Sailboat for speed record

[Enthalpy]

Hello to all sailors, record chasers, and enthousiasts in general!

 

The thingy sketched below is meant to be a sailboat - at least to the sense that wind moves it - and to be fast.

 

 

The sail, high in the sky like a kite, resembles essentially a glider. The centreboard, fully immersed, resembles a glider as well. A thin cable, possibly of steel, binds them.

 

Said sailboat has no hull at the surface: only the cable cuts through the surface, meaning a tiny drag there, and the ability to sail through rough sea and deep water. On the other hand, the need to control actively and permanently the sail and the centreboard intend this boat for artificial records only.

 

As the cable's angle tells, the lift can exceed the boat's weight many times, an other factor for speed.

 

I expect the centreboard to be set to drift a bit, so both it and the sail pull the cable forward, instead of the sail pulling both.

 

The safest option would replace the crew by a remote control, but one may want or have to put a crew on board. The centreboard is a bad location, even with an added hull, because of poor visibility and excessive risk in a collision. An added hull that floats when steady and is pulled in the air when navigating is one option. The sail is an other one, and then it resembles a glider a lot: the safest place to splash down if the centreboard is destroyed, but the most difficult to take-off - something unclear.

 

The cable is longer than drawn, and the centreboard far more smaler than the sail. A sketch from the side is coming and should explain the shape of the wing and the centreboard.

 

Marc Schaefer, aka Enthalpy

[Joatmon]

I thought to myself if this has a chance to work then it would also work with boats ( although presenting more water resistance because of the hull).

I soon found that there is presently quite a lot of interest in doing this and also some claims that it can be more efficient than a traditional sail. Just google - kite driven boat-.

[Externet]

The pilot gets shaken, later stirred; for a hulled similar design sailboat:

Enjoy ----->

[Enthalpy]

This is the windward view :

 

 

Both the sail and the centreboard are stiff to reduce their drag ; they should also have a more benign behaviour at high speed.

Notice both can orient themselves freely around the cable hook and have their own stabilisation, as inspired directly by the historical Greenbird

http://www.greenbird...ecord/the-craft

 

Yaw and roll stabilise as at an aircraft, but due to the cable and the two linked foils, pitch stability may require a new theory. To be clarified before putting people on board.

 

Cavitation is a difficult issue at the centreboard and should, sincee lift forces are equal, induce a higher drag than at the sail. Maybe the same shape as the sail can be made to work; but on this sketch, I represent an attempt with a highly swept wing to avoid cavitation. This is done at race boat propellers and at feeders for centrifugal pumps. As drawn here, cavitation at the cable won't neither disrupt the action of the stabiliser (the wing's tips). A different option would leave the wing's extrados cavitate fully - must be less good.

 

A profiled cable, as on aeroplanes, would drag far less than a round one... You find out how to prevent fluttering then. Many small stabilisers behind the cable, spread along its length?

 

Steel would make a narrow cable that drags little. Lighter polymer fibres can optionally be put parallel and impregnated to make a somewhat flexible cable; a company called Cousin then braids more fibres around them to protect them, hold them together and press the excess resin away.

 

Marc Schaefer, aka Enthalpy

[CaptainPanic]

If you want something like that "greenbird", why don't you just copy their design, and put some hydrofoils under it instead of wheels?

 

If you want something with a kite (a sail on the end of a cable is called a "kite"), your kite does not need a hull. In your picture, you show that the kite looks like a glider airplane, but the kite is connected to the ship (or whatever you call that bit that's in the water) by a cable. That cable (or rather multiple cables) should control the position, yaw, pitch and roll of the kite. With a simple kite, one cable can be enough, as shown here. There is no purpose for that hull. Your kite only needs wings, and nothing else. And any regular kite will work, but an airfoil is likely a good option. By the way, I only think that an airfoil is a good option because it is the design that the professionals use.

 

I understand that you want to build something with a hydrofoil for the ship, and a kite. It can be done, but you should take lessons from existing knowledge. For example, that kite is already in use on a BIG scale. Skysails (note: commercial link) builds huge kites for ocean-going cargo ships. It's a big fuel saver. Also, smaller sailboats use it (pictures here).

 

So, because all individual components seem to exist already, I conclude that your problem is mostly a control problem. The picture you've drawn looks inherently unstable, which means you need constant control.

 

Don't reinvent the wheel!

[Enthalpy]

Most of your questions are already answered. For instance:

I want no hull at the surface;

traction is to exceed weight, excluding hydrofoils in the sense they're traditionally understood;

one has to put the pilots somewhere;

stiff wings are known to be far better that a common kite;

"need to control actively and permanently" in my first post

 

and, yes, I know Skysails does somewhat similar things, as I stated in the thread originally linked in

http://www.scienceforums.net/topic/65217-rocket-boosters-sail-back/page__p__666596__hl__booster__fromsearch__1#entry666596

[CaptainPanic]

Most of your questions are already answered. For instance:

I want no hull at the surface;

traction is to exceed weight, excluding hydrofoils in the sense they're traditionally understood;

one has to put the pilots somewhere;

stiff wings are known to be far better that a common kite;

"need to control actively and permanently" in my first post

 

and, yes, I know Skysails does somewhat similar things, as I stated in the thread originally linked in

http://www.scienceforums.net/topic/65217-rocket-boosters-sail-back/page__p__666596__hl__booster__fromsearch__1#entry666596

What traction? Traction, according to wikipedia is defined as: "the maximum frictional force that can be produced between surfaces without slipping." But you're having something in water, and something in air, so it will always "slip". Water is newtonian, and the slightest force will cause movement.

[J.C.MacSwell]

Most of your questions are already answered. For instance:

I want no hull at the surface;

traction is to exceed weight, excluding hydrofoils in the sense they're traditionally understood;

one has to put the pilots somewhere;

stiff wings are known to be far better that a common kite;

"need to control actively and permanently" in my first post

 

and, yes, I know Skysails does somewhat similar things, as I stated in the thread originally linked in

http://www.scienceforums.net/topic/65217-rocket-boosters-sail-back/page__p__666596__hl__booster__fromsearch__1#entry666596

 

I think in principle you are on the right track. You are trying to maximize speed through the water using the energy available from the difference in velocities between the water and the air.

 

Efficiency, lift to drag, is key, the right balance of areas of the foils/wings and as already noted control, which is the toughest thing to get right in practice.

 

The interesting thing is the optimum depth for the foil and angle to the surface which will effect the drag of the cable (or cables). Normally depth is controlled with buoyancy or a system that reduces lift in the foils as the foil system rises toward the surface.

 

Similarly the wing or wings must be angled optimally and in the right direction for best thrust, minimizing drag, and maintaining the right altitude.

 

The rest is just "squeezing the pea" as hard as possible in ideal conditions...high wind, little turbulence and flat water.

[Enthalpy]

Plus some questions that my sketches above don't answer!

 

Like: how to keep the crew alive when the centreboard hits an obstacle, or loses lift..? We're speaking of speeds like 150km/h, that's why I like to have the crew in a cabin at the sail, so they can control the splash like a glider does.

 

And: how to first let the wing take off? Easy with a flexible kite, less so with a rigid wing, far less so if the crew is on board the sail. Maybe the sail must first take off by external means like a motorized winch.

 

Obviously my proposal is far from a complete concept, not to say a design.

[J.C.MacSwell]

Plus some questions that my sketches above don't answer!

 

Like: how to keep the crew alive when the centreboard hits an obstacle, or loses lift..? We're speaking of speeds like 150km/h, that's why I like to have the crew in a cabin at the sail, so they can control the splash like a glider does.

 

And: how to first let the wing take off? Easy with a flexible kite, less so with a rigid wing, far less so if the crew is on board the sail. Maybe the sail must first take off by external means like a motorized winch.

 

Obviously my proposal is far from a complete concept, not to say a design.

 

Just for the record...what is the current record? Just over 100Kmph?

 

Something about a motorized winch, even if prior to the timed attempt, rubs me the wrong way. What about using a "soft" kite assist to launch, which can be jettisoned after take-off, perhaps from a lightweight catamaran? Not that it really makes a difference to the main challenge...

[Enthalpy]

I too dislike any added engine... We're not building a steamer here! Alternately, gliders are commonly started with a bungee.

 

The current record is about 100km/h; one was established by a kite surf (youtube at 2m from sand banks...), and did I read that a hydrofoil improved it?

 

I'd like to rescue the rigid sail as it's more efficient and stable. Strong wind might be able to lift one if the sail is high enough above the floating fuselage and the centreboard serves as an anchor - perhaps maybe... Easier start was the goal of the intermediate hull for the crew. A jettisoned lift-off sail, maybe.

 

For sure, if one wants to set an official record, some definitions would need a double-check, like what a sailboat is.

[Enthalpy]

New speed record on 20th of November 2012, established by Vesta Sailrocket 2 at 59.23 knots (109kph), improved on 22nd at 63 knots (119kph).

 

 

Gratulations!

 

The previous record was established by a kitesurf, but Sailrocket uses the design where the sail and the keel are perpendicular to the line joining them, to create no overturning moment - as first documented by Bernard Smith in the 1960s.

 

http://www.sailrocket.com/

http://www.sailrocket.com/node/287 (zero moment design)

 

They still have one hull on the water at full speed, and their design is less unmanageable than my frenzy here.

 

Could there be intermediate steps towards my proposal, where no hull touches water? Maybe...

 

Ground effect wings could lift each hull yet maintain a stable altitude, as their lifting force increases near the surface.

See the Ekranoplane for instance: http://en.wikipedia....iki/Ekranoplane

The ride would be smoother on wings than on skis. Vesta Sailrocket 2's wing seems to use ground effect already, at one hull.

 

The swept keel design I sketched here above is supposed to help against cavitation, and its fastening aft of the foil help against ventilation - the swept design keeps the fastening near the lift center.

 

Marc Schaefer, aka Enthalpy

[alpha2cen]

How about this design?

Is force balance important at the high speed?

[Enthalpy]

See the keel or centerboard I sketched here in the message on 4 June 2012? The swept shape is meant to ease or avoid cavitation while the fastening aft of the trailing edge shall avoid ventilation - more so if the "leg" is swept as well.

 

This can be used as a hydrofoil as well, both for a sail or engine boat.

 

It goes without saying, but maybe better if I say it.

Marc Schaefer, aka Enthalpy

[Enthalpy]

A team tries to break the 1991 record for human-powered boat record
http://www.bbc.com/future/story/20170921-how-fast-can-a-watercraft-powered-by-humans-go
this time propelled by vertical movements of the sustaining foil used like a flipper.

On the newspaper's pictures at least, the foil's pillar has a crude connection to the foil's extrados, which must spark cavitation, ventilation and stalling.

My suggestion would be to provide a fastening behind the trailing edge or even at the intrados, and let the pillar rise behind the trailing edge as I sketched here on June 04, 2012.

I suppose a strong V shape isn't useful against cavitation at 20 knots, but it can give some pitch stability.

[Enthalpy]

The Syroco speedcraft tries to develop what I proposed, here are their Youtube channel and main description video:
UC1-4BeVLyF-g_qb3i4HoM9g - Blb2S6Ytngg

Their options (on the video, I suppose the craft doesn't exist yet, so many choices can evolve):

• Flexible sail, this differs from my proposal. Eases the start. Less efficient.
• Centreboard tied stiffly to the hull, this differs from my proposal.
• Floating hull near the water with the crew. Eases the start. Less safe than a hull at the wing.
• The centreboard is not swept. It would have helped avoid cavitation.

The sail and centreboard nearly perpendicular to the line joining them is a usual speedcraft design since Bernard Smith proposed it half a century ago. Leaving only the centreboard in the water is my idea, I believe. Much of the rest is from them, especially the design, while I only proposed a bare idea. But I'd have felt elegant of them to cite me.

Anyway, I'm happy that someone tries it.

[Enthalpy]

Luc Armant proposed the same idea before I did: leaving only the centreboard in the water
augredelair.fr (36MB in French with drawings)
and he's a member of the Syroco team. Best wishes to the project!

[J.C.MacSwell]

24 minutes ago, Enthalpy said:

Luc Armant proposed the same idea before I did: leaving only the centreboard in the water
augredelair.fr (36MB in French with drawings)
and he's a member of the Syroco team. Best wishes to the project!

Hi Enthalpy

Any English translation of that article? It looks like a good one.

Back when I was a kid sailing competitively I remember crossbow setting the record of 26.3 knots and doing rough calculations as to how to beat it (rough calculations was all that was necessary...the trick was stability and control, so making it actually work)

We now have ocean yachts that can average that for 24 hours in good though less than ideal conditions.

[Enthalpy]

Hi MacSwell, thanks for your interest!

I don't know any existing translation. The French document is a student's thesis. Google Translate maybe? Much of the document is verbose and loosely related with the innovation, so maybe the drawings can tell you where to let translate.

Searching for "Luc Armant" or for "aile d'eau" on youtube brings nice videos, easier to grasp and containing much the same information.

In addition to what I proposed later than he did, Luc Armant also conceived and experimented successfully human-free regulators for the sail and the centreboard, impressive achievement.