The Official Magazine of the Bluewater Cruising Association

Hillbilly Air

Rob Murray

Beneteau First 435 Sloop
November 30th, 2021

No, it’s not what residents of the Appalachians get when they ski moguls. It’s the jury rigging of cheap air conditioning on a sailboat for use dockside or when in storage in the tropics.

Avant was in El Salvador for almost two years; we determined that for our comfort aboard, and more importantly for the condition of the boat and gear when stored unused for two summers in El Salvador, that air conditioning would be a giant plus. The heat and humidity in the off-season in the tropics is intense, and temperatures in a closed up boat can reach 48°C (120°F) when stored in the water, and 65°C (150°F) when stored on the hard. Coupled with humidity in the 80-90% range and rain (sometimes inches per day), the mischief this causes to fabrics, plastics, wiring, sails, books and paper goods, and general household items is incredible. Mildew, oxidation, and general degradation are inevitable, but with air conditioning the rate is greatly decreased. With air conditioning, you can reduce the humidity to somewhere in the 50-60% range, and the temperatures to a much more benign 25-30°C (77-86°F).

If you can get power at a reasonable cost, fitting an air conditioner is not too hard or expensive.

There are three main options:

  • built-in (maximum cost, convenience)
  • floor-standing units
  • window mount units

Built-in Air Conditioner

Cruisers with built-in air conditioning systems report blocked water inlets for the raw water cooling systems, and these need to be cleaned out at least monthly, making their long term use while the boat is unoccupied more difficult to achieve. It’s also near impossible to get and install one here in El Salvador, so if you didn’t install one before you left, you’re probably out of luck.

Floor-standing Air Conditioner

Some cruisers here bought floor stand models, but found they were less than optimal as they 1) took up a fair amount of space inside the cabin, 2) needed external ventilation, 3) produced heat inside the boat, 4) were larger than similar powered window units, and 5) had to have water reservoirs emptied regularly (when air conditioners reduce humidity they produce water, and the water has to go somewhere!).

Window Mount Air Conditioner

On Avant we bought a simple 5,000 BTU window mount unit and fashioned a fitted plywood companionway board to hold it. We added a drain hose to the existing drip hole (push fit vinyl/PVC hose from the hardware store), and another overflow fashioned from a cut up milk carton (and more press fit PVC hose) in case the primary somehow became blocked. The hoses lead to a cockpit scupper, preventing the drips from the water produced from forming little algae pools on the deck. We added a snappy aluminized deflector shield (cut from a dollar store folding car window shade) to keep the cold air off the bottom of the sliding companionway hatch, as the cold air was causing condensation on the outside of the hatch and we didn’t want the extra moisture running on deck.

Hillbilly air, external view. Note drain hoses and custom-fit external catchment basin. Companionway board is simple plywood cut to fit, with an internal 2×4 ‘shelf’ on the inside to hold the AC unit.

Other cruisers in the local fleet have made boxes that fit topside hatches and hold the units. This takes more storage space, is more complicated to make, can be difficult to make adequately waterproof in topical rains, and makes it harder to securely lock the boat up, but works fine and makes coming and going through the companionway easier.

One of the nice features of the window mount units is that all the heat producing components are mounted outdoors, so no heat is introduced below.

Hillbilly air, internal view. Note professional cord management with clothes pegs, and high-tech insulated aluminized deflection shield to direct air away from underside of companionway hatch. (All accessories purchased at ‘Dollarama’ El Salvador.)

We chose a simple all-mechanical unit so it would come back on after a power failure in our absence. The fancier electronic control units, while beguiling with their softly glowing LEDs, remote controls and myriad options, would not automatically restart after a power outage (and outages are common here). Fortuitously, this was also a cheaper cost option. There is no need for fancy temperature controls, we simply set the unit to ‘10’ (maximum cooling) and the fan to ‘High’ and leave it running. It never gets cold, or even really cool (by Canadian standards) aboard, but the difference in our comfort is great. The waste heat generated and blown into the cockpit makes the cockpit even hotter, though, so we switch it off if we’re going to enjoy evenings topsides. When we’re home in Canada, away from the boat over the summer, we add a small, cheap 120v fan to augment air circulation below.

While it’s a minor inconvenience to step over the unit when going below, the difference in comfort and the life of our equipment and interior makes it all worthwhile. As I write this on a hot tropical afternoon, it’s 27°C (81°F) with 55% humidity down below aboard Avant, while outside it’s 33°C (92°F) with 85% humidity.


  1. Shona says:

    In Australia we call it a window rattler 😂

Leave A Comment

Your email address will not be published. Required fields are marked *