Have Boats Ever Been Built With Clear Gell Coat (or none) Below The Water Line?

[Deleted member 36384]

Have Boats Ever Been Built With Clear Gel Coat (or none) Below The Water Line?

I was looking at a yacht in my marina and she had bits of the antifoul cleaned off down to the GRP from below to over the boot top/waterline. There was a definitive line about 12" below the water line where the blue coloured gel coat just stopped. The remainder of the underwater part of the hull that I could see (where the antifouling had been cleaned away) was translucent resin. There was no edge between the resin and blue gel coat line, perfectly smooth transition and straight as you like on the curve of hull. It looked as if it had been moulded that way. The owner is adamant that the yacht has never been epoxy coated below the water line. Perhaps it's an old repair to the hull. Anyway, I was wondering if hulls used to be laid up with a clear gel coat or no gel coat below the water line. The yacht is an MAB from the pre 1980s. I am just curious.

 

[earlybird]

My She31 was laid up with clear resin below the water line. South Hants Eng had a reputation for high build quality.

 

[michael_w]

Yes. Lack of pigment in the gel coat helps increase resistance to osmosis. 12" below the waterline seems a bit odd.

 

[Sailingsaves]

I do not know but what a great idea you have given me and maybe others.

You can purchase nanoparticles (so called but not really nano sized) that give off multitudes off different colours depending upon angle of incident light = mix particles into resin or even paint and get yourself a shiny, colour changing boat. Now all we need is a colour that weed and barnacles don't like.

Do barnacles have eyes?

 

[prv]

Yep, KS is clear resin, with pigmented gelcoat above the waterline and clear below. When you scrape back the antifoul you can see the glass in the structure. The surveyor said this is useful to spot any very early signs of osmosis, that would be invisible in a white (or other coloured) layup..

PEte

 

[Deleted member 36384]

Thanks folks, something new learned today. Michael - the 12" is just a rough estimate, it was last month, perhaps the boot top has crept up on the boat as well over time. Interesting point Pete about the glass structure being visible. I know from some books that wicking looks like white strands in the resin. Is a fully saturated glass cloth with resin clear/opaque?

 

[Sailingsaves]

Yep, KS is clear resin, with pigmented gelcoat above the waterline and clear below. When you scrape back the antifoul you can see the glass in the structure. The surveyor said this is useful to spot any very early signs of osmosis, that would be invisible in a white (or other coloured) layup..

PEte

I believe this forum may be the most useful, educational and full to capacity of clever people type of thing I have ever come across = it is like the sailing club except instead of just the one or two clever people around this place abounds with clever people = I have learnt so much in just an hour it is better than any university I would imagine = I certainly regret going = wish I'd done an apprenticeship in something or other.

 

[Tranona]

Very common in that period as a reaction to fears of osmosis started to grow. Was considered a selling point for some builders. Not sure whether there is any empirical evidence that the process was effective. Improvements in resins and processes seem to have improved moulding quality and resistance to osmosis.

 

[stevebrassett]

There was an article in Yachts and Yachting many years ago about someone who had a new (National 18 I think) dinghy built, and he specified that it should be clear. That way any defects in the layup would be visible. When he collected it, they told him "That's a good boat - it was a right b*gg*r doing it clear".

 

[upcountry2]

All Trident Warrior 40's were built this way,very substantial boat, never heard of one with Osmosis, so perhaps it does prevent the onset of blistering...

 

[sarabande]

there was a racing mobo, called Tramontana, owned by Emil Savundra, which had no external pigmentation. From a distance, she looked pale taupe. Close up you could see the CSM.

 

[PlankWalker]

The early Rustler 36 hulls were moulded with clear gell coat below the water line, don't know about the later ones.

Plank

 

[Nigel_Ward]

Years ago I worked for the White Fish Authority.

Any GRP fishing boats built to their rules had to have clear gelcoat under the waterline.

One of our surveyors showed me why. When the mould is released you can see any moulding faults or shoddy workmanship straight away. If ther were any major faults the moulding would be rejected.

 

[johnalison]

When we went to the plant to see our Mystere built in 1973 at Fairways Marine they were building Fishers with clear gel below the waterline.

I think modern resins and widespread use of epoxy before antifouling have made the practice less important.

 

[[3889]]

From the P&H Kayaks website:
"Clear Hull
Both the kevlar carbon constructions can be made with a clear gel coat on the hull, allowing you to see the kevlar carbon underneath. This option shaves around 2lbs (2 LBS/3/4 KG) Depending on model. off a kevlar Carbon or Lightweight Kevlar Carbon construction and is perfect for those looking for a really light kayak. Some durability and stiffness is lost compared to a heavier construction due to the reduction in materials used and we recommend a keel strip is used with this option."

 

[billmacfarlane]

Some(or all) Sadlers were made with clear gelcoat below the waterline. My old 29 was certainly had it.

 

[Amulet]

Racing motor boat pleasingly called "Translucent" about 1969. Renamed "Nauti-Ford" I think later.

 

[charles_reed]

Yes. Lack of pigment in the gel coat helps increase resistance to osmosis. 12" below the waterline seems a bit odd.

Of course, as is common with cruising boats, the waterline may have risen from the design marks.

 

[DJE]

Some(or all) Sadlers were made with clear gelcoat below the waterline. My old 29 was certainly had it.

So does mine.

 

[greenalien]

In the late 1960's / early 1970s, while GRP technology was still relatively new, there was a 'rash' (sorry, bad pun...) of boats with osmosis. Part of the answer was to remove all filler and pigmentation in the below-waterline gelcoat and lay-up resin; also a new type of resin calles 'Isophthalic' came into use at this time, which helped to reduce the problem.
Tyler Yachts were another UK manufacturer whose mouldings are clear below the waterline.