UIM · Hull and handling

Modification of the OEM hull, UIM

Work on the OEM hull itself, from repairs to reshaping. A replacement or prototype hull, sponsons, the intake grate, the pump cover plate, trim tabs and the hood have their own rows.

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.

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This is one body's answer, not the sport's. You are bound by whichever body sanctions the event you enter. If you race more than one series, build to the stricter answer. The differences are set out in the rulebook comparison.

UIM lets a repair move the hull 5 mm from its original configuration, where IHRA and IJSBA allow 2 mm.

Where it stands, class by class

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.

What each answer below means

OEM part required

This comes off. Only the part the manufacturer fitted is allowed here.

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.

No rule published for this class

Unanswerable here. This class publishes no rule for the part and names no parent class to borrow one from, which is an absence in the rulebook and not a permission.

OEM part required 8 classes

The hull may be repaired but not otherwise modified, and a repair may not alter the original configuration by more than 5 mm.

• Ski Division GP4 · 501.01.02-02
• Runabout GP3 · 502.02.02-02
• Ski Division GP3 · 501.02.02-02
• Runabout GP2 · 502.03-02, 502.02.02-02
• Ski Division GP2 · 501.03-02, 501.02.02-02
• Ski Juniors GP3.2 · 501.02.02-02 · borrows another class
• Ski Juniors GP3.3 · 501.02.02-02 · borrows another class
• Ski Juniors GP4 · 501.01.02-02 · borrows another class

OEM part required 3 classes

Repairs may move the hull no more than 5 mm from its original configuration, and sanding, grinding and polishing are allowed only where the original shape does not change at all. · 502.01.02-02, 502.01.02-03

• Runabout GP4
• Runabout Juniors GP4 · borrows another class
• Runabout Ladies GP4 · borrows another class

No rule, this is an open class 3 classes

GP1 prints no article on work to the hull, so under its open-list reading a modified OEM hull is free while the craft stays within 280 cm long and 85 cm wide. · 501.04.01-03, 501.04.01-04

• Ski Division GP1
• Ski Ladies GP1 · borrows another class
• Ski Veterans GP1 · borrows another class

No rule, this is an open class 2 classes

GP1 prints no article on work to the hull, so under its open-list reading a modified OEM hull is free while the craft stays within 360 cm long (394 cm for Endurance) and 127 cm wide. · 502.04.01-03, 502.04.01-04, 502.04.01-05

• Runabout GP1
• Runabout Veterans GP1 · borrows another class

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.

• Endurance · 317.03
• Freestyle Amateur · 312
• Freestyle Free · 312
• Jet Raid · 317.01
• Offshore · 317.02
• Parallel Slalom · 313
• Ski Future Electric (SFE) · 302.01
• UIM Hydro-Fly · 900

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Modification of the OEM hull: 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.

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