Gel Coat over aluminum?

Any ideas on painting gel coat (the white paint used for fiberglass) over aluminum deck and hull? Is there adherence problem? The idea is to to have a smoother and brighter surface and avoiding the direct contact of hands on aluminum, as it is not very pleasant.

 

SamAlec,

To set you strait: a "gelcoat" is not white paint, it is a coat of resin 3-5 mm thick without any reinforcements (glass). It is the first layer applied in a female mold. It can be pigmented for color, most of the times white (everybody wants a white boat :!: ).
:idea: The get your alu boat smooth, you could use epoxy filler. This is common practice in the yachting industry, just takes a lot of sanding.
Keep me posted

Peter

 

Thanks, Peter.
I´m aware of that. Recently, my fiberglass boat recieved a "new painting" of gel coat over the existing gel coat. The reason was that the hull and deck were full of flaws, breaks and marks. A bigger portion of gelcoat was applied over these flaws and a new layer was applied over the entire boat. After that, was all sanded with thin "water" sand and shines like a new boat.
I thought of the same process over aluminum, mainly over sanded parts of the "skin", weldings etc.
My fear is that aluminum could oxidate between its outer portin and the gel.
I never knew epoxi filler. What is that, how do apply it and how is the final result, compared to gel coat?

 

Hi Sam,

Since English is not my native language, please bear with me.
A gel coat is generally based on a polyester resin. Epoxy filler is based no an epoxy resin. Filler is like plaster, and applied in the same way. But in different layers and with different colours, so you can see where the low spots are during the sanding. You use a sanding board of 80x15 cm (another vote on the metric system!).
I believe the finish is a million bucks, this is what is used on multi million mega yachts!


From the Hempel web page: http://www.hempel.com/

{Filling & Fairing

Filling and fairing will streamline the surface of your boat, giving improved through water performance from the hull and clean lines on the topsides. In cases where the substrate has been damaged, structural filling and fairing will be necessary.Filling and fairing is, as the term implies, a two stage process:FillingFilling is the application of a suitable filler product onto a rough, clean surface, to either fill a minor defect (spot fill) or to build a surface up to achieve a required profile.When spot filling, fillers should be applied with a filling knife or spatula. For large profile filling a wide filling knife or trowel is most efficient.Take care to use the correct amount of filler as the use of too much filler will require excessive time spent fairing. We recommend that you apply a number of layers of filler when filling deep holes or large areas as this will eliminate the chance of overfilling, or sagging on vertical surfaces.Filling should be carried out between coats, preferably primer coats, however, spot filling can be effectively carried out between undercoats.FairingOnce the filled area has cured fairing can be carried out. Fairing involves sanding the filled area and surrounding surface to an even profile.Spot FairingSpot fairing is best carried out by hand using abrasive paper on a cork block. Fairing large areasLarge areas can be faired with a range of tools. Rough fairing can initially be carried out using an angle grinder/belt sander with suitable grade discs, followed by a random orbital or orbital sander. Skill is required when using these tools to achieve a fair surface; it is often more successful to use a manual fairing board which, although slower, can produce a fairer surface.}

Hope this makes things clear!

Regards,


Peter

 

Painting and fairing an aluminum hull is not difficult. The best product to use, in my opinion (for whatever that's worth) is the new line of epoxy paints available (these were actually demonstrated for me by the manufacturers of HUB Fire Trucks) These paints stick like sh-@ to a Hudson's Bay Blanket, The main prep they do (at HUB) is rough sanding. We use acid etch prior to filling/painting here and largely oxidation between the metal and the paint is eliminated .Oxidation shouldn't happen AFTER the paint/epoxy/gel is applied, but you have remove any that is there before painting. What kinds of fairing problems do you have with your aluminum hull?

 

Sorry, folks, english isn´t also my mother language. I actually have no alu hull at this time. I plan to build one as soon as my sailboat is sold. My idea about this is that all alu hulls I have seen around, specially on sailboats are not finished, I mean, they are raw aluminum finished, with all weldings being showed up, with some kind of painting that gives me the impression of those old military vessels. I think that such hull and deck deserve a proper and elegant finishing.

 

Check out the Silver Streak 23 that I posted in the gallery. We had an Auto-body shop paint this after we acid etched the aluminum. On high wear surfaces we used ZOLATONE but automotive paint and clear coat for the rest.

http://www.boatdesign.net/gallery/showphoto.php/photo/2121/sort/1/cat/all/page/1