sanding and repainting little GRP boat. some help please????

[lucyboatgirl]

Hi lovely boaters

I am wanting to repaint my little 20foot grp boat. the last owner done a terrible job and the paint and the paint has half peeled off all over the place. The boat is not worth enough to buy specialist marine paint or anything so I'm thinking just sand her down a little and paint her.

I have never done this before and would be extremely grateful for any help or pointers.

I am thinking to sand her down medium grit then fine grit, then paint her with just weathershield paint or whatever from B and Q. Do you think this will stick? is there anything else you would recommend me using? What other advice would you give me in the prep? thank you thank you thank you 

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[Tony Brooks]

Its seems there was a lack of adhesion of the old paint so unless you address that the new paint is likely to fall off with the remaining old paint underneath it.

That lack of adhesion could be lack of keying (sanding), oil/grease not properly cleaned off, or silicon left on the surface from previous polishing. 

Personally I would try to remove the old paint (NOT WITH HEAT ON GRP!), the give it a wash of with panel wipe but make sure its the type that is supposed to remove silicon. The give it a good sanding with say 320 grit wet & dry, another wash off with panel wipe and when that has evaporated paint. You could do the first wash down with sugar soap solution to remove grease but I doubt it would touch silicon.

Happy to be overruled by a GRP boast painter.

[rusty69]

It may be worth trying to remove a bit of the old paint to see if you can clean /polish what is underneath, without re painting,although probably a bit of a long shot. 

[Murflynn]

I agree with Tony.  I think you can assume the gel coat is well and truly scratched and dulled, so use an electric sander (not the belt or rotary type - far too aggressive) with medium coarse (say 80or 120 grit) paper.  

I painted my yoghurt pot with Hempel Multicoat, no problems after 2 years.  Medium cost range and as it says on the tin it primes, undercoats and glosses, so one coat may be enough, but probably need two to get a good opaque covering.  I would avoid any paint where the tin says 'clean up with hot soapy water'; IMHO you need a proper oil based enamel where it says 'clean up with white spirit'.  

[lucyboatgirl]

Thanks so much for your help. Especially Murflynn!!! I have already sort of figured that the gel coat is never coming back to a good finish. the boat is thirty years old and has already had more than one coat of paint on it.

Thank you so much for your advise on sanding her and what paint to use. Exactly the information i was hoping for! But one more question, when sanding the old paint off am i in danger of doing any damage to the gel coat? What do i need to be worried about.

Thank you so much for your help

you are super helpful and kind

 

thank you 

thank you

thank you

x

[rusty69]

10 minutes ago, lucyboatgirl said:

But one more question, when sanding the old paint off am i in danger of doing any damage to the gel coat?

Unlikely unless you use really course paper or powerful sander. If the gel coat is a different colour to the old paint, you will see it come through when sanding. 

[Murflynn]

1 hour ago, rusty69 said:

Unlikely unless you use really course paper or powerful sander. If the gel coat is a different colour to the old paint, you will see it come through when sanding. 

agree.  

Use a mild sander (palm sander or vibrating pad) and keep it moving without too much pressure.  You should see the paint coming away in flakes, leaving a clean and smooth surface (the gel coat).  Taking 30 years of anti-fouling was a problem for me that the sander couldn't fix, but on the topsides the paint comes away leaving the much harder gel coat.  Unless you are very energetic, or use a drum or rotary sander, you won't do much damage to the gel coat except to abrade it slightly ready for over-painting.  Palm sanders are good up to a point for awkward areas, but the pads are pricey and the velcro system can get worn out so the pads fall off.  A simple sander like this has mechanical fixing and will do most of the work, using relatively cheap sandpaper that can be bought in rolls of the correct width.  http://www.ebay.co.uk/itm/BLACK-DECKER-135W-KA300-1-3-ELECTRIC-DETAIL-PALM-SANDER-ORBITAL-SANDING-PAD-/281834732653?epid=1705109470&hash=item419ea8bc6d:g:TOMAAOSwo0JWJ3fw

[dccruiser]

I totally refurbished a 27' dawncraft a few years ago including filling 108 holes in the hull (i counted them) where the rubbing strakes had been and the screws had rusted out... i used fibreglass to fill, a small detail sander and sanding blocks to key the hull then used Toplac to paint it and it came up like a new hull with a deep gloss white finish then used navy blue anti foul to just above the water line ... the topsides were covered in green moss and bought them back up to a good finish with scouring pads and the 20p a bottle cif type cream cleaner from the local supermarket ... did the canvas canopys with a scrubbing brush and washing powder and they too came out like new ... hope this helps

Rick

Edited July 26, 2017 by dccruiser

[Naughty Cal]

On 7/25/2017 at 19:43, rusty69 said:

It may be worth trying to remove a bit of the old paint to see if you can clean /polish what is underneath, without re painting,although probably a bit of a long shot. 

This^^^^^^^

We have seen several old boats stripped of paint and the gel coat underneath is actually in very good condition.

Worth a try.

[Murflynn]

that begs the question - why would anyone over-paint a gel coat that is in very good condition?

[Naughty Cal]

1 hour ago, Murflynn said:

that begs the question - why would anyone over-paint a gel coat that is in very good condition?

Because they are a bit thick.

Our neighbour has ruined his Norman by painting the superstructure.  All it needed was a wash!

[rusty69]

3 hours ago, Murflynn said:

that begs the question - why would anyone over-paint a gel coat that is in very good condition?

The topsides of our grp sailing boat looked like they needed painting when we first got it, cleaning and polishing did wonders. I guess the other reason to paint would be for a change of colour. 

Edited July 27, 2017 by rusty69

[cuthound]

1 hour ago, rusty69 said:

I guess the other reason to paint would be for a change of colour. 

Or that they particularly like rubbing down and painting... 

[lucyboatgirl]

thank you for all your help everyone. so happy we have a community who help each other out and share the knowledge to people who want to learn. so thank you everyone.

So looking to sand down the surface/abrade it for painting with a electric sander. then paint with hempel multicoat which i found here:

http://www.mbfg.co.uk/single-pack-topcoats/4112.html?gclid=EAIaIQobChMItYau44Ws1QIV7b_tCh0nZAfnEAQYASABEgLe1vD_BwE

But another question would be what would you clean down the sanded surface with before painting to remove grease and debris? Would just water do it or would you recommend something else?

Thanks for all your help x

 

[Tony Brooks]

As I said, that surface may still be contaminated by silicon so I would use panel wipe that is designed to remove silicon. By all means wash of first with water or sugar soap solution to get rid of dust and dirt but if using sugar soap make sure you rinse well with fresh water.

[lucyboatgirl]

thanks tony- you did say that i missed it. dont know what panel wipe is? just looking it up now. is there much of a difference between panel wipe and sugar soap????

thanks tony youve been mega helpful

 

x

[Mike Hurley]

When painting GRP or plastic car bumpers you should use an etching primer/plastic primer, otherwise the paint peels off as you have that problem now. Remove all traces of the old paint first. A local car body repair shop can show you what and how to use the primers.

[Tony Brooks]

No such primer was used when we (the painters - not me) painted GRP boats on the hire fleet but they were abraded well to give a key.

Panel wipe is spirit based. Sugar soap is some form of phosphate free soap. It can be bought in gallon cans from vehicle pint shop suppliers. About £15 and they may have smaller sizes.

[cuthound]

13 minutes ago, Tony Brooks said:

No such primer was used when we (the painters - not me) painted GRP boats on the hire fleet but they were abraded well to give a key.

Panel wipe is spirit based. Sugar soap is some form of phosphate free soap. It can be bought in gallon cans from vehicle pint shop suppliers. About £15 and they may have smaller sizes.

Halford also sell panel wipes at £1.49  fot 5. Might be easier to find a Halfords than a vehicle paint supplier.

http://www.halfords.com/motoring/paints-body-repair/fillers-preparation/halfords-paint-preparation-wipes-x5

[WotEver]

6 minutes ago, cuthound said:

Halford also sell panel wipes at £1.49  fot 5. Might be easier to find a Halfords than a vehicle paint supplier.

http://www.halfords.com/motoring/paints-body-repair/fillers-preparation/halfords-paint-preparation-wipes-x5

That's a well expensive way of doing it though when you can get 5l for £15 (okay, there's carriage on top of that). 

https://www.paints4trade.com/panel-wipe---5-litre-2296-p.asp?gclid=Cj0KCQjwwevLBRCGARIsAKnAJvcv-wRem-pmvri7b-OI6WYrHnPxXIam3-3F-LSBNDueTPSzRPprwW4aAs03EALw_wcB

If there's a local vehicle paint shop they'd probably sell you a litre for not very much if you took your own can/bottle. 

[Tony Brooks]

Probably wisely the OP does not seem to have given her location so we can not help direct her to a local suppler. If she feels able to give a very general area someone may be know a local supplier.

in Banbury there is such a place on the industrial estate between the main road and canal,  opposite the Morrison filling station.

[lucyboatgirl]

Thanks for so much help everyone. so i have got panel wipe and hempel multicoat which i think will be fine without a primer from reading about it as long as i make sure to abrade the surface before painting. but how do you recommend i do that? Going to sand it down with 100grit then what should i use to abrade it? a higher grit paper? how heavy do i want to go on it?

any advice greatly appreciated! I'm feeling quite confident about it now thanks to all your help. thank you x x x xx

[Murflynn]

if you sand the paint off with 100 grit you won't need to abrade it any further.

[W+T]

5 hours ago, lucyboatgirl said:

Thanks for so much help everyone. so i have got panel wipe and hempel multicoat which i think will be fine without a primer from reading about it as long as i make sure to abrade the surface before painting. but how do you recommend i do that? Going to sand it down with 100grit then what should i use to abrade it? a higher grit paper? how heavy do i want to go on it?

any advice greatly appreciated! I'm feeling quite confident about it now thanks to all your help. thank you x x x xx

Just sand away until all the paint in the area you are doing has gone, no further. Start lightly and if you feel confident add mor epressure but not so much as to strip it to fast, a bit slower then better control if it is come off easy.

And as Murf says it will be ok to paint after the 100 grit to prime.

 

I did all my 20 foot cruiser with a Makita palm sander and used 80grit. well a litlle with a cheap orbital sander but mainly the palm sander. 

 

Very therapeutic for the first 15spm then........OMG why did i start this lol

[lucyboatgirl]

Thanks murf and W+T, totally answered my questions. Thanks to everyone. This forum is such a great way to share knowledge and let people like me who dont know what they are doing learn and actually do things themselves. We need more of this in this world. Keep helping folks out you guys you have no idea how helpful it is to people like me who have the enthusiasm to learn but just need some guidance!!!

thank you thank you thank you!!!!

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