How do canards work?

[jacobsen1]

This may sound a little weird, but how are the raised and lowered? Does anyone have a drawing of how it's done? I was thinking it'd be an easy way to raise and lower a keel on a sportboat w/o needed a specific hoist as the loads/sizes of a canard on some of these giant boats would have similar loads as a small sportboat no? Maybe it's too much added weight?

Just an idea, but I have no clue how it's done on the canters.

 

[tyler]

i'm no expert.

I think SPEEDBOAT uses hydraulic motors that have pinch wheels. two wheels with the canard in the middle, roll it up/down.

I'd imagine smaller boats may use gravity and maybe a halyard to lift and lower them.

 

[johncurtin]

canards and daggerboards are 2 very different things..........

speedboat aint got no canards

 

[tyler]

ok. I'm a retarded non-expert.

WTF is the difference?

 

[Trovão]

les canards work quacking. :lol:

 

[Buckie Lugger]

I saw a video of Artemis (the old one), and it looks like they have a line from the top of the daggerboard that goes up to a block (attached to the mast?), and then down to a winch, which is driven by a coffee grinder.

I've got a feeling that some of the longer boards are very heavy, maybe 80 - 100 kg. So pulling them up by hand would be difficult.

Leopard has a hydraulic system to lift her boards, which is similar to Tyler's description of the Speedboat design.

 

[Presuming Ed]

Canards are ahead of, and aligned with the main lifting surface. They might articulate.

On most canting keelboats, daggerboards are the main lifting suface.

 

[savoir]

canards and daggerboards are 2 very different things..........
speedboat aint got no canards

Sure it does - two of them.

A canard is always forward of the main keel. Some are lifting while others are pivoting. The pivoting ones act like a forward rudder and are pretty rare these days. Their benefit remains unproven. Genuine Risk used to have one. Maybe it still does. A canard could also be fixed.

Most daggerboards are on shallow draft cruisers or canting racers and can be positioned anywhere. They always sit inside a cassette and are lifted vertically or close to it. Sometimes they are called drop keels or lift keels. On a cruiser they usually lift through the center of a stub keel. We already know what the daggerboards on a canting racer look like.

On Speedboat the canards and the daggerboards are different names for the same thing.

 

[Presuming Ed]

Sure it does - two of them.
A canard is always forward of the main keel. Some are lifting while others are pivoting. The pivoting ones act like a forward rudder and are pretty rare these days. Their benefit remains unproven. Genuine Risk used to have one. Maybe it still does. A canard could also be fixed.

Most daggerboards are on shallow draft cruisers or canting racers and can be positioned anywhere. They always sit inside a cassette and are lifted vertically or close to it. Sometimes they are called drop keels or lift keels. On a cruiser they usually lift through the center of a stub keel. We already know what the daggerboards on a canting racer look like.

On Speedboat the canards and the daggerboards are different names for the same thing.

Difference is that the main keel on Speedboat is not the main lifting foil.

Backlash of Burnham was a mid 80s IOR boat with a canard. Wonder what happened to her?

 

[savoir]

Difference is that the main keel on Speedboat is not the main lifting foil.

It's still the keel.

A canard can provide any amount of lift. The name comes from the forward position not the lift, or lack of it.

 

[ic198]

Sure it does - two of them. Sometimes they are called drop keels or lift keels.

I would only call them drop or lift keels if they were deliberately weighted to provide extra stability as well as lift- a daggerboard's only function is to provide lift, and while they are heavy as Buckie says, that is the structure in them, not deliberate- besides, they're on the wrong side to give extra stability.

Many of the 60s winch the boards down as well as up (gravity not enough to overcome friction). And in general you can't raise them once the boat speed rises to around 20 knots, which I think is what happened to Speedboat in her trans atlantic record attempt- she got stuck with her board down and the loads in it built until it broke

 

[Beast Rabban]

I don't think the boards on modern 60's etc. are canards. Canards are foils placed on front of the main lifting surface. Back in the day this was the keel,nowdays this is just a movable ballast holder. Times, as they say have changed.

Also a canard functions to form a slot so that the main foil provides more lift and stalls at a higher angle of attack. Boats like Speedboat have dagger boards.

 

[lesburn1]

In the past a canard was placed on the centerline of the boat before the mast and had a the ability to assist steering.

This drawing would be a canard, but a boat with a canard might also have a conventional rudder.

Also don't forget, when you are on land this canard can assist your understanding of hydrodynamics.

 

[ancientseawolf]

Canard is froggie for duck

In English it has been used to denote a deliberately false story....

All of which has nada to do with the question

It's a foil mounted ahead of the principal lifting foil

 

[entropy]

By definition, a canard is a lifting foil located in front of the main lifting foil.

A canard can be fixed or movable.

It's a pretty old idea in airplanes... the Wright Flyer had one! Most of the Rutan planes have 'em too.

A canard does'nt need to be in the same plane as the other foils..

A lot of planes will have a movable canard instead of a tail plane. A tail plane needs to push the stern down to bring the bow up. same deal with a rudder on a boat. In a plane, moving the canard up to get the bow up means you need less total lift to support the weight of the plane- less lift = less drag.

In boats it's a bit different. Usually on a boat with a canard, what we would traditionally consider a keel is just a structure to support ballast. The main keel will provide some amount of lift until it reaches horizontal. At some point, it just becomes symantics... is it a canard until the keel lift hits 0, then it's a daggerboard... ok, if you say so.

There are some cool things you can do with a canard arrangement unique to boats.. You can easily move the center of lateral resistance fore and aft. Want CLR forward..push the board down some. Running- pull it up and reduce wetted surface and move the CLR way aft. Some old CCA boats had trimming centerboards forward for this purpose.

Part of the theory is that spreading the lifting foils out fore and aft creates 2 areas of lower pressure under the peaks of the waves the hull makes at speed. This is supposed to lower the height and thus reduce drag.

If you want to get all salty mcfuck on the terminology.. daggerboards move straight up and down in a trunk about the same size as the board... like a laser. A centerboard can pivot on a pin like a 470 or be a daggerboard. If a board is not on centerline, it's a bilgeboard. A canard can be a daggerboard, a bilgeboard a centerboard or totally fixed or fixed but steerable like a rudder. It just doesn't matter what you call it! And.. any of 'em can be ballasted or unballasted.

Backlash was pretty far ahead of her time. She was designed by Julian Everitt and went through a bunch of different configurations. Her hull was was less distorted than the typical IOR boat of the day. She started out as a masthead rig, with canard, ballast strut, rudder. Wicked fast in breeze..not so good elsewhere. Then MH , no canard, fixed keel, rudder. This wasn't that great at all. Best iteration was back to canard,strut,rudder with a big frac rig. Boat was pretty competitive in that config.

 

[Scarla Narchy]

The system from DeltaDore with a jack and ropes





http://www.martin-raget.com/fr/accueil.asp

 

[Scarla Narchy]

but most Imocas dont have jacks

grpebel017.bmp

grpebel002.bmp



generali15.bmp

still from http://www.martin-raget.com/fr/accueil.asp

 

[equivocator]

Entropy has it right on the technical and terminology issues. On the earliest "CBTF" ("canting ballast twin foil") boats like the 60' Reichel Pugh designed Wild Oats, the 'canard' is a forward spade rudder. The reason for the canard is that when the struct for the ballast is 'canted' horizontal, the keel foil can no longer counteract the leeward side force of the sails, and without a forward foil, the "canters" would suffer from a high amount of leeway. A similar spade rudder canard configuration was also used on Pyewacket, Morning Glory, and Genuine Risk. It is especially efficient upwind. Maximus is slightly different, it has a fixed forward foil with a trim tab, instead of a forward rudder. Because rating rules prevent an articulatable foil from being retracted, these foils do not retract.

As suggested in Entropy's post, fixed foils are efficient when the boat is going upwind, but because they cannot be retracted, less efficient when the boats are reaching or running (especially at higher speeds), when leeway is not a problem so lift from a forward foil is no longer necessary, and drag from the canard becomes an issue. That led to the use of daggerboards on boats like Magnitude and Stark Raving Mad. These may be less efficient upwind, but can be retracted when reaching or running and they are not necessary to control leeway. I think these daggerboards are designed to have a small amount of slack in the box, so that the boards can rotate a few degrees to make them more efficient when going upwind.

Canting ballast bilgeboarders like Speedboat are slightly different, they use daggerboards that are off the centerline, and angled to be vertical when the boat is heeled 15-20 degrees, like an Open 60. These boards are toed-in to reduce leeway, and may be assymetrical. Because of the toe-in and assymetrical shape they produce a considerable amount of side force at high speed, which evidently accounts for the recent board failure during Speedboat's TA attempt.

Many of the canting ballast boats continually adjust the cant angle so that the boat maintains a constant angle of heel while moving through waves and variations in wind velocity. These boats use an engine driven hydraulic pump for this dynamic adjustment, which is why they are often accused of being "diesel powered sailboats."

 

[Dick Ishuge]

Entropy has it right on the technical and terminology issues. On the earliest "CBTF" ("canting ballast twin foil") boats like the 60' Reichel Pugh designed Wild Oats, the 'canard' is a forward spade rudder. The reason for the canard is that when the struct for the ballast is 'canted' horizontal, the keel foil can no longer counteract the leeward side force of the sails, and without a forward foil, the "canters" would suffer from a high amount of leeway. A similar spade rudder canard configuration was also used on Pyewacket, Morning Glory, and Genuine Risk. It is especially efficient upwind. Maximus is slightly different, it has a fixed forward foil with a trim tab, instead of a forward rudder. Because rating rules prevent an articulatable foil from being retracted, these foils do not retract.
As suggested in Entropy's post, fixed foils are efficient when the boat is going upwind, but because they cannot be retracted, less efficient when the boats are reaching or running (especially at higher speeds), when leeway is not a problem so lift from a forward foil is no longer necessary, and drag from the canard becomes an issue. That led to the use of daggerboards on boats like Magnitude and Stark Raving Mad. These may be less efficient upwind, but can be retracted when reaching or running and they are not necessary to control leeway. I think these daggerboards are designed to have a small amount of slack in the box, so that the boards can rotate a few degrees to make them more efficient when going upwind.

Canting ballast bilgeboarders like Speedboat are slightly different, they use daggerboards that are off the centerline, and angled to be vertical when the boat is heeled 15-20 degrees, like an Open 60. These boards are toed-in to reduce leeway, and may be assymetrical. Because of the toe-in and assymetrical shape they produce a considerable amount of side force at high speed, which evidently accounts for the recent board failure during Speedboat's TA attempt.

Many of the canting ballast boats continually adjust the cant angle so that the boat maintains a constant angle of heel while moving through waves and variations in wind velocity. These boats use an engine driven hydraulic pump for this dynamic adjustment, which is why they are often accused of being "diesel powered sailboats."

Thank you!!!!!!!!!! Both of you!