BaddJet concept build sheets · seated runabout · IHRA + IJSBA

Runabout class build sheets

A race runabout is the same fifteen assemblies as a ski, with a seat in place of the pole and, on most modern entries, a supercharger. Each class decides which assemblies you may change and by how much. These sheets show what every runabout class under IHRA and IJSBA allows, slot by slot, and how the legal choices combine into a build for speed, handling, rough water or a tight budget.

01Class matrix

The class matrix needs JavaScript to draw

    02Build sheet:

    Side view of a generic seated runabout with the fifteen build slots marked and coloured by how much this class lets you change each one

    What the rulebook leaves unsettled

      03Best setups for this class

      Concept direction, legal options only

      Each preset walks the levers in its own order of preference and takes the first option this class allows. A blocked option is skipped, never suggested. Each goal shows whether the build moves it up, down or about the same against a stock runabout. That is a direction, not a measurement.

      The preset comparison needs JavaScript to draw
      How the directions are set
      The effect table needs JavaScript to draw

      04Mix and match

      Pick one option per lever. A struck-out option is not legal in this class; select it to read why. A dotted option is one this body's rulebook does not track. A dashed outline means the answer is inferred from the rulebook's silence, not quoted from it.

      05Every part, slot by slot

      06How to read this

      Legality

      Every part status is a cell in BaddJet's part matrix, keyed to the class and the body. "Not listed" means the class is a closed list and the part is not on it, so it is illegal by inference and not by a quoted rule. "Silent" means the rulebook does not settle it either way. Neither is a citation.

      Limits

      A legal option with a limit says what kind: a size or figure to meet, an approval to get, a rule that depends on the machine, or OEM-replica parts only. Limits that depend on approval or on the machine are amber, because they can change what you are able to buy.

      Tuning direction

      Pitch, grate, ride plate and sponson effects follow from how a jet pump and a planing hull work: more grip in the water means more hookup and drag, less means more top speed and a looser hull. No manufacturer publishes a mapping from water condition to a setting, so no direction here is a recommendation from a racer.