Whether you want to get up to speed on some of the terms that you’ll hear on the PA and in the pits at our races, want to talk to a crew member or driver with a little more authority, or just want to do a deep dive into all things H1 Unlimited Hydroplanes, we provide a glossary of terms that make up and describe our sport.

Some of the terms are slang developed over the decades, some are from designers and builders and some are straight out of our rulebook, but keep in mind that the rules are the rules, and the descriptions below should not be misinterpreted as replacements for those found in our rule books.

Dig in, have fun, and we promise, there’s no test at the end! :- )

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

10 to the 5 Fifteen minute mark prior to the start of the heat – when the Start Clock begins counting down to 0:00. This when all boats will be loaded into the water at the dock and drivers will enter the cockpits to get ready for the race
1 Minute All boats must be on the course and running at the 1 minute mark on the Start Clock. If they are not on plane, they will not be allowed to take part in the race. Boats that leave the dock after the 1 minute mark has passed are disqualified
130 MPH To qualify for a race and receive qualifying points, all boats must make timed laps faster than 130 MPH. Boats that do not exceed 130 MPH will still be allowed to race, but do not receive points for qualifying
5 to the 5 Five minute mark prior to the 5-minute gun. All boats must be held at the dock until the 5-minute gun. The “5 to the 5” callout on the PA allows drivers to synchronize their watches to the Start Clock
5 Minute “Gun” Five minutes left to 0:00 on the Start Clock signifies the beginning of the heat and when boats are allowed to leave the dock. If a boat leaves prior to the 5 minute gun, they will be penalized one lap. We don’t currently use an actual gun or cannon to signify this point in time
80 MPH The minimum speed our boats are allowed to go during the milling period. Monitored by GPS and recorded, boats can be disqualified for going under 80 MPH for more than 5 seconds
Afterplane Area under the boat aft of the rear end of the sponsons to the rear of the boat
Air Mask All drivers wear a mask that allows them to breath if the boat should flip and they end up underwater. Contains a microphone for radio communication
Air Tank The driver’s mask is attached to an air tank that supplies breathable air in case the drivers ends up under water. The air tank is fastened in the area behind the cockpit
Air Trap Area under the hull that traps the air that forces the boat out of the water when running. Begins at the leading edge of the bullnose and extends to the afterplane
Allison V-1710 Twelve cylinder WWII fighter engine used in the U-3. Runs two turbochargers with water injection and makes 2500-3000 horsepower
Aluminum Sandwich Aluminum panels that have high strength aluminum or fiber honeycomb filler “sandwiched” between them. Form the frames and other panels in the boats. With the onset of carbon fiber, aluminum panels are finding fewer uses in hydroplane construction
Anchors Anchors hold the course buoys to the bottom of the river or lake. The anchors are marked via GPS so divers can find them to attach the buoy lines. On some lakes with deep bottoms, lines from the anchors are attached to floats near the surface to which the buoys attach
Angle of Attack Angle of any surface under the boat in relation to the waterline
Anhedral Describes the lateral (side to side) angle of the bottom of the sponson as measured against baseline of the transom. Anhedral means that the outside of the sponson bottom is lower than the inside. This is the case on the left sponson, and it helps the sponson skip across the water during the turn. Generally set to 3-4 degrees
APBA American Power Boat Association is the sanctioning body for power boat racing in the United States
APBA Gold Cup The APBA Gold Cup is the oldest motorsports trophy in the world, awarded since 1904. All winners get their name engraved on this perpetual trophy and it is the one race that every team strives the hardest to win. It also has different race rules, generally requiring four flights of heats
Assigned Lanes Assigning lanes is a method some racing series use to determine who runs in what lane. H1 Unlimited does not assign lanes – all drivers are free to fight for lanes prior to the start, and that’s what makes the period before the start almost as exciting as the race!
Beam The width of the boat. All H1 Unlimited hydroplanes must be between 12′-0″ and 14′-6″ wide
Bearing Out When a boat in an inside lane goes wide into an outside boat’s lane
Black Light Light source used during inspection of propellers after every run. Props are sprayed with Zyglo and viewed with a black light, which will highlight potential flaws in the metal
Blowover Occurs when a boat traps too much air under the boat, forcing the boat into the air and out of control
Bull Nose Aerodynamic panels on either side of the cockpit at the front of the tunnel. Both panels can be modified in length to adjust the amount of air trapped under the boat. Forms the beginning of the wing section
Buoys The course is designated by buoys and different colors signify different things. White buoys form the outer markers. Two white cylindrical buoys form the start line. Yellow triangular buoys mark the entrance and exits of the turns. Orange buoys mark the inside of the course. Orange with yellow stripe buoys mark the DMZ areas.
Burner Can Large round housing around the fan blades at the rear of the turbine engine where the combustion takes place
Canard Adjustable wing between the sponsons the driver controls with his left foot that helps control the attitude of the hydroplane. It also allows drivers to force the nose of the boat down if it rises too high
Canoe Another term for the sponson and the panels that extend down the sides of the boat. Sponsons are generally molded with these side panels as one piece.
Canopy Lid on the top of the cockpit that opens to allow cockpit access. Locks closed during racing and can be opened from inside by the driver, or outside by rescue personnel in an emergency
Capsule Training All drivers must undergo training in a actual capsule that is inverted in the water, usually in a pool, showing their proficiency at breathing and exiting the capsule
Carbon Fiber A resin-infused material that cures lighter and stronger than steel. Forms most of the structure of a modern Unlimited.
Cavitation Formation of vapor bubbles within the water at low-pressure regions that occur in places where the water has been accelerated to high velocities. Especially damaging if it occurs around the propeller
Center Line An imaginary reference line that extends down the true center of the boat. Always the center of the wing section
Center Section The area formed by the tunnel that incorporates the air trap. Combined with the curved deck, forms the shape of a wing and contributes to overall lift. Also know as the wing section
Chairman’s Option If a boat cannot complete a qualifying lap, they may still be allowed to race under a Chairman’s Option, provided they have qualified at another event or posted speeds above 130 MPH during a prior test. A boat may not be allowed more than two Chairman’s Options during a season
Chief Referee The head referee in charge of all other referees. Issues or certifies all penalties. Conducts Driver’s Meetings
Chines Line that separates one angle from another on the side of the boat or sponson
Cockpit The driver’s office
Combustor Where the combustion takes place in a turbine engine
Commitment Buoy The entrance buoy to Turn 2, where all boats must be in a lane and must stay in that lane through the start. Also called the Scoreup Buoy
Competition Directives Occasionally, rules need to be modified during the season and are outlined in Competition Directives. All teams will receive them in printed form and they are posted on the H1 Unlimited website. Also known as “CD’s”
Compressor Section On a turbine engine, air is compressed prior to adding fuel for combustion. The T-55 L-7 has seven stage compressor section (a series of seven blades and vanes), while the T-53 L-13B has five stages
Corral Area designated for Team Radio Operators (TRO) to occupy during the race. An H1 official will be included to pass official communications to the driver through their TRO
Coupler Connects the long shaft to the short shaft. Has bolts that attach to both shafts to prevent them from separating
Course Boat Boats that are generally used to ferry VIPs or others to various places on the course for observation or to Judge boats
Course Map Map that shows the layout of the course and all buoys that make it up. Will be distributed to teams during the Driver’s Meeting at the beginning of the race weekend and will be used by the teams for timing marks and to plot strategies
Cowling Large housing around the engine on turbine hydroplanes. Serves to allow air in and keep water out of the engine. The U-3 does not use a cowling for their Allison V-12
Crew Boat Boat designated to ferry crew members to a boat that has been damaged or in danger of sinking
Crew Chief The boss of the crew. Usually a racer himself. In charge of boat setup and strategy
Crew Members Every team has crew members that are specialists in specific areas like the turbine engine and propellers, as well as general crew that can work on all systems on the boat. Most crew members have decades of experience in boat racing at all levels
Curved Skid Fin All skid fins must be completely flat, with minor allowance for warpage. Curved skid fins were used in the past, but outlawed
Cut the Course Drivers can “cut the course” – go through the infield – to try and position themselves for a better starting position or to block another boat from getting a lane
Data Recorder Records boat speed on all boats and N2 RPM and fuel flow rate on turbines for review by referees. All turbine boats run with fuel flow rate and N2 RPM restrictions
Dead in the Water Boat is making no forward progress
Deck The top of the boat. Formed with a curve that functions like an airplane wing to give lift to the boat. Has hatches for access to all internal systems
Defueling The process of reducing fuel flow rate automatically if the N2 RPM rises above 118%. Monitored and recorded by the data recorder and read by the Technical Referee. Penalized if defueling is not performed
Dihedral Describes the lateral (side to side) angle of the bottom of the sponson as measured against the baseline of the transom. Dihedral means that the outside of the sponson bottom is higher than the inside. This is the case on the right sponson, and it helps the sponson skip across the water during the turn. Generally set to 5 degrees
DMZ Safety zones within the race course that contain rescue boats, judge boats or other course boats. Usually in the center and both ends of the course. If a driver enters a safety zone, it is an automatic disqualification. Also referred to as Safety Zone
DNF Driver did not finish the heat or race
DNS Driver did not start the heat or race
Driver The loose nut behind the wheel :-) Seriously, all H1 Unlimited drivers have decades of experience racing boats of all types, from outboards as 9 year-olds to 1 liter & 2.5 liter inboards up to supercharged big block Grand Prix boats. Some are from multi-generational racing families and those that have children are supporting their children’s racing careers
Driver’s Meeting All drivers and Crew Chiefs must attend a mandatory meeting where race officials will distribute course maps and any rule changes that govern the race. All questions regarding the course or race procedures will be answered in this meeting
Driver’s Rep A representative, almost always a qualified Unlimited driver, who can be summoned by a driver who wishes to talk directly to a referee to explain actions taken on the race course by other boats or by themselves
Drones We use a minimum of two drones during each race – one above each corner. The footage from the drones is transmitted live to our referees, allowing them to make calls based on the on-water action
Drop Sponson A design feature where the rear end of the sponson outboard of the non-trip is dropped lower than the deck. The lower profile helps reduce lift.
DSQ Driver has been disqualified from the heat or race. Can be for technical violations, driving violations or DMZ violation
Ear Plugs All drivers wear form-fitting ear plugs that contain their radio speakers, allowing them to hear their radio man over the noise of the engine
Echo Boat Boats that are placed in areas outside the start/finish line that will display flags signifying the condition of the course. Also called a Judge boat
EGT Exhaust Gas Temperature is monitored on the turbine engine. If the EGT rises too high, internal engine damage can occur
Electrical System Hydroplanes have multiple voltages: 12VDC for gauges and data recorders, 24VDC for turbine engine operation and 48VDC for the turbine engine starter motor
Encroachment A penalty called on a driver if he changes lanes in front of a trailing boat without the proper overlap
Engine Bay The area directly behind the cockpit that houses the engine, gearbox and oil tanks
Escape Hatch Door on the bottom of the cockpit that allows the driver to exit the cockpit if the boat flips. Has a window to allow light to enter and can be opened from inside or outside
Exhaust Manifold On the turbocharged Allison V-1710 12 cylinder piston engine in the U-3, the exhaust is routed through exhaust manifolds to run a single forward-mounted turbocharger per bank of cylinders
Exhaust Stacks On non-turbocharged V-12 piston engines, exhaust stacks are short pipes (either 1 or 2) attached to each cylinder that release the exhaust directly into the air. Now mainly seen on vintage Unlimiteds. Also known as exhaust pipes
Exhaust Pipe The large round pipe at the rear of a turbine engine where the hot combustion gases are passed out of the engine. Unlike a jet engine, the exhaust does not contribute any force to propel the boat
Fairings The uprights that hold the rear tail. Covered with a aerodynamic carbon fiber panels. Also known as tail feathers
Fence Aerodynamic device that “spoils” the air flowing across the right sponson while turning. Cuts down on the lift formed by that airflow, reducing the chance the sponson will lift and contribute to a blowover
Fight for Lanes In the milling period, all drivers can try to get their boat into whatever lane they want to start the race in – there are no assigned lanes (except for rookie drivers). This “fight for lanes” can be just as exciting as the race itself
Final Heat Last race of the weekend. Winner of the Final Heat is the winner of the event
Fire Extinguisher All boats must carry an extinguisher to control any fires in the engine bay and in the cockpit
Flags White Flag: One minute to start of the race or lead boat has one lap remaining. Yellow Flag: Hazardous condition on the course. Blue Flag: Possible penalty. Green Flag: Race has started. Checkered Flag: Race is over. Black Flag: All boats must return to the dock. Red Flag: Race has been stopped
Flare In cases of a race stoppage, flares may be fired in front of boats still running. It is the universal signal to stop the boat
Flights Heat groupings are generally referred to as “flights”, meaning Heat 1A and 1B are the first flight, Heat 2A and 2B are the second flight, etc.
Flip Can be caused by too much air under the boat (blowover) or from roostertail or skid fin water that gets under the boat, forcing it up and over
Frames An Unlimited hydroplane has multiple frames, or bulkheads forming the interior structure of the sponsons and the center section. These frames add strength to the assembly and are usually no more than 18″-24″ apart & run the length of the boat. All frames are mechanically fastened and glued in place
Front Spar A high-strength steel beam that spans between the middle portion of the sponsons and through the front of the safety cell, contributing to rigidity of the structure
Fuel Cell Rubber bladder that contains up to 60 gallons of Jet A for turbines or methanol for the Allison-powered U-3
Fuel Control The device on the turbine engine that controls the 4.2 gallon per minute rate that fuel is fed to the engine. The fuel control is notoriously finnicky and very sensitive to set up properly
Fuel Flow Turbines are allowed a maximum fuel flow rate of 4.2 gallons per minute. This is recorded for later analysis by referees and exceeding it can result in DSQ. Piston engines are not limited in fuel flow rate
Fuel Injection The Allison V-1710 V-12 in the U-3 utilizes fuel injection to directly inject the methanol fuel into the engine
Fuel Nozzles Turbine engines use nozzles to spray fuel into the burner can (combustion chamber). The nozzles atomize the fuel to allow it to burn efficiently. There are a total of 28 nozzles in the T-55 L-7 and 22 in the T-53 L-13B
Fuel Valve Because a turbine engine does not require electrical power except to start and will run as long as there is fuel to burn, an external fuel valve allows rescue crews to stop the fuel supply to the engine
Gearbox Power from the turbine engine is routed through the gearbox to propeller. It is a one-speed box and most are fitted with four gears. The gear ratio can be changed to suit course conditions
Go Fast, Turn Left What H1 Unlimited hydroplanes do very well :- )
Go Pro Cameras All Unlimiteds are required to carry at least two GoPro cameras during each heat that record onboard video footage to be used for referee decisions as well as promotional purposes
GPS All Unlimiteds are required to stay above 80 MPH at all times and this is monitored via GPS and recorded for later review by officials
Ground Idle The idle setting of the turbine engine with the helicopter on the ground (remember they are from the CH-47). If the driver lets off the throttle too quickly, they run the risk of the engine reverting to ground idle, which will almost always stall the boat and doom their race, as getting the engine back to full power will take longer than the 5 seconds they can stay below 80 MPH
H1 Unlimited The governing body of Unlimited Hydroplane racing in the United States and around the world
HANS Device Head And Neck System. Mandatory head and neck restraint that all drivers wear when driving
Heat Assignments All boats race in preliminary heats and they are assigned in a random draw
Heats Because all boats cannot run at once, the race is broken up into heats: 1A, 1B, 2A, 2B etc., with the goal to make it to the Final Heat. Final Heat placement is based on points collected in earlier heats
Heat Restart If a heat was stopped and if less than 50% of laps were not completed, the heat may be restarted. If the stoppage was caused by a boat, the boat that caused the heat stoppage is not eligible to take part in the restart and is not scored in the original heat
Heat Stoppage If there is an accident or unsafe condition on the course, the heat can be stopped by the officials throwing a red flag. All boats must return to the pits.
Hole Some river courses have underwater features that introduce low spots in the water that can spin a boat or cause it to hop out of the water, losing momentary control. The most notorious hole is in Turn 1 in Madison and it has been the scene of multiple incidents
Hook When the boat loses “traction” at the rear end and pivots to the left around the skid fin. Also called a spin
Hot End The back end of the turbine engine where combustion takes place
Hot Start If the driver does not turn on the igniters prior to engaging the fuel pump on a turbine engine, occasionally the engine will fill with raw fuel then ignite all at once, shooting flames from the back of the engine. This does no damage, but is spectacular to watch
Hydraulic Action Because water cannot be compressed, if it is forced under pressure into closed areas like cracks or gaps between parts (like our boats can do at 200MPH), the pressure can destroy the bonds of the material and break off parts very easily. All joints and bonding points for all parts attached to the boat are glued and sealed to prevent the occurrence of hydraulic action
Hysol Glue that is used in areas that require extreme bonding strength. Good for aluminum to aluminum bonding, or bonding of dissimilar metals, including aluminum to carbon fiber parts
Igniters All turbine engines require igniters to start the combustion process, and they work just like your gas stove or barbecue. If you are close enough, you will hear the “tick-tick-tick” of the igniters just prior to the turbine engine starting
Impound After the Final Heat, the two top finishers will be held for inspection, which generally includes weighing the boat to guarantee minimum weight and reading of the data recorder to insure integrity of the data. No work is permitted until the boat is released from impound
Inspections Prior to any boat taking part in a race, they must be inspected to insure safety. H1 Technical Inspectors will sign off on a 7-page list that covers almost everything making up the boat
Jet A The fuel used in turbine engines. The turbines can burn just about any diesel-based fluid, but Jet A is preferred
Judge Boat Boats that are placed in areas outside the start/finish line that will display flags signifying the condition of the course. Also called an Echo boat
Judge’s Stand The area occupied by the Chief Referee, Video Referee, Timing & Scoring Personnel and others at the Start/Finish Line. Also known as the Scoring Tower
Jumped the Gun Driver crossed the starting line prior to the Start Clock hitting 0:00. Results in a one lap penalty
Kevlar An extremely strong synthetic fiber used in bulletproof vests. Used in the manufacture of the Safety Capsule and RPBS (Rotor Burst Protection System)
Lane A lane is an imaginary boundary that includes the width of the boat plus 10 feet on either side
Lane 1 The inside-most lane on the course, next to the inner course marker buoys. A boat must stay within 20 feet of the inside course marker buoys to be considered to be occupying Lane 1. If a driver is in Lane 1 at the scoreup buoy, he must stay in Lane 1 throughout the entirety of Turn 1 after the start
Lane Violation A lane violation occurs when another boat enters the 10 foot area to either side of the a competitor’s boat
Leader The driver that leads the race. Generally will make the course longer for trailing boats by moving to an outer lane, forcing trailing boats to run wider. He can establish his lane wherever he wants on the racecourse, provided he has overlap to have changed lanes in the first place. The driver must hold their chosen lane throughout the turn
Length All H1 Unlimited hydroplanes must be between 28′-0″ and 32′-0″ wide
Lifting Sling Sling that attaches to four points on the boat to lift it into and out of the water. Each leg of the sling must be rated to hold 6,000 pounds
Live Stream Video All races are live-streamed on YouTube. Subscribe to get notifications so you don’t miss a second of racing action
Long Shaft Shaft that is attached to the output of the gearbox and extends through bottom of the boat
Magneto A magnetic-electric device that generates the high-energy spark on the Allison V-1710 in the U-3. Magnetos do not require an external source of power to produce a spark. Basically the same device that provides spark in your lawn mower
Methanol Methyl Alcohol. Fuel used by the turbocharged Allison V-12 in the U-3
Milling Period The time between when the boats leave the dock and the start of the race. Drivers are free to try and grab whatever lane they want for the start and they do this in the milling period. Sometimes called “the mill”
Minimum Weight The minimum weight of T-55 turbine-powered boat is 6575 pounds. For T-53-powered boat it is 3800 pounds and for a piston-powered boat it is 5775 pounds. Many new boats will weigh under these minimums and will add ballast to come up to the minimum weight, added in areas that help handling. As a boat ages and requires structural repairs, they will usually gain weight due to the material added in the repairs
N1 RPM RPM of the N1, or “Gas Producing” wheel in a turbine engine. This is what spins the compressor section and is not monitored or recorded by H1
N2 RPM Turbines have a maximum rating for “N2” – the RPM of the “Power Turbine” wheel. By rule, this cannot exceed 110% of the maximum rated RPM for more than 5 seconds. N2 RPM is recorded for later analysis by referees and exceeding it can result in DSQ. All turbine boats have lights that flash in the cockpit to warn the driver when they are over the 110% limit
NDT Non Destructive Testing. Propellers are inspected after every run for issues that may lead to failure of the prop. They are sprayed with Zyglo and viewed with a black light, which will highlight potential flaws in the metal
National Champion Driver & team that collect the most points during the season. Driver and Team Championships are awarded separately, as there is no guarantee that the winning driver and team will be the same
Nomex Fire-resistant material that is used in almost all of the articles that make up a driver’s apparel, like socks, shoes, suit and gloves
Non-Trip Angled surfaces on both sides of the boat. Can be referred to as the sponson non-trip or afterplane non-trip, depending on location
Off Plane When a boat is not skipping, or planing on the water. All boats must maintain a minimum of 80 MPH, so if a boat goes off plane it will normally be disqualified, as it will take longer than 5 seconds to come back up to 80 MPH
Onboard Video All Unlimiteds carry at least two Go Pro cameras during each heat and that video is uploaded to You Tube. It shows how incredibly beautiful and violent the sport of Unlimited Hydroplane racing can be
On Plane When a boat is skipping, or planing on the water. All boats must maintain a minimum of 80 MPH, so even if the boat is planing, it must be going at least 80 MPH in order to not be disqualified
Overlap Overlap is the minimum distance a leading boat must be ahead of a trailing boat to make a legal lane change. It is five boat lengths prior to the start or seven boat lengths after the start
Pedals The driver has three pedals to control the boat: a throttle pedal on the right and two canard pedals on the left. The canard pedal is unique in that it pivots, or in other words when one goes up the other goes down, and these control the action of the canard that allows the driver to “fly” the boat or force the nose back to the water
Penalties Boats and drivers may incur penalties for a variety of things: driving infractions on the water or technical violations, and they can take the form of time penalties, lap penalties, points penalties or disqualification
Pits Where all boats are parked and worked on
Points After each heat, boats are awarded points based on their finishing position. Points totals for the heats determine who will make it into the Final Heat. Points accrue toward National Championship standings
Practice All races include practice time for boats to test setups or allow drivers to get timing marks. There can be up to five practice sessions at any race
Propeller Limited to 16″ diameter and 3 blades. Costs around $15,000 and is good for 100 minutes of running time before it becomes a ticking time bomb, ready to come apart and tear up the back of the boat
PT Wheel “Power turbine” wheel that converts the energy of the combustion inside the turbine engine to rotary force that ultimately turns the propeller 
Qualifying All drivers qualify prior to racing in heats. Points are awarded based on qualifying speeds. Qualifying does not determine heat assignments
Race Course The race course can vary in length and can be 1 2/3 miles, 2 miles or 2.5 miles
Race Format H1 Unlimited races use the following format: Qualifying, Preliminary Heats and a Final Heat. All qualifying, heat races and Final Heat award points that contribute to the National Championships for drivers and teams
Radiused Edges In aerodynamic environments, corners that are exposed to airflow need to be radiused so as not to separate airflow on the part. In hydrodynamic environments, radiused edges are to be avoided at all costs due to the dramatic increase in drag that radiused edges create when in contact with water
Radio Man Team Radio Operator (TRO). In contact with driver via radio, informing him of the positions of other boats, timing information, official communications and strategy advice
RBPS  Rotor Burst Protection System or containment blanket. Made from Kevlar fabric, the blanket wraps around the hot end of the turbine and will contain shrapnel that exits the hot end during an engine explosion
Rear Spar A high-strength steel, aluminum or composite beam that spans between rear portion of the sponsons and through the back of the safety cell
Rear Wing The rear wing is adjustable, but it is not controlled by the driver like the canard is – it is bolted into place at an angle determined by boat setup. It is adjusted to trim the rear ride height of the boat
Referees We have two types of referees: those who watch the action on the course and call penalties based on driver behavior and those who monitor technical data and call penalties once the data recorders are read
Rescue Boat The rescue boat is stationed in the infield any time there is a hydroplane on the water and is staffed with a driver, scuba divers and a medical professional. They have tools onboard that will allow them to enter a damaged boat, and a backboard to safely transport an injured driver
Rescue Divers Our rescue teams include at least two certified scuba divers that can reach a driver if the boat flips and lands upside down. They are usually trained in medical techniques to insure they can assist the driver in case of medical distress
Rookie Driver To qualify as an Unlimited driver, he or she must run a minimum of 15 laps in testing above 130 MPH. Once qualified, they must runs two heats as the trailer boat and then another two heats usually to the outside of all other boats. Only then will they be able to fight for lanes at the start
Roostertail Large wall of water thrown up by the propeller. There are literally tons of water in the roostertail that can cause extensive damage to other boats that enter it
Rudder Steel blade located at the right rear of the boat that the driver turns with the steering wheel to steer the boat. It normally has a pickup for water that is used for cooling and lubrication
Rudder Bracket A welded bracket that locates the rudder away from the transom, allowing the rudder to be more effective by adding leverage
Rudder Quadrant Adjustable pivot located under the deck that connects to the steering cables and through an adjustable rod to the rudder
Rules All facets of the race, the boats, the technical specs and other areas are covered in multiple rulebooks, available on the H1 Unlimited website
Runners Panels on the bottom of the sponsons that can be adjusted for angle of attack and anhedral/dihedral
Safety Capsule Reinforced shell that forms the cockpit. Made from welded chromoly tubing, carbon fiber, Kevlar and bulletproof Lexan windows. It is egg-shaped at the back to help prevent damage in case of a rearward entry into the water. Also called the Safety Cell
Safety Zone Safety zones are areas within the race course that contain rescue boats, judge boats or other course boats. Usually in the center and both ends of the course. If a driver enters a safety zone, it is an automatic disqualification. Also referred to as DMZ
Salt Water Turbine-engined teams must take great precautions to minimize the ingestion of salt water. Salt buildup will cause pre-ignition in turbine engines which can lead to total destruction of the engine. Salt water also produces the fastest speeds the boats can attain, due to the additional density of the water
Scoreup Buoy The entrance buoy to Turn 2, where all boats must be in a lane and must stay in that lane through the start. Also called the Commitment Buoy
Scoring Tower The area occupied by the Chief Referee, Video Referee, Timing & Scoring Personnel and others at the Start/Finish Line. Also known as the Judge’s Stand
Seat Belts Seat belts are a six-point design with a quick release latch. Crew members are required to pull the belts tight as the driver cannot do it by himself, and when done correctly, drivers are strapped in so tightly it is sometimes difficult for them to breath
SFI SFI Foundation Inc. is an example of a certifying agency that certifies the driver’s suit is fire resistant
Shaft Log This is a tube that carries the long shaft as it extends through the bottom of the boat. It has a rubber seal to prevent water leakage
Shoe Extensions on the rear of the hull. Supports the back of the boat while running, with the right side usually shorter than the left
Short Shaft Shaft that connects to rear end of the long shaft and extends to the back of the boat. The propeller is attached to this shaft. Some teams prepare multiple short shafts with different propellers to allow quick changes – sometimes while at the dock
Showdown Format New in 2021, the Showdown race format splits the race weekend into two separate races, with preliminary heats and a Final Heat on both days. Only one qualification session is used. Points are awarded for qualifying and all preliminary and Final heats
Skid Fin Large steel plate mounted to the left side of the boat that digs in the water during turns and allows the boat to corner rather than skip on the water. May be adjusted in multiple dimensions to change handling of the boat, but must be completely flat – there is no concavity allowed
Skid Fin Angle Angle of the skid fin in relation to vertical. Always angled in at the bottom. A steeper angle will allow harder cornering at the expense of drag, while a shallower angle will lessen drag but may hop out of the water (unhook) in a hard turn
Skid Fin Box A very high strength braced area inboard of the skid fin that ties into the center section and is designed to take the tremendous forces the skid fin is capable of generating without coming apart
Skid Fin Bracket (Sponson) On the left sponson transom (rear edge of the left sponson), a bracket extends that the skid fin is attached to with high strength bolts through the skid fin. The bracket is attached to with high strength bolts and glue to the sponson transom
Skid Fin Bracket (Hull) On the left non-trip, there are multiple attachment points for the tie rods that locate the skid fin. These points are tied in with the internal structure of the skid fin box
Skid Fin Position The skid fin can be moved fore/aft on the skid fin bracket, changing the boat’s pivot point, allowing fine tuning of steering wheel input to the actual yaw of the boat. Generally, moving the skid fin forward will contribute to the boat making less yaw with a given steering wheel input while moving it back will contribute to a tighter arc, however many other factors will affect this parameter
Skid Fin Toe Angle Angle of the leading edge of the skid fin in relation to the center line of the boat. Can be adjusted in or out in tiny fractions of an inch, but will almost always be set exactly parallel to the centerline of the boat.
Skid Fin Water Large wall of water thrown up by the skid fin during cornering. Can easily flip a boat in an inside lane that slides outward into another boat’s skid fin water
Snorkel Large extension bolted to top of canopy that attaches to front of the cowling and is used during salt water races. Serves to keep saltwater out of the engine. Some teams include a moveable door at the opening of the snorkel to further prevent saltwater from entering
Spin When the boat loses “traction” at the rear end and pivots to the left around the skid fin. Also called a hook
Split Canard A canard that has a split in the middle, allowing both sides to have different angles of attack
Sponsons The forward parts of the hull that skip on the water. Right and left are different sizes and shapes. Supports the canard and sponsor decals
Start Clock The clock started by officials that counts down from 15:00 to 0:00, signifying the start of the race. Drivers synchronize their timers precisely to the Start Clock to allow them to make the best start possible
Start Fuel All turbine engines have 4 start fuel nozzles that provide a richer mixture of fuel to allow easier starting. Located near the igniters, once start fuel is ignited and combustion starts, the main fuel nozzles flow to continue the process
Start/Finish Line An imaginary line that extends between the two buoys that are anchored on either side of the starting area in front of the Judge’s Stand. Referees monitor the start with a video camera that allows them to determine if a boat has jumped the gun
Steering Wheel The steering wheel is removeable and has a “Press to Talk” switch the driver will press when he wants to talk to his radio man
Strobe Light If a boat stops on the course, the driver must signal to his radio man or turn on the strobe light on the canopy to signify he is OK. If this is not done, the heat will be stopped
Strut Supports the short shaft at the rear of the boat
Survey All race courses are surveyed by professional surveyors to certify the course distance. Distances are determined at the inner buoy line
Swim Step Short horizontal extensions from the bottom of the transom that allow for more surface that high pressure air under the boat can act upon for longer, contributing to more lift at the rear end
T-53 L13B Model of ex-military turbine engine used in the U-440. Features a 5-stage compressor section and makes around 1700 horsepower
T-55 L7 Model of ex-military turbine engine that most boats run. Features a 7-stage compressor section. Makes 3000-3500 horsepower
Tail Feathers The uprights that hold the rear tail. Covered with a aerodynamic carbon fiber panels. Also known as fairings
Tech Truck The H1 Unlimited truck that carries our gear from race to race becomes the area where the data recorders are read by the technical referee
Technical Referee The referee in charge of reading the data from the data recorders carried by each boat and issuing penalties based on that data
Telemetry One-way telemetry – from boat to shore only – is allowed. There is no radio control of any boat system allowed from shore
Tender Boat Boat designated to take over from a tow boat that will get the damaged or non-running Unlimited back to the dock
Tent Most teams will use a black tent that blocks outside light where they will check propellers using Zyglo and black light after every run
Tie Rods Rods that bolt to the skid fin and the non-trip skid fin brackets on the boat and are adjusted to insure constant tension so as not to loosen under race conditions
Timing & Scoring Two timers monitor all boats and time each lap while boats are running. The Scorer is in charge of certifying and producing the results 
Timing Marks In order for a driver to make a good start, he must know how much time it takes to make it from one point on the course to another. Drivers will usually use practice time to go slowly around the course to gather timing marks – the time between certain buoys – which will allow them to time their starting procedure more precisely
Tow Boat Boat designated to tow a damaged or non-running Unlimited back to the pit area
Trailer Boat A rookie driver must be the “Trailer Boat” – trail the field at the start for at least his first two races. Additionally, in a Final Heat, a trailer boat may be added, and is the boat that has the least amount of points. The trailer boat must not pass the start line less than 5 seconds after 0:00 on the Start Clock
Transom Vertical surface at the rear of the boat. Rudder bracket and tail feather braces are bolted to the transom
Tunnel (on boat) Area under the boat between beginning at the tip of the sponsons that is contained by the vertical surfaces of the sponsons and continuing aft to the transom
Tunnel (on water) If a driver is running behind two boats in the lanes to his left and right, he may get caught in a “tunnel” formed by the roostertails of the other boats. This is a very dangerous and scary place to be
Turbocharger Device that forces air under pressure into the engine. The U-3’s Allison V-1710 V-12 has two of them
U-Numbers All Unlimited Hydroplanes are assigned a “U” number and will race under that number for the duration of the season. The U number can be reassigned to a different hull if the team substitutes a boat for any reason
Unhook When a boat’s skid fin loses its grip in the water. Can be due to water conditions or when the skid fin angle is set too shallow. If the boat unhooks, it may slide outward a lane or two before getting enough “grip” to continue the turn
V-1710 Model number of the Allison twin-turbocharged V-12 piston engine in the Go3 Racing team’s U-3. Derived from the displacement of the engine: 1710 cubic inches (28 liters)
V-Brace The braces that support the tail feathers
Video Referee The referee in charge of viewing the drone video feed from each corner and calling penalties based on the video
Warning Lights Drivers have lights that flash as they hit limits for N2 speed, giving them a warning to back off the throttle so they do not exceed the N2 speed limit for too long
Washed Down When a trailing boat is caught in a leading boat’s roostertail or skid fin water
Waterline An imaginary reference line extending from the rear tip of the sponsons through the center of the propeller shaft that forms the line that other angles are measured against
Water Injection A method of injecting water/methanol mix into the turbocharger that allows higher boost pressure and/or less knock under load. Used on the U-3’s Allison V-1710 V-12
Wind Due to the aerodynamics of the Unlimiteds, they cannot safely run during high winds. Generally, wind speeds above 12-15 MPH will force cancellation of the race
Wing Section The area formed by the tunnel that incorporates the air trap. Combined with the curved deck, forms the shape of a wing and contributes to overall lift. Also know as the center section
Windows Cockpit windows are either 1/2″ thick polycarbonate or cut from bulletproof F-16 fighter canopies, forming a very tough barrier during flips or crashes
Winner Take All The winner of the Final Heat is the winner of the event. Points collected during the event count only toward the National Championship
You Tube Where all of our Live Stream video is available, as well as over 3,000 onboard and other videos
Zyglo Fluorescent dye penetrant used when checking metal parts for imperfections