GOOD  PRACTICE

I've included a few photos for future entries.  Perhaps you can guess what the article will be about.

Appearance vs. Functionality

Occasionally I am called in to fix a problem with another person's work.  Usually the workmanship looks good but the circuit is hooked up wrong.  Sometimes the wiring is actually quite pretty, all 90 degree bends and tie wraps every few inches.  I call this "knowing what it should look like rather than understanding how it works."

begun 6/30/06.  in progress. . .

Transferred to new site 

Dielectric Grease under reconstruction Using an insulating grease on electrically mating parts seems to be a contradiction. The stuff insulates. So why do people recommend putting it between conductive surfaces and expect minimal resistance between the parts? I was suspicious for years. I would not use it. For a while I coated the outsides of battery connections after they were complete, but that was pretty messy. Dielectric grease tends to get tracked around when someone touches it. It's difficult to remove completely and nothing (repeat: nothing) will stick to a surface contaminated by a film of silicone dielectric grease.   My problem was thinking of the stuff in the same category as high-pressure grease. High-pressure grease has a high mechanical film strength to keep parts separated even when they're not moving. Dielectric grease has essentially no mechanical film strength. When pressing parts together, it readily flows out of the way, allowing metal to metal contact. (it can get trapped between two rough surfaces where it insulates. It essentially cuts down the contact surface area.) Usually a silicone compound, dielectric grease resists air, water, oil, acids and solvents. It seals a connection and prevents oxidation or corrosion.   By all means coat those battery terminals after brushing them bright. Then attach clamps and cables. The grease will flow out of the way and allow a good mechanical connection to be a good electrical connection. The tracking problem can be mitigated by using the compound sparingly.    Dielectric grease is appropriate for electrical connectors exposed to water. I never count on it to make things waterproof by itself. Being transparent, its too easy to miss a spot.  Having such little viscosity and film strength, it's too easy to brush off. Its better inside mating parts. The substance is particularly good for RF coax connectors. Silicone grease has the same dielectric properties as air, namely a dielectric constant of 1, so coax connectors can be filled with the stuff and it doesn't change their transmission properties. As long as water cannot get at the connecting surfaces, corrosion cannot occur. Again: corrosion CANNOT occur in the absence of water molecules, but that's another story. I wrote a few things about keeping battery terminals clean and dry before I figured out the wonder of dielectric grease.   Dielectric grease makes a wonderful sealant to use every time you thread a stainless fastener into aluminum. It keeps water out (no water, no dissimilar metal corrosion) and you will be able to unscrew the parts years later. added 5/30/06

Ventilation and the weep hole - under reconstruction

June 16, 2007. An article in this morning's LA Times motivated me to write something about the virtues of weep holes and ventilation. I discovered I'd already done that a year ago in the article below. So I'll just add this preface. It seems that the Great city of Tulsa buried a '57 Plymouth in a "bombproof" time capsule under the courthouse lawn 50 years ago as a publicity stunt. (Bombproof? It was the 50's.) When they recently dug it up, the car was up to its hubcaps in water and encrusted with rust. Oops.   

Water will penetrate any space. If you want to keep something dry, give the water a way to get out again. If you want to avoid condensation, ventilate. There are places where it rains a lot and the humidity is high. So what. You would think ventilating would let moisture in. Yes, but it lets it out again too. Think about it. The sidewalk always dries up after a rain. Lots of stuff on a boat doesn't need to be waterproof. The main electrical panel is often sheltered enough that you'd have to sink the boat to get it wet. I have a couple of rules about waterproofing. The first is that some things cannot or should not be waterproofed. It's a corollary to the law of scuppers. When water cannot be kept out, give it somewhere to leave again. I see a lot of electric heaters inside boats for the purpose of fighting humidity and condensation. Sometimes I see dehumidifiers too. What a waste of energy. Ventilation will do the job better than either heaters or dehumidifiers. You do NOT want to seal up a boat to fight humidity. Install a solar powered ventilation fan, as I have on my boat. If you have musty compartments, ventilate them. This includes the bilge and the sail lockers. Somehow this is counter intuitive and people resist the idea. Oh well. 

Any re-enterable enclosure exposed to the elements is going to get water in it. I don't care what kind of gasket or how much sealant you use. Be it a navigation light, a radome or an instrument cluster, your only hope is to include a weep hole so the water can get back out again. Enclosed spaces breathe as ambient temperature changes shift the pressure of the air inside. If you wonder how water got inside your gauges and condensed in droplets on the inside of the glass, now you know. It seeped in as water vapor mixed with air through what could be microscopic openings. Very few displays are hermetically sealed. If you have a problem with moisture condensation there are two solutions. The first is counter intuitive. Drill holes in the gauge case (in back of the panel, obviously) to allow air to circulate and moisture to escape. Moisture wants to get out of the gauge just like puddles always seem to dry up. This assumes the interior of the boat is at least minimally ventilated so that water isn't condensing on surfaces inside and making everything rusty. VDO relies on it's illumination lamps to keep the gauge faces dry. The other way is to heat the gauge a little. Wire the illumination lamps to run at a lower voltage continuously and apply full voltage only when you really want to see them at night. Keeping the inside of the gauge just a few degrees warmer than the ambient will drive water out the same way it got in. You can also glue resistors to the outside of the gauge case as a heat source, but the pilot lamps will do. The only disadvantage of this approach it it uses a very small amount of power continuously. If your batteries don't get charged every so often, they could slowly run down. Don't worry about the lamps. Run a little below their rated voltage, incandescent lamps will last essentially forever. 

The other thing that people sometimes try to waterproof is a hollow sailboat mast. This is mostly a problem where the mast steps on the cabin top and water in the mast can drip down out of the ceiling. If the mast steps on the keel, the water will run into the bilge and you will never notice it. There are lots of little places water can get inside the mast, particularly if you have halyards running inside. A cabin-stepped mast leaks because wires for the navigation lights and VHF antenna enter the mast through a hole in the bottom. It's possible to construct a mast where most of the water runs out somewhere else, but usually when a leak shows up people do things like squeezing a whole tube of RTV silicone sealant into the hole where the wires come through. This can be effective in stopping the leak, but it will cost you later. Eventually you want to add wind instruments or radar and some more wires have to get into the bottom of the mast. I can sometimes break the sealant up with a probe and pull enough out with a hook or even drill past it to open up a passage for new wire or to get old wire out. Or you can pay a boatyard to unstep the mast to get the sealant out. I haven't damaged any existing wires yet by poking around, but you can be sure I will need to drill a hole in the side of the mast near the base so I can thread the new wires through the mess. 

*Note July 4, 2008. This next paragraph just shows how much one can learn by working on your own boat. Who wants water in the tabernacle core?* What a bunch of crap I wrote ignorantly: "My suggestion to solve the "mast water leaking into the cabin" problem is to yield and admit the water is going to come in. Then fashion something on the cabin ceiling to collect the leakage and route it to the bilge through a small plastic tube. It could look like a decorative cap over the wires coming out of the mast and the tube could probably be routed along with the wires and you'd never notice it. I've never gotten to try this yet, but I'll post a picture and a report as soon as I do." 7/4/06 revised 6/16/07

Good to be Insured; Better not to Need It.

This story illustrates some of the silly things I did when I first started fixing boats.  Needless to say, I don't lug these around any longer.  The CO₂ extinguisher fits nicely on my 28' Islander though.  Have you ever cleaned up after discharging a dry chemical extinguisher?  Dry chemical is inexpensive and effective, but it is also unbelievably messy if you use it.

I have heard it said that fire is the worst thing that can happen on a boat.   Not only does it burn to the waterline in minutes, it also leaves you nowhere to go but overboard.  Plus the boat is a total loss.

I take great care when working on live electrical circuits.  I believe in fusing all circuits at their source, just like the ABYC suggests.  This will prevent almost all electrical fires.  

But most older boat's primary circuits are not fused properly, and there are other little ways fire can break out, so the risk does not vanish completely.  Like many people who work on other people's property, I carry liability insurance.  Like most, I'd rather not use it.  

I spent ten years on a volunteer fire department in Colorado, the last several as Chief.  If I ever have a fire on a boat, I have enough experience to fight it.  With that in mind, I carry two fire extinguishers to every job along with my tools.  Its a lot to lug around, but having been a firefighter, I'm not going to just watch a boat burn for lack of the right tool.  The two extinguishers would let me fight a boat fire at two levels.

If the fire is small and contained, caught in the first fraction of a minute, I would probably reach for my 5 lb. CO₂ extinguisher.  CO₂ is good because it does not make a terrible mess like a dry powder extinguisher.  Dry powder is effective and inexpensive, but you don't want to clean up after.   CO₂ is also good for fuel fires and inexpensive enough that you can easily practice with it.  It can be bad because it takes a bit of skill to use and it doesn't work well out in the wind.  

My second line of defense is a 13 lb. Halon extinguisher, which is pretty big as Halon extinguishers go.  Halon is almost unbelievably effective at eating fire.  You have to see it to believe it.  Halon is drawn into the fire and chemically combines with every wisp of flame, stopping it cold.  Halon is a heavy molecule compared to air or CO₂.  It will settle in the hull, which helps prevent "flashbacks."  It also leaves no residue.  Halon will handle a boat fire better than anything short of one or two full-on 1-1/2" fire hoses.  Halon is the only last resort for fire you can carry.

Halon is quite expensive because it's also very effective at destroying the ozone layer, better than most fluorocarbons.  So it is considered very "environmentally unfriendly."  You don't really want to practice with it.  In fact, it would be illegal for me to practice with it.

So, is it socially responsible to buy and carry a Halon extinguisher? 

I believe the answer to that question depends largely on whether or not its your boat that might burn.

© Electric Marine, August, 2002