Hull construction

[Greg2]

The subject of resin infused sandwich hulls came up on Henryf’s Princess 55 new build thread and rather than drift his thread I thought it better to start a new one.

Our new build with work is a vacuum resin infused sandwich construction and the builders like it due to weight savings and strength. They build pilot boats that routinely operate in heavy weather and as they say their reputation depends entirely upon building a product that will do what they claim it will.

Noting JFM’s comments about solid lay-up below the waterline and sandwich above being the way to go got me wondering whether many builders of leisure boats have taken this route and whether there are known issues with such construction such as de-lamination or problems with repairs to damage.

We have recently looked at some offerings from Nimbus (used as opposed to new) who have been using resin infusion since 1997 but all the blurb I can find online only refers to vacuum resin infused sandwich construction and there is no mention of solid lay-up below the waterline. Anyone know about Nimbus and what they do with hull construction?
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[jfm]

...got me wondering whether many builders of leisure boats have taken this route and whether there are known issues with such construction such as de-lamination or problems with repairs to damage.
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Very many builders have taken this route - especially the higher quality builders. I would be questioning/avoiding builders who don't do it, because it is so much better.

Important not to confuse modern sandwich construction (which I love) with older stuff from 15 years ago (which can be quite worrying). Modern means vacuum infusion so there is no delamination risk, and CNC cut foam pieces.

 

[Hacker]

Nothing specific about Nimbus, but resin infusion is used to ensure full resin dispersion across the laid down mat and to use the pressure to ensure everything is “flat”. Can be used on both solid and cored sections, in effect its use is independent of the substrate. That is a function of desired strength v weight (and cost).

 

[Greg2]

Very many builders have taken this route - especially the higher quality builders. I would be questioning/avoiding builders who don't do it, because it is so much better.

Important not to confuse modern sandwich construction (which I love) with older stuff from 15 years ago (which can be quite worrying). Modern means vacuum infusion so there is no delamination risk, and CNC cut foam pieces.

Interesting. From what I can glean online Nimbus adopted ‘the energy-efficient sandwich hull and Divinycell application’ in 1985 and vacuum infusion in 1997. The only references to construction method I can find in advertising blurb relate to Vacuum-infused sandwich laminate with divinycel core, which doesn’t help with understanding the lay-up of the entire hull i.e. are they solid below the waterline.
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[NBs]

Hi,

I don't think any manufacturer (hopefully) makes the underwater part of the boat's hull a layer structure, aren't they always solid grp?

All the penetrations would be quite a risk of the core filling leaking through and getting wet, a small sloppy job, even if you use a pressure washer to clean the base and shoot the seal mass leakage. Another scenario that I wouldn't want the bottom of the snadwitsh would be to ground it to something hard like stone etc.

it would be a disaster to get the joint dry. Above the water, the triangular sandwich with vacuum filling is certainly quite good, especially in planing hull parts in boats, thanks to its lightness and stiffness.

There are a lot of Nimbus boats here and I haven't heard of any problems. I know one Beneteau Swift Trawler 42 with nasty extensive damage on one side, the whole side full of "spider's web" cracks, when the stuffing has flexed, when the boat is always parked on that side, but this is an exception.

In my trawler boat, I am more than satisfied with traditional solid grp where vinylester resin is used to prevent blisters + normal protection with epoxy primer paint in several layers. I once ungrounded its keel a little bit and it was easily repaired to new condition.
NBs

 

[jfm]

Hi,

I don't think any manufacturer (hopefully) makes the underwater part of the boat's hull a layer structure, aren't they always solid grp?

Several manufacturers have made cored bottoms in last couple of decades. Eg beneteau group, including their Prestige models, some of which were/are not vac bagged, and the bond between lower side of core and the outer skin of the hull was not good enough imho. I would choose to avoid these.

Fairline/Princess/Sunseeker/Sanlorenzo/Ferretti Group/many other good builders do not do cored bottoms, for the reasons I said on the other thread.

I mentioned compression loads in the other thread, and of course the other common compression load that I forgot to mention is sitting the boat on blocks when it is out of the water for maintenance. Another reason to avoid cored bottoms imho.

 

[Galey]

I’m looking for the oil recommended for Vosper mini fins. I don’t have the Manuel, and have a new boat with these installed. Many thanks ……Gale

 

[Petterml]

I would like to know more about the transparent gelcoat Princess uses under their boats, below the waterline. What advantages does it have? I noticed that the field in the bow between the sandwich and the hull below, where the stair strips end, is often somewhat uneven with a slightly poorer visual quality than the gelcoat that is on the sandwich, what causes this? Why does not Princess manage the same finish as the sandwich part here? I myself have a V39 where this is the case.

 

[Greg2]

I would like to know more about the transparent gelcoat Princess uses under their boats, below the waterline. What advantages does it have?

The builder doing our new boat at work also uses clear gelcoat below the waterline - I know one reason is that they can see that the lay-up is okay with no voids and if there are any then they can be fixed.
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[Portofino]

Ferretti group vac bag with transparent material on everything .None cored bottoms for the reasons JFM outlined .
The reason why they use transparent material , in other words ditch the gel coat colouring i was told was because despite best practice / techniques/ materials there’s always areas of un cured or incorrectly cured material .
If it’s colour gel coated you don’t see it or even with some sort of quality control when the thing comes out of the mould it gets missed .
Where as with transparent , what you see on the Princess bottom defects can be picked up and rectified.I was told they find them in every lay up btw .That’s a bit worrying for those folk imho who are buying vac bagged gel coloured coated hulls .

Then they spray paint them .Yup Itama blue and even Ferretti beige along with the bigger CRN s Pershings .
Its also BTW you can have any colour of hull for minimal cost = just supply a RAL number .
They have ( whole FG range ) been doing this since circa 2015 ish to nail down quality control .Not just the below the WL the whole boat hull+ topsides .

Think about vac bagging , are defects just geographically limited to below the WL ? Why not use transparent in evey vac bag item ?
FG do .

 

[Petterml]

Ok, good to know. Is the gelcoat stronger without colour? transoaren gc sounds like an advantage, why don't princess use this in marketing?

 

[Portofino]

The builder doing our new boat at work also uses clear gelcoat below the waterline - I know one reason is that they can see that the lay-up is okay with no voids and if there are any then they can be fixed.
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And identify defects above the WL in gel coat…….how’s he do that ?

 

[Portofino]

I would like to know more about the transparent gelcoat Princess uses under their boats, below the waterline. What advantages does it have? I noticed that the field in the bow between the sandwich and the hull below, where the stair strips end, is often somewhat uneven with a slightly poorer visual quality than the gelcoat that is on the sandwich, what causes this? Why does not Princess manage the same finish as the sandwich part here? I myself have a V39 where this is the case.

When it’s popped out the mould it will be super smooth on its surface all over assuming the mould was equally smooth .
Doesn’t matter what colour gel coat was used transparent or partially coloured .

If your boat looks markedly uneven in a area then assume it been redone , started transparent a defect was rightfully corrected , fixed but unfortunately the resulting final finish not up the same smoothness of the original mould smooth finish .

Or the moulds rough in that area , no additional quality control re finishing was carried out it’s just a coincidence where it is .
Moulds are expensive and have a life and do ever so slightly deteriorate with each time used and usage .You do see some real shockers still about new boats with ripples down the hull sides .
On the other hand you see hulls dead straight looking as if they are hewn out of solid granite .

The marque , size and price in my recent experience at shows has zero bearing on the hull visual quality.
Some builders can do it ( build then dead straight + smooth ) others are so so .
Worth looking out for at the next show or dock walking .

 

[Greg2]

And identify defects above the WL in gel coat…….how’s he do that ?

Perhaps more of an issue with the solid lay-up below the waterline?

 

[jfm]

Ferretti group vac bag with transparent material on everything .None cored bottoms for the reasons JFM outlined .
The reason why they use transparent material , in other words ditch the gel coat colouring i was told was because despite best practice / techniques/ materials there’s always areas of un cured or incorrectly cured material .
If it’s colour gel coated you don’t see it or even with some sort of quality control when the thing comes out of the mould it gets missed .
Where as with transparent , what you see on the Princess bottom defects can be picked up and rectified.I was told they find them in every lay up btw .That’s a bit worrying for those folk imho who are buying vac bagged gel coloured coated hulls .

Then they spray paint them .Yup Itama blue and even Ferretti beige along with the bigger CRN s Pershings .
Its also BTW you can have any colour of hull for minimal cost = just supply a RAL number .
They have ( whole FG range ) been doing this since circa 2015 ish to nail down quality control .Not just the below the WL the whole boat hull+ topsides .

Think about vac bagging , are defects just geographically limited to below the WL ? Why not use transparent in evey vac bag item ?
FG do .

That’s all 100% incorrect. You have posted this many times over the years, been corrected, yet you continue to repeat it. Quite odd really.

The finish on ferretti (the typical off white, and the bright white on some recent models) is gel coat. Not paint.

In the current range of Rivas, invariably silver of course, it is paint over white gel coat. The occasional big white (or partially white) Riva from the Argo/Corsaro/Dolce Vita series is white paint over white gel coat.

 

[Portofino]

That’s all 100% incorrect. You have posted this many times over the years, been corrected, yet you continue to repeat it. Quite odd really.

The finish on ferretti (the typical off white, and the bright white on some recent models) is gel coat. Not paint.

In the current range of Rivas, invariably silver of course, it is paint over white gel coat. The occasional big white (or partially white) Riva from the Argo/Corsaro/Dolce Vita series is white paint over white gel coat.

Nobody’s actually corrected me fwiw .

It’s what I was told by a few FG guys at one of the Monaco yacht shows .The 2019 one to be exact .
This is an invitation only show and you get a lot more time on the boats inc a wet raids out .A brand ambassador for the day very knowledgeable too .Mine is usually Italian from the Roma franchise , but I have the same conversations with the London dealer too ( being Eg tongued );

You meet dealers as well from all round the globe .This is in addition to your sales reps .

Even the Ferretti beige never mind the Itama blue and all the recent ish Pershing colours .Indeed I was challenged to “ test “ them and honestly you couldn’t tell they were painted .Well I couldn’t.
Paint tech for boats has exponentially improved the last decade .
As I said it’s driven mainly from a quality control of the vac bagging issue of detecting defects .

What you suggesting do them white and then paint over them makes no sense , why not do them transparent? If you a gonna go to the trouble of painting over

FG group also set up a separate tech / NVH centre and it feed innovation’s quality improvement’s across the ranges and sites .This transparent gelcoat for vac bagging and paint after defect correction hubs out of that .Along with many other behind the scene stuff to drive up quality.

As Greg has pointed out and the guy with the Princess , pics transparent gel coat with a paint job is the way to go if you vac bag .Good of Princess imho btw .

I distinctly remember how it entered the conversation…….I was helming a trad blue Itama 62 and when back at the dock I enquired about a “ white “ one from the previous years show ( actually not white a kinda cream ) and conscious of a recent F1 connected guy taking delivery of a red rosso Corsa 62 .Basically Itama we’re coming out all sorts of colours instead of trad blue and Pershing getting more adventurous colour wise . Against this conversation I asked how much for a gel coat colour change ? Thinking it pretty easy to sub out the gel coat for any other at the buyers request.

Only to be told “ they are all painted “ no coloured gel coat just give us a RAL number .

The knowledgable guy waving his arms around the dock “ they are all painted “
Even Ferretti beige I did specifically ask as then two forum members then had beige Ferretti and it’s a signature colour .
So off we trotted ( dog in hand ) on to a Ferretti for me to tap my finger nails , rub my hand , stroke the finish beige only to be told it was all paint !
BTW there Pershings we’re all colours .

I think the CRN s are painted too btw an equivalent to your new SL in build .So I can see why you are pushing back on a rivals transparent gel coating vac bagging .

Maybe SL Vac bag differently ? Get better results than Gregs manufacturer , Princess and every FG brand .Just saying why they use transparent and reporting on FG s usage .Make of it what you will . But knowing the reasons why some manufacturers have started to use transparent gel with vac bagging I would want to know why your manufacturer isn’t doing that ? Or turned around why Princess , Greg’s builder and FG have adopted it ?

But I got it from the horses mouth .

Everything you see below is paint over transparent gel coat .

 

[Portofino]

Ok vid here .Could be any of the FG brands .
You can see a Pershing in grey primer moved about , not the unfinished top sides decking ares not primed when it’s moved to the paint booth .
Also note the end 1/3 where they spray he whole lot , well the visible bits to customers spec colour .
Note the metal 140 at some point so they know there onions re paint theses days.Remember all metal boats are painted
you can glimpse unpainted interior , clear insides of plastic the hull s well in the vid .
Agreed it doesn’t show a transparent one popping out of the mould , but the gray / white beliw the WL has been through the quality control and basically primed.
They make all there plastic boats this way nowadays.

 

[jfm]

I've corrected you many times. You may have been told this by some yacht sales folks who (evidently) don't know tons about yacht building, but that doesn't make it right.

I don't want a long drawn out debate, but this forum is quite a decent source of yacht information, so when someone (mainly you) posts something that is 180 degree incorrect, it's useful (imho) for it to be corrected. I'm also not trying to "push back on a rival" - I didn't have to buy a Sanlorenzo and could have easily bought the same size Ferretti if I thought they made better hulls (and saved €1.5million in the process).

I have been to these factories; you haven't. I have also looked closely at these boats, as you have too (at yacht shows). You amusingly state that you couldn't tell they were painted - the reason is that they weren't .

Two pictures below:

• The first is a Riva Argo 28m hull arriving at the La Spezia factory (which I have been to) by barge from Ferretti's moulding factory. I think we can agree that if this yacht is to be painted (which it is, in silver) it hasn't been painted at the time of this picture. It has white, not clear, gelcoat.
• The second picture is Ferretti Custom Line at the FG factory in Ancona. I hope you can also agree that at this stage of build, the yachts on the left would not yet have been painted if it were going to be painted - it doesn't even have the exhaust duct pod attached to its hull yet. White gelcoat, not clear, and as you will see it is highly polished because it is the finished surface.

So it's just not correct that all FG hulls are made in clear gelcoat then painted. These pictures are not wrong.

 

[jfm]

Ok vid here .Could be any of the FG brands .
You can see a Pershing in grey primer moved about , not the unfinished top sides decking ares not primed when it’s moved to the paint booth .
Also note the end 1/3 where they spray he whole lot , well the visible bits to customers spec colour .
Note the metal 140 at some point so they know there onions re paint theses days.Remember all metal boats are painted
you can glimpse unpainted interior , clear insides of plastic the hull s well in the vid .
Agreed it doesn’t show a transparent one popping out of the mould , but the gray / white beliw the WL has been through the quality control and basically primed.
They make all there plastic boats this way nowadays.

Not sure why you're posting that. Nothing in that video shows clear gelcoat across the FG range, which is unsurprising because the video covers only high end Pershings, which have plenty of carbon and epoxy resin elements, and are always painted, usually silver but sometimes painted white (as you know). But your "Everything you see below is paint over transparent gel coat" statement in #16 remains incorrect, as my photos above prove.

 

[jfm]

Remember all metal boats are painted

Thanks for reminding me - yeah I nearly forgot that. Lucky to have you here

(Team Dashew and plenty of others would disagree, but that's neither here nor there)