Dry Weight
Dry weight is closely related to displacement, and it’s the number you’d get if you hung an empty boat from a scale. Dry weight isn’t always included on specification sheets, but it’s vital if you intend to tow or transport your boat.
To give you a better idea of the dry weight of different vessels, we’ll use a short list of common boat sizes by LOA (length overall) in feet. Keep in mind, the weight of a boat differs based on hull material, mast type, and many other factors.
- Dinghies (less than 12’): 100 to 200 pounds
- Small Sailboats (15’ to 20’): 400 to 2,500 pounds
- Medium Sailboats (21’ to 25’): 2,500 to 5,000 pounds
- Cruising Sailboats (27’ to 32’): 7,000 to 12,000 pounds
- Large Sailboats (35’ to 40’): 12,000 to 30,000 pounds
What factors contribute to the weight of a sailboat? Hull material makes a huge difference in dry weight. Older wooden cruising vessels with deep keels often weigh thousands of pounds more than an equivalent-sized fiberglass boat. Also, sport and racing sailboats sometimes weigh a fraction of an average consumer cruiser.
A sailboat’s mast and rigging contribute to the weight as well. Solid hardwood masts sometimes weigh hundreds of pounds more than hollow masts, and heavy brass deck equipment adds up. It doesn’t take long for equipment to increase the weight of a boat.
Displacement
How is displacement different than dry weight? First of all, you can only calculate dry weight when a boat is empty and dry. Displacement is equal to the weight of a boat, along with everything (and everyone) aboard at the time of measurement. This includes water, fuel, deck equipment, interior cushions—you get the picture.
The most common measurement of weight for sailboats is displacement, and it reflects the weight of a loaded sailboat in the water. We measure displacement by calculating the weight of the water volume a boat displaces. This unit is vital in boat design. A vessel will sink if it weighs more than the water it displaces.
There’s a simple way of picturing the concept of displacement. Imagine a cup of water filled to the very top. Now drop in a coin and measure the amount of water that spills out. The weight of the spilled liquid is the displacement of the coin.
Oddly, the displacement value of a boat means slightly different things in salt and freshwater. Saltwater weighs 64.1 pounds per cubic foot, while fresh water weighs 62.4 pounds per cubic foot. That means a boat will displace more freshwater because saltwater essentially ‘pushes harder’ upward on the craft.
So, how does displacement translate to weight? You can get a general idea of how ‘heavy’ a boat is using a simple calculation, shown below.
(Displacement/2,240) / (LWL x 0.02)^3
1) First, you’ll need to convert the displacement (in pounds) to long tons. Simply divide the displacement by 2,240 to get your answer. Put this number aside for a moment.
2) Next, find the length at waterline (LWL) of your boat, and multiply it by 0.01. Take this value and raise it to the power of 3. It should look something like this: (LWL x 0.01) ^3
3) Finally, divide your first number (in long tons) by the result of the previous calculation to get your displacement to length ratio.
The displacement to length ratio is useful for a number of reasons. Using this simple number allows you to determine the weight class of a boat, so you’ll know what it’s suitable for. Below, we put together a list to help you understand the differences using a D/L ratio of 40 to 400.
- Ultra-light (race boats): 40 to 89
- Light (race or trailer-sailboat): 90-179
- Medium (day boat/light cruiser): 180-269
- Heavy (cruising sailboat/offshore cruiser): 270-359
- Very Heavy (heavy offshore cruiser): 360-400+
Generally speaking, sailboats built before 1950 typically have a heavy D/L ratio. A boat with a ratio over 300 handles much differently than a light vessel, and many consider heavier boats to be more ‘seaworthy.’ Of course, it’s not always that simple, but the general rule still applies. Using what we know about displacement, it’s time to go over our final weight measurement.
Tonnage
Tonnage represents the volume of the enclosed space on a boat, using the same concept as displacement. Salt and freshwater tonnage differ for the same reasons as well. Tonnage and size are directly related, and this unit gives you an idea of how much cargo you can carry before overloading. Cargo tonnage is measured in long tons, similar to displacement. Simply divide the tonnage (in pounds) by 2,240 to get your cargo tonnage value.
Why Weight Matters
While we haven’t mentioned every way of weighing a sailboat, you can gain a lot from understanding dry weight, displacement, and tonnage. For example, you’ll need to know the dry weight of a boat to determine if your vehicle can actually tow it. If a vessel weighs 15,000 pounds, you’ll probably want to avoid it unless you have a permanent mooring or a heavy-duty pickup truck.
Displacement and dry weight are closely related. Displacement is equally crucial for determining a boat’s capabilities. Heavy, deep-keel sailboats generally handle well in rough seas, but you probably won’t be racing with a high D/L ratio. If you understand what your intentions for a boat, it’s imperative to comprehend displacement and D/L ratio.
Tonnage is essential to understand, especially for offshore cruising. Using this value, you can calculate how much food, water, supplies, and how many people you can take aboard. Ignoring any of these values can spell disaster for any captain but understanding sailboat weight ahead of time ensures you’ll know what you’re doing.
Examples
Now that you have a grasp of sailboat weight measurements, it’s time for some real-world examples. We found the specifications of three common sailboats so you can get an idea of what to expect.
How Much Does A Catalina 30 Weigh?
This 30-foot sloop is one of the most successful production fiberglass sailboats in history. It was built by Catalina Yachts between 1972 and 2008, with over 6,000 units. We chose the Catalina 30 because it’s an ideal example of a medium-sized all-purpose cruising sailboat. This versatile sloop is well suited for coastal cruising and some offshore passages.
Dry weight clocks in at 10,200 pounds, with a D/L ratio of 291.43. This sailboat is an ideal general-purpose cruising vessel.
How Much Does An O’Day 25 Weigh?
Despite being only a few feet shorter than the Catalina 30, the O’Day 25 is a much different boat. This popular day cruiser has a displacement of only 4,007 pounds, which is less than half of the Catalina 30. The O’Day 25 falls into the medium weight category with a D/L ratio of only 193.16. Comparatively, you can immediately see how these two common fiberglass boats differ. The O’Day 25 will be much easier to tow, yet less suitable for long offshore passages.
How Much Does An Atkin ‘Eric’ 32 Weigh?
This 32-foot wooden sailboat was designed decades ago for offshore sailing. While dimensionally similar to the Catalina 30, this boat is significantly heftier with a displacement of 19,500 pounds. Despite only being 2-feet longer than our Catalina at the waterline, the Atkin Eric has a D/L ratio of 418.81 making it an extremely heavy boat!
Conclusion
From a distance, all three of our examples would look similar in size and above-water characteristics. Below the surface, we find something very different. Each of these vessels is suitable for different things, and how much they weigh plays a vital role in their uses. Now that you know how to interpret the weight of a sailboat, you’ll be prepared to choose one that best fits your needs.
