so bad itís almost criminal. Thatís not how you build an oceangoing boat!
Well, I agree with you regarding screws. Like I said, the area I fixed had screws on our 2012 L450. I don't know about the rest of the areas, as most are not that visible without removing cabinetry backs.

For whatever it's worth, we spent 3 seasons in the S. Pacific and saw some major, to us, storms and waves. Our L450 took care of us. We never felt unsafe.

You get what you pay...
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Old 24-05-2019, 13:32   #6
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Re: New Beneteau's - How is the decks secured to the hull?

Thanks for posting those links Gord!

When I get home tonight I'll have to take a look at the toe rails. One thing I noticed is that the rails are not running the full length of the hull, rather there are quite a bit of space between some sections.


@boom - On your old Lagoon, did you have a polysulfide compound that was exposed on the exterior?

One thing I noticed in the first link posted by Gord was that it's from 2014 and I believe the model is different than the new models.

I'll post a photo of the boat tonight, but I definitely feel like there are large gaps in the deck joint that do not have the screw/bolts.

Given that these are intended to be coastal cruisers and not world cruisers, I dont see it as a TERRIBLE design, rather something that should be kept in mind when buying a boat older than a few years.
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Old 24-05-2019, 13:39   #7
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Re: New Beneteau's - How is the decks secured to the hull?

Dan-
Think about all the complaints you've heard about "can't get that goddamn 5200 off!". The material they use may not be 5200 but it is similar, it ain't budging if it was applied to clean surfaces. The mechanical fasteners are actually just there to hold the deck and hull together while the adhesive sets and cures, which can take a full week.
Remember that commercial airliners and combat aircraft have important bits like the wings GLUED on. It can work.
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Old 24-05-2019, 13:40   #8
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Re: New Beneteau's - How is the decks secured to the hull?

Note that the second link, for the Oceanis 38.1 (September 04, 2018), specified a ďHull-deck joint screwed, bonded ...Ē - no mechanical fasteners mentioned.
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Old 24-05-2019, 15:37   #9
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Re: New Beneteau's - How is the decks secured to the hull?

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ďOur hull to deck joint with wide return flange is one of the strongest in the industry. It is chemically bonded (polyurethane mastic) with mechanical shear fasteners (screws and nuts/bolts) - 100%reliability with no recorded failure in millions of miles of tough ocean conditions.Ē
I wonder... does the definition of "failure" include leaks? To me it does. But I am suspecting to Bendy-toy it does not.

There are lots of ways to build boats. More bad ones than good ones. Screws to secure deck to hulls--even if the are glued together with "polyurethane mastic"--doesn't cut it for me for anything except a day sailor.

I was shocked when I discovered that Catalina secured some of their stern pulpits to the hull with self tapping screws. The idea of a deck secured that way just boogles my mind.

But it IS cheap...
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Old 24-05-2019, 16:34   #10
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Re: New Beneteau's - How is the decks secured to the hull?

@hellosailor - yes I would agree that 5200 or similar product is NOT going to come off. That **** is on there for a very long time if not forever. I am more concerned on long term horizon about leaks. My port lights were bedded with 5200. Those bastards were an incredible bear to get out, yet it was only 5 years ago when they were done. They had to be removed because they leaked.

5200 is an excellent adhesive, yet I question its sealant abilities. Having a deck joint sealed with something similar is fine, but if the external sealant fails, water will enter.

Aircrafts have a much better reputation with routine maintenance than the marine industry. Also they are bolted on aswell, not just glued.

@bill - that doesnt surprise me. These manufacturers are in an increasingly competitive industry. To operate a successful business they need to be as efficient as possible to get the boat down the line and onto the owner.

Not saying it's right but they are trying to reach a market of people that otherwise would not be reachable
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Old 24-05-2019, 16:56   #11
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Re: New Beneteau's - How is the decks secured to the hull?

I can definitely see where the toe rails are secured down, but seeing the stern wall is only adhesive sealants. I find it quite interesting.Click image for larger version

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Old 24-05-2019, 17:13   #12
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Re: New Beneteau's - How is the decks secured to the hull?

also when the stern deck to hull joint can be underwater .. like the picture shows .. you can assume the builder has taken the path of least resistance with construction.
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Old 24-05-2019, 17:16   #13
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Re: New Beneteau's - How is the decks secured to the hull?

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Originally Posted by chowdan View Post
I can definitely see where the toe rails are secured down, but seeing the stern wall is only adhesive sealants. I find it quite interesting.Attachment 192639Attachment 192640Attachment 192641Attachment 192642
Interesting! The toe rail pic shows a bung. All very well, but what's under the bung? Self tapper or a proper screw/nut/backer? And in the last pic, is that u-bolt thing the "chain plate" for the split backstay as it appears? I'd wonder what structure is under the deck there, and how it distributes the stresses from the stay into the hull? Surely does not inspire great confidence in this observer!!

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Old 24-05-2019, 18:32   #14
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Re: New Beneteau's - How is the decks secured to the hull?

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Originally Posted by Jim Cate View Post
Interesting! The toe rail pic shows a bung. All very well, but what's under the bung? Self tapper or a proper screw/nut/backer? And in the last pic, is that u-bolt thing the "chain plate" for the split backstay as it appears? I'd wonder what structure is under the deck there, and how it distributes the stresses from the stay into the hull? Surely does not inspire great confidence in this observer!!

Jim
I believe they would be self tappers based on the link Gord provided.

On this boat, cleats are not on top of the toe rail, as such, the toe rail is just tapped in by screws(I assume).

The u-bolt is exactly what you thought it was - the "chain plate" for the split back stay. They use that design for all plates EXCEPT the fore stay - which is an actual stainless plate

I would love to see the under side structure aswell. Not of just the back stays, but of the shrouds as well.

Here are a few more photos - mid ship cleat(secured from under the deck) and shroud "chain plates". Click image for larger version

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Old 24-05-2019, 20:04   #15
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Re: New Beneteau's - How is the decks secured to the hull?

Oh, my... this is on a 38 footer, isn't it? I guess that those u-bolts must work most of the time, and I'd hope that the shrouds are tied into a bulkhead or a knee that distributes stresses to both hull and deck, but, as I said, not confidence building for me. The rigs on Bennies don't seem to be falling over all the time, so they must be adequate. I wonder if the u-bolts are supposed to be replaced every 5 years like the brass through hulls?

The cleat doesn't look so badly done though. It's placed in the area where the deck overlies the inward-turning flange of the hull, and (if there is a decent backing plate) that's a pretty strong point to attach to. Lots of boats use such a scheme for deck cleats.

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