Last month I outlined a number of proven strategies for preventing the nightmare of a fire on board ("Fire on Board
"). I thought I would continue in a similar vein this month by taking a look at how to avoid, and if necessary, cope with that companion offshore horror—
Avoidance Water mostly gets inside boats due to indifferent maintenance. Some water comes through the deck or the cabin sides, but bedding failure is rarely a source of dangerous flooding. That is not to say that failing to maintain the bedding under deck hardware is of no consequence. On the contrary, water leaking into the deck core does far more damage, in the aggregate, than flooding, but core damage is a subject for an article at some other time.
So a prudent mariner must ask himself, what items require maintenance to prevent flooding? First on the list is the stuffing box. Depending on an automatic bilge pump to handle a leaking stuffing box is folly. I learned this dramatically one evening when I stepped off the companionway ladder into eight inches of seawater over the cabin sole. Had I come a few days later to check on the boat, the consequences might have been catastrophic.
A properly adjusted stuffing box does not drip at all unless the shaft is turning. I am always astonished at how often I hear the splash of water being pumped overboard from unattended boats moored around me. I suspect their owners don't realize that the stuffing box is leaking as much as it is. That, however, is a lame excuse. It only takes a minute to worm your way in behind the engine and shine a light on the stuffing box to see what is going on. Often you can even check it by looking under the engine from the front, perhaps with the aid of a small mirror. If you don't know what is going on with your stuffing box, grab a flashlight, take a look, and find out.
In general, the only challenge to stuffing box adjustment is access. Where you can easily reach the box, you simply back off the lock nut—by turning it clockwise—then tighten the packing nut until the leak just stops. Tighten the lock nut against the packing nut and you are finished—sort of. A conventional stuffing box depends on a continuous drip when the prop is turning to lubricate the shaft, so you will need to check your adjustment the first time you use the boat under power. A rate of two to three drops a minute is sufficient, but a few extra drops a minute won't hurt, as long as the dripping stops when the shaft stops turning. If you cannot get this result with a half turn or two of the packing nut, the packing needs to be replaced.
Often the reason a stuffing box is allowed to drip is because it is nearly inaccessible. If your boat suffers from this all-to-common design flaw, I strongly recommend that you switch to Drip-Free packing. This low-friction packing compound is not cheap, but it dramatically reduces how often the box will need adjustment. And because the compound is self-lubricating, the box doesn't need to drip at all, even while the shaft spins. Just be careful not to over-tighten the packing nut. The box will feel warm after the shaft has been spinning for a while, but it should never be too hot to touch.
While you are checking the stuffing box, also check the setscrews, bolts, or pins that lock the shaft into the coupling. The condition of the packing won't much matter if the shaft drops out of the boat. Also examine the hose and clamps that attach the stuffing box to the stern tube. This hose must be double clamped on each end. Shaft drip tends to corrode these particular clamps on the bottom—where you cannot see—so loosen each clamp and rotate it 360 degrees to check it. If you see any rust, replace the clamp. Hose clamps on a boat are like the proverbial horseshoe nail for want of which the war was lost. And while you're in the neighborhood, you should also take a look at the stern tube to make sure it is not separating from the hull. You will need the aid of a mirror to view both sides.
|"All underwater thru-hulls require a proper seacock."|
Next in your flood risk checkup, inspect all other hoses connected to underwater thru-hull fittings. Hoses should be pliable but not spongy, and they should not be cut, worn, or cracked. If the thru-hull tailpiece has sufficient length, the hose should be double clamped. Give all these clamps a 360-degree inspection and replace any that don't look new.
All underwater thru-hulls require a proper seacock. Not all boat manufacturers have been diligent about following this imperative. If your boat has thru-hulls without seacocks, plan to correct that at your very next haulout. Also take a close look at how the seacocks are attached. They should be bolted to the hull, not simply threaded onto the thru-hull. Otherwise, only the very thin wall thickness of the thru-hull where the threads are cut stands between you and the bottom of the ocean.
It's also important to exercise all your seacocks. If this is part of your normal maintenance—like checking the engine oil or adding water to the batteries—the valves will turn easily. If they are frozen open, your boat's first line of defense against a failed or detached hose is missing. Service the seacock. If that fails, replace it.
Nothing provides greater protection against hose or clamp failure than closing seacocks when you leave the boat unattended. Get in the habit of leaving seacocks closed except when the boat is in use. It is particularly wise to close seacocks connected to any below-the-waterline toilets. If the toilet in your boat overflows when you fail to close the flush valve, a little trash in that valve can sink an unattended boat when the seacock is left open.
Finally, take a look at your bilge-pump discharge fittings. They need to exit the hull where they are unlikely to become submerged. That means that on any boat that can bury the rail, bilge pumps should not discharge to the side. If the pump runs while the discharge opening is submerged, when it shuts off it sets up a siphon that brings the ocean aboard. Trying to cope, the pump will try to run more or less continuously until it burns out or flattens the battery. Then the water flows only one way—into the boat. Unless you hear the motor—unlikely in rail-burying conditions—you won't know the pump is running because the discharge is submerged.
Which brings up one more flood precaution: Equip your boat with a high-water warning light in the cockpit. Wire it in parallel to the float switch that triggers the automatic bilge pump and you will know how often the pump is running—an excellent early-warning of looming trouble. If your pump doesn't use a float switch, then install one just for the warning light. The idea is to become aware of rising water before it gets so deep that you are unable to identify the source.
|"Despite every safety precaution a sailor takes, stuff happens."|
Coping Despite every precaution you take, stuff happens. That reality is reason enough for every boat owner to equip each below-the-waterline thru-hull fitting with a tapered, soft wooden plug. Drill a small hole through the plug's narrow end and attach it to the thru-hull with strong thread. Then mount a mallet near your largest congregation of thru-hulls.
The bigger risk—assuming you are vigilant about maintaining valve, hose, and clamps—is from collision with a submerged object. If this happens, a tapered plug could still prove useful for a puncture, but the breach is more likely to be a ragged and irregular tear. A closed-cell cushion held against the breach makes an effective crash mat. Or stuff the hole with blankets, pillows, towels, or what have you. You can also affect a semi-permanent repair with a piece of plywood pressed against this cloth or foam packing and held in place with a wedged boathook or spinnaker pole. You don't need to ship plywood on board just for this purpose; a locker lid can be pressed into service.
The first priority with a hole or puncture is always stemming the flow. Pumping can go on simultaneously, but never in place of closing the hole. Even the biggest onboard pump will ultimately lose to a two-inch break, so close the hole, and then worry about getting the water out of the boat.
Unfortunately, there can be a liner, furniture, or a tank between you and the damage. If this is the situation, drastic measures will be required to save the boat, and unless you have the requisite tools aboard—a sharp hatchet and a powerful pry bar—the game is lost at the outset. Don't stow these tools low in the boat or they may be inaccessible just when you need them
Slowing the flow from the outside by stretching a sail over the damage sounds feasible, but it simply does not work if the breach is in a concave section of the hull. Even with the tear in the best of locations, getting the sail stretched over it in anything but calm conditions can be very difficult. So always try to get to the damage from inside the boat first. If that proves impossible, getting a small headsail over the side is worth a try.
Of course you don't want to overlook any advantage of getting onto the other tack. Maybe you can lift the damaged area out of the water, and even if you can't, the closer to the surface you can lift it, the lower the flow rate will be.
Equip your boat with the biggest bilge pump you can put aboard. Don't fall into the "small boat, small pump" trap. I've always found that the smaller the boat, the quicker it fills. I favor a two-pump installation—a small float-actuated pump to take care of everyday leaks and a high capacity "crash" pump mounted higher in the bilge, with or without a float switch. Because the big pump never runs—except when you test it—it is always ready to be called into action. And mounting it higher reduces the "head," which improves the discharge rate.
There are innumerable other pump options, including expensive belt and shaft driven pumps. But pumping always comes in a poor third behind preventing and arresting the ingress of water. Keep up your maintenance, watch where you sail, and the ocean should stay outside where it belongs.
Stemming the FlowWe recently stumbled upon an interesting device designed to help stem the flow into a punctured or damaged hull. The aptly named Subrella essentially spreads a membrane over the hole or damaged area and then draws that tight by way of tension applied to a lanyard from inside the boat as well as the pressure of the water itself.
The device is manufactured in three different sizes to accommodate different sized holes. Depending upon where the boat is damaged, the Subrella can fully stem the flow or at least slow it. Of course if the hole exceeds the size of the membrane, then it will hardly do more than slow down the flow of water. For additional information on this product, log on to the manufacturer's website at http://members.aol.com/subrella97.
Beyond the Bucket Brigade by Brian Hancock
Sinking at the Dock by Mark Matthews
Rethinking Sinking by David Schaefer
SailNet Store Section: Bilge Pumps