What Size Sea Anchor Do I Need?

ByMathew F Updated on

The size of your sea anchor depends on your boat’s size and weight. For parachute anchors, diameters range from 6-20 feet. For series drogues, size is determined by the number of drogues. More drogues or larger diameters create more drag, helping maintain boat position in various sea conditions.

There is one fundamental difference between sea anchors and drogues which is the placement of them from the bow or stern.

I’m going to cover sizing for both so you don’t end up with more questions than answers.

In all boating activities, safety is paramount. A sea anchor or drogue is one of the least spoken about and yet important life-saving appliances. 

Key Takeaways

  • The larger the boat, the larger the sea anchor required to provide adequate drag to slow it down
  • The rode must be nylon and 10 to 15 times the boat’s overall length in heavy weather
  • The sea anchor’s drag is a crucial factor when selecting its size. The size of the sea anchor determines its drag capabilities

Factors To Consider When Sizing a Sea Anchor

Before determining what size sea anchor is needed for your boat, it’s beneficial to refresh your knowledge with this introduction to sea anchor use.

Sea anchors, commonly parachute anchors, are used to keep boats facing wind and waves. They open like parachutes in water, maintaining rode tension.

Made of lightweight materials like nylon or Dacron, their size, determined by diameter (6-20 feet), depends on the boat’s size and weight. They’re used in open seas to hold the boat’s position in moderate to high conditions.

That being said, the factors that must be considered when selecting a sea anchor are:

The boat’s size and weight are critical factors when choosing a sea anchor. 

The larger the boat, the larger the sea anchor required to provide adequate drag to slow it down. 

The boat’s weight also affects the size of the sea anchor needed. A heavier boat requires a larger sea anchor to create enough drag to slow it down.

The size and shape of a sea anchor will also depend on the specific conditions in which it will be used. A larger sea anchor may be needed to provide adequate drag in particularly rough waters.

A sea anchor that is too small for the conditions will not provide enough drag to slow the boat down or help it maintain direction, while one that is too large may be difficult to handle, deploy, and retrieve. 

It’s important to consider the maximum wind and wave conditions the boat will likely encounter and choose a sea anchor to handle them.

The length of the line connecting the sea anchor to the boat is essential. 

The rode must be nylon and 10 to 15 times the boat’s overall length in heavy weather. A stainless steel swivel is highly recommended. Multi-hulls must also rig the rode to a bridle, with each leg being 2-2½ times the boat’s beam and rigged to the outer hulls.

Too short a line can cause the boat to pitch and roll, while too long a ride can reduce the effectiveness of the sea anchor. 

There are two opinions (rules) regarding how long the rode should be:

RuleDescription
Rule One – Relative To The Boat LengthThe rode should be roughly twice the boat’s length.
Rule Two – A Fixed Length Determined By The Vessel WeightLight vessels should have a minimum of 300 feet of rode. Heavy boats or vessels with excessive windage should carry 300- to 600 feet of rode.

How To Determine the Correct Size

The sea anchor needs to be correctly sized to perform how it is intended.

The seams are reinforced with nylon webbing. Nylon lines with a minimum strength of 1,500 pounds are joined at the rode end to a shackle with strength from 17,000 to 52,000 pounds.

A correctly sized PARA-TECH Sea Anchor will likely never experience the loads it is capable of taking.

The sea anchor’s drag is a crucial factor when selecting its size. The drag is the force the sea anchor creates when it is deployed into the water. The size of the sea anchor determines its drag capabilities. 

A larger sea anchor creates more drag, while a smaller one creates less drag. It’s essential to choose a sea anchor that can generate enough drag to slow the boat down in the expected wind and wave conditions and yet is small enough to be easily deployed and retrieved.

A good rule to follow is that the worst-case scenario should be followed. Select a sea anchor slightly larger than you think you’ll need to ensure it can handle even the roughest conditions.

Most manufacturers recommend that the anchor size relative to the boat size follow the general values in the list below.

Boat LOADisplacementSea Anchor SizeSea Anchor WeightLine Diameter
Less than 20 ft.Less Than 4,001 lbs.6.0 – 7.0ft.6.0 lbs.1/2″
21 to 26 ft.Less Than 8,001 lbs.8.0 – 9.0 ft.9.0 lbs.5/8″
26 to 34 ft.Less Than 11,999 lbs.8.0 – 12.0 ft.12.0 lbs.5/8″
34 to 41 ft.Less Than 24,999 lbs.12.0 – 15.0 ft.20.0 lbs.5/8″
41 to 49 ft.Less Than 39,999 lbs.15.0 – 18.0 ft.25.0 lbs.5/8″
49 to 91 ft.Less Than 94,999 lbs.18.0 – 24.0 ft.35.0 lbs.5/8″ – 3/4″
90 to 121 ft.Less Than 199,999 lbs.24.0 – 32.0 ft.55.0 lbs.3/4″
121 to 151 ft.Less Than 301,000 lbs.32.0 – 40.0 ft.110.0 lbs.7/8″ – 1″

Thanks to the Drag Device Database, PARA-TECH Sea Anchors now come with a Deployable Stow Bag for easier deployment, avoiding inflation on deck. The bag is simply tossed overboard.

Unlike a drogue, these Sea Anchors ensure your bow faces the wind, resulting in a slow leeward drift as seas pass beneath.

The Sea Anchors, made of high-strength nylon, are four times stronger and heavier than surplus parachutes, previously used as Sea Anchors. The lines in the storage bag are tubular nylon.

A general rule of thumb is to use one drogue for every 10 feet of boat length. For example, a 40-foot boat would require a series of drogues with four drogues.

A helpful rule for sea anchors is that the sea anchor diameter should be roughly 1/3rd the boat’s length. For example, a 48-foot boat would require a sea anchor with a diameter of around 16 feet.

🛡️ Safety Considerations

A safety protocol must be observed when the sea anchor is deployed.

  • Always send out the trip line and floats first, and remember sea anchors are deployed from the bow drogues from the stern.
  • Payout about 50′ of rode (line) as the boat drifts away from the sea anchor.
  • To hold it momentarily, snub the line using half a turn on the cleat. Wait for a minute for the drift anchor to open.
  • Always keep tension on the rode and pay out the rest of the line.
  • You may need to add chafe guards to prevent the rode from deteriorating.

A sea anchor or drogues should be regularly checked to ensure they are fully intact.

They must be removed from the storage bags, spread out, and inspected carefully. If there is damage, contact the nearest agent to see if they can be repaired.

Keep the rode carefully wound, ensuring no knots will make it hard to release in rough weather. 

After figuring out your sea anchor sizing, the next step is to learn when to use a sea anchor.

You must practice deploying the sea anchors and drogues. This will give you an understanding of what is required before you deploy it in “anger.”

Emergencies: In the event of engine power loss, using a Sea Anchor will point the bow into the seas, keeping the boat from rolling in the trough, thus making repairs easier. The boat is also held in its last reported position, making it easier for assistance to find the disabled boat. 

Practicing deployment and keeping the tension on the rode beforehand may be the difference between abandoning the vessel and staying on board with control maintained.

When deployed, always keep the tension in the sea anchor rode.

Once the storm has died and you’re ready to move on, it’s time to pull in the anchor rode slack.

The retrieval float that should be at the end of your trip line will provide a location for you to motor toward.

Using a boat hook, grab the retrieval float on the windward bow. Carefully pull the rode in, and the now collapsed anchor should follow.

Written by:

Mathew F

I’m the founder and chief editor here at Sailing Savvy. I spent a decade working as a professional mariner and currently, I mix those experiences with digital publishing. Welcome, and I hope that we can be the hub you need for safe passage.