Electronics, GPS and VHF, Part 3: Construction of the Mahogany Panels

The mahogany panels, custom cut for the Garmin GPSmap 541s
Those who upgrade their electronics often find that their new devices do not fit their old holes. The new device is either too large, too small, or simply not the same shape as the old one. In these circumstances, the sailboat owner is faced with two choices - either he can fill the existing hole with fiberglass, and then cut a new hole, or he can cover the existing hole with a panel of wood or plastic, and then cut a new hole through this panel. The primary benefit of the first option is that the new hole will be just the right size. This, of course, will allow for a nice, well-sealed fit. The downside of this option is that the filling of an old instrument hole can be a time-consuming chore, and it can be one that has less-than-pleasing results, unless of course the surface is well-faired, well-sanded, and well-painted. In the refitting of Oystercatcher, my Ericson 25, I had no plans to repaint my deck. Therefore, I decided that the filling of the old instrument holes was not a task that would be wise for me to undertake. Accordingly, I opted to create a panel to cover these old holes. From my standpoint, the panel would serve two roles - one practical and the other aesthetic. First, it would serve as a sturdy surface for the mounting of the device. Secondly, it would serve as an attractive trim piece. In other words, it provide an aesthetically pleasing frame that would not only accent the shape of the device, but also complement the mahogany found elsewhere on the boat. In this posting - the third of seven - I describe how I created these mahogany panels that would cover these holes.
As is often the case, I started this little project with a cardboard mock-up, or I should say mock-ups. I didn't take any pictures of these mock-ups at this stage in the game, but I can say that it took a good bit of cutting and re-cutting to figure out their proper size. The exterior panel had to be big enough to cover the two holes, but it couldn't be too big. Otherwise there would be problems matching it up with the interior panel. What do I mean by this? Well, the exterior side of the cabin trunk is completely flat.
The interior, however, is not. There is a piece of fiberglass which runs the length of the companionway - sort of like a lip. On this fiberglass lip there is a piece of teak. It forms a frame of sort along the side of the companionway. As you can see in the picture below, this frame is not far from the instruments and thus the instrument holes.
Satisfied with the mock-ups, I cut the two panels to the appropriate sizes. Note that the one on the right is slightly longer. This is the interior panel. I wanted it to be slightly longer so there would be plenty of wood for the washers and nuts, which would be on the interior.

Next, I drew reference lines on the exterior panel. These would help me in the drilling of the holes for the screws, and in the cutting of the hole for the GPS.
For the drilling of the holes, I used a screw-set, i.e., a bit that allowed me to drill each hole and countersink each hole, all in one step.
I drilled and countersunk the first hole, at the top of the panel. Before countersinking all of the other holes, however, I put the GPS template down, just to see how much room I had to work with. As you can tell from the picture below, I had very little. Ideally, this panel would have been about an inch wider on each side, but as I said, I was restricted on the interior of the boat by the frame around the companionway.
Why so many screw holes you might ask? Well, I had to make sure that this panel would form a nice, water-tight seal around its edge (with, of course, the proper sealant applied).
You might also ask why I would situate the GPS on the upper end of the panel rather than in the middle of it. All I can say is that, to me, this looked better. From a practical standpoint, it also meant that the backside of the GPS on the inside of the boat would be slightly higher and thus more out-of-the-way.
The template provided with the Garmin flush-mount kit (which I purchased independently of the Garmin GPS) was helpful. Unlike many other templates I've used for other things I've purchased for this boat, this one had a sticky back. It also had clear instructions on where to drill holes and cut holes.

Given that this piece of mahogany was only about 3/8 inch thick, I had to be especially careful, when cutting the hole, not to apply too much pressure with the jigsaw. This mahogany was tough, and I doubt I would have broken it, but why tempt disaster? For more on the type of mahogany I used for this project, see my article, "Companionway Hatch Construction." See also the Label on the homepage for "Southern Lumber."
The Garmin, flush-mount housing fit just right in the hole. Note the rubber bezel around the housing.
The GPS dry-fitted with the cover in place.
Keep in mind that throughout this process, I had not yet screwed the panel into place on the face of the cabin trunk. When the time arrived for me, at last, to screw it into place, I began with the hole at the top of the panel. This allowed me to pivot the panel to achieve a level position.

The interior as it appeared after I had drilled all of the holes.
Now it was time to make use of the cardboard mock-up once again.
Having partially installed the exterior panel, I could now get a good sense of how exactly the interior panel could fit against it. The screws from the exterior provided precise points by which I could orient the interior panel, or I should say "mock-up." Notice that in the picture below I have trimmed the mock-up on the top right corner so that it will fit within the frame of the companionway.
Using the mock-up as a guide, I trimmed the interior panel to size. Then, I clamped the exterior panel to the interior one, and scribed the cut-out for the GPS housing.

Afterwards, I dry-fitted the interior panel. It just barely fit. Nevertheless, it did a great job concealing the original holes. It should be clear now why the interior panel was necessary. Without it, the installation of the GPS would have look shoddy, and the hole, through which it would have been mounted, would not have been as sturdy and well-supported.
The construction and installation of the exterior and interior panels had brought this project much closer to completion. It was still necessary, however, to cut out the two layers of fiberglass between the two panels, so that the GPS housing and the GPS itself could be situated within the panels. This next part of the project is the subject of my next posting.
This ends this posting on how I constructed the mahogany panels for the Garmin GPS that I installed in Oystercatcher, my Ericson 25.

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