Have I made a mistake ?

[winsbury]

Doing the final bits of a 9 month project to get the boat in the water and just realised a possible mistake that could delay be for another couple of weeks: there's a gap between the keel and hull at the front part of the keel - it is just the way the mouldings are made and not a fault but its difficult to get a paintbrush into because of the angles so I had intended to fill and fair it with Sikaflex before the final Coppercoat goes on. The problem is I forgot to put the Sikaflex in when I prepped the hull and the weather is now perfect for putting the coppercoat. According to Sikaflex, 291 will take up to 12 days to fully cure if its 1cm thick but

1. does it need to fully cure before overcoating with coppercoat or woudl 24 hours to let the surface cure be okay ?
or,
2. would I be better off doing the coppercoat and then filling the gap afterwards with sikaflex hence leaving the small sliver (no more than 30mm x 5mm ) as unantifouled naked sikaflex ?

 

[prv]

I have a feeling the coppercoat would crack off the sikaflex anyway, due to movement.

Also, on our freshly-coppercoated boat, not every square millimetre of her is done anyway - they deliberately left the through hulls and the saildrive, so there will still be a small tin of antifoul deployed each year. No hardship to dab a bit on the bare patch at the same time.

I'd get the coppering done and sikaflex after.

Pete

 

[Lakesailor]

If it's not actually sealing a gap that would leak why not use marine filler. Goes off in an hour, tops.

 

[winsbury]

I have a feeling the filler would crack as the keels will probably flex a little especially since its been sat on its trailer for the best part of 18 months hence a flexible filler was my first choice. I think I'm going to go with Pete's suggestion, not only because it saves me a ton of time but reading other threads there are lots of worries about cracks around the keel to hull join which although perfectly normal for the most part, are nevertheless difficult to assess when covered in AF. By having the sealant over the top of the coppercoat it should be more apparent if joint is failing and exactly where.

 

[geem]

use WORKS. Its moisture cured and can be painted. The coppercoat is likley to crack as it isnt very flexible. you should be able to paint over the WORKS in 24 hours.
A pal used sikaflex on his keel joint and it all came out. I suggested WORKS and after a season and winter afloat it is still intact. its also £6 per tube from out local hardware shop

 

[pampas]

+1 for works, comes in clear and white, sealed a window last week in the RAIN

 

[BERT T]

Use CT1

 

[alteredoutlook]

Use CT1

+1

 

[EwanClark]

I'm a bit late to this thread, but for the benefit of others that may come across it in the future, please note that Coppercoat will not bond to Sikaflex.

When/where possible, use a solvent-free two-part epoxy filler that sets hard. A few days later, abrade the surface to provide a good key and then apply the Coppercoat.

 

[winsbury]

The hard filler wasn't appropriate in my case as it was the keel to hull joint which inevitably always has some flex. Talking to the boatyard when she was lifted in they suggested painting those areas with normal anti foul or accept that there would be some growth on the areas that cant be copper-coated. I decided to put her in the water without AF on the joint so will see what it looks like in a few months on the basis that perhaps the flexing and proximity of coppercoat will keep growth and barnies to a minimum.

As an experiment I painted a few dabs of coppercoat on the flexible PVC mudguard of our trailer to see what happens to it when it dries. Its now 2 months on and very hard, easily passing the fingernail test. Predictably it has started to flaked off at the edges ( the PVC is very smooth hence this is no surprise ) and carefully peeling it off in a sheet shows it will flex to about 10-15 degrees without cracking so I'm inclined to think that it would survive on a moderately flexible substrate provided it was keyed sufficiently.

 

[aitchem]

Do we not put coppercoat on through-hull fittings.?
..................why not.?

 

[EwanClark]

Two-pack epoxies like Coppercoat tend not to bond well with self-finished metals such as bronze, brass and stainless steel, hence most people do not bother trying to apply it to their through-hull fittings. You can if you wish and it'll do no harm, but there is a good chance that the coating will flake away from these parts.