Funny thing about cruising in southerly climes. The water is warmer and the sun is brighter. Even as finely-insulated a vessel as a Malo has to expend more energy to keep cold things cold in its refrigerator. Even if GB has already insulated all the voids around and behind said refrigerator, it will still have to work harder as the sun shines on the part of the boat's hull nearest the fridge. A contiunuously running fridge can really deplete the battery reserves of a boat at anchor.
We learned that cruisers in the hot sun have a way of easing the fridge's burden: they hang reflective material over the side of the boat's hull facing the sun, where the fridge is closest to the hull. The reflective material is a standard reflective visor that drivers use to shade their cars' dashboards from the sun. In Mexico, a basic auto visor sets one back about US $3 - the cheapest boat equipment ever. We were so excited we bought two.
Some cruisers stop here and just hang the auto visor over the side of their boat. Which appears to help. Others, though, aim for even more energy efficiency. So, following the advice of those more experienced in these matters - other cruisers and a Mazatlan refrigeration mechanic/boat engineer - I cut the two auto visors to 35" long (their original height of 23-1/2" was just fine), and stitched them together (to improve the overall R-value, I guess), then weighted the bottom with a series of five 2-ounce fishing weights, the better to stabilize the shield against the breeze and wave action.
But that's not all: covering the auto visors with white fabric seems to protect them from the elements and improves their reflectivity, according to folks who have studied the matter. We used what was available in town and bought ourselves the finest pure-white shower curtain US $13 could buy. Cut it roughly in half and had a pice of vinyl fabric 37-1/2" wide and 52" long - enough to fold around the auto visors and stitch the sides closed, and hem the top with an inch to spare above the top edge of the visors. GB set 3 grommets in the top hem so we could tie the finished sun shield to the Fox's hull at the stanchions and lifelines. We hang a fender or 2 over the side on top of the sun shield to keep it in place in light breezes. However, we've found that fenders alone don't keep the shield in place when the wind blows above 15 knots or so - still a few bugs to work out.
Energy results: this sun shield appears to have improved the fridge's efficiency in the sense that it allows the fridge to run colder, on a lower-energy setting does not have to run constantly. We haven't crunched actual numbers to accurately determine our true energy savings, because daytime temperatures can fluctuate widely; we're lazy; other activities get in the way (like cocktail enhancement). But I have seen that with the afternoon sun shining on the refrigerator's side of the hull and the sun shield in place, the fridge has an inside temperature of 34.3 degrees F. It's chillin'.
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