What Is A Daggerboard In Sailing?

A daggerboard is a retractable centreboard used by various sailing craft, such as catamarans and sailboats. They are vertical fin-like structures found on the centerline of the boat, which can be raised or lowered vertically to provide stability and reduce sideways drift. Daggerboards are best thought of as an underwater sail, sometimes called a foil, and are often misunderstood in terms of their function.

A daggerboard is a retractable keel that can be raised or lowered vertically, providing stability and reducing sideways drift. It is the heart of a multihull, offering better pointing ability than an equivalent model equipped with fixed stub keels. Daggerboards can vary in shape, whether asymmetrical or curved, increasing lift while sailing.

A weighted keel or centerboard stops leeway and keeps the boat upright. A canted keel only keeps the boat upright. An unweighted keel is subject to incredible side forces to prevent the boat from slipping to leeward and providing lift.

Daggerboards are best thought of as an underwater sail, sometimes called a foil, and just as a sail above the water needs trimming, so does the sail under it. The daggerboard is a key component of a multihull, providing better pointing ability than other types of centerboards.

What is the difference between a daggerboard and a keel?

• PROS. A daggerboarded cat will sail consistently higher into the wind than a cat with keels. Typically between 5 to 7 degrees higher. This added speed and pointing ability represents a significant safety feature when cruising because it enables you to claw off a lee shore or to arrive at an upwind destination with far greater alacrity. Sometimes you cannot “run for cover” – you must “beat for cover.”
• A daggerboarded cat, all things being equal, will sail at least 2 knots faster, on average, than a catamaran with keels simply because it isn’t carrying the enormous fixed hydrodynamic drag (i.e. wetted surface) of two long and deep fixed keels. This added speed is a significant safety feature for long-range cruising. Not only are long passages cut shorter, reducing exposure to adverse weather, but should one encounter adverse weather it is much easier to either run from it or avoid it entirely with proper weather routing. A faster boat always increases one’s options, and therefore increases safety, when cruising.
• A daggerboarded cat typically draws 2 to 2.5 feet less water than a cat with keels. As such, the sailing grounds and potential anchorages available to a cat with daggerboards are considerably larger than those available to a keel cat.
• In extremely severe seas daggerboards enable the skipper to adjust the balance of his catamaran by raising and lowering the boards. When sailing in large cross-seas you typically raise the leeward daggerboard entirely and lower the windward board half-way to prevent being tripped over by a breaking wave. A keel cat is stuck with the keels down, all the time – as such, there is no way to prevent the boat from “tripping over herself” in storm-force conditions.

• CONS. Daggerboards are very costly to construct. A builder must create dual dagger-boards as well as dual dagger-board trunks, along with the winches and pulleys to raise and lower them. Dual daggerboards add about $30,000 to the construction cost of a 45 foot catamaran.
• Dagger-boarded cats are not a good idea for bare-boat chartering because bare-boat sailors run aground a lot. Even if they are told to raise the dagger-boards when they are not beating, they forget which results in broken daggerboards. Charter sailors do not care about performance, so there is no sense offering them a costly option they will likely break.
• Daggerboards that are not carefully installed by a professional shipyard can rattle in their trunks. This is annoying. A well built cat will not have this problem.
• If you are not a careful navigator and operate near shallow waters with your daggerboard(s) in the down position and plow into a hard reef at high speed, you will do serious damage to the bottom of your boat. While most daggerboarded cats have mini-skegs to protect the rudders and saildrives from a grounding, a high speed collision with a reef could do major damage to the bottom of your catamaran.
• Daggerboard trunks take away a modest amount of interior room from the inside of each hull.

• MISCONCEPTIONS ABOUT DAGGERBOARDS. Daggerboards are for racers only. Not so. I am convinced this myth is propagated by builders who do not offer dagger-boards due to their cost.
• Daggerboards are complex to operate. Not so. Unless you are sailing upwind they are always in the raised position. When you sail upwind you simply uncleat the boards and let them drop. To raise them you simply pull a few turns on a winch. It is easy to operate daggerboards.
• You cannot beach a daggerboarded cat. No so. A properly built daggerboarded cat is easily beached and indeed can beach much closer to shore. The entire bottom of a well built daggerboarded cat is solid fiberglass.
• Since high volume production catamaran builders must sell nearly 50% of their yachts into bareboat charter, it is not surprising that none of their models have daggerboards. At the present time there are just four production builders of daggerboarded cats: Catana, Outremer, Sud Composites, and Dolphin. There are of course a wide range of custom and semi-custom dagger-boarded cats on the market, particularly in New Zealand and Australia.
• For the most part, daggerboards are preferred by serious offshore voyagers who insist that their catamarans sail upwind swiftly and as high as a monohull. They also want a catamaran that is considerably faster than a monohull on all points of sail, not only because they enjoy sailing fast, but because it is safer.
• We sell a lot of used catamarans at The Multihull Company. Most of them have keels. As for me, if given a choice, a dagger-boarded cat is my preference. But I am a true enthusiast!

When to use daggerboard windsurfing?

Beginner level. If you’re just starting to windsurf, we advise you to choose a wide, big volume board with a daggerboard, which will help you to make your first runs and then progress to the next level. The wider and bigger volume the board, the more stable it will be.

Beach range boards are the best adapted for beginners. They are wide, voluminous and incredibly strong, made using our TOUGH TEC (Polystyrene/Polyethylene) construction system, and have a daggerboard to help you get back upwind even when the wind is blowing offshore.

Beginner to intermediate level. Some of the Breeze board range also have a daggerboard, making them perfect for learning and progressing too. Once again, your body weight will be the deciding factor in your choice:

What is the difference between a leeboard and a keel?

A leeboard is a form of pivoting keel used by a sailboat largely and very often in lieu of a fixed keel. Typically mounted in pairs on each side of a hull, leeboards function much like a centreboard, allowing shallow-draft craft to ply waters fixed keel boats cannot. Only the leeward side leeboard is used at any time, as it submerges when the boat heels under the force of the wind.

A disadvantage, where there is an inadequate fixed keel, is that they typically ship (bear) little ballast, which being on the far side delays the onset of unballasted craft’s heeling, that is, to put up a good, constant resistance against the wind. The classical, archetypal definition of ballast is a low, central weight to optimise centre of mass, reduce turning moment and therefore resistance to the boat keeling over, however tends to be higher in self-righting vessels. Modern developments allow them to act as a speed-enhancing lifting foil.

Leeboards existed in China from at least the eighth century on warships that “held the ships, so that even when wind and wave arise in fury, they are neither driven sideways, nor overturn”. Leeboards for stabilizing junks and improving their capability to sail upwind, are documented from a book by Li Chuan. The innovation was transmitted to Portuguese and Dutch ships around 1570. “The Portuguese experimented with caulking their vessels in the Chinese manner and the Dutch probably added leeboards to their craft that were copied from Chinese models.”

How do you use a daggerboard?

As the boat slides sideways through the water. And our lured or our downwind. Board will be fully retracted offering no resistance if the board if the boat is hit side on by a large breaking wave.

Can you windsurf without a fin?

Without the fin our windsurfing board would mostly drift sideways from the side force of the sail. The board would provide a little bit of opposing side force to resist the sideways drift, but not enough to effectively thrust the board forward. So we need to select a fin with the proper overall character to match the sail and board we are using. Most windsurfers know that we need a big enough fin to resist the side force of the sail. If the sail is too big for the fin we are going to get spin-out (stall). While area of the fin can be used to compare fin size, there are many other factors besides area that affect lift and spin-out.

Here are other factors that will affect lift and spin-out: 1. The rake of your fin: A fin with a lot of rake, like a weed fin, will produce less lift, so you may get spin-out more easily. A fin of the same area that is straighter up-and-down will generate more lift. 2. Your speed: The faster you go the more lift your fin will produce thus reducing the amount of spin-out you might get.​ 3. The shape or profile of the fin: Different fin shapes produce more of less lift thus affecting spin-out. 4. The geometry of the foil (cross section of fin): The shape and thickness of the foil affects the performance of the fin. 5. Aspect ratio: If we divide the square of our fin length by the area of the fin we get aspect ratio. High aspect ratio basically means long and narrow while low aspect ratio means short and fat. Generally, high aspect ratio will produce less drag while low aspect ratio will produce a more maneuverable fin. 6. Angle of attack: This is the angle between your fin (board) and the direction you are traveling. Yes, you read that right. Our boards are not actually traveling in the direction they are pointed. There is a very slight sideways travel which creates an angle of attack for our fin to generate lift from. 7. The water density: Salt water is a little more dense than fresh water which is why things float better. The denser salt water also gives your fin a little more lift and a little less spin-out. This concept of fluid density also explains why the lift from a small fin can equal the lift from a much larger sail. Water is much more dense than air, and so the smaller fin can resist the force of the larger sail because more lift is generated from the denser water. 8. Moment of inertia: When you pressure the heel of your rear foot with your body weight there is a large amount of leverage (moment of inertia) that is exerted against the fin. The fin must resist this leverage. When this leverage against the fin is greater than the lift that the fin can produce the whole board will spin-out. The wider your board, the greater leverage you will apply to the fin when pressuring your heels thereby increasing spin-out. 9. Air under the board: If the front of your board is too high relative to the back, or if your board is bouncing a lot, you can force air under the board. This air can travel onto the fin and interrupt the flow of water over the fin thus reducing lift and causing spin-out. Make sure you have the proper sail and mast to match your board and water conditions to prevent bouncing (click here for an article Know Your Sail) 10. Imperfections on the fin: Chips, scratches, and roughness on the surface of your fin can affect the performance and cause spin-out. Even one small strand of a weed stuck to the fin can interrupt the flow of water against the fin and cause spin-out. 11. Size of your sail: We already briefly discussed this in the paragraph above. A bigger sail produces more lift, and requires a fin of greater lift to resist the bigger sail (all other things being equal). So, use a smaller sail. You can learn to ride smaller sails. Here is a whole article on Riding Smaller Wave Sails.

Of the eleven items above I want to focus on one item in particular, NUMBER 8, because it makes a HUGE difference in performance. You can easily improve your riding by making a few adjustments to avoid spin-out while riding small fins. The wider your board the further the edge of your board is from the fin. When you put weight on the heel of your rear foot at the edge of the board it can cause spin-out as we noted above. You could certainly put a big fin on the board to generate more lift and get rid of the spin-out, but we don’t want big fins when we are wave sailing. We want to be maneuverable and have less drag. We want everything smaller. So how do you go small AND reduce spin-out at the same time? It’s really pretty simple. Get your body weight over the center of the board, NOT on the edge of the board. How do you do this? First, make sure you have a modern “wave sail”, not a freeride sail. Wave sails are designed with a center of effort that is higher up on the sail as you will notice from the higher clew grommet and less area in the foot of the sail. This higher center of effort allows the sail to pull your body more over the center of the board (click here for an article Know Your Sail). If you put the same size freeride sail on your wave board the freeride sail will shift your body weight out onto the edge of the board over your heels because the center of effort is much lower in a freeride sail. This will increase spin-out unless you put on a bigger fin. If you put on a big fin and a freeride sail, however, it would defeat the purpose of wave sailing. So use a wave sail. Next, use longer harness lines and lower booms. This will get your sail more upright so that you get maximum power from the smaller sail you are using. Drop your hips lower to compensate for the longer harness lines and lower boom. Your knees are forced to bend more with your hips now dropped, and bent knees can absorb the energy from bounce that would otherwise transfer to the fin and cause spin-out. It’s a whole package deal. Today’s compact wave boards have wider tails than traditional wave boards, so it is very important to keep the weight off of your heels to avoid spin-out. I also like a wave sail designed with less luff curve so that the mast stays more flexible. That way the force from a gust of wind does not transfer through the mast and down to the fin thus causing spin-out.

Do all catamarans have daggerboards?

Generally, daggerboards are used on smaller rigs such as 10 to 40 feet for racing but there is a large number of custom and semi-custom catamaran builders who offer daggerboards as an option. Daggerboard rigs may be faster than fixed keels because fixed keels have so much hydrodynamic drag by the shape. Some makes which utilize a daggerboard design are: The Mirror Dinghy, Laser, Vanguard 15.

• ^ a b Hankinson, K.. Rigging small sailboats. Bellflower, Calif.: Glen-L. Keel daggerboard rudder. (n.d.). Retrieved March 22, 2015, from mecaflux.com/en/keel(permanent dead link) daggerboard rudder.htm
• ^ a b “Upstate NY explorers ID rare boat in Lake Ontario”. Associated Press. December 13, 2008. Archived from the original on January 24, 2013.
• ^ Multihull Keels and Daggerboards | Catamaran Dealer. (2009, March 12). Retrieved April 8, 2015, from aeroyacht.com/2009/03/12/multihull-keels-and-daggerboards/ Archived 2015-01-03 at the Wayback Machine)
• ^ The Blade. Retrieved April 7, 2015, from toledoblade.com/local/2014/09/08/Rare-dagger-board-schooner-discovered-in-deep-water-off-Oswego-N-Y.html
• ^ (Boat Builder)
• ^ Firebird Catamaran. (n.d.). Retrieved March 22, 2015, from firebirdcat.com/technical_information.htm/technical_info_daggerboard.htm Archived 2015-02-08 at the Wayback Machine

Look up daggerboard in Wiktionary, the free dictionary.

What is the difference between a leeboard and a daggerboard?

A daggerboard is a removable vertical keel that is inserted through a “trunk” in the center of a vessel’s hull, usually amidships. Daggerboards are usually found in small sailing craft such as day sailers, which are easily handled by a single person. Daggerboards are not usually ballasted but are locked in place by a clip or pin. Unlike a centreboard, which can be set at different angles to the hull of the boat, daggerboards are generally limited to a single perpendicular position relative to the hull. If a daggerboard is located off center, it is called a leeboard or a bilgeboard.

The characteristic which differentiates daggerboards from other centerboards and swingkeels is that daggerboards are easily removable, even when the boat is underway. Centerboards and swingkeels, common alternatives to fixed keels, can pivot up and down but are fixed to the hull. The freedom of movement of dagger- and centerboards allows them to swing or slide up into the hull of the boat, which is advantageous when sailing in shallow waters. The pivoting centerboard or swingkeel can swing up when it strikes an object which helps prevents the sort of damage to which fixed keels or daggerboards are subject. Daggerboards can be raised and lowered as needed but will generally be damaged if not retracted before impact with the bottom or with floating objects.

Many small sailboats use a daggerboard instead of a fixed keel. This allows these boats to be more easily moved on trailers, sailed in shallow waters, and easily beached. Daggerboards also afford an opportunity to reduce drag when racing because they can be retracted when not needed (i.e. when sailing downwind or in very light winds).

What causes daggerboard planning?

The big broad daggerboard would load up at speed and if you let the board heel very much the board would want to lift right up to the surface and cause what we always called ‘daggerboard planing’.

Thread starter sail(plane) ; Start date Aug 14, 2018 ; This site may earn a commission from merchant affiliate links like Ebay, Amazon, and others.

I could never understand the why (and I haven´t felt the difference either, but that could be my lack of skill). The daggerboard (lets ignore rudder), basically, MUST balance the sideways force of the sailplan. But the daggerboard lift is not only proportional to area; it depends of course on angle of attack and speed. So, my reasoning is if you raise the daggerboard, you decrease the area, and the new balance will be found with the daggerboard at a higher angle of attack, higher CL, same sideways force. Of course you will be decreasing the aspect ratio, more drag, but in the end everything will balance with a higher angle of attack, less than the stall angle, because if it is stalled your are not sailing anymore. So, why does a raised daggerboard depower the boat? Will that increase in angle of attack reduce the sails angle of attack? (too lazy to start drawing vectors). Thanks.

Less lever arm, same thing as if you could shorten your mast by a couple of feet when overpowered.

What is the purpose of a centerboard on a sailboat?

Purpose. A centreboard (often called a lifting foil in a modern racing dinghy) is used to provide lift to counter the lateral force from the sails. This is required for sailboats to move in directions other than downwind, since the force of the sail is never closer than 45 degrees to the apparent wind.

A centreboard or centerboard (US) is a retractable hull appendage which pivots out of a slot in the hull of a sailboat, known as a centreboard trunk (UK) or centerboard case (US). The retractability allows the centreboard to be raised to operate in shallow waters, to move the centre of lateral resistance (offsetting changes to the sailplan that move the centre of effort aft), to reduce drag when the full area of the centreboard is not needed, or when removing the boat from the water, as when trailering. A centreboard which consists of solely a pivoting metal plate is called a centerplate. A daggerboard is similar but slides vertically rather than pivoting.

The analog in a scow is a bilgeboard: these are fitted in pairs and used one at a time.

Lt. John Schank (c. 1740 – 6 February 1823) was an officer of the British Royal Navy and is credited with the invention of the centerboard. Schank, however, gave credit for the idea to British Brigadier General Earl Percy.

What does a dagger board do on a sailboat?

You can pull the dagger boards up and reduce the amount of surface. Area that’s touching the water which therefore reduces the amount of drag. It’s actually a fairly significant amount of speed that.

What is the difference between centerboard and daggerboard catamaran?

Centerboards or “swing boards” rely on a pivot point at the top of the board allowing it to swing 90 degrees vertically and retract horizontally in a wet cavity built into the bilges in each hull, while daggerboards penetrate only vertically through bearing boxes in each hull. These deployment differences can dictate the shape of the boards thus changing the performance of the catamaran.

Pros:There are plenty of reasons for choosing centerboards for you KC54 or KC62. One of the top pros is the safety factor for sure. Here at Kinetic Catamarans, our centerboards are driven by push button line drivers governed by proximity sensors. We have integrated “fuses” or a weak spot in the line holding the board down which would break upon grounding or hitting a submerged object. The boards are buoyant and would float back up into the case with minimal damage to the leading edge. An inspection is recommended if this scenario plays out however with easy access to the line drivers and a quick replacement of the fuse we are off and sailing again.

Cons: Centerboards although very safe do take a small performance reduction. Having the lateral resistance retract into a box built into the hull not only governs the shape of the board but also leaves an open cavity for water turbulence to occur, which can disturb the water flow down along the hull and over the rudder. Another performance hit occurs when you want only a percentage of your board down, the lateral resistance is reduced dramatically.