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What is RC Boating?:

RC boating is a hobby where model boats, sometimes scaled down from their life size counterparts, are run (and often raced) via radio control (hence, "RC"). There are many forms of RC boating, including sail, electric, steam, gasoline and nitro powered. IMPBA, as a sanctioning body, primarily focuses on racing the nitro/gasoline and electric varieties. The following gives some brief information on types of powering, hull classifications, size categorizing, and IMPBA heat racing formats.

 

Power

 

Sail - A sailboat is powered primarily, as one might guess, by the wind. Sails catch the wind and move the boat just as in the life-size version. Radio control is used to move the sails and rudder to the positions needed to catch the wind and propel the boat in the intended direction.

 

Electric - Electric boats come in a wide variety of types, including submarines, tugboats, boats for show, and boats for racing. These boats are powered the same as the more well known RC cars, by 6 to 12 cell nicad battery packs. Electric boats are quieter and cleaner than the nitro and gasoline types, and therefore more easily accepted on small, urban, running sites. Although typically noted as being much slower than the nitro and gasoline boats, this sector of the hobby continues to gain speed and enthusiastic support from hobbyists.

 

Nitro - So named for the fuel they burn, nitro boats use nitro-methane as their power source. These boats tend to have more speed than electric boats, and generally get more run time. Whereas batteries for an electric boat must be recharged after one run, a nitro boat can simply be refilled with fuel and sent out for another run. Each run typically lasts 5-10 minutes. Expect to pay more, initially, to run a nitro boat than electric, and pay at least $15 per gallon of fuel. The cost increases if you like the higher nitro (50% and up) for your boats.

 

 

 

 

 

Gasoline - Typically large boats, these are powered by gasoline in so-called "weed whacker" engines. Run times exceed those of nitro boats and of course the fuel is less expensive. In IMPBA racing, many people running "large scale gas" use the same hulls as the nitro boaters, but adapt them for gasoline engines.

 

 

 

 

 

Hull Classifications

There are two major classifications of hulls which are addressed in the IMPBA guidelines: mono hulls and hydro hulls. Within the hydro hull segment, there are eight approved classifications, although three are typically noted: outriggers, catamarans, and tunnel hulls.

 

Mono Hulls - This type of hull has a continuous wetted surface when operating at racing speed. Their shape is in the form of a V, probably the best known to people as the boat hull used in the popular TV series Miami Vice. They are noted for their ability to slice through rough, choppy water. The hull has no discontinuities between, or steps in, the wetted surface running at more than a 15 degree angle with keel; and no point on the hull cross section can be deeper in the water than the center keel. The hull can be lap straked (at least one strake on each side of keel), but the strakes must not be as low as keel. Single step and multiple step hulls that do not meet this last criteria are considered hydro hulls.

 

 

 

 

 

Outriggers (hydro hull) - The 3-point suspension, 4-point suspension, and multi-suspension hulls, as classified by IMPBA fall into this category. Along either side of the main portion of the boat are sponsons which do not run the length of the boat. These sponsons may be in the front, at the rear, or both. When racing, the sponsons and the propeller are typically the only parts of the boat touching the water.

 

 

 

 

 

 

Catamarans (hydro hull) - As with the tunnel hull, this type has full side sponsons, running the length of the boat. With an extended free board, they resemble full-sized offshore racing hulls.

 

 

 

 

 

 

 

Tunnel Hull (hydro) - These are a variation of the 3-point design, but the sponsons run the full length of the boat. This creates a tunnel or cushion of air that is trapped along the length of the boat, helping it move faster.

 

 

 

 

 

 

 

 

Engine Sizing

 

IMPBA has distinct classes that separate nitro and gasoline boats by the cubic inch displacement of their engine (or combination of engines). They are class A (up through .110 ci), class B (.111 through .219 ci). class C (.220 through .300 ci), class D (.301 through .458 ci), class E (.459 through .670 ci), and class F (.671 through 1.8308 ci). For steam, there is a single class H (up through 1.8308). For electric powered classes, a combination of the motor, bearing, magnets, and number of cells Sub-C or smaller determines the class. Classes are N-1, N-2, O-1, O-2, O-3, P, Q, S, and T (see the rulebook section for more detail).

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