S/V Hello World's Travel Log

fridge box construction

(Boat nerd disclaimer - this blog post is going to be boring. It's mostly about what I did to build the box liner, where I screwed up, and how I fixed what I did wrong in the first place. If you want to know how to build a fridge, read on. If you could give a crap about building a fridge, here's some kittens singing Led Zeppelin.)

I thought constructing the box for the fridge interior would be messy and smelly and itchy and fairly time consuming. I underestimated how much by orders of magnitude. As a caveat: this was my first fiberglassing project. Coming into this part of the fridge project, everything I knew about how to fiberglass I learned on the internet. In articles on the internet, it looks pretty straightforward. Those articles always have some guy in snappy coveralls, safety glasses, safety respirator and safety gloves without a single speck of resin in his hair or on his elbows or up his nose. Those articles can kiss my ass.

Box Construction

I used 1/2" marine ply to build out the walls of the box. I had visions of the wood slowly turning into mush over the years so after cutting the pieces out and dry fitting them, I coated the individual pieces in epoxy. Before installing the box walls, I put in a moisture barrier between the box and insulation. I chose Reflectix insulation sealed with foil tape. In areas where the insulation didn't mate perfectly with the marine ply box walls, the Reflectix gave me some wiggle room to compress it. I wanted to avoid any air gaps right next to the box walls where condensation could build and introduce moisture into the insulation.

I then installed the epoxied box walls. I soon learned that the void created by the insulation resulted in a space comprised of not a single 90 degree angle. Because the Reflectix had some give to it, I was able to get the walls into something resembling plumb. I did have to brace the walls at a few spots where the insulation behind them wanted to bow the walls out.

After bracing the walls, I screwed the walls to the aluminum angle iron I installed underneath the counter top. Then I spent a frustrating and f-bomb filled couple of hours filleting the seams with thickened epoxy will hanging upside down and working around the braces I installed. The take-away lesson seemed to be that I was too stingy on the epoxy filler and should have thickened the mixture more than I had (I used mayonnaise consistency, should have used peanut butter consistency). I was using West Systems Low Density fairing filler which is fortunately easily sandable and results in a pretty forgiving material. In the end, I got the fillets installed but spent another few f-bomb filled hours sanding down the sloppy results.


Next up was the actual fiberglassing. This the point that I learned fiberglass cloth's natural tendency to unravel. It will unravel when you try to coat it with epoxy. It will unravel when you cut it. It will start unraveling you pull the scissors out. I gave one piece a sideways glance and the next thing I knew, it turned into a pile of unrelated fibers. This meant that when I wet out the cloth I applied to the box walls, I had strings dangling off the seams all over the place. These strings combine with the resin to turn into sticky, adhesive epoxy boogers. Grab one to get it out of the layup and it will unravel seven or eight other ones. I finally just ended up leaving the errant strings in place and sanded them down after the resin cured.

I added fiberglass to the box interior both to waterproof the wood but to also give the interior seams strength. I used one or two layers of 10oz. cloth on the walls themselves and three or four layers in the seams, particularly in the floor. All these overlapping layups resulted in a pretty lumpy finish, especially in the floor. I mixed up some more thickened epoxy and liberally slathered it all over the place. I poured a thick covering on the floor and let it self level. This gave me a layer I could fair without grinding away all the strengthening layers I put in place at the seams.

After everything cured, I washed down the walls with scotchbrite and water to remove the blush (I never saw any but read that West Systems epoxy blushes so I did it anyways). I then went to work on it with an orbital sander and 60 grit discs. As I got closer to fair, I moved up to 80 and then 100 grit discs. I discovered that epoxy + fiberglass is pretty workable material. After all the lumps and drips in the original layup, I was able to fair it all out pretty smooth.


Here's where I went off the reservation a bit. I was determined to find a paintable, food safe, impact resistant finish for the interior walls. I scoured the internet for such a thing. I asked the folks at the local fiberglass shop. I asked at the local chandlery. I hit up the sailing and cruising forums. I even hit up the boat refrigeration forum (talk about a niche site). No one had an answer for me.

So I fell back to a default position that I had a sinking feeling was not going to go well. I chose to use epoxy but add a white pigment to it. I didn't choose this because I thought it would be the easiest or best solution. I chose it because I never could come up with a better idea. Pigmented epoxy has any number of problems in this application but I'll give you the greatest hits:

  • Epoxy is a two part solution that requires some healthy mixing. That healthy mixing introduces air bubbles which will lovingly transfer into your finish. When they pop, the surface looks cratered and pock marked. I've tried using a blowtorch to knock out the bubbles with limited success (and unlimited possibility of burning our boat to the waterline). I also tried misting denatured alcohol on the surface (I was smart enough to not try this at the same time as the blowtorch trick) which took care of the really small bubbles but didn't help with the large bubbles that surface after an hour or so.
  • The liquid carrier for white pigment is actually just resin. Which means if you add too much pigment, you can throw the resin/hardener ratio off and the epoxy will never cure. So you have to be very careful about how much pigment you add. Which means each coat you add doesn't have much coverage for the colors behind it. Which means you have to add 5 or 6 coats in order to produce a solid white color.
  • You have about a 45 minute window about four hours after you apply a coat to apply the next coat. When you need 5 or 6 coats, well... do the math. It makes for an ugly Monday morning after rolling epoxy at 4AM.
  • Epoxy has so much viscosity that it can't help but sag or run on a vertical surface. I could also never get it to self level so my attempts at rolling and tipping resulted in seeing all the brush strokes. "Why didn't you cut the epoxy with some thinner?" asks everybody I mention this to. Because the 5 or 6 coats I had to add would have turned into many, many more.

In the end, I chose to add a ton of coats of sorta messy epoxy (I believe I counted 10 coats across two different sessions) and then work it down into something decent looking. I learned from surf board building forums (click here for the coolest wood & squid surfboard you'll see all day) that you can build up a nice looking gloss with epoxy. Here's what I did to get a glossy finish from a very messy epoxy application:

  • Knocked down all the drips and sags with 80 grit
  • Faired surface and smoothed out pock marks with 100 grit
  • Further sanding with 220 grit and then 320 grit
  • Wet sanded with 400 grit
  • Wet sanded with 600 grit
  • Wet sanded with 800 grit
  • Wet sanded with 1000 grit
  • Wet sanded with 1200 grit
  • Took a buffing wheel attachment on a drill and worked a polishing compound into the surface
  • Washed off the polishing compound and had a beer

The end result? Not bad. I sanded through the coverage in a few spots so you can see shadows of the colors behind the white epoxy but mostly in areas you can't see so I don't care. The rest of it came out pretty nice. It also results in a glossy surface that will be much easier to clean than if I had left it matte.

The last piece of the box construction itself was to add a removable bottom on the floor so any foodstuff doesn't end up sitting in water at the bottom the fridge. I order a simple sheet of polycarbonate from Tapp Plastics, drilled drain holes in it, rounded the edges, and drilled a couple finger sized holes to be able to remove it. The final test of the box construction was to check the results were true to the original design. Is the height of the "beer can well" the exact height of a can of beer? See for yourself:

This part took forever partially because we took the summer off to put on a new bowsprit and windlass (long story, I'll tell you later) and partially because it was just way harder than I thought.

Next up? How to build a fridge lid. I know, I can hardly wait!