The yacht "Joker"

Joker is an autonomous yacht controlled by a computer receiving information from the GPS (Geostatioary Position Satellites). The yachts position is transmitted daily using a satellite telephone and hopefully the position and track will be updated onto this website. In coastal waters we have the facility to listen to voice commands given by the computer to the rudder and sail controls. The speed, position, course and way points will also be spoken. This facility was originally devised so that it would be easy to set up the boat but it has proved to be an entertaining feature and may be left in the final design.

More details of "The Microtransat Challenge" are here

The Microtransat

This is an informal competition between amateur inventors to design and operate a small robotic sailing boat across the Atlantic Ocean. Competitors have decided that the maximum length of the boat should be four metres and that propulsion and on-board equipment should be by provided by renewable energy.

How the Microtransat could benefit Mankind

Acquiring meteorological data mid ocean has hitherto been performed by sea-going weather ships and satellites. These are expensive and energy consuming. Hopefully technology gleaned from the Microtransat could lead to inexpensive autonomous weather boats, which could be remotely programmed to sail to a station somewhere in the ocean. They could then gather data about the ocean and the atmosphere. This data could perhaps be helpful in understanding climate changes and investigations into sea life.

How our project started

John Silvester is working on an on-going project to use computers to assist in driver training. Over a decade ago he teamed up with a local inventor Robin Lovelock of Sunninghill Systems http://www.gpss.force9.co.uk/ for advice on the application of Global Positioning (GPS) to the project. Years later John came across a small article about the Microtransat in a sailing magazine. As a one-time yacht owner and having built robots for competitions, the Microtransat appealed to him. Naturally John called on Robin for advice.

Co-incidentally Robin had hands-on experience tracking bottles fitted with GPS receivers and radio transmitters, which were thrown into the English Channel. He was also associated with a competition to fly autonomous planes across the Atlantic. Naturally Robin was very enthusiastic to help with the project.

Within a short time Robin had written a working version of the software and wired up a functional rig to steer a toy boat. It worked perfectly and is in a state of constant further development. His work can be viewed at http://www.gpss.force9.co.uk/autop.htm

Provisional journey plans proposed by John

Our provisional start day is June 11 2013 (my son James' birthday) from Poldhu, Lizard Point, (54'01'59.74N, 05'06'51.24"W) the most southerly part of mainland England. This area is a particularly hazardous stretch of coastline, it was historically known as the "Graveyard of Ships". It was from this place that Marconi sent his first transatlantic message from a large 12kW transmitter designed by Flemming (inventor of the thermionic valve and the 'Right hand rule') The area is now run by The National trust. The boat will be sent to St John’s, Newfoundland, unfortunately known as the wettest and cloudiest city in Canada. It was at Signal Hill , St.Johns that the first transatlantic message was received. The bay can be seen on google Earth at position 47'34'53.62"N 52'44'10.44"W This northerly route during summer time would give us longer daylight periods since the sun hardly sets, although cloud cover could reduce the efficiency of the solar panels. However the cold air will improve the efficiency of the solar panels. http://www.newton.dep.anl.gov/askasci/eng99/eng99455.htm) We did a simple experiment verified this.

The orthodromic (shortest) distance is about 1,800 nautical miles though we expect the boat to travel almost twice this distance due to perturbations due to unfavourable winds and steering errors. Our tiny 1 metre prototypes can achieve an average speed of about 1 knot (about 0.5 metres per second) but we expect to average at least 2 knots when fully developed and having a 4 metre waterline length. Thus the journey will take about in the order of 2000 hours (or 80 days, almost 3 months).

Design Considerations of Joker

Long hulls can be driven faster at non-displacement speed than short ones. Wikipedia hull speed Designing a long hull, 4 metres in length will allow a hull speed of about 3 knots. Naturally this hull will have a greater wetted area than a short one and will be at a disadvantage in light airs. However light airs are uncommon in mid Atlantic. Note that a 60kg hull of this length will have an immersed cross sectional area similar to the open end of a Wellington boot.

The craft should survive 70 knot winds and 6 metre waves.

See http://www.passageweather.com/maps/natlantic/mappage.htm Unfortunately weather in the Atlantic can be worse than this. However 'the balance of probabilities' are that 'Joker' will not encounter conditions worse than this. A light yacht with a length 4 metres could easily become air-born unless the freeboard was minimal. Waves will therefore wash right over the hulls so the foot of the sail must be held high enough to avoid the crests.

'Joker' should be able to right itself if completely inverted.

Clearly a conflict arises here because freeboard results in buoyancy, yet freeboard should be avoided. Clearly stability in 'Joker' must involve an element of a low centre of gravity and a buoyant mast. A hull with plenty of beam will resist a capsize but will be difficult to right should a complete knock-down occur. A hull with a great deal of beam but little buoyancy would be the best compromise. Unfortunately this results in increased skin friction and the extra drag may slow the boat.  To this end a trimeran hull was considered to give the best compromise. The outboard hulls should each have slightly less displacement than the entire vessel. The centre hull should displace slightly more than the total displacement of the boat. The front of the middle hull section should displace as much as possible to allow the boat to recover if it was 'pitch-poled''

It should be resistant to solid water hitting it.

A trimeran will clearly offer less resistance to the solid water than a flat-decked mono-hull with a similar beam.

It must be light so it can be manhandled easily by two people.

We imposed a design weight of about 60kg so that two people could easily manhandle 'Joker'. Clearly if the hull is 4 metres long the maximum cross sectional area of the hull would be about the same as a 150mm drain pipe.

No component should exceed 2.75 metres in length.

This would allow for easier transportation and storage.

The boat should be unattractive to aquatic mammals.

Experiences from the crews of long distance sailing racers indicate that this is a problem. A U-tube video from a competitor has shown a dolphin playing around their boat. 'Joker' will be very light and make an interesting toy for such critters. An electric fence type device will ward off these animals.

The hull should resist fouling.

The crossing will take about three months so plant growth could be significant. This would slow the vessel down. A copper anti-fouling will be applied.

The rudder

It must be long so that it retains its grip on the water when in part it may be out of the water.

The hull abaft the mast will have a shallow draft.

Forward leverage on the mast will raise the stern. A shallow draft aft will result in the stern rising and reducing the displacement at the stern. This will reduce the forward tilt of the hull.

A fin will be needed at the stern.

Directional stability will be reduced when sailing with a following wind. The fin will maintain stability and reduce the chances of broaching.

The mast will have a constant cross section and be foam filled

This arrangement will help the hull to self-right. A float atop the mast may be needed to increase this effect.

A wind vane will be situated at the masthead.

It is safest to mount this out of harm’s way.

Masthead Pod

This is a simple epoxy fibre globe partially filled with foam which protects the electrical gear and has buoyancy to prevent a complete capsize. A wind sensor sits above this pod.

Current design

Centre Hulls

These are epoxy-aromatic polyamide tubes about 200mm diameter. Epoxy is used as it does not need to be mixed in batches - additional resin mixed into the pot revives the original mixture. It does not give off harmful vapours so can be used indoors. Aromatic polyamide has better scuff resistance and any fibres which escape will be less of an irritant in a domestic environment. It is stronger than fibreglass and is used in bullet proof armour, car tyres and sails of racing yachts.

The tube is filled with two part polyester resin to confer impact resistance to the tube and render it unsinkable. A line of small holes were drilled along the tube to vent the foam. The tube was filled horizontal so that the foam did not collapse upon itself as it expanded and cured.
Within the centre line of each tube, a 25mm tubular aluminium backbone was encapsulated. These tubes are 4metre long. Each hull is made in three parts. Each he centre hull is 2 metres long and has oval end plates angled at 70 degrees through which the aluminium tube emerges. Custom made aluminium mast attachments fit by the end plates which allow the masts to emerge from the hulls at angles of 70 degrees from both the front and rear and converge at the mast tops. The protruding aluminium tubes also serve as attachment points for the front and rear sections and also the 5mm thick aluminium keels.
Thus each hull has masts and keels at each end.

End Hulls

These are identical and reduce drag. It may be possible to use these as ballast tanks for steering and trimming the boat. In the event of a pitchpole, they will fill with water and allow the vessel to right itself. They are still at the design stage.

Keels

These are simple thick aluminium plates designed to confer directional stability and to provide sufficient righting moment in the event of a capsize. Aluminium is an excellent conductor of heat and are attached to the centre hulls by plastic which melts at a low temperature. This allows us to alter them to achieve the correct balance to the boat. They will sweep back at an angle of about 45 degrees to avoid weed.

Masts

These 25mm tubes form a pyramid with a base of about 2 metres and an apex of 3 metres. This triangulated structure obviates the need for rigging wires. The apex will support wind sensors and most of the electronics out of reach of the majority of high waves.

Sails

These are still in development. They will be rigid aromatic polyamide cloth strengthened with epoxy resin and foam filled. The cross section will be symmetrical and the thickness just over 25mm. When feathered they will have a coefficient of drag of less than a tenth of bare poles. They will pivot near to their centre of effort and be free to rotate about the mast on Teflon bearings. A number of methods of sail control are in development. Early experiments showed that a craft can be steered well using sail angles alone.

Masthead Pod

This is a simple epoxy fibre globe partially filled with foam which protects the electrical gear and has buoyancy to prevent a complete capsize. A wind sensor sits above this pod.

Latest developments

Robin’s latest boats are packed with lots of monitoring equipment. A forward pointing video camera monitors the sails and track whilst a rear view mirror displays rudder direction. Routines within the steering chip produce sounds relevant to signals given by this chip to servos controlling the vessel. Naturally gps information is sent back to the operator and this is converted to the track made by the vessel which, at base is overlaid on an aerial view of the lake and way points programmed into the steering chip. It may seem very Heath Robinson but it really makes it easy to interpret the movement of the boat relative to servo inputs. As a sailing enthusiast I can compare the computers input to how I would steer the yacht. There is usually complete agreement. This video shows developments since this project started -

Future Developments

Sailing on an inland lake is a world apart from braving the Atlantic. I am confident that we can produce a hull configuration which could cope with dramatic waves. One problem yet to be solved is the change in sail balance experienced at diverse wind speeds. There are a number of solutions which can be applied to this – work continues.

This evocative picture shows our French competitor undertaking a sea trial -

To be continued...

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Apologies for any broken links. Much like our yacht, the site is still in a state of constant development.