Jeanneau structural grid construction... is it unique?

[ronstory]

Last weekend we when to a very wet and rainy Seattle boat show. We weren't planning on looking at any particular boat, but ended up spending the most time with the Jeanneau and Bavaria folks.

What intrigued me about the Jeanneau construction was the hull. Rather than the Beneteau styled glued in liner that is dropped in and hull and forms a second skin on top of that actual hull that hides the hull fiberglass from view, they had a liner with grid of structural ribs that formed boxes. They cut out the bottoms of the boxes during assembly and then glue in the rib/box matrix to the hull just like a liner.

However after the grid is glued and cured they then go back and layup fiberglass over where the grid contacts on the hull. That seems like the great compromise of ease of assembly but still have full inspection access of the actual hull.

Jeanneau only does this step on the boats 40 ft and larger. Does anyone know of any other builder that do this or is just unique feature of the larger Jeanneaus?

[Barra]

I got into a dispute with someone on here last year for pointing this technique out. They were adamant it was no longer being done on new jeanneau so what model were you looking at?

Seems like a superior approach to a glued liner for sure. Possibly on a par with a layed up grid. If they are still doing it not sure why they don't market it more but these days it's all about designed comfort not build quality for many.

[Tillsbury]

My Bavaria is somewhat like that - structural fibreglass grid glassed to the hull immediately after laying up the hull so there are no secondary bonds - not glued. All the spaces between the grids (i.e. Bilge areas and undersole storage) are the hull itself. I looked at a few boats with inner liners including Beneteaus and a Farr but surveyor and I agreed that everything was far too unknown and suspicious - not for me.

This is pre-GFC though, I don't know whether they are still like that.

[Marathon1150]

Our 1985 Beneteau uses something very similar to this. There is no skin but the structural components are bonded to the hull and between those components the exterior hull material is accessible. I'm not sure when Beneteau stopped doing this but I have seen "First" models made in 1990 that use a skin.

[ronstory]

Originally Posted by Barra

I got into a dispute with someone on here last year for pointing this technique out. They were adamant it was no longer being done on new jeanneau so what model were you looking at?

2020 Jeanneau 490 #73974, you could see the where they had glassed over the flange around the structural ridge. It looked really solid and the sales rep pointed out that unl fike aull liner, no water is getting under this "grid" liner.

Seems like a superior approach to a glued liner for sure. Possibly on a par with a layed up grid. If they are still doing it not sure why they don't market it more but these days it's all about designed comfort not build quality for many.

Yes, Agree. I would be making a big deal of the construction technique.

[ronstory]

I found a video of the Bavaria construction process from 2015.

https://www.youtube.com/watch?v=f5Et2R0oIJY

the liner install starts at 3:36.

The interesting thing was that the bavaria liner "butts" at a right angle and then they seem to glue/epoxy it the hull.

The Jeanneau had a grid with a right-angle 2" flange that formed a mating surface to the hull. Then they glassed over that flange with the hull.

I wish I had taken the time to take a pic.

[Tillsbury]

That's the same way it was done on my 2005. The grid goes on with thickened resin and the tabbing joins the two. Doing it immediately after laying up the hull makes the whole thing one lump of fibreglass.

I guess the actual tabbing method isn't important as long as it's strong. The point is that you can see if there's any cracking or structural damage to grid or hull, and repair it properly if necessary. On some boats I saw with liners there was cracking or obvious repairs to the liner, and it's absolutely impossible to tell what happened or if the repair was done properly, or if the hull or hull / liner join is intact.