Thread: Painting guide/help

Originally Posted by highace1

I did also notice that the tanks seem to have a silvery finish to them, anyone know what it may be? It looks as though it has been brushed on. Old sealer perhaps?
Ace

Penetrol Aluminium most likely. Seriously!!!

http://www.floodaustralia.net/produc...l_aluminum.htm

Thomson's Water Seal is a wax based water "resistant" product. Frankly, it shouldn't even be let near a boat. If you put it on raw wood, you'll have to mill a 1/16" or more of the surface off just to be able to finish it with something other then Thomson's. Many of the land based water repellants are wax based and should be used on boats.

I don't believe that Penetrol cures anything remotely similar to an epoxy. Epoxy is two molecules, that when mixed have a violent reaction, the results of which destroy the two molecules and form a whole new one. Penetrol just evaporates, leaving it's solids behind.

I don't have Penetrol listed as a water vapor barrier in testing, though I suspect someone somewhere has done it in comparison with shellac, varnish, polyurethanes, etc. I suspect it will be lower then varnishes, just like traditional oil finishes, though, it will likely be much higher then the 20% to 25% protection you can get from a traditional "Dutch" like oil finish. Good varnish will offer nearly 70% protection, 3 pound shellac nearly 80% and the polys in the 85% bracket. Marine epoxy is in the high 90's. If I had to guess at Penetrol's abilities, I say it was in the 50's.

The hands down choice among the big builders (Herreshoff, Nevans, etc.) before truly waterproof coatings and adhesives came to be (around WWII) was shellac. The 3 NY 30's that were just restored (relaunched this last summer), were classic double planked by Herreshoff Manufacturing in the very early 20th century. When the outer layer of planking were removed, the inner layer was found basically intact, as a result of the shellac and muslin used between the layers. This is a pretty good service life.

Originally Posted by PAR

I don't believe that Penetrol cures anything remotely similar to an epoxy. Epoxy is two molecules, that when mixed have a violent reaction, the results of which destroy the two molecules and form a whole new one. Penetrol just evaporates, leaving it's solids behind.

No it doesn't evaporate, it cures chemically by reaction with oxygen. Penetrol contains no solvents. That's why it is like epoxy as it seals the surface completely to the air. Not like varnishes, shellac and PUs at all which dry by evaporation and are not water or air proof. That's why it is so suitable for boats. Products like POR15 do the same, only on metal surfaces.

No it doesn't evaporate, it cures chemically by reaction with oxygen

If this where the case, then the old can of Penetrol I have on the shelf should have a skin on the inside, which it doesn't.

and PUs at all which dry by evaporation

Polyurethanes cure by reaction with moisture.

Penetrol isn't a magic liquid, it's just a well refined set of oils. The very first sentence of the Australian "Fact Sheet" is the product's description . . . "Penetrol is an air-drying, film forming, deeply penetrating mixture of natural oils. It does not contain linseed or fish oil, has a low odor and is non-toxic when dry. With a penetrating power 3 times that of water it goes deep into the substrate and forms a strong bond for subsequent topcoats." . . .

Lovely, slightly misleading "fluff" but nothing of substance. For what it's worth, all oils of this level of refinement will "deeply penetrate . . . 3 times that of water, etc.". In the USA, products are required to have a MSDS (Material Safety and Data Sheet), which describes what it is, VOC's the types of hazards, etc. (http://www.duspec.com/DuSpec2/docume...umentId=664738)

Those of you that are familiar with this type of product will instantly recognize what it is.

Don't get me wrong, I use the stuff all the time, but I also was a Chem. E. major in collage.

Now I might be wrong, but the USA version and the Aussie version may be different as the MSDS clearly have linseed listed, though the "fact sheet" supplied on the Australian site says no linseed. In honesty, it's probably tung oil, which preforms better anyway. Maybe there's an Australian version of a MSDS and we can compare the two.

Originally Posted by PAR

Polyurethanes cure by reaction with moisture.

Well at least some do, the moisture cured urethane family, other urethanes cure by reaction with various catalysts such as iso-cyanates.

Guess how isocyanates cure . . .

Good news! The purchasing for materials has begun. Unfortunatley i may just miss the end of the sailing season, depends on how long i take to finish it off.

I also had the oppotunity to visit the Port Hunter Sailing Club yesterday. They were running a couple of sprint races with a NS14/MG mix and then came out the 16ft Skiffs (very nice i might add). I also saw for the first time the Flying Ants, they seem to be a nice little boat. May have to get my son into one when he grows up a bit more.

Overall a very friendly bunch of people, all willing to help out. I will be going back for sure.

Ace

What rollers do you recommend for epoxy and top coats?

Thanks

Ace

There are specialist epoxy rollers with thin foam and plastic sleeves - generally cut them into thirds and use with a 75mm wide cage/handle.

With the paint there is a discussion going already.

MIK

Originally Posted by highace1

What rollers do you recommend for epoxy and top coats?

Thanks

Ace

Mick has already commented on the ones with the plastic sleeves. I've also found recently that even these can fail if the glue used to bind the foam to the plastic insert cannot cope with the heat generated by the epoxy. What happens is the foam just slides off the plastic tube.

The ones sold by Bunnies and other hardware outlets as suitable for PU don't work with epoxy unless you are only doing a quick job where the heat doesn't get a chance to build up.

I went back to where I bought my epoxy and glass, and bought the proper ones that can take the heat. I use the West System, and believe me, the roller gets very hot. So much so that at the end of the job when I removed the roller from the roller frame, the metal was too hot to hold.

Edit: Also, buy the ones that fit the wire cage type of roller, not the small diameter ones that fit the pin type rollers.

I thought i would post a quick update. Most of all the glueing has been done except for the upper skins for the tank and a few other little bits that will have to wait for the weather to clear up. It has been so humid here!

Once that it done, i can start prepping the interior for paint and then flip it over and start the hull filling etc.

I must admit that working with epoxy isnt as bad as what i thought it would be. I ended up getting the slow hardener to give me some extra time with the warmer days we have had.

Things are slowly, which was expected. Ill miss the end of the sailing season unfortunately but ill take it out any way.

Ill post some pics soon

CHeers

Ace

Finally i have been able to get somewhere on my project. All the tank has been rebuilt, with the squaring off. The ply i got (4mm) wouldnt take to bend that i had. In the end im glad i did it that way as i think it looks quite good and still fits in with the rest of the boat.

Everything has been filled and primed. Im in the process of applying the undercoat on the hull. I think its two coats on so far.

As far as sanding is concerned, i noticed when using the roller is leaves the little dimples. Is it just a matter of sanding till they are all smooth? or can i speed up the process by doing something else?

Cheers

The stipple left by a roller can be easily removed by locking the roller in place (your finger) and very lightly dragging the roller back over the work. Another method, which will come in handy on the top coats, is to tip off the coat as you work with a fairly dry brush. Most of us use foam for this, which leaves little to no brush marks and removes the stipple of the roller. For more detail use the search tool and look up "roll and tip" techniques.

Thanks for the tip, i have heard of that technique before. I tried it a bit with the first coat of undercoat but it seemed to leave a fair few lines in the finish. Am i right in saying that undercoats/primers are thicker and have less "flow" than a top coat? I havent had a look at the top coat as of yet so im not sure.

I have 2 coats of undercoat on at the moment, ill give it one more coat with a good tipping as well. Ill see if i can smooth it out a bit.

Cheers