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Building a Custom NavPod Instrument Housing?

posted Jun 30, 2011, 5:54 AM by Christopher Hubbell   [ updated Jul 1, 2011, 12:21 PM ]
I've been going back and forth in my mind on the decision of how to present my chart plotter and auto pilot control head.  My first strategy was to mount the AP on a NavPod rail mount off the side of my pedestal guard, and then attach the plotter... Somehow...  That plan was trashed when I saw that the NavPod for an ST-60 size instrument was the size of 3 or 4 stacked instruments.  I hate clutter, and I don't want my housings any bigger than absolutely necessary.

The second plan was to use a NavPod to house both the plotter and the AP.  After staring at dimensions for a few hours I came up with one model that sort of had the right height and width, although not as proportional as I'd like.  Unfortunately, these things have way more depth than necessary, and again, would look pretty huge at my boat's helm.  On a big boat none of this matters.  In a tight cockpit, everything matters.

The biggest observation that soured me on the NavPod is the cost.  It's nearly $400 for the plastic box that fits my instruments.  I've laid up quite a bit of fiberglass, and I really have trouble understanding how these devices need to cost $400 with modern assembly techniques.  Yet another example of the Marine tax I suppose.  While I can still make that work into the refit budget, it feels like throwing money away.

My current line of thinking is to put together a custom box built from 1/4" high end plywood.  Pretty much all plywood these days uses waterproof glue, and the high end stuff I have left over from a previous project is very straight.  I'll then put somewhere between 1 and 3 layers of fiberglass cloth over it for strength and weatherproofing.  I believe that just 2 layers of epoxy would do the trick, so I'll probably be closer to 1 layer of cloth.

Rather than using epoxy fillets inside, I will use square strips at either 1/2" or 3/4" depending on what scrap wood I leverage from my pile.  These will be epoxied in place, and then filleted at top and bottom edges.  The purpose of these strips will be to add material to the corners to allow me to use a good round-over bit all the way around the box.  That's important not only for fiberglass layering, but also for safety.  The entire inside will be "painted" with two coats of un-thickened epoxy for water proofing and durability.  I doubt I'll bother with fiberglass on the inside.

The box will attach to the pedestal guard either with U-bolts or #10 screws and acorn nuts.  I haven't decided which way I want to go yet.  The last detail is how I'll allow the box to open and close for wiring access and seasonal removal.  I'm thinking about a access plate in the bottom approximately 4" square.  That should allow access to the internals with minimal impact on the box's overall strength.

I'll fair the outside with Microlight, then either spray it with a nice Krylon white enamel, or use Brightsides rolled and tipped.  Again, not sure which one I'll use yet, but I think either will look great.

What will all this cost?  I already have all the wood I need, so that part is free.  I expect I'll need about $30 in epoxy and another $10 to $20 in cloth.  So, do I choose $400 and a so-so fit with my needs, or do I chooses $50 and a prefect fit?  I think you already know which way I'm leaning.


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