Gel Coat fade on fiberglass boat?
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Category: Saltwater Fishing
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URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=102931
Printed Date: 27 May 2026 at 10:11am
Topic: Gel Coat fade on fiberglass boat?
Posted By: AlexTee
Subject: Gel Coat fade on fiberglass boat?
Date Posted: 06 Aug 2014 at 6:08am
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OK so im new to all this, I have a fiberglass boat which has gel coat fade. (From not being covered outdoors) Does anyone know how to repair this? Or would i have to get it clear coated at a paint shop? I was thinking it would just need to be cut and polished but i dont know what the effects of a cut and polish would do to a boat. Any products you guys would recommened? Or shops and prices? Thanks,Alex
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Replies:
Posted By: Steps
Date Posted: 06 Aug 2014 at 9:33am
Bad chalking off on gelcoats is generally due to rather a casual attitude to the proportions of resin and hardeners at the factory.... no different to modern 2 pot isocyanate car paints...
to much hardeners an u get Free harder in the product, not enough and get free unreacted resin...
A cut and polish.. works well, but this depends very much on the thickness of the gelcoat , be it how thick when laid up the moulds or how many times its already been cut... ideally u should have between a 18/1000" to 25/1000" thickness.
So assuming i have enough meat to work with, and real bad chalking....start with a coarse cutting compuond to cut MOST of the chalking off.. u may even consider something like a 600 grit wet sandpaper, then coarse cutting compound...
With the coarse paper compound dont take right down to now chalking.. just use these to fer most off , then cut polish as if it is only lightly chalked as per instructions on the gelcoat cutter polish u have purchased.
leave all edges outside cnrs till last, it is very easy to cut into (thin) these area a lot harder than flat areas.
Painting... well in my books a re paint, like cars, is when serious damage , repairs have taken place... or the gelcoat has already been cut back and u can see very easy right thru it over huge area. (which is basically damage)
if u get a co polymer floor polish, and wipe 2 to 4 layers over faded chalk areas that have been thoroughly cleaned down a nd dries (water blaster ) that will bring a semi shiny nom slippery surface back... this stuff require ammonia to strip off ... like floors, but on a boat that make a crappy job to do... this surface will wear. and discolour in a salt environment.....but if the surfaces are not walked on, a routine maintenance of a aerosol tyre shine and rag wipe brings up a nice finish
To remove other dis colouration , like browning of the bottom of the hull, phosphoric acid (rust kill) without epoxy etc additives... a 60/70% soln that diluted down to 5/6 %....then wiped on , left over night then water blasted off... then do the tyre shine... like brand new
About 70 to 100ml of the made up soln on a rag will do the full hull, bottom sides of a 5.5 to 6m hull.
Caution thu... any epoxy hull chip and minor repairs need to be replaced with gelcoat.. and any minor/ chips damage needs to be sealed before and tyre shine or polish is used.
A small dremel to clean out the chip and roughed surface, makeup the gelcoat... wipe into the damage, and before it sags, lay some masking tape tight over...u can then sand. the cut the area to blend in later....
Personally I dont bother with the finishing....I repair/ seal any damage as it may happen when home...then one day when bored will finish all of them off at the same time with the boat hanging high off a hoist
PS common sence.. "tyre shine" above is the clear stuff , not the black stuff.
"Work hard at being lazy" means quick regular maintance and u wil have an orginal 1970s/ 80s glass boat looking like it has just rolled off the factory floor.
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Posted By: Tagit
Date Posted: 06 Aug 2014 at 9:43am
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For a badly chalked hull I would start with 1200grit wet & dry sandpaper using plenty of water. Change the paper regularly as it wears. Use a cork sanding block on the flat surfaces. Only take off the worst of the chalk like this as the gelcoats are often thin and you can rub right through them. Use cutting compound on a cloth and then wax to finish the polishing. Be extra careful to only use cutting compound (no sandpaper) on all the edges and corners. This is where any previous polishing is most likely to have rubbed the gelcoat very thin. Once you have a bit of a shine, don't keep rubbing looking for 'perfection' or you might find yourself looking at the glass under the gelcoat. For chips and dings there is a product called Flowcoat which is easier for the amateur repairer than gelcoat as it does not need added waxes or air exclusion etc to harden. You can buy tints for flowcoat to match your hull colour, but it is a bit of an art to get it perfect.
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Posted By: fishz
Date Posted: 06 Aug 2014 at 10:55am
Have had good results in past with mould release wax used for polishing fibreglass moulds.
cheers Rodger
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Posted By: AlexTee
Date Posted: 06 Aug 2014 at 1:06pm
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Great info thanks for all the help guys, just to confirm is gelcoat the black strip that goes along the side of the boat? Its never had a cut & polish ever since it was brought (05 yes long story)
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Posted By: Tagit
Date Posted: 06 Aug 2014 at 2:26pm
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Gelcoat is the coloured outer layer of your fibreglass hull. It isn't painted. They lay gelcoat into the molds and then lay the fibreglass over it to build the boat. The gelcoat bonds to the fibreglass and looks like a paint finish. On most boats this is the white colour unless you have a multicoloured hull.
What part of your boat is actually 'chalky'?
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Posted By: Steps
Date Posted: 06 Aug 2014 at 2:59pm
Further to Tagits and my post above....
If one uses normal gelcoat that is used for inside moulds, and the surface is not sealed, it remains sticky and a ***** to sand back
As Tagit mentions , they add a styrene wax, which floats to the surface and seals the air off.... or using the masking tape, to stop sagging, and level the surface off a small repair does the same
The brand that seems most common on shop shelves is Norski.. I have noticed that if notn sealed it doesnt have a sticky surface, so assume it has styrene wax added... so it may not be suitable for laying up in a mould and backing with glass fiber and resin.
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Posted By: AlexTee
Date Posted: 06 Aug 2014 at 4:10pm
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http://www.trademe.co.nz/motors/boats-marine/motorboats/auction-537096818.htm" rel="nofollow - http://www.trademe.co.nz/motors/boats-marine/motorboats/auction-537096818.htm It is the black stripe on the side of the boat as seen on this boat. where the Haines Signature is displayed. ( Not actual boat but similiar
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Posted By: FizFisho
Date Posted: 06 Aug 2014 at 4:35pm
Most chandlers have the right products.
Ive cut n polished (not literal) a few of my boats over the years, i never bothered with the white, but the blue gel coat stripe on a haines 492f for example looks so much better when its shiny and richer in colour.
Best way to avoid it, maintenance. Thats the truely down side to owning a glass boat, its not park and forget after a trip.
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Posted By: AlexTee
Date Posted: 06 Aug 2014 at 5:33pm
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So all i would need is to cut and polish? do you have any products you could recommened?
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Posted By: skidoggg
Date Posted: 06 Aug 2014 at 5:51pm
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emergel for gelcoat polishing ...
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Posted By: Steps
Date Posted: 06 Aug 2014 at 6:02pm
Best way to avoid it, maintenance. Thats the truely down side to owning a glass boat, its not park and forget after a trip.
Interesting port of view.. thu never had a ally .. it notable there are far fewer older ones of those than 'glass
regardless thu, and this applies to everything .. maintenance is the essence to stuff being reliable and long lasting... what I describe above keeps a glass boat in good nick.. and it only takes a few minutes
Hell my lawn mower is 1950s reel mower, my daily driver for the last 30 odd yrs is near on 45 yrs old
The secret is maintenance.....and a little basic maintenance means "working hard at being lazy" I means dont need to fix things.. nor have the expense or waste time doing so.
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Posted By: AlexTee
Date Posted: 06 Aug 2014 at 7:32pm
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So all i need to do to get the shine back on the black stripe on my boat is to cut and polish with a normal car cut & polish compound or is there a marine one for the job?
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Posted By: Tagit
Date Posted: 06 Aug 2014 at 7:51pm
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Car stuff will do it if you have some. Some of the good quality marine ones are definitely better than the average car ones, but they will all work with a bit of effort.
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Posted By: AlexTee
Date Posted: 06 Aug 2014 at 7:53pm
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Thanks for clearing that up Tagit . Will get this done ASAP. Cheers
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