Fantasy Unlimited Hydroplane Racing

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A Guide to Engines and Violations

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HydroDan's Deck2Deck Racing Inc.

It is true: the unlimited class of hydroplanes are not actually unlimited. In fact, several rules have been implemented that specify boat size guidelines, design parameters, safety considerations, as well as power output. In general the current fleet of unlimiteds are turbine powered by Vietnam War-era Lycoming T-55 L7C helicopter engines. One experimental craft (Kelly Stocklin’s U-18) employs a smaller T-53 model. Other reciprocating (piston) engines are allowed by the governing body; however, none are actively racing at the current time.

Rules with respect to the power output of the turbine engines can be confusing to some and puzzling to others, but there are good reasons for these rules. Firstly, the stock of these ~60 year-old military surplus engines is dwindling and costs continue to escalate every year. In fact, it has been reported that a purchase of a new motor can cost in the ballpark of 50,000 – 100,000 US dollars. With supply low and costs high the two main reasons for the rules are as follows:

The limits placed on the output of the engines are intended to mitigate wear-and-tear and save costs for the owners of the race teams.

The limits are also designed to bring some level of parity to the sport so that lesser-funded teams have a chance to beat those with deeper pockets.

There are two main violations that you will hear with respect to the output of the turbine engines:

  • Fuel-Flow violations
  • N2/RPM violations

Without being overly technical, these rules are reasonably easy to distinguish and understand.

Fuel Flow violation: The governing body, with the approval of the team owners, has mandated a fuel flow to the turbine engines of 4.1 gallons per minute (GPM) of fuel. The fuel flow is monitored on the boats by special equipment to ensure all teams are running at or below the allowable levels. If a team is found to be over 4.1 GPM of fuel it is considered to be a fuel flow violation. Depending on the length of time the motor is receiving fuel over the 4.1 GPM maximum, the penalties begin with a monetary fine for an isolated occurrence and go as far as a disqualification for a flagrant violation.

N2/RPM: Just as your car engine has manufacturer ratings and performance specifications, so too does a Lycoming turbine engine. The factory-rated revolutions per minute (RPM) of the output shaft is ~15,330. The hydroplanes are allowed to produce an output RPM off 110% of this factory rating. When a team exceeds 110% RPM it is in violation of the rule. Punishment for such a violation can carry a monetary fine or a disqualification, depending upon the length of time the engine over-revs.

So yes, these unlimiteds have limits. And these limits are designed to save costs and provide parity. We hope this essay helps you to better understand and distinguish the potential penalties you may hear called during a race weekend.

Posted on: Aug 01 2014 08:14 PM UTC Edited on: Aug 01 2014 08:16 PM UTC
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