2-pack application advice

A

Avocet

Well-Known Member
Joined
3 Jun 2001
Messages
30,549
Location
Cumbria
Visit site
OK, the weather is finally good and settled, the boat is primed and flatted, and I'm running out of excuses not to paint it! I can't find anyone to come and spray it for love nor money, so I'm going to have a go myself.

The boat is outdoors and I've heard in the past that 2-pack can go dull if the humidity gets too high. This stuff is Epifanes Polyurethane. The data sheets says it can be applied between 12 and 30 degrees C, and between 50 and 80% humidity. Today, the little thermometer / hygrometer I left next to the boat said it was 84% humidity at 21.30 tonight. It's not reading 90+ %. The data sheet says it will be "dust dry" in 2 hours at 20 degrees, overcoatable after 24h. I can be pretty confident that we'll see peak temperatures of 25 degrees tomorrow up here.

My question is: Does anyone know if it's Ok for the humidity to go above 80% AFTER the paint is "dust dry", or am I still likely to have problems? Hopefully, it'll go on mid-morning, so it should get a good 7-8 hours above 20 degrees and below 80% humidity.
 
My experience with polyurethane is that it goes hard fairly quickly. It was not the same as yours and I think the seller might have offered a quick or slow hardener. Anyway the humidity should drop as temp rises so i reckon you should be fine. Do be careful of the spray and your lungs. At one time the spray was considered very toxic (that may have changed ) but proffessionals use positive air supply type protection. Me I just brushed it on. yes you can tell but more from scratches I have touched up since. good luck olewill
 
Avocet said:
I can't find anyone to come and spray it for love nor money, so I'm going to have a go myself.
Click to expand...

DON"T!! The reason nobody is willing to do it for you is because it is bloomin' dangerous. Generally 2-pack manufacturers advise against spraying it for that reason.

If you absolutely must, you need full forced air respiration kit.

Much better to use a pad and tip off, even if you're as ham fisted as me with paint.

As for humidity, in my experience with paints they will bloom if the humidity goes above stuff all until it is pretty well fully dry. Do it in the morning and it'll be fine before the evening dew, which was what you measured.
 
SAPurdie said:
DON"T!! The reason nobody is willing to do it for you is because it is bloomin' dangerous. Generally 2-pack manufacturers advise against spraying it for that reason.
Click to expand...

Somewhat exaggerated response there. It's true that air fed masks are recommended, it's also true that some people are sensitive to 2 packs, but I doubt that you'll find any manufacturer who recommends not spraying the stuff at all. Two packs are routinely sprayed all the time. If your car has accident damage, odds are it will be resprayed with 2 pack.

However, unless the OP has experience of spraying, I agree that hand application would probably be easier to get an acceptable finish. He could easily end up with runs and/or an orange peel finish by spraying. Having said that, he's probably out there spraying away as I write!!!
 
Last edited:
Alas no! "He's" been out several times this morning and the hygrometer is still in the mid 80s! I think I've blown it for today now, to be honest. Pity, but I'm hoping the next few days will be better. It'll cost me some time off work, but hey ho - I've been waiting to do this for 6 years now!

The reason I want to spray is because Avocet has a moulded rubbing strake which, itself then has a moulded cove line and decorative bits in it. I tried roller and brush with the primer and to be honest, applying the paint and tipping-off round the complex moulded shape was an absolute nightmare. I ended up letting it harden and rubbing it down again and then spraying. True, the finish was less-then-perfect, but better than I could get with brush, roller or pad. I'm "getting better" at spraying, but I've got to the point where I just want me boat back!!!! As WilliamH says, by the time I've bounced it off a few pontoons and touched it up again, I probably won't care any more as long as it's all the same colour!

I'm OK for personal protective equipment, (I've got all the "toys", in fact, it's just experience that I lack!) and yes, it's commonly sprayed in bodyshops (the data sheet for the paint has all the recommendations for spraying). Added to that, I'd be working outdoors, which gives added security.
 
bigwow said:
Be care with the over-spray, we "sprayed" a car which was 50 feet away!:rolleyes:
Click to expand...

Good point. Yes. I'll be careful of that - although the boat is a fair distance from anything at present.

OK, "Before" photos:

PICT0024s.jpg




[IMG=http://s38.photobucket.com/user/Avocet1/media/PICT0029.jpg.html]
PICT0029.jpg



[IMG=http://s38.photobucket.com/user/Avocet1/media/PICT0027.jpg.html]
PICT0027.jpg



The entire topsides were like that. More on the higher bits, less on the bits that got less sunlight (like under the stern counter).


"During" photos:

[IMG=http://s38.photobucket.com/user/Avocet1/media/PICT0018.jpg.html]
PICT0018.jpg


[IMG=http://s38.photobucket.com/user/Avocet1/media/PICT0017.jpg.html]
PICT0017.jpg


This was basically just using a router to "machine" the gelcoat off in strips - leaving some original gelcoat each side and then filling it with a mixture of epoxy and microballoons. The theory was that I'd do that and use the old gelcoat either side as a guide so that I didn't lose the line, then go back and do the remaining "white bits". In practice, it didn't work too well at first - ended up ever so slightly "faceted" - almost looked like a planked wooden boat for a while! Then Oldsaltoz taught me the trick of using the back edge of an old saw blade and forcing it round the curve of the hull when spreading the filler. That worked better. I then took a rough mould off the £%^&*ing cove line and rubbing strake so I could use it as a "3-D spreader" for the epoxy. Unfortunately, no photos of that (you wouldn't believe how sticky things got, and it was only partially successful, if truth be told...)

[IMG=http://s38.photobucket.com/user/Avocet1/media/DSCF0729_zps7146529f.jpg.html]
DSCF0729_zps7146529f.jpg


Having turned the entire thing brown, I then put the high-build primer on it...

...and rubbed most of it off again...

...and put some more on...

...and so on, until it looked like this:

[IMG=http://s38.photobucket.com/user/Avocet1/media/DSCF6355s_zpseb229fa0.jpg.html]
DSCF6355s_zpseb229fa0.jpg


and then tried rolling some epoxy primer on to it, but it came out like this:

[IMG=http://s38.photobucket.com/user/Avocet1/media/1sthalf1.jpg.html]
1sthalf1.jpg


So I ended up spraying it - which was a bit better.

...and that's as far as I've got really.
 
Last edited:
Hmmmm. This spraying lark is harder than it looks! Took the morning off today and thought I'd give it a go. Was very pleased, initially, with how it was going on. Good gloss. Unfortunately, by the time I'd finished one side, I refilled the gun, went back, and to my horror, saw a fair few runs! I'd have expected it to run pretty much within the first 30 seconds of going on, (if it was going to) but it seems to take a good 15 minutes! Oh well... I guess I need to wait the full 7 days now for it to harden properly before I try to flat them out and put the next coat on?
 
That's the trouble with spraying when you don't do it often, you don't get the knack of it 'till you've finished!

My top tip is to make sure you have someone preparing the next lot to go in the gun as you're spraying. Trying to eek out the last bits to get to the end of the hull always seems to result in runs. So, keep the gun topped up.

I also soak a rag in thinners, and wipe that regularly over the nozzle to unclog it as I go, but clear the spray of any drips of thinners with a quick blast before pointing it back at the boat.

I resorted to spraying because I failed miserably at the tipping off approach and ended up removing the whole coat and starting again with the spray gun as:
a) I couldn't possibly have made a worse job of it
b) I hadn't spent 5 months prepping the thing to perfection to have anything less than a perfect finish on it.

Oh and mask off EVERYTHING - the over-spray just gets everywhere.
 
Ta for that. I think I made the common mistake of trying to cover up too much in one go. In fairness, I tried putting it on quite thick, waited for a minute or two and thought "great!, No runs!" so I did the whole side like that. Any tips for avoiding future runs? This is the first time I've used a viscosity cup and I must say it was a bit thinner than I'd have mixed it if I'd been using single pack "by eye"! Would mixing it thicker help with the runs next time?
 
I find that several fine coats, the first one just a mist coat, is a lot more successful than one heavy coat, as you have discovered.
 
Thanks, yes, I'll definitely do that next time. The data sheet says it's over-coatable after 24 hours (but will need rubbing-down again if left more than 48 hours). Would you leave the 24 hours between each of the light coats though? (Peak daytime temperatures here are currently in the low 20s, night time temperatures in the low-mid teens).
 
No do not leave much time between coats, just enough for the previous coat to flash off and you can put several coats on in this way, just build it up gradually coat on coat.
 
bigwow said:
No do not leave much time between coats, just enough for the previous coat to flash off and you can put several coats on in this way, just build it up gradually coat on coat.
Click to expand...

Thanks. I might get another bite at this on Thursday morning. Do you reckon I'd be ok wet - flatting the runs with 360 wetordry and trying it then?
 
Right, all the runs flatted-out with wetordry (used wet). Any recommendations as to what I ought to wipe the hull with before putting some more paint on? Thinners? Acetone? Tack rag?
 
Thanks for that.

Well, I did get to put another couple of coats on in my lunch hour today and...

...has anyone got any tips for:

(a) getting rid of orange peel and
(b) getting dead flies out of it?!

This time, I think I went too far the other way. I was so scared of it running that I probably didn't put enough on at a time, so it's all rather orange-peely and bits of it are more, well..."pebble dash" really!
 
Avocet said:
Thanks for that.

Well, I did get to put another couple of coats on in my lunch hour today and...

...has anyone got any tips for:

(a) getting rid of orange peel and
(b) getting dead flies out of it?!

This time, I think I went too far the other way. I was so scared of it running that I probably didn't put enough on at a time, so it's all rather orange-peely and bits of it are more, well..."pebble dash" really!
Click to expand...

Hi Avocet,
Good to see you finally got some nice paint on her.

Have you called any of the local panel and paint shops and told them you have everything set up, scaffolding. masking, mixing and you need a bloke with his favourite spray gun to turn up and do his magic, then leave you to do all the clean-up.

It would take perhaps a hour of his time and save you days potentially.

This stuff starts drying as soon as it hits the air, so orange peel could be that you are too far off the surface.

The best results I have seen was done by applying a mist coat (dries in minutes) then a half coat, also dries very fast, then a final and full coat.

The previous coats seem to help the final coat hang on or grip better so no runs unless you go overboard.

Best of luck.
 
You must log in or register to reply here.

Share this page

Top