The Misadventures of Mounting a Masthead Meter

Excited to get our new Garmin GWS 10 wind instrument mounted atop the mast and feeding info back to our chartplotter, I started Sunday afternoon by removing the mainsail and rigging the MastMate. I had four items on my checklist, run a new halyard, mount the new wind instrument, drop the NMEA 2000 cable down the mast, and change the bulb in my steaming light.

It should have been a straight-forward project … emphasis on should have.

MastMate05

For my first run up the mast, I packed a stubby phillips-head screwdriver, a stubby flathead screwdriver, a tiny phillips-head screwdriver, and a pair of pliers.

The steaming light, which I’d never serviced before, had phillips-head screws. Unfortunately, one of my screwdrivers was too large. The other was too small. No worries, I’d get it on the second trip.

I climbed upwards to the masthead.

I needed to unscrew the anchor light that I’d just installed a few months ago to then remove the top plate of the mast. This time my screwdriver was the correct size, but because I’d brought the stubby one, the handle wouldn’t let me get the tip on the head of the screw.

On my old boat I had many extra halyards, so it was easy to hang a bag on one and run tools up and down. We don’t have that luxury on Gimme Shelter, which is why I was planning to run a new halyard.

I climbed back down and reshuffled my selection of tools. Then I made my second climb.

This time I opened the steaming light and pulled the bulb, although it didn’t look burned out.

I got back up to the top, removed the anchor light, and opened the top of the mast.

As I moved the new sheave into place at the front of the mast, I realized that the new halyard would have to be run inside the mast, but I had no holes for it to run back out of the mast. No worries, I’d move that job to the end of the list, and if I had time I’d go grab a padeye and drill a new hole for it.

I came back down the mast and set to work drilling and mounting the Garmin GWS 10 wind instrument.

Within a few minutes I had the wind instrument mounted and found a replacement light bulb for the steaming light.

GWS10mount

The day was getting better.

I made my third climb up the mast with wind instrument in my backpack and the NMEA cable tied to my belt. I started running the cable down the mast and then sent Mary to go pull it out the bottom.

We ran into a small problem — there were no openings in the bottom of the mast.

I just assumed that since there were other cables running out of the foot of the mast that we’d be able to fish the new cable out as well. I assumed wrong. I came down from the mast and drilled a new hole.

masthole

That’s when I ran into an even bigger problem — our mast was full of foam. And it wasn’t just a little bit of foam, it was 6′ of foam all the way from the foot of the mast to the cabin top. There was no way to poke a cable through.

I climbed up the mast for the fourth time and pulled all of the cable back out of the mast, then dropped it back down the side of the mast to Mary. I screwed the mast light back on and secured everything at the masthead and made my way back down to the steaming light.

This trip I’d packed a multimeter, so I checked the fixture only to find I was getting plenty of current. I then jiggled the bulb and found that if it was in the fixture cockeyed, it would come on, but when it was properly seated, it didn’t work at all.

I spent a few minutes cleaning it with a wire brush but got not improvement, so I left the steaming light as an unsolved mystery and climbed back down.

At this point my legs were toast, I had a new hole in the mast, but not in the place where I needed it, and the steaming light still didn’t work. However, the wind instrument is now mounted.

MastheadwithSensor

Next weekend we start again securing the NMEA cable to the outside of the mast and take another shot at getting the steaming light working again.

Lessons learned

I wish I’d connected the anchor light with a waterproof plug instead of splicing the wires together. If I had used a plug I could just leave the light fixture connected when I remove the top of the mast. It would have made this project much easier.

I should have done more research on my mast. I should have checked to see if it was open at the bottom for the wiring, although I don’t know how I could have known it was full of foam. I also assumed I could run the new halyard externally, but that proved impossible without a spinnaker crane.

Installing a NMEA 2000 backbone

One of the things we liked about our new Garmin chartplotter that we installed in December was its connectivity.

DSC07547

The chartplotter was our first electronic device with a NMEA 2000 plug.

NMEA stands for National Marine Electronics Association, and 2000 is the standard set for communication between devices. Garmin sticks with a NMEA 2000 nomenclature, but Raymarine SeaTalk, Simrad Simnet, and Furuno CAN are all rebranded NMEA 2000 systems that only need a plug adapter to be compatible.

Theoretically, any two NMEA 2000 devices will connect and communicate with each other no matter the brand. However, since we’re starting from scratch when it comes to the electronics on Gimme Shelter, we decided to stick with Garmin as much as possible.

The first step to setting up any NMEA 2000 system is to install the backbone. We went with this Garmin NMEA 2000 Starter Kit that cost about $60 through eBay.

NMEAstarterkit

The only directions that came with this kit was the diagram on the label. That’s it. It’s THAT simple. However, I chose to hook the yellow cable, which is the 12 volt power cable, to the chartplotter circuit on the back of my breaker panel instead of directly to the battery.

DSC08069

Once it was tied into the power system, I started adding T connectors. (Note that there was terminator plugged into the open end of the backbone when I finally took the photo.)

Tconnectors

The starter kit came with two T connectors and two terminators. I ran a cable from one T to my chartplotter. I ran the other cable to my GWS 10 Wind Instrument.

GWS10

I switched the chartplotter to the “gauges” setting, chose wind, and … nothing.

Nothing happened at all. It didn’t work.

I stared at the diagram. I retraced my wiring. I pulled the breaker panel off again and re-checked my power connection. It just wasn’t doing anything.

I finally resorted to Google and almost immediately I found out the most important detail of this system.

NMEA 2000 doesn’t work unless there is a terminator on every open T plug!

The starter kit had come with two terminators, and I hadn’t bothered to put them on. I figured they were just to keep the dust out or something. Wrong. It turns out there’s a resistor in those terminators, and unless they’re on the open plugs, no signal gets sent anywhere.

So after plugging a terminator onto the end of the backbone, I turned on the chartplotter again. This time I had success!

windinstrument

Now all it takes to add new devices to my system is another T and a NMEA 2000 cable.

Of course, setting up the backbone was the easy part. The real fun starts this weekend when I climb the mast to drop a new cable and mount the wind instrument.