Mounting Solar Panels on a Small Boat

By Connie McBride ,

The final installation is a clean one with no moving parts

When my husband, Dave, and I bought a 29ft sharpie as a summer home, we outfitted her with much of the old gear from our 34ft Creekmore, Eurisko, including her composting head and solar panels. We planned to buy equivalent new parts for Eurisko when we moved back aboard her. But reality rarely matches theory.

Researching solar panels for the first time in 13 years, we discovered that much had changed. Panels produced higher output for their size, but larger panels were being manufactured to meet the ever-growing demands of boaters. Our usage had actually decreased over time as our three children grew up and moved off the boat, and the space allotted for the installation of solar panels remained the same. Most panels were too big for the only place on the boat we were willing to install them, between the two aft-most lifeline stanchions. The two 50-watt panels we had sold with our sharpie produced more than enough electricity for our simple lifestyle, but we could not get new equivalents to fit the space available.

Tabs were welded onto lengths of aluminum pipe, which were then cut in half

After much searching, we purchased two 100-watt monocrystalline panels for $319 from Renogy, along with a charge controller. (Monocrystalline panels offer a higher output for the same surface area as polycrystalline.) Though they were the correct physical dimensions—with barely an inch to spare—we had not considered their weight. Only after they arrived did we realize that having 16-plus pounds hanging from the top lifeline, supported by a leg that extended 21in past the rail, was not going to be feasible. The method we had used to mount our smaller, lighter panels was not going to work with these new monsters.

The brackets are tensioned with eyebolts; not visible here is the Starboard backing plate

To address the issue of weight on the lifelines, we decided to install a stainless steel tube between the stanchions to hang the panels on, and while trying to agree on the best place to do so, we had our greatest epiphany of the project. What if instead of hanging the panels from their edges, we did so from their middles? Only about 11in would overhang the boat when the panels were horizontal,and at the maximum, only half the panel weight would be cantilevered. With a vague plan, we started assembling.
In our final configuration, the 1in stainless steel tube is attached to the aft two stanchions by stainless clamp-on jaw slides, just above the lower lifeline. Rather than relying on the setscrews, we through-bolted the tube to these fittings. Holding a solar panel vertically so that its top edge was just below the top lifeline, we marked the height of the tube on its frame. This mark was not in the center of the panel, because the panel would not clear the toerail at that height. Now that we knew where the panels would sit in relation to the pipe, we had to find a way to mount them in a manner that allowed us to adjust them.

Clamp-on jaw slides secure the stainless steel tubing to the stanchions

Dave started with two 1¼in lengths of 1in inside-diameter aluminum pipe. He had a machinist near the marina weld two squares of aluminum stock to each of these, off-center, with some space between them. Dave then sawed edgewise down each ring of pipe, just off center. Since one of the “halves” is greater than a semicircle, it must be slid onto the stainless tube, but this also means it cannot pop off. After drilling holes in the two tabs of each bracket, he held these to the panel (at the previously marked height) to determine where to drill the accompanying holes in the panel’s frame. He then cut out two backing plates of Starboard, drilled them to match the holes in the panel frame, and installed T-nuts. Finally, he cut a 1/16in stainless sheet and bent it to the shape of the brackets to act as a safety—if a weld breaks, we won’t lose our panels.

When we are under way, the panels are tilted vertically

For the top holes, we used eyebolts (rather than bolts) through a washer and nut (to give a flat bearing surface), creating a “handle” that makes adjusting the panels easier. To adjust the panels, we loosen the eyebolt, tilt the panels to the desired angle and then retighten the eyebolts. By using 1in ID aluminum pipe for the brackets, there is continual surface contact between the bracket and the pipe, creating enough friction to hold the panels easily. Otherwise, the bracket or the pipe would be point-loaded and more force would be required to keep the bracket from spinning.

The panels clear the winches so they can be tilted toward the sun when it is on the opposite side of the boat. By loosening the eyebolts two turns, the panels can be slid fore and aft on the stainless tubing to remove them from the shade of the bimini or to accommodate dock lines. We do not usually sail with our panels raised, but in calm seas with light, predictable wind, we have the option. We are aware that any shadow on a solar panel greatly decreases its output, but monocrystalline panels are more shade tolerant and we have twice the number of watts that we need, so a small shadow is acceptable. The dissimilar metals (aluminum and stainless) can also become a concern if you are not careful. Any time we assemble a project aboard that requires two metals to come in contact, we separate them with either a hard barrier (nylon washers, for example) or lanolin. In this case, each piece was liberally coated with lanolin to protect the metals.

The panel deployed to catch the midday sun: the cat likes the shade!

As the market continues to grow, no doubt solar panels will increase in capability and variation of sizes. For those looking to install panels for the first time or replace old panels, mounting them so that they pivot between the lifelines makes installing large, heavy panels more feasible.

Connie McBride and her husband, Dave, sailed away in 2002 on their 34ft Creekmore, Eurisko. After many years in the Caribbean, where they raised their three sons aboard, they are now empty nesters, meandering their way around the tropics

March 2016

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