Preparing a boat for painting - what grade sanding disk?

[canalboat77]

I know in an ideal world before repainting a boat you would remove all the previous paint down to steel (on about the top section - nothing under water.) If you don’t have time to do that what grade sanding disk would you take the boat down to. Last year (different boat), I think we went down to 180 grade before we painted - does that sound right?

 

Thanks

[David Mack]

Depends how good a finish you want!

For roughing up the existing coating to remove loose material and give a good key for the new paint quite a course grit is fine, but you might want to use a finer grit for the finish coats.

Edited October 10, 2021 by David Mack

[Tracy D'arth]

For a simple home brush paint job  to an acceptable standard 180 or 200 grit will be fine in an orbital or dual action sander. Do not use a rotating disk, the score marks will always show.  If you have  or hire a belt sander then I would use a finer grit on a second pass before priming with say 360 grit.

 

The sanding scratches will not be as obvious as the brush marks!

 

Try a small area first. Sand it down and paint it, if it looks rough, use a finer grit.

[Chris101]

I have never painted a boat but I've been lurking on here a good while for good reason. Won't be long before I'm asking lots of daft questions.

I have however restored a fair few old machines like Meddings pillar drills and so on. All good finishing is mainly down to preparation and application. 

Craftmaster and Paragon are excellent purveyors of quality paint.

Personally I'd go flap wheel in a 4" grinder for bad situations then 60 to 180 to 240 /280 Random Orbital Sander for a great finish followed by building primer levels and undercoat and prepping methodically  between each.

Getting the right colour undercoat is also important.

Roller on and a decent oil brush like purdy to take off and fast technique will give a good result. There's no real shortcuts.

There are some great tips here:

https://www.craftmasterpaints.co.uk/hints-tips/

 

Kurust is an excellent rust prep solution for small areas before painting if prepping is done well beforehand to bring back to bare.

 

I'll go back to my lurker corner now!

Good luck.

 

Chris

 

 

Edited October 11, 2021 by Chris101
absentminded foolery.

[David Mack]

23 hours ago, Chris101 said:

Personally I'd go flap wheel in a 4" grinder for bad situations

I found that the best option for getting a mix of peeling and sound paint and some rust back to a clean bare metal finish on Belfast's roof. Slow though.

[Chris101]

29 minutes ago, David Mack said:

I found that the best option for getting a mix of peeling and sound paint and some rust back to a clean bare metal finish on Belfast's roof. Slow though.

You could always look at floor sander discs I suppose for a 9" grinder. They are usually marketed as bits to get into corners when using an upright floor sander. They are fairly flexible but have enough body to hold form on the curves of a boat.