UIM · Hull and handling
Legal in all 16 UIM classes that publish rules. The envelope differs by division, not by class.
This page is UIM only, and the bodies do not agree. The same part under IHRA and IJSBA. Which one applies to you is decided by whoever sanctions the race you enter.
The Ski and Runabout envelopes are genuinely different numbers (52 vs 63.5 mm channel, 50 vs 63.5 mm drop, 126/153 vs 92 cm length). A sponson listing needs a per-division answer, not one UIM figure. Both differ again from IJSBA's 91.45 cm / 63.5 mm.
24 classes, grouped where the same rule gives the same answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules. 8 of them borrow another class’s rules and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook. 8 publish no rule for this part and name no parent to borrow one from, and are grouped together at the end.
Legal, with conditions 5 classes
TWO REAR SPONSONS required. Max 92 cm each side, 100 mm protrusion, 63.5 mm channel, 63.5 mm below the hull intersection, minimum 6 mm thick.
Legal, with conditions 5 classes
Max 2 per side. Max 126 cm each, 153 cm total with two sets. Max 100 mm lateral protrusion, 52 mm vertical channel, 50 mm below the hull side/bottom intersection, 50 mm below the lower bond flange. Minimum 6 mm thick if aftermarket.
Legal, with conditions 3 classes
Max 2 sets. Max 153 cm each, 210 cm total. · 501.04.02.02
Legal, with conditions 2 classes
Two rear sponsons are required, each at most 92 cm long, protruding no more than 100 mm, with a channel and a drop below the hull intersection of at most 63.5 mm each and a thickness over 6 mm; sponsons fixed inside the bond flange may not protrude outside it. · 502.04.02-02
Legal, with conditions 1 class
Max 153 cm each, 210 cm total, via the Kawasaki SXR1500 derogation. · 501.03.02
No rule published for this class 8 classes
No component rules are published for this class and no single parent class is named, so this part cannot be answered for it. That is an absence in the rulebook, not a permission.
Aftermarket sponsons: if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.
Every UIM class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.
Hull and handling · two and four stroke · legal in 16 of 16 answered, all with conditions