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:
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.
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, 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.
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!
We bought an extra main sail fitting fot he jib boom, i.e., both boom are 6 mm carbon fiber tubes. 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. 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.