The matt finished area of the hull, would not have been like that originally. It implies that at some time in the past the antifoul has been removed using a wet grit/sand blaster, which is a very good way of removing antifouling paint as it also provides a good key for the new paint.

Are you sure that you are actually back to the gel coat?

It could be that you have reached some epoxy paint.

Now you have your boat all clean, I would strongly advise that you get some polythene sheeting from a builders merchant. tape it to the hull to form a curtain that nearly reaches the ground. Then leave the boat to dry out until the spring. You should then apply an epoxy paint to protect the hull from osmosis / future water ingress into the hull substrate. Either BLakes or International have a good leaflet on this.

Regarding the waterline, the original one will probably be too low, all boats get lower in the water due to all the kit we keep piling onto them.

If you put the antifouling on to the same level it was before you should be just fine!

Can you remember roughly where the waterline was in relation to the antifoul/boot top before the boat came out of the water? Our Sigma had a groove in the hull from the original mould that showed where the waterline theoretically ought to be (although of course it depends a little on how much anchor chain/water/diesel etc you carry).

It's always a good idea to have some antifoul (about four inches?) above the waterline, or this part of the topsides will become fouled as the boat is not always sitting bolt upright in mirror calm water! Depending on which antifoul you use, you may want to use a different type for the boot top. If you use eroding antifoul, it is a good idea to use hard for the boot top, otherwise you will find the soft antifoul rubs off on your dinghy when you come alongside.

It is a bit of a chore, but you can always scrub round the waterline to smarten up a hard  boot top if it does start to get grubby.

David/Cathy

Many thanks for your contributions.

I am confident that I am back to the gelcoat - among the many layers of a/f there was a creamy layer which could have been an epoxy coat as you suggest David, but it has gone! I am grateful for the cover it up and let it dry out suggestion but probably another year. She had been out for 7/8 months when we bought her beginning of May so I think she had dried out pretty well and thankfully, the gelcoat looks in good nick. Anyway, we are hoping for some winter sailing this year!!

Cathy, I have been checking photos taken while she was in the water to pinpoint the relationship between waterline and boot top - I suspect the gap was more than the 4" you suggest, but from all the advice I have garnered I will follow yours and David's advice and anti-foul to the original height. The suggested hard a/f for the boot top sounds sensible - I will be using eroding elsewhere. The original a/f did rub off on the Dinghy - and being black, made everything look particularly scruffy.

Thanks again.

Hi to everybody this may be of interest.

The antifoul I use on the east coast The river Crouch  Flag is made in Burnham  on Crouch it seems to work quite well in that area and is not a bad price at around £40 a tin.

As we all know antifoul stripper is very expensive here is a cheaper alternative, its mixture of caustic soda and wall paper paste follow instructions for the strength of caustic soda for paint stripping but mix it into the paste this lets it stick to the hull.  I think the suggestion of covering it with cling film is good idea and would improve its action and stop it drying out.

It should be left on for about 24 hrs, but will depend on how many layers there is, a friend did his 37 footer for £20, one will still have a bit work to finish the hull off but that's  the same with the dear strippers too

And don't forget to ware the usual protection also collect all the scrapings you will get brownie points from the yard 

Good sailing to all 

Caustic Soda will not damage the Epoxy or the cloth. However, are you certain it is Epoxy resin that was used and not Polyester Resin, the latter can be eaten away and generally softened up by Caustic Soda and most proprietary strippers.

Suggest you try a small area to see what happens.

You will need to be careful to keep the strpper off your topsides or you will be into a complete repainting job.

On the basis of admittedly limited experience (one hull on a single occasion), my concern is that the chemical strippers, while helpful with multiple layers of old antifoul, do not remove the need for mechanical scraping entirely - we had to apply considerable elbow-grease to get the boot top back to the gelcoat despite applying two layers of stripper.

Maybe we were too impatient...