Help! An idiot asks some topsides painting questions....

[Mirelle]

Burned the boat off, raked out stopping, hardened up seams, restopped with linseed oil and white lead putty. So far so good. But, since it is 16 years since I last did this to the boat (I was much younger and fitter then, too!) I find I have forgotten lots of stuff that I once thought I knew, and the paint makers seem to have changed everything....

EG...

(1) I habitually wipe over with thinners (white spirit) on a rag, before painting, and I think that if I paint before the surface is quite dry it goes on better. Anything wrong with this?

(2) Priming coats. If the tin says one thinned coat and four full coats that's what I do. Am I alone?

(3) Sanding between coats. The paint people seem to say that you don't need to, if you stay within their minimum overcoating time. But I cannot bring myself to follow their advice, and I sand between coats anyway. Am I mad?

(4) Trowel cement / knifing stopper. This now comes in a tube, called "One part quick drying filler". Smells the same, though. I habitually use this stuff after the third, fourth and fifth priming coats, not with the undercoat, because if you wait until the undercoat you sand right through the primer back to bare wood. Is this madness also?

(5) Two coats of undercoat, one coat half undercoat half enamel, one coat full enamel, yes? Or is this hopelessly out of date and wrong?

Grateful for advice!

[NormMessinger]

1-- no but...

2-- no

3-- yes

4-- no

5-- Um, re the half 'n' half. Never heard of such a thing.

Next.

-Norm

[Mike Field]

Hey, come on, Norm. What's that "but" for? Are you hedging your bets?

My answers would be --

1. Not unless it's a water-based paint.

2. No.

3. No.

4. Doesn't sound like it.

5. Agree with Norm.

You are having a fun time, aren't you?

[Mirelle]

Yes, all the boat's Christmases have come at once - new keelbolts, new floor to frame bolts, 8 new floors, new mast step, three new bent frames, two grown frames partly renewed, new seacocks, regalvanise and rebolt the chainplates, strap up the stem scarph - all this and painting too!

I have told her that this is IT, no more!

[John R Smith]

Andrew

I can't pretend to be a great expert on this, but I certainly have done a hell of a lot of painting over the last two years. In fact, Mark at the local chandlers can't believe the amount of paint we have bought!

So far, the long-term results are not proven, of course. Nonetheless, IMHO -

I always wipe down with white spirit when varnishing, and often when painting too. Pulls off the dust, degreases the surface, can't do any harm methinks.

Seems like a lot of primer to me. One or two coats should be fine, I would have thought.

There are two objects to sanding. One is to promote adhesion between coats, or when overcoating old paint. The other is to flatten the surface. If you need to do neither of these (second-coating undercoat, for example) then don't sand.

You can use filler/stopper for fairing at any stage, really, but it is best to do it after you have some paint on to use as a guide coat (revealing imperfections).

International advise using a 50/50 mix of undercoat and topcoat as you describe. Frankly, it just seems a bit of a fiddle to me. Two coats of each is my preferred option.

Well, we shall see. If mine has all fallen off again by next spring I shall crawl off and hide someplace http://media5.hypernet.com/~dick/ubb/smile.gif

John

[NormMessinger]

Well, if Mike is going to kick my but around I must elucidate.

1. No, but it probably isn't necessary to get the paint on before the thinner flashes off. I believe the chemist once said a wipe of thinner helped break the surface whatsies so a better molecular bond could occur. Thus a wipe down is wise for that reason and to remove dust.

3. Um, well, er... What is the purpose of sanding between coats. Unless the last coat has totally cured, and one does the surface wipe thing, sanding isn't all that important for cohesion. Yes? So you put on a coat sand half or three quarters of it off, put on another, sand....

5. I wondered if the reason for the 50/50 mix was to tint the undercoat so the top coat would cover. Undercoat is a bit cheaper than the top coat but it can't make that much difference. My inclination would be to follow the instructions on the can and hope it was written by the paint chemists and not by the marketing department.

Now I gotta get out of here and do something about the paint that is chipping off Prairie Islanders deck.

/s/
Norman G. Messinger
Chief Forum Blatherskite

[Bruce Hooke]

I will second the opinion that the other reason to sand, besides adhesion, is to get a smooth surface. Part of the point of all those layers of primer is to fill any slight irregularities in the surface, but that only works if you sand between most (or all) of the coats to take off a little of the primer in the high areas. The other key to making this work is using a sanding pad that is fairly firm so that it bridges any irregularities.

My thinking on the trowel cement is apply it after the first coat of primer and expect to sand through the primer in places. Better to sand through that first coat of primer than sand through all 4 coats...

I also suspect that the reason for the 50/50 mix might be to tint the primer, although it seems like you could do this with a lot less than 50% paint. This is an excellent idea for dark colors but sort of pointless if you are planning on white topsides. It does help, of course, to have some color difference between the paint and the primer so that you can more easily see where you have painted.

[Ian Wright]

(1) Dunno, but I wipe with thinners/white spirit and let it dry,,,,,,

(2) If you are useing metalic pink (International) or metalic grey (Blakes) on bare or nearly bare wood get as much primer on as you can. If the can tells you four coats then do four coats plus what's left in the tin,,,,

(3)Sand for a key if you are over time but sand to get rid of the drips runs sags and insects anyway, but never sand primer,,,,
(4) Interfill 100 above the waterline P38 below. Only after the first undercoat. Thereafter keep trowel cement and putty knife by you at all times untill the 50/50 coat.

(5) That's what I do except I use Permaglaze undercoat, NOT marine. A quarter the price and much better coverage.

So now I know why I didn't see you out sailing this year,,,,,,,,,

IanW

[Mirelle]

Thanks a lot, everyone. My method (filling between the later priming coats) is an attempt to get at least a couple of priming coats on at "full film thickness", when the surface is reasonably fair, before going to the undercoats. Seems like I make a lot of work for myself.

The "half and half" thing is very old fashioned; because of the colour scheme I have (pale blue, which takes a white undercoat) I like it, because I get an undercoat near to the right colour and sanding enamel is no fun at all; another point in its favour if, like me, you are painting at an odd time of year is that you can leave it like this till spring and then rub down and put a full gloss coat on. Ah, well, back to the paint can...once more unto the brush, dear friends, once more, or fill the shed up with our sanding dust....

[This message has been edited by Mirelle (edited 10-01-2001).]