MicroMagic class rules


We propose the MicroMagic as a third class for WRSC 2011. Main advantages of the boat include the small size (0.53 m), great performance, limited boat building effort (the Graupner kit contains everything you need to build the bare boat for app. 160 EUR), and relatively low cost (if you can solder, you could build a robotic boat with a decent GPS starting from app. 1000 EUR). The provisional class rules are defined as follows:

  • The hull and deck must be from the Graupner kits (either MicroMagic or racing-MicroMagic)
  • The hull must be unmodified, while the deck layout may be changed (e.g., to add openings)
  • The keel fin and rudder must be from the Graupner kits (either MicroMagic or racing-MicroMagic)
  • The material, shape and weight of the keel bulb may be altered, as long as it is not harmful to the environment
  • The jib and main sail may not exceed the dimensions of the Graupner kit sails
  • The type of rig is open, as long as the limitation regarding the sails is fulfilled and the boat fits into a sphere of 1 m diameter (excluding sensors / antennas mounted on the mast top)
  • The boat must be human controllable throughout the races
  • The boat must communicate its true GPS position to a central server at a frequency of at least 1 Hz (the communication protocol will be published soon)
As a one design class, no handicap will be applied, i.e., the first boat to finish wins the race. We will further refine and explain the rules well before WRSC.

FAQ

  • What components do I need to buy to build an rrMM boat?
    We will give more details on our boats, but generally, you will need the Graupner kit, 3 servos, a GPS unit with board (e.g., ublox LEA4T), a GPS antenna (e.g., ublox ANN), a microprocessor and board, a communication link (e.g., Free2Move bluetooth F2M03GXA-S01), and some talent to actually build boat and boards.
  • Doesn't it take far too long to build an rrMM boat?
    Not really. Building the actual boat from the Graupner kit will take about 4-5 days. Building the control and GPS boards will take another 4-5 days each, depending on your soldering skills. Building a long range USB bluetooth antenna takes maybe 2-3 days. So if you find somebody to build the boards, you can have a boat sailing within 2-3 weeks.
  • Isn't a boat that small limited to really calm weather?
    Well, we wouldn't recommend participating in the Microtransat. However, the MicroMagic is a surprisingly stable boat with great performance from 1 - 3 Bft. There are heavier keel bulbs available, allowing great sailing in up to 5 Bft, and possibly beyound. The really limiting factor are waves, particularly with 15 - 50 cm length. Have a look at our video to see the robotic boats in action.


Boat design


In this section we will illustrate how we customized the kit boat to build a robotic racing MicroMagic. We assume you have bought the Graupner Kit, so you have all basic parts needed for the constructionbuilding the boat. Here you can find more details.

Deck


Servo Foresail We have opted to mount the servos on the deck, and to add an 'inspection hole' in front of the mast to have access to the bow region. While it is possible to control the sails with sheets, we wanted to get the actual sail position from the servos. Moreover, being able to back the sails, particularly the jib, can be helpful, e.g., when tacking. We placed the servos close to the mast using a cutter knife to carefully cut out the openings. The servo openings are reinforced by a wooden frame. One big disadvantage of mounting the servos on deck is the need to make them waterproof. We found that some servos without ball bearings are fairly water resistant, Stern but we have also experimented with covers, e.g., made from fingers of rubber gloves. Similarly to the sails we move the rudder with a dircet link (2 mm CFK rod). We have also added a power switch and an opening for the GPS antenna in the cockpit. As the latter is not moving, we simply sealed it with hot glue.

Hull


The hull was built as shown in the manual, though we would recommend paying extra attention to the sterntransom, where the glue became lose in two of our boats. We put a wooden mounting into the bow holding the carbon tube for the foresail boom. Also, pay attention when glueing the keel mounting to the hull: it has to be perpendicular!

Rigg


We bought an extra main sail fitting fot he jib boom, i.e., both boom are 6 mm carbon fiber tubes. Mainsail In out first attempt, a servo level was made of plastic and glueed to the bottom of the boom joint. Note that we used a small 2 mm carbon rod as bew axis extending into the lever, and a second small rod to keep the lever aligned with the bottom part of the joint. Depending on the servo position, the main sail will generally not cause singularities. Fockbaum However, to cover a larger angle, we mounted the jib level on the opposite side and attached a small stopper onto the deck at the maximal angle. Because of the different axes represented by the joint and the forestay, a boom vang adjusting to the sail angle needs to be designed. One option is a suspension made of ball bearings, though in our current design we simply build a triangular boom vang using the block that came with the kit.

Partners Universitaet zu Luebeck Beltec GmbH