Fibreglass roof, does it need repainting?

[LoganHarrow]

Hi,

 

I live on a 1976 Dartline 45ft narrowboat, and the roof is made of fibreglass. There are areas on the roof where the paint is cracking and exposing the fibreglass.

 

does this need to be repainted ASAP or is fibreglass durable enough to withstand being slightly exposed?

 

any advice would be grand.

 

Logan

[Tonka]

10 minutes ago, LoganHarrow said:

Hi,

 

I live on a 1976 Dartline 45ft narrowboat, and the roof is made of fibreglass. There are areas on the roof where the paint is cracking and exposing the fibreglass.

 

does this need to be repainted ASAP or is fibreglass durable enough to withstand being slightly exposed?

 

any advice would be grand.

 

Logan

Once you start painting fibreglass you have a job for life. Can you take a photo of the bit as it may just need a bit of gel coat or some form of filler 

[LoganHarrow]

[LoganHarrow]

[Mad Harold]

My last grp boat had lots of "spider cracks on the roof.Sanded and applied gel coat filler and re sanded (a long job because the filler I bought set like concrete!)

Yours looks worse than mine was  so I suggest the same treatment.

I would use a power sander on the gel coat filler otherwise you will be sanding untill the cows come home.😄

[BEngo]

That looks to be typical paint separating itself from the GRP underneath.  It won't  come to harm in the short term, but will get worse. 

 

Either sand to feather the edges to the light blue layer ( which I think is the GRP gel coat)  and touch in with primer, undercoats and top coats or sand it all down well and repaint.  Be gentle.  You do not want to expose the glass in the GRP. Get paint that is suited to use on GRP.

 

N

[LoganHarrow]

Thanks, I’ll look into that. What would happen if I left it though? Would the fibreglass get damaged?

[LoganHarrow]

3 minutes ago, BEngo said:

That looks to be typical paint separating itself from the GRP underneath.  It won't  come to harm in the short term, but will get worse. 

 

Either sand to feather the edges to the light blue layer ( which I think is the GRP gel coat)  and touch in with primer, undercoats and top coats or sand it all down well and repaint.  Be gentle.  You do not want to expose the glass in the GRP. Get paint that is suited to use on GRP.

 

N

Thanks 👍🏻 

[rusty69]

Someone I know applied flowcoat over a cracked fibreglass roof as a repair for a leaky roof. 

 

I wonder if that is what has happened in this case. 

Edited July 23, 2023 by rusty69

[Tony Brooks]

I think the gel coat is badly crazed where the pain has lifted off, so i expect the rest will be similar. I would get all the old paint off anfddo what Mad Harrold suggests.

[LoganHarrow]

3 minutes ago, Tony Brooks said:

I think the gel coat is badly crazed where the pain has lifted off, so i expect the rest will be similar. I would get all the old paint off anfddo what Mad Harrold suggests.

Thanks, I’ll look into it

[Tony Brooks]

3 minutes ago, LoganHarrow said:

Thanks, I’ll look into it

 

There is a paint stripper designed for use on GRP, but it is expensive. There is a topic where Alan talked about it somewhere on the forum.

[rusty69]

22 minutes ago, LoganHarrow said:

Thanks, I’ll look into that. What would happen if I left it though? Would the fibreglass get damaged?

It depends if those cracks you can see go right the way through. Does it leak? 

[Tonka]

9 minutes ago, Tony Brooks said:

 

There is a paint stripper designed for use on GRP, but it is expensive. There is a topic where Alan talked about it somewhere on the forum.

Peelaway but cannot remember which number

[Alan de Enfield]

11 minutes ago, Tony Brooks said:

 

There is a paint stripper designed for use on GRP, but it is expensive. There is a topic where Alan talked about it somewhere on the forum.

 

Most paint stripper will attack and weaken fibreglass)

 

There are very few brands that are 'safe' to use with GRP - see below for the one I used'

 

Paint it on thickly - cover it with the supplied polythene sheets, wait a few hours and peel the sheet off. It will take up to 10 coats of paint off at a time.

 

I have some videos of peeling it off but the forum will not accept the format, so just a screen shot.

 

 

 

Edited July 23, 2023 by Alan de Enfield

[LoganHarrow]

21 minutes ago, rusty69 said:

It depends if those cracks you can see go right the way through. Does it leak? 

It doesn’t leak, I get the odd drip through condensation but nothing bad like a proper leak

[rusty69]

10 minutes ago, LoganHarrow said:

It doesn’t leak, I get the odd drip through condensation but nothing bad like a proper leak

That's good. 

 

My main concern is if water gets in and it freezes. 

 

I would want to be certain that is paint you are looking at, and not painted flowcoat (topcoat) before proceeding with an action plan. 

 

May be worth contacting someone like eastcoast fibreglass supplies for advice. 

[Francis Herne]

[EDITED slightly] If the fibreglass is made using epoxy resin, will be damaged by the UV from sunlight if not protected. This will reduce its strength by up to 30% and possibly cause surface crazing.

 

[as rusty69 points out it could well be polyester without the same issue]

 

It looks like under the peeling top coating there's another pigmented layer (maybe the original gelcoat) which should be ok, but if any patches are scraped back to the underlying clear/brownish fibreglass you should cover those with something fairly promptly.

Edited July 23, 2023 by Francis Herne

[rusty69]

1 minute ago, Francis Herne said:

The epoxy resin in fibreglass will be damaged by UV from the sun if not protected. This will reduce its strength by up to 30% and possibly cause surface crazing

Whilst that is true, there is a high probability that it will be polyester based resin, not epoxy. 

[Francis Herne]

10 minutes ago, rusty69 said:

Whilst that is true, there is a high probability that it will be polyester based resin, not epoxy. 

You're quite right.  I was thinking in terms of epoxy by default because of my own experience with canoes where it's much more common - particularly stitch-and-tape ones because epoxy adheres to wood far better than polyester.  On something like this, now you point it out, I agree it's almost certainly polyester.

[Mike Hurley]

If you sand it back to bare fibreglass/gel coat i think you use an etch primer for the new paint to bond to, same as when painting aluminium. Thats what we did a million years ago when i painted cars/trucks.

[Bargebuilder]

Some years ago I had a grp cruiser with decks that looked very similar to those of the OP, with flaking layers of paint accumulated over many years of previous ownerships. I carefully removed 98% of the old coating with a polycarbide disc on a cordless angle grinder. These discs can be aggressive, so a light touch is needed, but the process is actually quite quick. After much research, I repainted the deck with Zinsser Allcoat, a water based paint that is often used on uPVC. It rolls or brushes on very quickly and easily with a matt or silk finish as desired and sticks phenomenally well to plastics. After three years there has been no cracking or flaking and the colour is pretty much as rich as it was on the day I applied the paint. 

 

Yes, once painted grp will need to be refreshed with another coat every few years, but I have been very impressed with the Zinsser product and expect it to last for 5 years or more.

[LoganHarrow]

In the meantime before I can get it sorted, is it worth putting gorilla tape over these areas to at least give some protection?

[Bargebuilder]

14 minutes ago, LoganHarrow said:

In the meantime before I can get it sorted, is it worth putting gorilla tape over these areas to at least give some protection?

I'd be surprised if that was necessary and anyway, you'd struggle to get a good seal against water with such an uneven surface.

 

If, when you are ready to start work, you give the prepared surface a few drying sunny days to dry out before painting, the paint should stick well. Zinsser Allcoat is water based after all.

[LoganHarrow]

12 minutes ago, Bargebuilder said:

I'd be surprised if that was necessary and anyway, you'd struggle to get a good seal against water with such an uneven surface.

 

If, when you are ready to start work, you give the prepared surface a few drying sunny days to dry out before painting, the paint should stick well. Zinsser Allcoat is water based after all.

Cheers 👍🏻