Painting boat with 2-pack paint - few questions

[slawosz]

Hi,
I realized that current time (well, if lockdown will be released), is very good for me to paint my boat using 2-pack paints. No set plans this year etc. etc, gives plenty of time. Currently on the sides it has quite nice car emanel and toplac + interdeck on the top, primed with precote.
Boat is 24 foot, narrow fin keel Achilles 24.
My idea is to sand everything down (this will be fun), fill in dents with West System with fairing compound - not to get perfect smoothness. Then cover boat with lot of layers of Interprotect - even recommended maximum 5. Then perfection undercoat (ideally 1 layer - is it enough?) and paint at the end. My idea is to build good 'base' for years to come- I think with this setup, repainting be much easier as it will require sanding current layers, and then layer of undercoat and 1 or 2 of 2 part paint. Does it makes sense?
I understand that before painting boat, I have to get rid of all layers, including primer, to bare gelocat?

Basically, my goal is to have best abrasion resistance possible with easiest possible maintenance - if there is easier way, please advice me.

 

[Quandary]

I presume you have already read all the many threads on techniques for doing this? Seems like this year is an opportunity to do the full job as you describe. You will have some responses recommending 'easier' paints Like Toplac but if it is maximum durability you are after you are right to use two pack. Not a great surface area in an Achilles and not too high which should make it easier,( and cheaper) than a 40 footer.

 

[William_H]

I have used 2 pack for my hull and deck and find it easy to touch up each winter with just a brush. Mind you the finish is not brilliant smooth but I can easily fix damage etc. However as you know 2 pack will not go onto one pack pant the solvents in 2 pack will dissolve react with the old paint. I don't think it worth while trying to remove all the old one pack pant. Just use a one pack again. ol'will

 

[lw395]

Hi,
I realized that current time (well, if lockdown will be released), is very good for me to paint my boat using 2-pack paints. No set plans this year etc. etc, gives plenty of time. Currently on the sides it has quite nice car emanel and toplac + interdeck on the top, primed with precote.
Boat is 24 foot, narrow fin keel Achilles 24.
My idea is to sand everything down (this will be fun), fill in dents with West System with fairing compound - not to get perfect smoothness. Then cover boat with lot of layers of Interprotect - even recommended maximum 5. Then perfection undercoat (ideally 1 layer - is it enough?) and paint at the end. My idea is to build good 'base' for years to come- I think with this setup, repainting be much easier as it will require sanding current layers, and then layer of undercoat and 1 or 2 of 2 part paint. Does it makes sense?
I understand that before painting boat, I have to get rid of all layers, including primer, to bare gelocat?

Basically, my goal is to have best abrasion resistance possible with easiest possible maintenance - if there is easier way, please advice me.

To be clear, we are talking about the sides of the hull, above the waterline?
I don't think all those layers of different materials between the gel coat and the paint will help at all.
I think it would be better to fill and fair the polyester gelcoat with the same material,
Different materials will expand and contract differently from the base gelcoat and where they vary in thickness, this will show up on the gloss surface.
Lots of layers is lots of opportunities to get varying thickness and lose the fair shape of the hull. This will be very visible if you get a decent gloss at the end of your work.

The 2 pack paint may react with old paint remaining in old scratches etc. You can either remove every trace or use a less demanding paint.
A 24ft boat, it might be worth getting it sprayed by a place that does cars or vans.

 

[KREW2]

I've just done the topsides on one of our club boats with Hempel polygloss 2 part. This boat has been well used as work boat, mooring boat and ferry for the last 35 years
Preparation is always the key factor. In my case nearly two months with a heat gun to remove old decals and sanding back with 50 grit on a random orbital sander. I was doing it indoors so a vacuum attachment and good mask were essential. Then lots of filling, I found International Watertight 2 part filler very easy to use and it sanded down well with 120 grit, then with 180, and finally 240 grit.
After cleaning with a tack cloth the first coat of primer went on this helps to show up any scratches that you have missed, so a bit more filling and sanding before a final coat of primer, then a going over with some fine wet and dry, another wipe down and ready for the gloss.
I did the "Roll and Tip" method for the three coats of gloss. You will need rollers that don't dissolve and a good quality brush, and an assistant. I bought some more expensive west rollers which didn't even do half of one side before disintegrating, so I went to Tool Station who do a very good solvent resistant roller for half the price.
I can find flaws if I look hard, but over all I am very pleased with the result. Lots of members have commented favourably, and I was flattered when a local boat builder gave it the thumbs up.

 

[jwilson]

Yes you need absolutely all non-two-pack paint off.

Whatever you do, for application get the temperature and humidity conditions right including for the drying time. From experience I once got the final application too late in the day the paint went dull and failed to go off hard, and remained sticky for weeks, before I aws finally able to sand it back and recoat. That was 25+ years ago with International two-pack. Eventually I recoated with Awlgrip which seemed more forgiving. Perhaps paints have got better?

 

[slawosz]

I presume you have already read all the many threads on techniques for doing this? Seems like this year is an opportunity to do the full job as you describe.

I did, but I like to have inputs from other, as its quite a commitment. With lot of uncertainty from lockdown, and possibility of launching in July, now its best time to do the job. Normally I split weekends between boat and family activities like camping, summer half-term trip. Now its not gonna happen, my wife will support few weekends in the club.

To be clear, we are talking about the sides of the hull, above the waterline?

Deck as well.

I don't think all those layers of different materials between the gel coat and the paint will help at all.
I think it would be better to fill and fair the polyester gelcoat with the same material,

I am afraid I don't fully understand above. So idea is to get rid or all layers of old paint, using 665 Bahco scrapper and orbital sander, then fill some dents with filler.

Different materials will expand and contract differently from the base gelcoat and where they vary in thickness, this will show up on the gloss surface.

What you mean by diffent materials?

Lots of layers is lots of opportunities to get varying thickness and lose the fair shape of the hull. This will be very visible if you get a decent gloss at the end of your work.

Some visual imperfection won't bother me. My main goal is to have solid paint job for years to come. Current paint is fine, but when I was pressure washing my antifouling end of last season, it turned out that some of the paint come off.

The 2 pack paint may react with old paint remaining in old scratches etc. You can either remove every trace or use a less demanding paint.
A 24ft boat, it might be worth getting it sprayed by a place that does cars or vans.

Regarding old scratches, I believe that epoxy undercoat (interprotect) will not react with tiny bits of old paint (in scratches etc)?

Preparation is always the key factor. In my case nearly two months with a heat gun to remove old decals and sanding back with 50 grit on a random orbital sander. I was doing it indoors so a vacuum attachment and good mask were essential. Then lots of filling, I found International Watertight 2 part filler very easy to use and it sanded down well with 120 grit, then with 180, and finally 240 grit.

Wait, 2 months? How big was boat? I thought I could do all sanding within 4 full days top, plus few visits during week for filling dents with filler....

Whatever you do, for application get the temperature and humidity conditions right including for the drying time. From experience I once got the final application too late in the day the paint went dull and failed to go off hard,

I am aware of it. But for my advantage, I have longest and warmest days of the year coming.

Thank you for your opinions. I have few new things to consider for this rather major job.

 

[slawosz]

Oh, and I just checked regarding boat history. Last 2 paint jobs were done in car/boat shop. But boat was on hard since then. Person who did this left 'window' on transom with original name on white surface, possibly gelcoat. It is possible then that there are only 2 layers of paint, applied professionally, which maybe makes this job easier?

 

[lw395]

If you're not worried about 'visual imperfection' you are spending a lot of time and materials for not much.
I think it will be a lot of work to get decent finish over interprotect. Sanding recently applied epoxy is a nasty job, some people get allergies from it.
One problem you will have is that if you don't make an excellent job of sanding the epoxy smooth, you will break through the undercoat when you try to sand that.

You obviously have a strong opinion about the way forwards and seem to be looking for endorsement that it's the best way. I don't think so. That's my opinion, others are available.

But good luck with however you proceed and do let us know how it goes. Painting is not my particular expertise, so I'm willing to see new ways.

The best boat I painted was with a Dulux polyurethane house enamel. I practised and found tools and techniques which worked for me, in that climate with that paint. I used a foam 'Jenny' brush. Worth a try, but different people with different techniques, different paint on a different day may do better with other tools.

 

[SvenH]

Epifanes has multi marine primer, 1-part air drying that can be painted with 2 pack polyurethane. And it can be used over 1 c systems.

 

[slawosz]

If you're not worried about 'visual imperfection' you are spending a lot of time and materials for not much.

My biggest 'worry' is lack of time to do proper paint job, during next seasons, and after reading about 2 packs, I understand that when they are applied, they last for years. Before covid I never thought about 2-packs, too much hassle.

I think it will be a lot of work to get decent finish over interprotect. Sanding recently applied epoxy is a nasty job, some people get allergies from it.
One problem you will have is that if you don't make an excellent job of sanding the epoxy smooth, you will break through the undercoat when you try to sand that.

You obviously have a strong opinion about the way forwards and seem to be looking for endorsement that it's the best way. I don't think so. That's my opinion, others are available.

I wouldn't call it strong opinion. I am highly biased regarding 2-packs. I am looking for good encouragement or good reason why I shouldn't do it. I am trying to get many pros and cons. Then decide myself what should I do. For example, you made a good point about sanding epoxy, which I did not known about. Now I will do some research on it. This is is very useful for me.

 

[slawosz]

Epifanes has multi marine primer, 1-part air drying that can be painted with 2 pack polyurethane. And it can be used over 1 c systems.

Its like dream came true Where is the catch?

 

[KREW2]

Wait, 2 months? How big was boat? I thought I could do all sanding within 4 full days top, plus few visits during week for filling dents with filler....

The boat is 18 foot, yes two months aprox from first day of prep to the day I put on the first coat of gloss. I was doing anything from 1 to 4 hours a day for 4 days a week. Some times I would only do an hours filling then leave it. Next day sand and fill again as required It depends on the state of the hull, this was bad, and the finish you want to achieve. This boat had had 35 years of abuse, gouged, scratched and crazed from stem to stern.
From 10 feet away it now looks like new.

 

[Ian_Edwards]

Besides the obvious sanding. cleaning and masking, you need to be sure that the paint that's already on the boat is compatible with 2 pack polyurethane.
If the paint isn't comparable it'll wrinkle and look a mess. I don't know enough about the pain that's on the boat to advise, however, if you get some 2 pack thinners from the same manufacturer as the paint you intend to use, and dampen a cloth with it then tape it to the paint, if it wrinkles it's incompatible, if it doesn't it's probably OK. I say probably because the the thinners is highly volatile and will evaporate quickly, the paint will remain in contact much longer before it completely cures and the solvent disappears. This may cause wrinkling after several hours.

I'd do this before you start, if the new paint is 2 part comparable then just sand and all is good, if it's not then either use a less demanding paint, or strip the whole lot off, back to something which is compatible.

You could use a barrier coat, but that's just adding layers of paint and the paint underneath may flake or be much softer than the 2 pack, which could cause problems in the long term. I' be planning on the long term, at £40+ for 750ml it's expensive paint.

I've used 2 pack ever since it was fist introduced, and if it is done properly, it's hard to beat. I have a pair of wooden oars, which I painted with 2 pack International white at least 10 years ago, when I had some leftover from another job. They are on their second inflatable dinghy, and they get used and abused, used as punt poles pushing off from rocky beaches, thrown into and out of the dinghy, the paint is scratched, but otherwise in good condition.

A couple of other observations from years of using the stuff; you need to be careful to get an even cover, apply sparingly, it runs easily, especially if the weather is cool. Read the instruction, there are minimum and maximum over coating times, which are temperature sensitive, if you leave it too long you'll need to re-key it. After you finished it takes quite a while to reach full hardness. If you can still smell the solvent, it's not fully cured. Make sure you use the 2 parts in the correct proportion, not a problem if you are mixing full tins but more difficult if you are only doing a small mix. I use a small cheap digital scale and weigh the two parts, I find that easier then trying to judge volumes.
I hope this helps.
Cheers
Ian

 

[Akestor]

2 part polyurethanes are very bad rolling and tipping. They are made for spray application. I successfully did the topsides with an HVLP spray device after I miserably failed trying to roll and then tip. Unless the boat is wooden, painting the top sides with spray gun is the way to go. I did an epoxy primer and sanded, then applied the first coat, sanded again with 220 before the final application. No sanding between layers will result in orange peel. Also, you need to find the sweet spot of air/paint in the gun, and the speed of hand move. I practiced spaying on a square foot on the boat, quickly erasing the paint with a cloth and nitro solvent, until I was ready to do the job.

 

[lw395]

Bearing in mind that for spraying two pack, you need a proper air-fed respirator.
A great many boats have been beautifully painted in two pack without spraying.
Not by me I hasten to add. My painting is a bit 'launch it before anyone looks too closely' by comparison.

 

[KREW2]

Spraying is regarded as the better option, but not always possible. Done properly you can get a very good result with roll and tip, and a lot of manufacturers instructions give you tips on how to do it. Like everything else the more you do it the better you get.

 

[SvenH]

Its like dream came true Where is the catch?

I guess the biggest one is that you cannot sand through the stuff if 1-c paint is underneath...

 

[KAM]

Regarding painting two pack over single pack. When I bought my boat it was already painted. The original paint turned out to be 2 pack Perfection but the colour had been discontinued and I had assumed it was single pack Toplac. For 10 years I was touching up the hull with single pack. When it came to a full repaint last season I re checked the original paint and discovered my mistake. Anyway after experimenting I decided it was safe to repaint with 2 pack. There didn't seem to be any problems overpainting the single pack areas despite dire warnings even on quite large areas. I just used two pack gloss Jotun straight on top without any problems there don't seem to have been any adhesion or reaction problems. I'm not reccomending this but it might help anyone with a similar dilemma.

 

[saab96]

Some practical advice from having painted three boats several times with 2 pack. The paint is usually wonderfully smooth to apply but tack dries too quickly to go back over any of it, so your plan must be to keep moving ahead once you start. Get some scaffolding in place so that you can move quickly the whole length of the boat. Use big brushes – I used 4inch – with quality bristles that won't be eaten by the solvents. Have several brushes because paint will probably harden on the bristles and scratch the coat before you finish one side. Once you start you will only be stopping to mix more paint and add necessary thinners. Get the consistency right at the start and then expect to add thinners as you progress along the hull. Keep the wet edge moving. Do not go back for holidays or runs – you will snag the paint. Leave them till the next coat. Do not try to remove flies with your brush (or at all). Leave them even if they are large and staggering about in your wet paint in their death throws. The brush snag to the paint will be worse than their foot prints. Leave them till the next coat. Have a helper to move scaffolding ahead of you, to have the two paint parts and thinners ready, to have spare brush to hand, to be shouted at when the tension gets all too much. Paint only with long and easy, smooth vertical strokes. You cannot paint horizontally and then flatten off vertically because the paint may go off before you complete your finishing stroke and you will be snagging. If painting outside, choose your weather. Try to get a good spell of several days. Start as early as the day allows so you never risk the evening dew. Make sure you have done all the prep before you put brush to paint. Use masking tape to get clean lines around fittings. The paint itself should give a wonderfully hard and smooth finish but don’t expect to be free of brush marks when you look closely.