Now that I'm finally home, I reread everyone's posts and thought about this more. Attached are a few more pictures to further this discussion. To summarize what's probably going on, along with my opinion,
The boat is a 18 year-old Tartan. In my opinion, the boat is well maintained and was ready for the passage to Hawaii
. All of the critical systems were replaced or upgraded, though as we discovered, a few things lead to problems along the way.
The rust is mostly concentrated around the stanchion bases and the rub-rail. Photo
"race start" shows a clean deck (yes that's a whale outside SF Bay). Photo
"14 days later" shows the stained deck (with an small experiment cleaning
the deck using Barkeepers Friend on stbd by cockpit).
It is interesting that the "bow" picture shows staining on the bow pulpit by the nav-light. As seen in photo "bow-light" the nav-light also shows serious corrosion at the base and further on the inside of the fixture. The bow-light stopped working a couple days into the trip. The nav-lights were on at night for stern light.
There were also signs of corrosion inside the stbd cabin light in the v-berth. During the trip, I did notice that the stbd run of cabin lights were not working properly. The LEDs were flickering and sometimes wouldn't light. After the race
, I measured the voltages and saw 8 volts at the forward electrical
connection and along the starboard side. I also noticed a few bad electrical
splices along the run.
I agree with Panacea, it sure looks like accumulated build-up of rust, poor bedding and possibly poor quality screws at the stanchions and the rub-rail. Chainplates and the standing rigging
are clean -- probably due to better quality stainless.
The fact that the bow-light stopped working early in the trip and was awash in sea-water throughout, implies to me that with each wave breaking over the bow, 12 volts was emitted into the salt-water and created a stray current
. Per "bow-light" photo, the 12 volt plus and minus contacts were exposed to salt-water and they corroded. This appears to be caused by a broken plastic gasket
between the base and lens. Also, the bottom screw holding the lens to the base was stripped. The fixture was not sealed, wet, exposed to sea-water and energized for 8-10 hours per day. I believe this introduced current into the boat and accelerated the corrosion on the lower quality stanchion screws.
Likewise, there is a 4 - 6 volt drop along the interior
stbd cabin lights electrical wiring
. The v-berth portlight appears to be leaking, letting salt-water into the light fixture, photo "wet-cabin-light". My original thought was this introduced stray current into the boat and to the nearby common grounding wire connecting the stanchions. This clearly is a problem, but after discovering the bow-light, I don't believe the interior
cabin lights are not the major cause.
It is possible that this is not related to any stray electrical current throughout the boat. Instead, this might be completely due to poor quality screws and bedding. Over the years, the screws may have been corroding away and the rust may have accumulated at their bases and deck core
. Only when washed out by constant breaking waves over the sides, did the build-up leach out and stain the deck/sides.
A lot of folks at the yacht-club thought the problem was due to the SSB installation
. Their claim is the ICOM
manual describes grounding the radio
and tuner to the stainless steel
stanchions, etc. using copper foil (I verified this on page 55 ic-m802.pdf installation manual). I don't have an ICOM
802 (on my wish-list); I have an old SEA 235 radio
. My installation manual describes connecting the antenna
tuner to a suitable "RF ground" and no reference to grounding the radio to the RF ground. In discussing this with SEA radio technical support, "the ground stud on the radio is duplication of your DC minus battery
connection, should be connected to a close ground if the DC minus lead is very long. The critical connection for the RF ground is the stud on the antenna
tuner...". I didn't see a lot of RFI issues on this boat.
The SSB was used for at most an hour per day and was not connected to the common grounding wire between the bow pulpit, stanchions and stern pulpit. I can't imagine any stray current between the radio 12 volt ground and ships ground or RFI creating such a severe case of corrosion. Furthermore, I've used the same radio, antenna and Kiss-SSB ground on 2 different boats (similar offshore conditions) and never seen this problem. I don't believe the SSB had anything to do with this.
I plan on measuring the voltage between the stanchions and seawater - I will do this once the boat is home. I also am going to try to simulate waves breaking over the bow-light, to see if that changes the voltage reading. That would confirm my belief that the bow-light introduced current to the stanchions. Good thing this is only 12 volts!
Aside from the electrical issues with the bow-light and cabin lights, I'm now concerned about poor bedding and accumulated corrosion at each of the stanchion bases. Years of accumulated water build-up might lead to damaged deck core material that requires more extensive repairs
. We didn't have a chance to remove a few of the stanchion screws to see the extent of the problem. Once the boat is home, we'll certainly remove them all, check for core damage, rebed and replace the hardware.
I welcome further discussion on this, though we won't have the boat back for a few weeks.