Not legal 1 class
W.7.3.2 permits no external hull modification, so no extension may be added, and the pump cover plate extension under W.5.1 is answered on the ride plate row. · W.1, W.7.3.2
IHRA · Hull and handling
Hull extension, IHRA
Rear extensions, bow appendages and planing surface extensions added to the hull. Ride plate extensions, trim plates and trim tabs have their own rows, and where a class counts a transom extension as a trim tab (X2 Vintage) or bars it (Sport Spec), this row gives the same answer.
This page is IHRA only, and the bodies do not agree. The same part under IJSBA and UIM. Which one applies to you is decided by whoever sanctions the race you enter.
Where it stands, class by class
29 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.
What each answer below means
- Not legal
- This comes off. The rules refuse it in this class.
- Not permitted, not listed in the rules
- Treat it as coming off. The class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list, so this is our reading rather than a rule we can quote at you.
- Legal, with conditions
- Keep it, but measure it: the rules permit this part only inside stated limits.
- No rule, this is an open class
- Probably keep it. The class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms, and this is our reading rather than a permission anybody wrote down.
Not legal 1 class
DD.1 allows hull work only forward of the intake grate, so nothing may be added at the rear of the hull. · DD.1
Not legal 1 class
U.5.1 bars any hull extension attached to the transom. Only fixed trim tabs, answered on their own row, may reach past the hull, by up to 100 mm (3.94 in). · U.5.1
Not legal 1 class
DD.4 requires the OEM hull, with lightening the only change it lists, so no extension may be added. · DD.4
Not permitted, not listed in the rules 15 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
Legal, with conditions 2 classes
A bow appendage that diverts spray and stabilises the craft may be added if approved and built to the original specifications. Any other extension is a modification of the OEM hull, which the class admits within its 97 in maximum length.
- Ski 1100 Modified · R.1, R.6.1
- Ski 1500 Modified · Q.1, Q.6.1
Legal, with conditions 1 class
Yamaha SuperJet two-strokes only, as M.6.2.1.1 allows: the extension may be no wider than the hull's planing surface, may reach no more than 100 mm (3.94 in) beyond the end of the original planing surface, and may carry no hazardous skeg, rudder or fin. Every other eligible model has no extension allowance on this closed list. · M.6.2.1.1, A.2.2, J.1
Legal, with conditions 1 class
T.5.1 counts an extension mounted to the transom as a trim tab, so it must be fixed in position and reach no more than 100 mm (3.94 in) past the original planing surface, the same answer as the adjustable trim tab row. · T.5.1, T.6.4
Legal, with conditions 1 class
No Ski GP clause names an extension, so one counts as hull modification and must stay inside the plumb-bob outline of the upper deck bond flange without fins, rudders or skegs. Trim tabs, on their own row, may reach 100 mm (3.94 in) past the original planing surface. · K.8.1, K.7.1
Legal, with conditions 1 class
No Sport GP clause names a hull extension. V.1 admits a modified OEM hull, so an extension reads as hull modification inside the 120 in maximum length, and trim tabs stop 100 mm past the original planing surface. · V.1, V.8.1
No rule, this is an open class 3 classes
The class states only what it bans and calls itself run what you brung, against a section DD preamble that says anything unlisted is illegal.
- Drag, 2 Stroke Unlimited · DD.12
- Drag, Stand Up Unlimited · DD.10
- Drag, Unlimited · DD.6
No rule, this is an open class 1 class
CC.1 opens an extension because section CC names none, and of the CC.5.1 hull limits the one that reaches it is that a fabricated part may create no safety hazard. · CC.1, CC.5.1
Hull extension: 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 IHRA 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 6 of 29 answered, all with conditions