There are two classes of boat allowed:

  • The sailing class permits only wind power for propulsion. The hull overall length (LOA) is restricted to two point four (2.4) metres.
  • The non-sailing class permits any source of propulsion. The hull overall length (LOA) is restricted to two point four (2.4) metres.


There are two divisions for different levels of autonomy:

  • The autonomous division does not allow waypoints to be changed or for any message to be sent to the boat that could change its course. Publicly broadcast data such weather forecasts, ice observations and AIS transponders can still be received and processed on-board the boat. Data which is not publicly available or requires reprocessing must be accessed via a proxy running on a Microtransat server.
  • The unmanned division allows any data to be sent to the boat, even if this causes it to change course.

Section A: Safety

  1. Safety should take priority over winning.
  2. Competitors may not attempt to inhibit other competitors by intentionally colliding with or obstructing their boat or by interfering with radio and electronic equipment.
  3. All radio equipment must comply with appropriate International regulations.
  4. It is highly recommended (but not required by the Microtransat rules) that each boat should be equipped with a navigation light which is turned on during the hours of darkness. It is up to competitors to decide on their lighting setup and is their responsibility to ensure that their boat meets any legal requirements for lighting in all countries which the boat might visit. Based on informal advice from the Irish and US coastguard we suggest that either a single white light or tri-colour red/white/green light should be used. This should be visible from all directions at a distance of at least 2 nautical miles.
  5. Boats must take appropriate precautions to avoid collisions and comply with COLREGs (The International Maritime Organisation's Rules for Prevention of Collisions at Sea). This might include the user of obstacle detection sensors such as RADAR, RADAR reflectors, brightly coloured panels, warning labels/flags, AIS receivers/transponders and avoiding known shipping lanes. Each team must decide the exact precautions they wish to take.
  6. The boat owner is liable for any damage caused to their boat or by their boat. The organisers take no responsibility for any damage caused.
  7. Boats must remain outside any defined exclusion zones.
  8. Competitors must arrange permission for the boats to operate in the waters of their chosen country of departure. Competitors are also responsible for arranging permission for their boat to enter the waters of their destination country and other countries along the way. Competitors are recommended to remain in international waters where possible and to request that the relevant authorities issue a notice to mariners to warn other boats of their presence.
  9. Additional safety recommendations are available from the safety recommendations page.

Section B: Tracking of boats and transmission on data

  1. Each competitor will be required to provide their boat's position to the organisers via a web or email interface at least once every 6 hours. Competitors are free to decide how this information is obtained and transmitted. A map showing each boat's position will be provided on this website. Any boat which fails to transmit for more than 10 consecutive days or a total of more than 15 days will be disqualified.
  2. In addition to transmitting position data, each boat must keep a record onboard of its position at least once every 6 hours. A copy of this must be emailed to the Microtransat mailing list upon completion. It is recommended that competitors should log data much more frequently than this, ideally at least once per hour.
  3. Competitors may transmit status information such as battery state from their boats.
  4. (Autonomous division only) During the race competitors may not transmit software updates, new waypoints or remotely control the boat. Any competitor which does will be disqualified. However if a competitor wishes to implement such features for use in an emergency or after the race, then they may do so on the understanding that their use during the race will result in disqualification. The jury may request to examine satellite phone bills, log files or computer code if they suspect data has been sent to the boat. The boat may receive any publicly broadcast signals such as weather forecasts, ice observations or AIS traffic data. Data may also be downloaded from the internet onto the boat. If data needs to be reprocessed before its transmitted to the boat then the reprocessing code must be run on a server provided by the organisers. All inputs and outputs to this code must be logged and the jury may request to examine the source code or logs from the reprocessing system. The unmanned division is exempt from this rule.
  5. Each boat must carry the contact details (address, email and/or phone number) of its owner for anyone who might happen to find it. This could be be through writing them onto the boat itself or by writing on paper that is laminated or stored inside a water proof container. All competitors are advised to include in this a short explanation of what the purpose of the boat is and where it is supposed to be going, as this may help to avoid confusion and wasted time by anyone who might find it.
  6. In the event that a boat completes the race but has not fulfilled the requirements of rules B1 and B2. Then the jury will consider other evidence and decide if this is sufficient for the boat to be deemed to have completed Microtransat. Evidence submitted may include:
    • Regular transmitted tracking reports, considered by the jury to have been sufficiently frequent. e.g. remotely received reports every 6 hours, without long periods of loss.
    • Position estimates from Iridium Short Burst Data transmissions that did not include a GPS data embedded inside them. These should only be considered where the Circular Error Probable (CPE) radius is less than 10. See page 20 of the Iridium Short Burst Data Service Developers Guide for a technical description of this system.
    • Recovery of a GPS log, either via remote communications, or physical recovery.
    • Photographs, video or written evidence by trusted observers. e.g. maritime patrol aircraft or Coast Guard ships.
The jury will decide if the evidence, and the source of the evidence is sufficiently trustworthy. This rule does not negate the requirement to conform with rules B1 and B2. Boats which do not have remote tracking systems and data logging capabilities capable of transmitting/logging once every 6 hours and having a reasonable chance of functioning for the entire race will not be allowed.

Section C: Criteria for entry

Every boat entered must fulfil the following criteria:

  1. The sailing class will have no source of propulsion other than wind. The non-sailing class may use any propulsion source, including the wind. Wind turbines which directly drive a propeller are permitted in the sailing class. Wind turbines which charge a battery (or use some other kind of energy storage system) to drive a motor to turn a propeller are not allowed in the sailing class.
  2. (Autonomous division only) The boat must be fully autonomous, no operator control is allowed.
  3. The boat must be energetically autonomous, carrying on board any required fuel, batteries and electricity generating equipment.
  4. The maximum length (Length Over All or LOA) of the boat must not exceed (2.4) two point four metres. This includes anything which extends from the hull such as rudders, bowsprits and antennas.

Section D: The competition

  1. The aim of the competition is to sail an unmanned boat between Europe and North America or North America and Europe in the fastest possible time. The boat must cross both of the lines specified below in sections D.1 and D.2.
  2. Competitors must start between March 1st 2021 and January 31st 2022 (or whenever this date is extended to under rule H2).
  3. Competitors are responsible for transporting themselves and their boat to the starting line.
  4. (autonomous division only) An approach of at least 40 nautical miles to the start line must be sailed autonomously.
  5. Before departing, each team must choose a circular target area of 25km in radius, centred along their chosen finish line. A boat will only be considered to have finished the race when it gets within 25km of the central point of the target area. It does not matter which direction the boat enters the target area from. The boat must either add at least one point to its GPS log or transmit a position update that indicates it is inside the target area. The position of the line will be defined by linear interpolation using the points specified in sections D1 and D2.
  6. A boat which runs aground must begin sailing again without any human intervention. If human intervention is required then the entry will be disqualified and must start the competition again. Human intervention includes physically moving the boat or (autonomous division only) remotely controlling it.
  7. The boat must travel along or under the surface of the water.

Section D.1: Eastern start/finish line

Click here for a map showing this line. Click here for a list of these points in CSV format.

  1. The line is between 55 degrees North and 16 degrees West, 51 degrees North and 16 degrees West, 46 degrees North and 11 degrees West, 44.5 degrees North and 13.5 degrees West, 37 degrees North and 13.5 degrees West, 35 degrees North and 20.5 degrees West and 25 degrees North and 22 degrees West.
  2. An approach of at least 40 nautical miles to the start line must be sailed autonomously.
  3. Any team sailing from Europe to America must use this as their start line.
  4. Any team sailing from America to Europe must use this as their finish line.

Section D.2: Western start/finish line

Click here for a map showing this line. Click here for a list of these points in CSV format.

  1. The line is between 48 degrees North and 47 degrees West, 45.5 degrees North and 47 degrees West, 40 degrees North and 65 degrees West, 30 degrees North and 77 degrees West, 20 degrees North and 59 degrees West and 10 degrees North and 56 degrees West.
  2. An approach of at least 40 nautical miles to the start line must be sailed autonomously.
  3. Any team sailing from America to Europe must use this as their start line.
  4. Any team sailing from Europe to America must use this as their finish line.

Section E: Judging Criteria

  1. How quickly the boat crosses the Atlantic between the designated start point and the team's target end point.
  2. A handicap will be calculated by the jury based on the boat's hull length using the following formula: Time Corrected = Time * square root(length in metres)/square root(2.4 metres). Length will be measured as the distance from the farthest forward point to the aftermost point, in the region between the deck and the bottom of the keel. This includes rudders, transom flaps, wedges and any sensors in that region, but excludes any equipment located above the deck, such as bowsprits, antennas, sensors and other equipment that hydrodynamically will not contribute to speed.
  3. In the event of no boat reaching the finishing line, no winner will be declared.
  4. The result will be given by the jury within one week of the a boat crossing the finish line. During this time each competitor will submit a complete log of positions (minimum of one every 24 hours) along with any contest or comment to the jury and to all other teams.

Section F: Notifying the organisers of your attempt

  1. Before departing please email with the following details:
    • Organisation Name and location (town/city and country)
    • A link to your website
    • Boat Name(s)
    • Measurements (absolute length, hull length, beam and draft) in metres. Hull length must be measured from the furthest forward point to the furthest aft point including rudders, transomflaps and wedges. Absolute length is the hull length plus any above deck extensions such as bowsprits, antennas or anything else which doesn't contribute to the hydrodynamics of the boat.
    • Weight in kilograms
    • Which class you are competing in (sailing or non-sailing
    • Which division you are competing in (autonomous or unmanned)
    • Which route you intend to take (East to West or West to East)
    • Details of your power source(s), actuators, computers and communications systems
    • Details of your hull and rig design
    • Any other interesting information about your boat
    • A photograph of your boat
    • A link to a video of your boat sailing autonomously
    • The latitude and longitude of your target point on the finish line

    You may submit these details as a sign of your intention to compete, long before departure. This may help to improve publicity and show potential sponsors that you are registered.
  2. As soon as possible after you launch email the date, time and GPS co-ordinates of the position where you launched the boat to
  3. Regardless of whether or not the attempt was successful, if the boat is recovered, then the following details must be sent to the Microtransat mailing list within one week:
    • Details of where and how the boat was recovered
    • A photo or video of the recovered boat and if possible of the recovery itself
    • Details about the physical conditions of the boat, any signs of collision/damage, bio-fouling, salt corrosion, water ingress etc.
    • A copy of any log files which have been recovered

Section G: The Jury

  1. The organisers will select a jury of 3 people. They will rule on whether or not a boat has completed the race.
  2. The jury will consist of one chair person and two ordinary members. The chair person will be responsible for communicating the decisions of the jury and gathering evidence from the teams.
  3. The jury members will be appointed before the first boat starts the competition and will remain in place until the last boat completes or is disqualified. If a jury member needs to discontinue their duties then the organisers will appoint a suitable replacement.
  4. The jury members will have appropriate background experience. They must be familiar with the Microtransat Rules, the International Rules of Sailing, the International Rules for the Prevention of Collisions at Sea (COLREGs) and with robotic sailing general. They should have prior experience of robotic sailing, such as having made a previous Microtransat attempt, attended a WRSC or SailBot competition, been involved with the development of a robot boat or other robotic systems such as an autonomous underwater vehicle or unmanned aerial vehicle.
  5. Jury members will not be part of a team competing or intending to compete in the Microtransat (in the year they are appointed).

Section H: Future modification of these rules

  1. A review of these rules will begin in December 2021 for the 2022 Microtransat. It will be open to discussion from any interested party via a mailing list.
  2. If the review of these rules is not complete by January 31st 2022 then these rules will be extended until the review is complete.
  3. This rule has been deleted, it covered reducing the maximum length to 2.4 metres.
  4. This rule has been deleted, it covered a temporary extension to rule H3 for boats over 2.4 metres who registered before December 31st 2016.
Background by Jenna Bash on Unsplash