Skim coat patchy faired surface before painting?

Background:

I decided it would be worthwhile to fair the lumpy hull of my Kaholo 14 with MAS microballoons (mostly at a frosting-like consistency).  I ended up using two small containers (quart each?) of the MAS balloons.  This added quite a bit of weight (I would guess a pound or two), but at least the hull looks a lot more fair (especially near the middle of the board, where the panels on both sides of the middle frame were something like 1-2 mm low about 6-10" from the center of the board bottom.

I went through 3 iterations of finding low spots and then sanding things fair until I couldn't take it anymore, and I'm ready to paint.  The hull surface is about half "fairing compound" (in patches, of course) and half neat epoxy (all MAS).

Question:

I heard in a West System instructional video on fairing that one should apply 1-2 coats of neat epoxy over a blotchy faired hull to ensure that the paint goes on as uniformly as possible - is that right?

I'm planning to use EZpoxy (seafoam green) w/o primer.  I don't like adding more weight since the board is already heavy, but life is full of tradeoffs.  If it would take an up-close inspection to tell the difference, I'll skip the skim coats and get on with painting.


10 replies:

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RE: Skim coat patchy faired surface before painting?

Here is a link to the video on fairing, by the way.  I found it pretty helpful, but my goodness what a tedious process it is!

https://m.youtube.com/watch?v=hyaC3YF7QfQ

RE: Skim coat patchy faired surface before painting?

I've been using epoxy/phenolic microballoon mix as a fairing compound for decades and I have to disagree with West. Once you put on the neat coat of epoxy over that lovely smooth faired surface, the first thing you're going to have to do is sand it all again to smooth out the application. This will result in removing a lot of the epoxy that you just put on. That has always seemed to be a waste to me.

Other sources have claimed that since the fairing process sands open the balloons you end up with a porous surface that must be sealed before painting. They forget that the balloons are microscopic. They look like an extremely fine dust to the naked eye. Any ruptures expose an even smaller cavity which the first coat of paint or the primer easily fills.

These days I have settled on simply sanding down to #220 and painting that surface. I've always used System 3 paints for my hulls and with rolling and tipping they can result in a yacht quality finish. (Note the word "can". The painter's skill is also very important. My first boats don't look anywhere as nice as my later ones.) Those paints never had any problem bonding to sanded microballoons.

The main thing I found for reducing weight and making the sanding manageable was using a long board and starting with #80 paper. That let me quickly get the excess fairing compound off and gave me a much smoother surface than an ROS. Then I finished off with #120 and #220, also with the long board. When faired, most of the compound was gone and the boat looked leprous as hell. While it looked bad, this was good. It meant that the fairing compound was only filling the depressions in the average surface, resulting in minimum weight. If you feel that you may have too much fairing compound still on your boat, you may want to consider another sanding session with a longboard, especially if you've only used an ROS up til now.

So, to sum up, in my opinion you don't need to apply epoxy coats to sanded fairing compound.

Good luck,

Laszlo

 

RE: Skim coat patchy faired surface before painting?

Laszlo,

Thanks for sharing your hard-won wisdom once again.  I still have a lot of fairing compound on the board despite using a homespun longboard with 80-grit because the bottom panels had some serious peaks and valleys, but I have also sanded off a lot of fairing compound and have taken it back to neat epoxy in the flatter areas.

I will go ahead and paint after filling the last few pits (and maybe helping them cure faster with a heat gun) and sanding with the longboard at 120 and maybe 220.  Slogging through adding two more epoxy layers, waiting for curing, and sanding (for the 3rd+ time) is not something I want to do given that our lovely PNW summer is passing me by.  Grateful to know it's safe to take the simpler route.

At some point I want to find out how I could have "faired" the bulkheads while assembling the board so I can avoid this kind of exercise in the future.  The deck is kinda wavy too, but I'm just gonna live with it (and maybe use satin varnish) dince it's evident only at low angles.  Not interested in fairing it with neat epoxy (weight, time).

RE: Skim coat patchy faired surface before painting?

 

 

Laszlo,

Do you have a source for System Three paints other than the primer?  I used to use their Pennant paints for my kayak decks but the System Three website no longer lists them.  They were great paints.  As far as I know they were the only 2 part, water-based topside paints on the market.   Yes, Totalboat sells a water-based one part top side but I have not impressed with their water based varnishes and have not tried their topside paints.

Milesi makes some superb two part, water-based cabinet paints that are very tough but I have afraid to try them on a boat,   

David

RE: Skim coat patchy faired surface before painting?

Wow! The last time I bought their paints was 4 years ago. Then I bought WR-LPU, it was before Pennant TopCoat.

That really sucks! I thought their paints were the best out there. The 2-part water cleanup made it really easy to use and the cross-linker made the last coat hard as a rock.

So Fisheries Supply claims to have it in stock, but as a special order only. Definitely call before sending money and keep in mind that it would have to be at least 2 years in the can by now.

Laszlo

 

RE: Skim coat patchy faired surface before painting?

FWIW, I was in Fisheries Supply recently and did not see any System 3 paints on the shelves (obviously doesn't necessarily mean they don't have it).  I remember seeing EZ Poxy, Epifanes enamel, Brightside (discontinued), Toplac, and Awlgrip or Alexgrip, and Marshall's Cove enamel (local Kirby's equivalent).

RE: Skim coat patchy faired surface before painting?

  For a sailboat I am currently finishing up I used EZPoxy with the additional Performance Hardener.  I rolled it with a white foam roller.  I was very pleased with the results. 

RE: Skim coat patchy faired surface before painting?

Good to hear.  Did you also tip it?  Sounds like perf enhancer should help reduce brush strokes.

RE: Skim coat patchy faired surface before painting?

   No, I did not tip with a brush.  After applying the paint and distributing it uniformly, I "tipped" with a final, no pressure, pass of the roller to break the bubbles.  While some bubbles remained after this pass, they disappeared as the paint settled.  Even with the performance enhancer work quickly to maintain a wet edge.  I did not thin.

That said, a sailboat is easy compared to the deck of a kayak where the cockpit rim makes it hard to maintain a wet edge.

RE: Skim coat patchy faired surface before painting?

In my opinion, their paint is the greatest. The crosslinker hardens the finished paint to the consistency of a rock, and the two-part water-based cleaning makes it incredibly simple to use. I am now building a yacht, and I used EZPoxy with the performance hardener added. I used a white foam roller to roll it. I am rather pleased with the outcome.

https://m.youtube.com/watch?v=hyaC3YF7QfQgeometry dash subzero

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