One of the problems encountered by sailors adding gear to their boats is where and how to mount it securely with easy access. Samples of such equipment are macerator pumps, Y-valves and associated plumbing, watermakers, antenna tuners, fishing rods, and the like. Rather than search for a nearby existing bulkhead on which to mount new equipment, it is frequently better to fabricate a 1/2-inch marine plywood mounting base off the boat and fiberglass it against the inside of the hull. Many times an adjacent bulkhead – in the head for example – is not suitable for mounting equipment and makes mounting the equipment and operation of its valves and plumbing or wiring difficult if not impossible.
The objective is to mount equipment so as to provide easy mounting and access. In many cases, the best location is against the inside of the hull. The beauty of making up a mount to fit the inside of the hull is it can be entirely cut to fit and fabricated off the boat using a shoreside workbench and power tools, minimizing boat power consumption and dust. The mounting holes can be pre-drilled ahead of time. It’s even possible to make up an entire electronic console to mount above the nav-station with sliding bases for electronic equipment. A head Y-valve installation is described; an easier fishing rod or antenna tuner installation follows the same steps. A macerator pump, washdown pump and watermaker will require a similar careful study of plumbing and fitting as a Y-valve.
With the valve or pump in hand, the first step is to move it about against the hull to find the best orientation, keeping in mind operation, maintenance, wiring, and the necessary plumbing to follow. Holding the valve in one hand, the distances from the top and bottom of the valve to the hull are measured. This becomes the rough size of the mount. As with all head plumbing it should be as short as possible with very few right-angle bends. The Y-valve can be mounted against the inside of the hull at almost any workable orientation. A stiff cardboard template can be cut to fit the hull curvature and used to help fit the mount. The mount should be several inches larger than the Y-valve to allow for adequate support and space for the fiberglass tape.
Generally for the mount to be nearly vertical, a plywood spacer will be needed at the top to allow for the top-to-bottom curvature of the inside of the hull. Most hulls are compound curves, which means the mount will be curved at the bottom and the spacer will be curved to fit at the top. If the hull is curved a great deal the top spacer will be much larger than the bottom spacer and can double as a shelf. The mounting base for the Y-valve need not be perfectly vertical; in fact, it may ease operation if the mount is at an angle.
The mount and spacer are first made up square and then trimmed to fit the hull curvature. The cutting and fitting will usually take several tries. The cardboard template can be cut and used to help shape the plywood mount. Fortunately, the assembly need not fit the hull curvature exactly since the two-inch fiberglass tape will easily span 1/2-inch gaps between the mount and hull. It will look fine when it’s painted.
The mount and top and bottom spacers are screwed and cemented with 5200 together at right angles at the top and bottom and the Y-valve placed in position on the mount. If through-bolts rather than wood screws are to be used to hold the Y-valve in place on the plywood mount, now is the time to think of how to tighten the nuts. Properly sized woodscrews or sheet metal screws are easier to use and hold well in 1/2-inch plywood. Make sure the screws are not so long as to exit the plywood on the back side and nick the hull.
Once the plywood mount has been shaped to fit the hull curvature and the Y-valve mounting holes are pre-drilled, two-inch fiberglass tape is cut to length top and bottom to hold the mount in place. Reasonably quick-drying West System epoxy or similar fiberglass resin is painted on the tape to hold the mount in place using a one-inch throwaway foam brush. If the area is particularly difficult to get at the tape can be epoxied to the mount off the boat and allowed to dry before the mount is set in place. Be careful to only epoxy 1/2 the tape on the mount!
The unepoxied half of the tape is bent to attach the mount to the hull. The mount can be held in place with wedges, clamps, or 5200 while the tape is pressed against the hull and painted with epoxy resin. The ends of the tape that inevitably appear and harden can be clipped or filed off later. The entire mount is then painted the color of the inside of the hull. The Y-valve is screwed to the mount and the plumbing completed. The hardest part of the project is locating the valve to allow short, straight plumbing, easy access and valve operation. Because of the compound curves you will typically measure, cut, and try several cardboard templates before the plywood mount is fabricated.