On my own sailboat, I have a water ballast system. I was unsure about the stability and efficacy of this system at first. From my experience, a water ballast sailboat, in place of a lead keel boat, is an incredibly worthwhile and effective option to consider when purchasing a sailboat.
What is a water ballast sailboat? A water ballast sailboat has a water reservoir on board instead of a lead keel. Water is taken on board and fills the bottom 25% of the hull. The water in the ballast tanks acts as a counter weight to prevent the wind from blowing the boat over in strong wind.
A water ballast sailboats does have some impressive upsides, but there are some concessions you need to make if you are considering purchasing or chartering this design of sailboat. Below are some important details of both a water ballast system and how they compare to a standard lead weighted keel.
How a Water Ballast System Works
The source for stability on a water ballasted sailboat is the weight of the water in the tanks. The water ballast keeps the boat from rocking back and forth much in the same way a lead keel boat does. If the energy input is sufficient, the boat will roll one way, then the other in both systems. Water ballast stability does not refer to total stability. All sailboats heel over.
Keep in mind these two key principles. The water in the ballast tank takes on the shape of the hull and the floor of the cabin above it. As a general rule, water will always find true level.
When the boat lists or heels over, the water line lifts up and out of the water on one side. The water line on the other side then dips below the surface. As the boat rolls to one side, the water in the ballast tanks is lifted out of the water for a brief moment. Gravity then kicks in and pulls the ballast tank water back to level.
Water Ballast Tanks In Action During Sailing
In keeping with the principles above, when wind pushes on the sails, the boat will tend to lean over. The water in the ballast tanks will be raised up out of the surrounding water as the boat heels over. The further the boat is pushed over by the wind, the more ballast water is being raised above the water the boat is sailing in.
The weight of the water ballast multiplies as the boat is pushed further and further over, until a balance is achieved between the wind force and the gravity pulling level on the ballast tanks. With practice, you can find this balance and maintain it based almost entirely on the amount of sail you have flying at the time.
With the practical application of water ballast systems explained, let’s get into some of the functions of properly and safely working one of these systems.
What Exactly Are Water Ballast Tanks?
Water ballast tanks are large water compartments designed to take in the water that the boat is floating in. They are located under the floor of the cabin of the sailboat. Water ballast tanks typically run most of the length and width of the sailboat. From outside the sailboat, the hull area from the waterline and down is almost completely filled with water. The ballast tanks are manually filled once the boat is placed in the water.
How Are The Ballast Tanks Filled?
There are two key components to a water ballast system on a sailboat. The plug and the vent. The design and innovation on how they are filled and emptied may differ from one brand of boat to another, but the principles are all the same.
The first component is the plug. This is usually located at the lowest point of the sailboat under the water line. This plug opens and closes and allows water to flood and drain the ballast tanks. This plug is opened and closed from inside the cabin of the sailboat using a long rod.
This rod reaches vertically from the plug to the floor of the cabin. It operates the plug, allowing it to be pushed down and away from the hull to open. When the tanks are full, the rod is pulled up, which seals the plug inside or up against the hull, and closes off further water flow.
There is also a vent located beside the plug rod that must be opened while flooding the tanks. This must be open in order for the displaced air to escape as the water in the ballast rises. Once the tanks are full, the plug needs to be closed (rod pulled up) and the vent sealed off in order for the ballast water to keep from entering in the sailboat cabin.
What If the Ballast Tanks Remain Empty?
Empty ballast tanks can be a real hazard on a water ballast sailboat. This may be a point of contention when considering the purchase of this kind of sailboat. Imagine if you will what would happen to an inflated balloon if you glued a roll of dimes on it and set it afloat. Gravity would obviously take hold of the weight and pull the balloon over.
The same principle is at work on a water ballast sailboat, but not necessarily to the same extreme. I have seen capsize reports on the news where too many people were on the deck of an empty water ballast sailboat, and it turned over.
Now, capsizing is not always the case. In situations like the one above, the capsized vessel was overloaded along with having empty ballast tanks. Other factors could also contribute such as being oversailed and in rough water conditions.
In normal sailing situations capsizing would not normally happen. For example, a small family out for an afternoon could board a water ballast sailboat, and forget to fill the ballast tanks.
What they would immediately notice is the sailboat constantly rolling from side to side at the smallest wave, or the slightest movement of people around the boat. Anyone aboard would know something was not right and take stock of the situation and remedy it. Keeping your balance on an empty-ballast-tank boat is no easy task.
Filling and draining ballast tanks is all a part of owning or operating a water ballast sailboat. Hazardous situations arise due to fairly extreme negligence, but they still can happen.
Benefits of a Water Ballast System
Water ballast boats have some unique advantages. If hitting bottom or shallow water sailing is in your future, you would certainly benefit from a water ballast boat.
Fixed keel boats with a lead keel usually have a fairly deep draft in comparison to water ballast boats. Water ballasted boats can get away with a center board, a dagger board or a swing keel since the stability is governed by the water weight and not the keel weight.
This means you have an abundance of anchoring options not available to the majority of sailboats. On top of that, having easy access to shore means I can have a campfire, set up tents and chairs on shore, let the kids run wild until bedtime, and the boat is just a few steps away.
On my own Macgregor 26D, I only need 15 inches of water once the centerboard and rudder are pulled up. This means I can be in very close proximity to shore while at anchor. I have had several tenders from other boats approach me to help while at anchor, because I appear to have run aground. When I explain the water ballast system to them, they smack their head and have a laugh and head on back. It’s really quite amusing.
Drawbacks to a Water Ballast Sailboat
In all honesty, the worst part of a water ballast sailboat is the amount of space the ballast tanks take up overall. In a keel boat, the weight is condensed by the weight of the lead. The floor of the boat can be lower, making for a great deal more headroom than a water ballast sailboat.
Water needs more space for the same weight as lead, and therefore the floor is much “higher” in the cabin of my boat than on a lead keel boat. I can not stand up in the cabin of my boat. I’m 6’2″. There are not a lot of boats under 30ft that I can stand all the way up in, so that’s how I rationalize the discomfort of my boat. First world problems, I know.
Related Questions
Where can/should I dump my water ballast tanks?
There are actually laws that prohibit the dumping of balast tanks in some areas. These laws pertain to vessels that come from remote or foreign parts of the world where ecosystems are very different. Sometimes ballast tanks draw in organisms and planlife that can turn into invasive and unwanted species in a foreign port.
Dumping ballast tanks should always be done at least 10 miles offshore before approaching a foreign port. If you can only dump your ballast tanks once the boat is out of the water, please ensure to do it when you are well inland to prevent the spread of invasive species.
Will the sailboat sink if I forget to close the plug and vent?
This actually happened to me, so I thought I’d share. My 1989 Macgregor 26D did not sink when I forgot to close the ballast plug and vent. I can only attribute it to a safety feature built right into the design of the boat. I don’t really know. All I know is I was distracted by a busy boatlaunch, a motor that didn’t want to start, and a mess of kids bounding around all over the boat. By the time I remembered I nearly had a heart attack. I jumped down the stairs and looked at the ballast vent, and it had stopped filling on its own. I closed everything up and had a great day!