New Chainplates

Clark November 30th, 2016

I had to remove a few chainplates for an unrelated project and one of them broke upon removal. I guess I can count myself lucky it happened this way, rather than in full combat mode. Only 49 years old, and it just fell apart in my hand! I plan to write a strongly-worded letter to these Alpha England people about the quality of their product:

I blame the dreaded crevice corrosion:

Years ago I read something about replacing stainless chainplates with titanium, which is stronger, doesn’t corrode, doesn’t crack, and yada yada. I looked into it, and Holy Halyard Slaps! For the price of two simple (meaning flat), small, titanium chainplates I could buy enough 316 stainless bar stock in AND A BRAND NEW DRILL PRESS, which was long overdue:

Upon further reflection, I might have made them out of silicon bronze, but if my 316 stainless chainplates last half as long as the old ones I’ll come out winning. Brion Toss has a good riff on the subject here.

After getting my bar stock from and my new benchtop drill press from good old Sears, I set to work. Cutting was straightforward with an angle grinder with a stainless cutting disc, followed by a grinding wheel.

Drilling holes was also straightforward, using the slowest speed on the drill press, and lots of cutting oil. The old chainplates were countersunk for flat head screws. This would not only be a lot of work, but it seems to me it reduces strength by removing material, and provides a lot of hidey holes for crevice corrosion. My new chainplates will have non-countersunk holes and round head screws, with heads standing proud.

Then comes the hard part: They say the way to prevent corrosion is to polish the chainplates to a mirror finish. I was more or less successful at this, but I started my sanding with a 50-grit disc on an angle grinder, which left some irregular gouges. In the real metal polishing world they have all kinds of wheel sanders for the heavy stuff. I moved up into my higher grits with an orbital sander, then stainless polishing compound on a polishing wheel. All went well, but in the final result I could still see the gouges from my angle grinding. I’d say it’s good enough, and still qualifies as a “mirror finish,” but a mirror finish on some ridges and valleys left by my aggressive angle grinding. I think a belt sander would do a better job, but my belt sander broke.

While I was at it I replaced the backing blocks on the interior with G10. The old backing blocks were teak:

I’m on a kick lately of using butyl rubber, instead of polysulfide, for bedding deck hardware. Which is better? Ask me in twenty years. With butyl rubber it’s a long process of gradually tightening the fasteners over days or a week, as it is stiffer stuff, and takes a long time to squeeze out and find its place:

What Is It?

Clark November 8th, 2016


I was working on a boat in a dry storage area in San Leandro, California, when I saw the boat above. What this strange aperture in its side? On closer inspection the outside of the aperture has fixed vents, made out of plywood:

This outside part does not rotate. In the middle is a galvanized steel pipe, which is designed to rotate, as it is supported by several carrier bearings athwartships:

But on the other side of the boat this axle just sticks out an inch through another hole in the topside, with nothing like the contraption on the starboard side:

I’ve been noodling on it for a few weeks and have absolutely no idea. It wasn’t some thoughtless lark, because the vent thing on the starboard side is very symmetrical, and took a lot of work.

A sideways jet engine? Some sort of revolutionary propulsion system? Something not even meant for water; an unrelated project for which a fiberglass runabout just seemed like the right raw material? I’m stumped.

Advanced Electrical: Galvanic Isolator Case Study

Clark November 4th, 2016

Once I was buying a galvanic isolator in a West Marine store, when a West Marine employee, of all people, was really insistent that I shouldn’t buy it: “Those things are a scam! They don’t do anything. I have it on good authority that they’re a big waste of money!” He had that look in his eye, so rather than get all marine electrician on his ass, I just said, “Well, my customer wants it, so I think I’ll buy it all the same.” There are a lot of misconceptions about the purpose of a galvanic isolator, and what it can and can’t do.

Flash forward to this week when another friend/customer calls me down to his boat, says his zinc anodes are being eaten too quickly and he’s thinking about a galvanic isolator. When I get there he shows me a propeller shaft anode that a diver had replaced just over a week before, and it’s already over a third eaten. To get to that stage should take a few months.

A galvanic isolator will sometimes, but by no means always, solve the anode-eating problem. A galvanic isolator is installed in-line along the safety ground (grounding conductor, green wire) in the shore power connection, so of course if you’re not plugged into shore power at a dock, then you’re barking up the wrong tree.

My customer was plugged into shore power, but being a thorough guy I unplugged him from shore power and did a galvanic survey of all the underwater metal items on his boat using a reference cell, dangling in the water, connected to a digital multi-meter. All the numbers came up about right for a standard fiberglass boat, his bonding system was all intact, and he had the right amount of zinc anodes to protect his underwater metals.

But if we plugged in his shore power cord, his hull potential changed by about 200 millivolts. Aha, problem found, but people want to point to some AC problem, since this is coming from the AC shore power cord. Nay. Galvanic corrosion and stray current corrosion are caused by DC currents.

In fact, I could measure half an Amp of DC current by putting my Amp clamp, on the DC setting, around his shore power cord.

If your boat is bonded properly then all of the major metal parts, above and below water, are bonded together, usually using big green wire. It will also have an AC safety ground, also usually green wire, connecting all the AC outlets and appliances, just like at home. These two systems cross-connect at one, and only one, point. So, when you plug into shore power, your boat is connected, via the safety ground, to the safety ground system on every other boat on the dock, and thus to the bonding system and all the underwater metals, on every other boat on the dock. What could possibly go wrong?

My customer may have been doing everything right, but since his bonding system is connected to his AC safety ground system, and since his neighbors’ boats are the same, and since they’re all connected together via the AC safety ground wires in their shore power cords, his zinc anode was protecting his boat plus the boat next door, or maybe down the way, or maybe all the boats down the row. But even though it’s via the AC shore power cord, it’s galvanic corrosion, which means a DC current.

It could also be stray current current corrosion, that is, corrosion caused by an electrical current, but stray current is still a DC thing. AC current just doesn’t cause or accelerate corrosion in normal circumstances.

Whether his half an Amp of DC current came from pure galvanic action or stray current corrosion is beyond my pay grade. I tend to think the latter, because half an Amp is quite a bit. Maybe there’s no way to tell, but the solution, in any case, is a galvanic isolator.

A galvanic isolator blocks low level DC currents from traveling down the AC safety ground.

It doesn’t do anything about galvanic corrosion within the confines of the boat it’s on, thus the corrosion survey before zeroing in on the galvanic isolator. As a marine electrician, I think I had to go this route to rule out other causes beforehand. If I just slapped a galvanic isolator on there without poking around, I’d have to advise him to have his diver come back in another two weeks to check the anodes, and this would cost more than my additional poking around.

Before the galvanic isolator was installed:

And after:

Voila! But two days before I’d read .5 Amps, instead of .3 Amps. What changed? I don’t know, but .3 is still bad.

As a boat owner who is constantly/often plugged into shore power, should you just slap one on as a matter of course?: Yes

Will it solve your problem with fast anode depletion?: Probably maybe.

But even if you don’t have a problem now, you may in the future, as your fate is tied to all those other boats on the dock, so it’s good insurance. It’s especially good insurance when you compare the couple hundred bucks for the galvanic isolator to the financial ruin of a devoured prop and shaft, keel/keel bolts, outdrives, et al. It’s not just about saving anodes; it’s about saving what gets eaten after the anode is gone.

Likewise, it will not solve a stray current problem within your boat. If you’ve got nasty old exposed bilge pump wires sitting in the bilge water, you might just stray current your keel off.

And a galvanic islolator only protects against low level DC, up to 1.2 or 1.4 Volts, so if there’s some banzai stray current issue in your marina, which creates a voltage higher than that, the isolator won’t do anything, but this would be unusual.

It used to be that a galvanic isolator could fail, not only negating its anti-corrosion purpose, but creating a potentially deadly break in the AC safety ground. So after that they made it so you had to have a monitoring system that would warn you if its function was compromised. Now, galvanic isolators are fail safe, meaning that if they lose their anti-corrosion function they still maintain their AC safety ground function. They are still supposed to be tested annually. If you’ve got an older galvanic isolator, you should replace it with a fail safe.

There is a magic box called an isolation transformer that makes all of this go away, but isolation transformers are big, expensive, and heavy, so not practical for the average sailboat…unless your sailboat is steel or aluminum, in which case you should pony up and make the space.

Teaching Marine Electrical Seminar In Sausalito This Saturday

Clark October 25th, 2016


How many wrong things can you find in this picture?

If you happen to be in the Bay Area this Saturday, October 29th, I’m giving a marine electrical seminar at Spaulding Marine Center in Sausalito, where I will teach electrical excellence, simplicity, and how not to get electrocuted. They suggest a $50 donation and always provide a great lunch. Starts at 10:00AM; goes to about 2:30. Please RSVP. Link here for registration

Electrical Basics: Bus Bars

Clark October 17th, 2016

IMG 2377

Just twenty or thirty years ago the electrical system on the average sailboat was very simple. It had two batteries connected to an OFF-1-2-BOTH battery switch, and all the loads were fed from there:
IMG 2313
On the back of the battery switch were three studs: one for each battery, and one for the common, that is, the terminal that connects to the alternator and all the loads:

IMG 2314

The battery switch for this Catalina 30 is this way. In addition to the connection to each battery, the battery studs on the back of the switch are good places to connect the outputs for the shore power charger, the voltmeter, and the bilge pump, all things we want permanently connected to a battery, and never turned off.

On the common terminal of course is the big cable connected to the engine’s starter, and the feed wire to the main distribution panel, which in this case is just a 10 gauge wire: ah, the days of such simplicity. The back of this switch might be a little crowded, but all of these wires fit.

Today the electrical system on the average sailboat is more robust and complex. With just the aforementioned connections to the battery terminals – voltmeter, charger, bilge pump, maybe the memory wires from a stereo or other electronics – the studs are already too crowded. On the common terminal, forget it. You might have the big cable to the starter, a big cable to an inverter or inverter/charger, big cable to the windlass, and a good-sized cable to feed the main distribution panel, which now supplies a radar, a refrigerator, and a range of modern comforts.

All these cables simply won’t fit, and according to the ABYC standard, you shouldn’t stack more than four ring terminals on a stud anyway.

Enter the bus bar. Give yourself some breathing room!

A bus bar simply expands your single stud into four or more. A large gauge cable, and nothing else, connects to the common stud on the battery switch. The other end connects to the bus bar, where you’ve got a row of big studs for all the other connections. The same could be done for one of the battery connections if you find you’ve got too many cables and wires that need to be connected directly to a battery, without a switch in between. Generally speaking, we want to keep our battery terminals clean. Manufacturers sometimes dictate otherwise, as with some electrical system monitors and chargers, but we should endeavor to have nothing but the supply cables connected to our batteries.
IMG 2369

The bus bar is even more necessary on the negative side, where the negative cables from the batteries, negative ground from the engine, inverter, windlass, corrosion ground (green wire), and feed to main distribution panel, all must connect. Might also note here that bus bar covers are equally important, as they make for a lot of exposed, live metal:
IMG 2367

Many older boats foresaw this scenario, but it was before off-the-shelf bus bars, so they just added distribution studs, or what Blue Sea Systems now calls a Power Post, but one stud just isn’t enough. These are overcrowded and a bus bar would create more room, make circuits easier to trace, and ahem, that thing about no more than four ring terminals to a stud?:
IMG 2231

Now Blue Sea Systems has gone plum crazy with the PowerBar 1000. It’s the Super Jumbo Extra SuperMax GT version of the bus bar. I have yet to find use for one, but when I do I’ll know I’m serious:
IMG 2342IMG 2343

Remember, good wiring is not only electrically sound, but easy to follow. Wherever you find yourself running out of room and trying to cram too many terminals in a tight space, even if it’s electrically sound, it will be difficult to service and trace in the future. A relatively cheap and simple bus bar is often the solution.

Boat Command CONNECT! Meets Smoke Alarm

Clark August 1st, 2016


The manufacturers of Boat Command, the boat monitoring platform, didn’t build the system with a smoke alarm option. It’s got all manner of sensors, inputs, and alerts, but no smoke alarm, and if you read Boat US’s statistics on boat losses and insurance claims, fire is number five. Stats aside, the main things I worry about while I’m away from my boat are flooding (that’s a big number 1), fire, break-ins, theft, and dead batteries. These are the main reasons I installed the Boat Command system, but it does lots of other neat stuff too. Full disclosure: as a marine electrician I install a lot of these systems, and I’m a dealer for the product.

While neither Boat Command nor the smoke alarm manufacturers make it obvious, it’s a very straightforward to add a smoke alarm to the system. As you can see from the photo above, the right place for a smoke alarm on my boat is about a foot from the Boat Command CONNECT! base station, so running the wires was a snap.

Within the Boat Command platform are several functions that can be renamed and repurposed. One of these is the High Water Alarm, which is just a normally open (NO) relay to ground, designed for the connection of any old float switch: Float is down, circuit is open and no alarm; float goes up, circuit closes and ALARM! via text and/or email, and on the Boat Command dash board. Since Boat Command has “belt and braces” coverage for flooding, via detailed activity monitoring on two bilge pumps AND the high water alarm, I could repurpose my high water alarm as a smoke alarm. On my boat the second bilge pump essentially IS a high water alarm, as in, if it triggers then something is seriously wrong.

Repurposing is very simple: On the drop-down menu on the Boat Command dashboard select Boat Settings/Inputs, where you will see various inputs, all of which can be easily renamed. Just change High Water Alarm to Smoke Alarm and click Save Input Settings:
Screen Shot 2016-08-01 at 10.21.49 AM


Screen Shot 2016-08-01 at 11.14.07 AM

Simple enough so far. Now, onto the smoke alarm. The smoke alarm manufacturers don’t advertise it either, but on what is commonly called a “Four-wire smoke alarm,” two of the wires are, guess what?, a normally open (NO) relay, which closes when the alarm is triggered. I think the reason they don’t advertise it is that these smoke alarms are usually part of large networks that connect to a sophisticated central monitoring computer. Think 90 smoke alarms on six floors, all connected to a central panel. They’re not used to selling just one to some dude for a single-unit installation.

The two sides of the relay are two out of the four wires. The other two are for 12 or 24-Volt DC power. This is another great feature: it means that the smoke alarm can be powered from the same terminal strip as the Boat Command base station, the smoke alarm is powered from ship’s power, and you will never have to change batteries or deal with annoying chirping noises.

Here is the base of the smoke alarm, with the + and – terminals being ship’s positive and negative, and the two A terminals being the two sides of the relay. It doesn’t matter which way you connect to the two A’s. I happened to use 4-conductor cable with red, black, yellow, and green wires:

I used this smoke alarm, but again, I’m 98% sure that any four wire smoke alarm will do the same thing. It cost about fifty bucks.

Then I just had to connect the two power wires from the smoke alarm (red and black) to the + and – connections on my Boat Command terminal strip. One side of the relay circuit (the green wire, in my case) also connects to ship’s negative; the other side of the relay (the yellow wire) connects to the orange wire from the Boat Command wiring harness.

I tested it, with real smoke, and yes, a deafening alarm blasted out of the smoke alarm, which was especially blood-curdling within the enclosed confines of my boat, and fourteen seconds later I got a text from Boat Command saying “Smoke Alarm triggered for Condesa.” Now, given that it takes me fifteen minutes to get to my boat from home, it’s hard to say how much good this would do with a real fire, but I’d rather know than not know, and there are people I could reach by phone who are closer than I am.

The Truth About Watermaker Membranes…

Clark June 24th, 2016

…is that they’ve gotten pretty cheap.

In not-too-distant past replacing a single membrane on a small watermaker was a $600-$800 hit. Now, as with so many other things, you can go online and buy a membrane for $150-$220. And it doesn’t matter whether you’re replacing a 20-inch membrane or a 40-inch – the two most common sizes – the price is the same.

Before I go any farther, when a watermaker is performing poorly it is seldom the membrane, but the membrane is the first thing people want to blame. You must first ensure that everything else is within spec before you condemn a membrane. This means that the system must be doing exactly what it’s supposed to do with regard to flows and pressures, and still making crappy water (low quantity or high salinity). Pumps must be pumping the quantity of water they’re supposed to pump, at the right pressures, or water quality and quantity will suffer, even with a perfect membrane.

Membranes don’t just up and fail, or rather, when they do it’s a one in a thousand thing. When they fail they usually decline slowly, over a period of 5-10 years, sometimes longer, or they fail because they were abused (chemical damage, lack of flushing, or lack of pickling…tsk tsk).

Cautionary tale over. $150-$220 for a membrane still isn’t free, especially if you’ve got a system with multiple membranes, but it changes the game somewhat. Say you left your boat in a hurry last season in the Caribbean, and you’re not 100% exactly, positively sure you stored the watermaker properly. You could fly back to the Caribbean armed with various cleaning chemicals, your fingers crossed, and the prospect of buying a membrane anyway, at Caribbean prices, or you could just buy a membrane online, stick it in your baggage, and replace it as a matter of course. Guess work averted.

Likewise with the long term view: At this price you might just replace your membrane(s) after 4-5 years when you suspect they’re fading, and be done with it. An older or fouled membrane can often be brought back among the living by chemical cleaning, but the chemicals can be expensive and the cleaning process can take hours of hands-on time, and soaking overnight, with various buckets and hoses strung about in awkward places.

I don’t mean to encourage gratuitous membrane replacement, filling the worlds landfills with used membranes, but you get the idea. And it’s no sure bet a new membrane will make better water than an older one. There is a lot of variation in membranes, even the exact same part number from the exact same production run, so if you’ve got an older membrane that is still performing well, stick with it. I’ve seen them perform within spec for up to 15 years.

Final caution: new membranes are shipped stored in nasty storage chemicals. The membrane must be flushed for at least 20 minutes to remove the chemicals, or it will be damaged when the system is pressurized. With a new membrane installed, run the system unpressurized for at least 20 minutes before making water.

Final final caution: Membranes don’t have long shelf lives in their packaging. If you’re thinking you’ll just buy a spare membrane to have on hand for a few months or years down the road, this is a bad idea. The membrane will undoubtedly be dead after, say, six months.

Replacing a membrane is quick and straightforward, as long as you’ve got access to the pressure vessel end cap, and room to slide the membrane out. Here is a video on how to do it on a Spectra. The process is similar or identical on other types of pressure vessels. The only thing you really have to remember is to keep the brine seal on the correct side:

New Cooling System on Perkins 4.236

Clark June 16th, 2016

This upgrade is common to all older Perkins diesels (the Perkins 4.108 is probably the most common Perkins found on boats). Bowman, the company that made the marinizing equipment for Perkins, has re-engineered things over the years, so that instead of having a combination header tank and heat exchanger on one part of the engine, and a water jacketed exhaust on another, they combine it all into a combination header tank/heat exchanger/exhaust manifold.

These engines were originally fitted with oil coolers. Now in some cases they say you can do away with the oil cooler unless your engine is run very hard. Since mine chugs away at about 1400 RPM cruising speed, I did away with the oil cooler.

At 50 years old, my old header tank was disintegrating (one surveyor took a very dim view of this), as was the heat exchanger stack, so that the whole business relied on a lot of polysulfide sealant and JB Weld. The old oil cooler failed spectacularly about five years ago, both blasting hot oil all around the engine room and filling the crank case with sea water. This is why one should always carry several oil change’s worth of oil at all times.

The first hurdle, and the only real engineering/fabrication part of the job is to modify the intake. If you look at the picture above, at the top of the picture you’ll see the air intake duct sticking out over the exhaust manifold. This would not do, as the new part would attach right there. The intake duct must be cut off and moved somewhere else. There are several ways to skin a cat, but I decided I wanted to keep my intake duct right in the middle, the way Perkins engineered it, but sticking up instead of out to one side.

I went off to my normal machinist/metal fabricator guy, to find a sign in his window saying he wasn’t taking any new work and would be closing up shop. I tried another place nearby, stood in the middle of his shop leaving him a voice mail, and never heard back. Found another metal fabrication place that was backed up four months. Left it at one place: They said they’d get it done the next week, didn’t, didn’t even bother to call me, then took off on vacation. I want back ready for battle, found the doors wide open, nobody home, and my parts sitting right where I’d left them two weeks before. I took my parts and my card and took my business across town. Is this telling me something? Should I be learning to weld? Is it just a Bay Area thing, or is it getting hard to find good tradesmen in this world?

At the second or third stage in this frustration I decided I’d go at it alone as much as I could, leaving only the welding to be done by a pro. The first step was to cut off the intake duct with a hack saw, which was satisfying and straightforward:

Then I went to and ordered a few pieces of stock, some aluminum tube to make the new duct, and some aluminum plate to cover the hole where the old duct had been. I used a 2-1/4-inch hole saw to drill down into the intake, making a home for the new duct. After a fair amount of cutting, sawing, and filing I had my pieces finished and ready for the welder:




Here are the old, tired bits that went away:

On top is the old exhaust manifold, which broke when I removed it. It was raw water cooled. The exhaust manifold on the new bit is fresh water cooled. Methinks this is a change for the better.

Here is the new bit, painted and ready for action:


There were many other little bits and bobs to source, customize, and fit. I had a brand new spare water pump, so I installed that while I was at it, replaced the transmission cooler for the same reasons as the heat exchanger, repainted where I could, and replaced all the engine hoses, as they were getting on twenty years. And I got one of those K and N washable air filters, since that’s what all the kids seem to be getting these days:


So far very happy with the modification. It did away with about fifty pounds of ancillary crap on the engine. Seriously, I’ve got a giant box of stuff, which I can barely lift, which is no longer needed, and this doesn’t even include the old header tank or exhaust manifold. And I’ve now got about another foot of space between the front side of the engine and the engine room bulkhead, which is great because the core of my electrical system is on this bulkhead.

The only problem is that she seems to run too cool. My wife asked, “Isn’t that good? You installed a new cooling system and now it runs really cool?” Excellent logic, but not exactly right. There’s a right temperature, which for Perkins is something like 160-180F on the cooling water. Mine seems to be barely tipping the gauge at about 120F. So now it’s off on a bay cruise with digital thermometer in hand to figure out if it’s an instrumentation problem or if she’s really running cool. Yes, I bought a new thermostat in case that’s all it is.

The Future Is Here: Bottom Cleaning Nanobots

Clark April 1st, 2016

With copper-based antifouling paints just being banned in Washington state, the writing is on the wall. We’re going to have to figure out an an environmentally-friendly way to keep the critters from growing on the bottoms of our boats. That’s where BottomBot comes in.

Dan Stein, BottomBot’s CEO says, “We took our technology from the medical industry, where nanobots have long been in development. There is a family of nanobots designed to be released in the blood stream to remove plaque from the insides of your arteries. These nanobots aren’t quite ready for prime time in medicine, for safety reasons, but the bottom of a boat is much less sensitive than say, your aorta.”

BottomBot’s first product in in beta testing on 25 boats in the Pacific Northwest. Sam Stanton, a beta tester, says, “It’s like having a bunch of little pets. I can’t see them of course, but sometimes at night I think I can hear them. It’s not perfect yet – some parts of my bottom stay cleaner than others – but my boat hasn’t had any antifoul on in for eight months, and these are quite fertile waters, and the nanobots seem to remove all the growth.”

The base product for a 40-foot sail or power boat includes 2000 nanobots and a charging station. The charging station looks like a scoop for a thru-hull, and each nanobot must make its way back to the charging station once a day, where its tiny battery gets magnetically recharged.

“Our biggest hurdle was getting them to stick to the bottom.” says Stein “It was fine while the boat was sitting the the berth, but once a boat hit 8 knots a lot of the bots washed off, and this got expensive. We experimented with a ferrous bottom coating, so the bots could attach magnetically, but this just exchanged one metal-based bottom coating for another, and introduced corrosion issues. We ended up with a patented design where the nanobot is shaped like a limpet, and moving water actually helps it stick to the bottom at high speed. Still, a few get lost, and some fail, every week, so every year or two you’ll need to replace a couple hundred bots to retain good cleaning ability on your entire hull.”

Each bot has simple directional programming that sends it out over the bottom in random direction. “It works kind of like a bunch of Roombas,” says Stein, “Then each bot has a tiny scraper, and just removes anything softer than epoxy as it moves along.”

Initial pricing is expected to be over $15,000 for a 40-foot boat, but the prices are expected to come down. “When you consider that this gets you out of doing bottom jobs forever, it eventually pays for itself,” said one of the beta testers.

“The boat’s bottom ends up free of marine growth, but eventually there is this accumulation of grey goo.”

Global Ship Traffic Via Satellite and Terrestrial AIS

Clark March 4th, 2016

What chance does a humble cruising boat have out there? Not a lot of places where it’s safe to sleep on watch.

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