Cleaning GRP decks (gently)...

MagicalArmchair

MagicalArmchair

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My much loved Albin Ballad is looking somewhat grubby on her decks. She has Poliglow on her hull (a polymer coat to make shiny again her chalky gelcoat, which incidentally I heartily recommend.), so anything too caustic will strip that right off.

Mostly its ingrained dirt into the GRP decks and into the non slip mouldings, as well as the occasional rust stain. What products and tools do you scrub, wash and then treat your decks with with the most success?
 
Ecover heavy duty boat wash and a domestic nylon-bristled scrubbing brush. As good as anything else I've used and makes me less concerned about sluicing heinous chemicals into the water.
 
I had to do this job the other day preparing a mates boat for sale, I used a strong solution of non bio detergent...Aldi as it happened to be handy, sloshed on and allowed to stand, scrubbed and rinsed off, difficult stains were attacked with cream cleaner, and rust streaks treated with oxalic acid solution, came up very well at very little cost.
 
I use the Starbrite product and am very pleased with it; it also came out tops in a test conducted in one of the monthly magazines. However, you will need an oxalic acid product for the rust, depending on what area you need to treat, either buy it and mix it yourself, or if for a small area, get some Y10 for convenience.
 
I have a non-slip pattern moulded into my decks, and I find that nothing works quite like a pressure washer, though a nailbrush and soapy water do pretty well too.
 
JumbleDuck said:
I have a non-slip pattern moulded into my decks, and I find that nothing works quite like a pressure washer, though a nailbrush and soapy water do pretty well too.
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.... nothing works as well as a pressure washer in knocking off tiny bits of GRP in moulded deck non-slip patterns: they are always resin-rich and hence brittle. They can also open up tiny just sub-surface air bubbles in the gelcoat if there are any. Also good at finding (maybe also creating) leaks.

Detergents and nylon scrubbing brushes are gentler, though harder work. And as others have said oxalic acid for rust marks.
 
Starbrite product is very good and also recommend it.

Don't make the mistake and buy the similar boatwash by starbrite.

If you do, top tip to save time in using it is to throw it straight in the bin at the chandlers and go to the pub. Decks will look the same but you'll feel better.
 
jwilson said:
.... nothing works as well as a pressure washer in knocking off tiny bits of GRP in moulded deck non-slip patterns: they are always resin-rich and hence brittle. They can also open up tiny just sub-surface air bubbles in the gelcoat if there are any. Also good at finding (maybe also creating) leaks.
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I haven't noticed anything like that, yet. Mind you, I have a fairly low powered pressure washer and use it with circumspection.
 
jwilson said:
.... nothing works as well as a pressure washer in knocking off tiny bits of GRP in moulded deck non-slip patterns: they are always resin-rich and hence brittle.
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I wonder what the pressure of a washer is against 80 kg of human pressing down throught 15 cm2 of sea boot?
 
JumbleDuck said:
I haven't noticed anything like that, yet. Mind you, I have a fairly low powered pressure washer and use it with circumspection.
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Camelia said:
I wonder what the pressure of a washer is against 80 kg of human pressing down throught 15 cm2 of sea boot?
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I too routinely use a pressure washer (small Karcher), and I've never noticed any problem with it removing bits of plastic. It works FAR better than a brush, and can get into areas that are inaccessible unless you want to use a toothbrush!

Karcher specify a pressure of 110 bar. 80 kg over 15 cm2 is 4.6 bar! So, there's no comparison. However, a breaking wave or slamming could easily exert much higher pressures.
 
AntarcticPilot said:
It works FAR better than a brush, and can get into areas that are inaccessible unless you want to use a toothbrush!
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Also great for removing bits of old sealant from around anything it's aimed at. Great for finding leaks which would have happened anyway sometime in the next few years. Not quite so good if you didn't want to find them just yet.
 
Camelia said:
I wonder what the pressure of a washer is against 80 kg of human pressing down throught 15 cm2 of sea boot?
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Vastly higher, if you get the nozzle really close up to shift an ingrained bit of dirt. Even with a low powered domestic PW at 100 bar the water can hit the deck at a pressure of well over a ton per square inch, big industrial ones much higher. I have seen several modernish boats with loads of tiny black speckles on deck and cockpit surfaces: pressure washer opened up many minute air bubbles in the resin, which then of course collect dirt. To small to fill, but big enough to show (and let moisture in).

It seems to be much more common on complex detailed-finish deck mouldings than on smooth hull surfaces, logical as these are much harder to get a perfect glass-resin mix on.

Plenty of people get away with pressure washing decks for years, some regret it though greatly.
 
laika said:
... Great for finding leaks which would have happened anyway sometime in the next few years. Not quite so good if you didn't want to find them just yet.
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jwilson said:
... Even with a low powered domestic PW at 100 bar the water can hit the deck at a pressure of well over a ton per square inch
Plenty of people get away with pressure washing decks for years, some regret it though greatly. ...
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So potentially great, if you're not careful, for creating leaks at windows or deck fittings that would not have existed before?
 
jwilson said:
Vastly higher, if you get the nozzle really close up to shift an ingrained bit of dirt. Even with a low powered domestic PW at 100 bar the water can hit the deck at a pressure of well over a ton per square inch, big industrial ones much higher.
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100 bar is 1450 psi and 1 ton is 2240 lb, so the absolute highest you could get in that case would be 0.65 tons per square inch. In practice it would be much, much less. 100 bar is the pressure across the nozzle, and when the water emerges it is, by definition, at 1 bar. Of course it's moving fast, and so you get some force from the momentum change when it hits anything, but bearing in mind nozzles losses and the spread out of the jet, I'd be quite surprised by anything over 20 bar (290 psi) on contact.
 
colind3782 said:
People have been using industrial pressure washers on their hulls for years
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Yes for hulls, mine is done every year by the yard on haulout, and again by me later to get the bits the yard miss - ie where the slings were. As I said earlier though the problems seem to come (if they do, and they sometimes do) on complex shape/finish deck/cockpit mouldings. I won't let a pressure washer up much past the waterline, and certainly not near windows, hatches or any teak.

If you doubt what water can do go to a water jet cutting firm: I watched them cut half inch thick steel with water, though the pressure was in the several thousands of bar.
 
jwilson said:
If you doubt what water can do go to a water jet cutting firm: I watched them cut half inch thick steel with water, though the pressure was in the several thousands of bar.
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Yes indeed. Pretty impressive stuff ... but quite a lot more than a domestic pressure washer will do!
 
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