Re-coating a Carbon Fibre mast

[Ian_Edwards]

The coating on the carbon fibre mast is damage and needs work this winter, see photo below.
The original Selden coating failed (2007), and it was re-finished by Silvers Marine in 2014 using Blakes, but I'm unsure of the exact spec'.
The coating has failed again.
I plan to wet sand off the old coating with wet and dry by hand, I was thinking of using 300 grit.
Then Finishing with a 2 pack Polyurethane clear coating.
The mast is undercover in an unheated shed.
Any advice on whether 300 grit is course enough and which 2 pack polyurethane to use.
I've always used International Perfection 2 pack (but never on carbon fibre), but I've had suggestion that Awlgrip might be better in this application.
I really want to get this right with a clear finish that will last for years and years!
Any tips on application would also be appreciated.

 

[Old Harry]

what have Selden / International said about what you propose to do

 

[lw395]

I've done a few.
Where possible, scrape the old coating off with a blade.
That way you remove all the coating and none of the carbon epoxy layup.
Minimal sanding with very fine paper.
Any black dust is obviously a sign you're removing carbon....
International 2 pack varnish.

I'm sceptical about doing it somewhere unheated this time of year. In the past I've patched up the end of a bowsprit outdoors and had the coating go cloudy due to damp (I assume).
Also it tends to get runs if left to cure too slowly in the cold.

Maybe a tent of some sort in the shed and some heaters?

 

[Ian_Edwards]

what have Selden / International said about what you propose to do

If you have ever tied to ask Selden about anything you'll know the answer that question, they simply refer you to your local agent.

 

[jaypea]

I've done a few.
Where possible, scrape the old coating off with a blade.
That way you remove all the coating and none of the carbon epoxy layup.
Minimal sanding with very fine paper.
Any black dust is obviously a sign you're removing carbon....
International 2 pack varnish.

I'm sceptical about doing it somewhere unheated this time of year. In the past I've patched up the end of a bowsprit outdoors and had the coating go cloudy due to damp (I assume).
Also it tends to get runs if left to cure too slowly in the cold.

Maybe a tent of some sort in the shed and some heaters?

+1
Its a frequent topic of discussion for the RS300 fleet, many use single pack but then face re-coating every other year at best so 2pack is deffo better way to go. If you can get it done under cover...do so

 

[dom]

If you have ever tied to ask Selden about anything you'll know the answer that question, they simply refer you to your local agent.

The trouble is, while I understand carbon dust isn't carcinogenic, it can become so subject to the resin/binding agents.

That's why you really need the manufacturer's input as a starting point. This paper might be of some interest:
http://www.hse.gov.uk/research/rrpdf/rr503.pdf

 

[lw395]

The trouble is, while I understand carbon dust isn't carcinogenic, it can become so subject to the resin/binding agents.

That's why you really need the manufacturer's input as a starting point. This paper might be of some interest:
http://www.hse.gov.uk/research/rrpdf/rr503.pdf

I would imagine dust from carbon fibres would treat your lungs much the same as asbestos.
Epoxy can give you big big problems.
I'm a wimp these days, dust mask for dry sanding most things.
But if you're getting signifcant carbon dust off your mast, you is doin it wrong and it will be bendier than it used to be!
Bad bodger! No beer!

 

[Ian_Edwards]

The trouble is, while I understand carbon dust isn't carcinogenic, it can become so subject to the resin/binding agents.

That's why you really need the manufacturer's input as a starting point. This paper might be of some interest:
http://www.hse.gov.uk/research/rrpdf/rr503.pdf

I'm aware of the potential hazards of sanding the mast, and hope to minimise the risk by using wet and dry, wet, so that the dust doesn't fly and I can capture it in a bucket of water, I'll wear of protective suit and gloves. I'll also add some detergent to the water to try and eliminate any contamination left over from any release agent which may have been used during manufacture.
I'll clean the mast with IPA and then a tack rag before applying the 2 pack.

My comments about Selden come from bitter experience, I've tried to get info' on the mast before, with zero success, and I bought a new boom from Selden the a couple of years ago, ordered in October, for delivery in February, I got it in early June, no explanation of why it was so late, and a continuous drip feed of delays, on almost a weekly basis, which made it very difficult to plan.

 

[William_H]

I would strongly suggest paint in white or solid colour. The epoxy will deteriorate in UV hence the need to paint. Now if the old coating just flaked off then yes use 2 pack polyurethane. If it was a result of chafing or damage that you might expect to happen again then go for a simple one pack paint which can easily be touched up. Plus of course no need to sand off the old coating. In any case try a strong solvent on the old coating which may indicate if it is a 2 pack or just an oil based paint. If it remains robust with solvent then perhaps you could just paint over with 2 pack. Of course much also depends on the finish you demand. If you want perfection then you have a lot of work ahead of you. For me touch up even with 2 pack is the way to go giving less than perfect finish which is easily brought back to acceptable condition. ol'will

 

[MikeBz]

I would strongly suggest paint in white or solid colour.

Absolutely. If you're not that bothered about the carbon bling then paint it with a good 2-pack paint (Awlgrip/International/Hempel etc.), the UV protection will be a lot better.

 

[lw395]

Absolutely. If you're not that bothered about the carbon bling then paint it with a good 2-pack paint (Awlgrip/International/Hempel etc.), the UV protection will be a lot better.

True.
I had a couple of dinghies with white Superspar carbon masts.
I saw one of them in the summer, the original paint on the mast was getting a bit tatty but intact after probably 20 years.
Still had my calibration marks on it!

 

[MikeBz]

True.
I had a couple of dinghies with white Superspar carbon masts.
I saw one of them in the summer, the original paint on the mast was getting a bit tatty but intact after probably 20 years.
Still had my calibration marks on it!

If I remember correctly some early white Superspar carbon masts had a thick layer of filler under the paint, so even if the paint fell off they were still UV proof.

Given how long your calibration marks have survived maybe the OP should just go over it with an indelible marker

 

[lw395]

If I remember correctly some early white Superspar carbon masts had a thick layer of filler under the paint, so even if the paint fell off they were still UV proof.

Given how long your calibration marks have survived maybe the OP should just go over it with an indelible marker

I think I used one of those 'paint pen' things?
Or it could have been that green loctite stuff that goes on like nail varnish.