Wednesday, May 8, 2019

Lightning damage report and spaghetti wiring

As I promised in an earlier post, I wanted to circle back and do a final tally of damage and repairs from our lightning strike. I will also provide a bit more detail about our electronics setup. This post will concern nothing else, and I will return to our travelogue next post.

If you arrived at this post via a direct link, the background is that we took a direct lightning strike a little over two weeks ago. I described the event and posted video, including a spectacular capture of the bolt itself, in this blog post. I posted some additional damage photos in this one.

All of our VHF antennas are on our mast except one, for the flybridge VHF radio, which is clamped to the frame of the flybridge soft-top. It is this antenna which served as the entry point; the strike blew out the coax at the base of the antenna and arced to the frame, where it was conducted down through the aluminum house, into the steel hull, and then out into the sea via the hull anodes.

The most striking and obvious damage was to the antenna itself. The strike cause the upper 18" of the fiberglass casing to explode, sending fiberglass shards in all directions. Probably the single most expensive piece of damage was the resulting hole in the Weblon fabric of the soft top, where one of the shards was shot through it like a bullet, landing on the flybridge settee. (Photos are in the posts linked above.)

I plan to repair the soft top with some self-adhesive fabric repair tape for ten bucks. But if we were filing an insurance claim for this, the whole top would be replaced, and when last we had that estimated, back in Charleston when we repaired it from storm damage, it would have run a couple thousand. We opted to repair it at the time instead, for around $500, with the shop estimating it would only last perhaps another year. That was two years ago so it is on borrowed time, anyway. We're glad we have a hole in an old piece of Weblon that already has patches (from where we removed antennas), rather than in a new top that they wanted to sell us.

Two pieces of equipment fried outright. One was a Furuno RD-30 NMEA display on the flybridge which displays depth, speed, and water temperature. I acquired a used spare for that display some time ago, which I've now placed into service. The other was a SeaCAS GPS/AIS receiver, which provided a completely separate and redundant position and AIS data feed to the also separate and redundant plotting computer at the pilothouse settee, where the off watch sits. SeaCAS is out of business and there is not really a replacement for this piece of hardware, so the backup plotter is now fed from the AIS transponder.

For absolutely everything else that had damage, that damage was limited to serial port hardware.  All of Vector's navigational electronics are interconnected with NMEA-0183 signals, which consist of ASCII text sent over RS-422 or RS-232 serial lines at 4800 or 38,400 bits per second (BPS). These sorts of signals are sent and received by circuit chips known as UARTs, or Universal Asynchronous Receiver/Transmitter chips. UARTs are particularly sensitive to high-energy pulses, and they are infamous for burning out even from current induced on the serial line by nearby equipment such as large motors.

It's not surprising, then, that the electromagnetic pulse from a lightning strike was enough to fry a whole bunch of UARTs. Unfortunately, UARTs are typically soldered directly to the main boards of most equipment and so once they're gone, the entire device needs to be replaced. This was the case with our very newest piece of gear, a VHF radio with integrated GPS and AIS receivers.

The radio itself, including all its whizzy AIS features and other bells and whistles, is perfectly functional, but the two NMEA data ports that send GPS, DSC, and AIS information to other equipment are now silent. I had to just buy a whole new replacement radio. I tried to sell the take-out to someone who doesn't need the NMEA output but found no takers; it's been relegated to the spares locker.

The four-port USB-to-serial adapter on the main chart computer was another casualty, as was the USB port on the computer itself to which it was connected. The computer has four USB ports (also built-in to the main board) and so I just plugged the replacement adapter into a different port. A small USB hub that I had lying around allows me to consolidate the two keyboard/mouse dongles into a single port so we still have one available for file transfers on a USB drive.

One of the UARTs that was lost was one of the four built in to the main Radar/plotter in the pilothouse. That port principally drives the backup input to the autopilot, to be used only in the event that the main plotting computer becomes inoperative. A couple of other items that were eavesdropping on that output had to be redirected elsewhere, but otherwise we don't notice it's gone.

I might just as easily have swapped the main board out of the identical flybridge radar/plotter display, which itself does not use any of its NMEA ports. But then I am putting two working radar/plotters through risky surgery rather than one, so for $200 I bought a third display that had some screen damage to use as an organ donor. It will be a good source for other parts should they be needed in the future.

Lastly, one of the UARTs in the J300X autopilot computer went out. I swapped in a spare for that as well, leaving me with two spares needing replacement: the J300X, and the RD30 from the flybridge. That makes a total of eight serial ports lost in the strike, in addition to the three inside the two fried devices.

This is what we've spent on repair/replacement items:

Shakespeare 5104 VHF antenna$50
SIIG 4-port USB serial adapter$50
Mini USB hub (to replace bad port)$10
Used RDP-149 radar for main board$200
Standard Horizon GX2200 VHF with AIS  $350
Used J300X autopilot computer$150
Used RD30 NMEA display$150
Fabric repair tape$10

None of these numbers, of course, accounts for the value of my time. I've likely spent close to 30 hours already on fixing everything, and I'm not done yet. A marine electronics tech would charge north of $100 an hour for this work, and what's worse, it would actually take them longer. That's because there is a certain amount of time involved in just sorting through an existing system and understanding how everything is put together.

This is, in part, the reason why so many electronics problems on boats end up being solved by an entirely new system. It's far easier for an installer to just get a BrandX radar, a BrandX plotter, a BrandX autopilot, and a BrandX depth sounder, plug them all together with the cables supplied by the manufacturer, and know that it's all just going to work. Between the cost of the components and the labor of running new cables all over a fully finished boat, an electronics failure like a lightning strike can thus easily run close to $30,000. It can also waylay your boat for four to six weeks waiting for parts and techs.

I have detailed notes in a bound composition book about how everything on Vector is wired together. I've also, over time, combed through the tangle of wires that comprised our NMEA "junction" when we got the boat, lying in a wad on the floor under the helm, and arranged them in neat terminal blocks fastened to the backboard, so rewiring signals may be tedious but is not the head-scratching exercise it once was.

The complexity of the interconnection diagram means that making changes to the handwritten copy in my notebook can be an exercise in frustration. I mostly have to draw it anew each time I make a change. Having been at sea with no Internet for the last day, I finally climbed enough of the learning curve on a new drawing program to get a halfway decent diagram made up. Now I should be able to make changes electronically without having to draw the whole diagram over again by hand.

It's not perfect by any means. Trying to keep it on a single page meant I did not have room to put all the NMEA sentences being sent next to each line as I had wished, for example. And I had to take a couple of shortcuts to keep things readable. For example, the actual control boxes, under the helm, for both the autopilot and the stabilizers are omitted, with the autopilot control head and the stabilizer fin itself standing in for them on the drawing.

While the drawing is really for troubleshooting and re-configuring the NMEA serial connections, I found it useful to include some of the other connections as well, because it is not always clear just looking at a black box what sorts of connections it has. So the radio frequency (RF) pathways are included, as are the Ethernet that connects the radar repeater display, the RobNet (proprietary Simrad/Robertson network) that connects the upstairs autopilot control, and the "AD10" heading signal supplied to the radar by the autopilot, required for ARPA.

I used different colors for the two different NMEA bit rates, and the direction of signal flow is indicated by arrowheads. Some NMEA connections are shown as bidirectional, but that's for drawing clarity. Such a connection is really two circuits, one in each direction, and an outgoing "talker" is allowed to have more than one incoming "listener." Where a device has multiple ports, the connection is identified with the port it goes to, as labeled on the device.

The connectors seem to run amok on the page because I did not want two lines of the same color to cross. The connection between the two depth displays does not really run down to the bilge first, for example. The connection to the stabilizer control doesn't go to the bilge, either; the control box is under the helm, and solenoid control signals run from there to the bilge. And the connection from the AIS transponder to the Radar/plotter does not really run all the way around the room. Such is the nature of schematics.

A printed copy of this drawing is being posted at the NMEA junction block under the helm, and another copy will be kept in the Operations and Procedures binder we keep at the helm. When a display suddenly stops working it's helpful to know what upstream devices are actually supplying the information.

As it stands today, everything shown on the drawing is working, with the lone exception of the NMEA data connection from the radar/plotter (Data4) to the autopilot computer (NMEA2). Both of those ports are still dead, and will be replaced when we get enough downtime to do it. As I wrote earlier, that connection has never been used (except for testing) and would only be used should some catastrophe befall the main plotter.

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