classes of radio sailing boats recognized by the International Radio Sailing Association (IRSA) who are recoignised by the International Sailing Federation are: (from smallest to largest). International One Metre (IOM) The IOM class rules specify a monohull of maximum length 1000 mm, with maximum draught 420 mm. There is a minimum weight of 4000 g, which makes homebuilding of competitive boats possible. The IOM has three one-design rigs. To keep costs down, hull materials are restricted to either wood or glassfiber, while masts and booms are restricted to either aluminium or wood. (International One Metre Class Association) International Marblehead A Marblehead has a maximum length of 1290 mm and a maximum draught of ca 700 mm, but no minimum displacement. Up to six rigs are allowed, the tallest being about 2200 mm. International Ten Rater International A Class (A), the largest of the international radio sailing classes. Other classes of international significance include the CR-914 the RC Laser, the Micro Magic, and the RG-65. The Bottle Boat is a low-cost alternative to these classes. Largely constructed from waste items (bin bags for sails and soft drink bottles for the body), it represents an environmentally friendly entry to the sport. Racing power boats There are dozens of types and classes of race boats. They are mainly organised by engine type and hull type. Race: Circuit and Straight line is established at National and International levels Engine: Electric, Glow Plug, Flash Steam and Gas (petrol) Hull: Mono, Hydro, Cat, Outrigger and Eco (self righting jelly mold shape) Classes are further divided by battery type and count, Engine CC, Deep V Mono, Stepped Mono, sub surface and surface piercing prop's etc. Power boats are typically Fast electric or internal combustion, (ignition engine or glow plug R/C engine based) and some are steam powered (conventional type, and also flash steam). (At one time some boats used engines working on the compression ignition principle. These were not diesels in the true sense of the word but the modelling fraternity frequently referred to them as such. A few enthusiasts still operate such engines.) The power is commonly used to rotate a submerged propeller, aircraft propeller or jet which in turn provide the thrust to move the craft. Typically power boats have two controls, rudder, outboard motor or stern drive and throttle control. Powered scale boats will often have additional remote-controlled functions to improve realism, e.g. sounding