Black spots all over boat in marina; do I have any recourse? How to clean?

[Sailorbob8599]

Originally Posted by Pete7

Do you have something called "Traffic Film Remover" in the US. Its what the truckers use to clean lorries. The big advantage is that its cheap, £10 for 5 litres of concentrate and it goes a long way. Using a soft brush it cleans all the normal city dust and muck that collects on the deck. It can be used need but gloves recommended because it will strip oils from skin. Also does a good job on the purple bird poo we have problems with at this time of year when they eat blackberries.

Pete

LORRIES ???

[Uncle Bob]

Originally Posted by Sailorbob8599

LORRIES ???

Yeah, dem big fings wit lotsa wheels wot carry tons of crap.

[Wotname]

And driven by a lorry driver .

[Sailorbob8599]

Originally Posted by Uncle Bob

Yeah, dem big fings wit lotsa wheels wot carry tons of crap.

WOW! you sound like my English buddy. I had almost forgotten they refer to trucks by that strange term.

[SVTatia]

Originally Posted by Uncle Bob

Yeah, dem big fings wit lotsa wheels wot carry tons of crap.

Not only zat, some even carry a derrick!!!

[Nicholson58]

Originally Posted by Sailorbob8599

LORRIES ???

That was his girlfriend’s name

[David M]

My first guess is mildew. SoftScrub with bleach and a little elbow grease with a soft deck brush will remove it...and SoftScrub will not damage the gel coat. Coarse deck brushes do put micro scratches in the gel coat. Soft scrub removes all kinds of nasties, not just mildew.

Try that before getting upset with the marina management.

[model 10]

[QUOTE=JPA Cate;. Do not attack it with rubbing compound. Gelcoat is actually little bubbles, and the compound will cut the tops off, leaving voids for filth to accumulate in, and the only repair for that is re-gelcoating.

I think you are confused on that point. Micro ballons, to which you refer, are not standard in Gel Coat. Gel is often sprayed and buffed.

[Montanan]

Originally Posted by JPA Cate;.

Do not attack it with rubbing compound. Gelcoat is actually little bubbles, and the compound will cut the tops off, leaving voids for filth to accumulate in, and the only repair for that is re-gelcoating.

I think you are confused on that point. Micro ballons, to which you refer, are not standard in Gel Coat. Gel is often sprayed and buffed.

Agreed, microballons are typically used as filler in resins to thicken the viscosity and extend and / or reduce the weight of the resins but I have not seen them used in the Gelcoat that is the presented / visible side of the component. The Gelcoat layer is thin so one needs to sand it lightly, such as 1,000 grit paper to rub out surface stains, penetrating stains require removal and then recoat of a Gelcoating.

Gelcoat or 'Gel Coat' is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite. The most common gelcoats are thermosetting polymers based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state. They are cured to form crosslinked polymers and are subsequently backed with thermoset polymer matrix composites which are often mixtures of polyester resin and fiberglass, or epoxy resin which is most commonly used with carbon fibre for higher specific strength.

The manufactured component, when sufficiently cured and removed from the mould, presents the gelcoated surface. This is usually pigmented to provide a coloured, glossy surface which improves the aesthetic appearance of the article, such as the surface of a boat hull.

Many marine craft and some aircraft are manufactured using composite materials with an outer layer of gelcoat, typically 0.5 mm to 0.8 mm (0.02 in to 0.03 in) thick. Gelcoats are designed to be durable, providing resistance to ultraviolet degradation and hydrolysis.

Specialized gelcoats can be used to manufacture the moulds which in turn are used to manufacture components. These require very high levels of durability to overcome the mechanical and thermal stresses encountered during the curing and demoulding processes.

Suitable resin chemistries for the manufacture of gelcoats vary, but the most commonly encountered are unsaturated polyesters or epoxies. Within each of these categories, the resin chemistries are further subdivided.

In addition to any pigment a gelcoat will, if necessary, contain a thixotropic additive to assist its tenacity to vertical portions of the mould whilst it cures.

[Uncle Bob]

Originally Posted by JPA Cate;.

Do not attack it with rubbing compound. Gelcoat is actually little bubbles, and the compound will cut the tops off, leaving voids for filth to accumulate in, and the only repair for that is re-gelcoating.

I think you are confused on that point. Micro ballons, to which you refer, are not standard in Gel Coat. Gel is often sprayed and buffed.

Ann is I believe demonstrating a level of experience that some obviously just don't have. Many fibreglass products mass manufactured have an impeccable initial finish that when sanded later in life reveal small irregularities within the surface resembling bubbles, which as she said, leave small voids that collect residue. Most that have dealt with this, wish that sanding or even coarse compounding hadn't been done.

[a64pilot]

Originally Posted by JPA Cate;.

Do not attack it with rubbing compound. Gelcoat is actually little bubbles, and the compound will cut the tops off, leaving voids for filth to accumulate in, and the only repair for that is re-gelcoating.

I think you are confused on that point. Micro ballons, to which you refer, are not standard in Gel Coat. Gel is often sprayed and buffed.

Nothing at all to do with microballons, however Gel coat is a lot like paint, in that it’s a porous material with a shiny surface, once you get through that surface, your into the porous part.
Ever had an old car that if you waxed it, it looked new, but in a couple of weeks it would be dull again?

However Gel coat is like that old car, once oxidized, your most likely buffing and waxing to make it shiny again.

[john61ct]

> Gelcoat or 'Gel Coat' is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite. The most common gelcoats are thermosetting polymers based on epoxy or unsaturated polyester resin

Just post a link to wiki, no need to copy paste in bulk. Also helps for us to know the source

[Kenomac]

Fallout from large ships in the area which burn bunker oil. Common in large harbors like Los Angeles. Soap and water should get it off.

[Montanan]

So as to avail the forum members a visual understanding of what composite layering looks like, please find provided below scanning electron microscope images of cross sectional views of laminate composites made with two different fiber reinforcing fabrics, The layer below the white arrow in each of the cross sectional images is the Gelcoat layer. The layer on the bottom is just a portion of the cross section of the supporting mold structure. The tip of the arrow indicates the boundary between the Gelcoat layer and the infusion resin. Note that the gelcoat is very solid [does not have discernible voids] and the Gelcoat layer has made an excellent bonding with the infusion resin, again with out any air gaps. The white circles and streaks on the upper part of the images are the fiber reinforcement filaments. These images reveal excellent layup. Ordinary production processing tends to have some voids / air gaps, not many if the work is done correctly to draw out the gases. The scale is denoted on each of the images, the image on the right is a closeup rendering of a portion of the image on the left. FYI, the diameter of a human hair is about 50 micrometers. 1000 grit sandpaper has particles averaging a diameter 10.3 micrometers, so when you lightly buff out a truly smooth surface with microgrit paper you are actually imposing smalls gouges leaving a bit of a comparatively hazy, non-lustrous surface.

[Uncle Bob]

Originally Posted by Montanan

So as to avail the forum members a visual understanding of what composite layering looks like, please find provided below scanning electron microscope images of cross sectional views of laminate composites made with two different fiber reinforcing fabrics, The layer below the white arrow in each of the cross sectional images is the Gelcoat layer. The layer on the bottom is just a portion of the cross section of the supporting mold structure. The tip of the arrow indicates the boundary between the Gelcoat layer and the infusion resin. Note that the gelcoat is very solid [does not have discernible voids] and the Gelcoat layer has made an excellent bonding with the infusion resin, again with out any air gaps. The white circles and streaks on the upper part of the images are the fiber reinforcement filaments. These images reveal excellent layup. Ordinary production processing tends to have some voids / air gaps, not many if the work is done correctly to draw out the gases. The scale is denoted on each of the images, the image on the right is a closeup rendering of a portion of the image on the left. FYI, the diameter of a human hair is about 50 micrometers. 1000 grit sandpaper has particles averaging a diameter 10.3 micrometers, so when you lightly buff out a truly smooth surface with microgrit paper you are actually imposing smalls gouges leaving a bit of a comparatively hazy, non-lustrous surface.

Your search pics of glass structure doesn't change the fact that many gelcoat finishes when heavily buffed or sanded leave a surface that is imperfect and appears to have minuscule pits that appear to be tiny bubbles that have been sanded or buffed open. This is the experience of many that have tried to improve aged gelcoat. I can only guess that you have never encountered this.
This is not to be confused with the scratching that can be experienced from poor sanding technique.