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Hydroplane Programme Covers


Words: James Pernikoff
Pictures: Stephen Lane, Jack Lowe


So what really is a hydroplane? As the name implies, it is a "boat that flies." While early step hydros were still essentially boats, the modern three-point proprider is as much airplane as it is boat. With so little of the hull touching the water at speed, the craft is predominantly riding on an air cushion, so it could also be thought of as a surface-effect vehicle.

The typical modern Unlimited is about 30 feet long, 14 feet wide, and weighs about 6000 lbs. While early boats were mainly mahogany, there is relatively little wood in a modern boat. The rest is a combination of aluminum honeycomb, carbon-fiber composites, fiberglass, and probably some titanium around the engine bay.

The most prominent features of the hull are the two sponsons at the front outside of the boat. These represent the widest, lowest, and most-forward parts of the hull. The upper surfaces are part of the aerodynamic package, and the lowers are part of the hydrodynamic package, and both are important. The back ends of the bottom surfaces represent 2 of the 3 "points" the boat rides on at speed (the 3rd being the lower half of the propeller, hence the term "proprider"), while the inside vertical faces are the sides of the tunnel that channels the air the boat rides on. Each sponson and the narrower area behind it, running to the back of the hull, is often built as a single assembly called a "canoe."

The section between the sponsons is often built separately. It consists mainly of the ram wing, on top of which is the central body which houses the driver and the drivetrain. The ram wing is a true airfoil, and the smooth bottom is the roof of the tunnel, pierced only by the propeller shaft and its fairing. (Unlike racing cars with their inverted airfoils to provide downforce, on a hydro all airfoils are upright, as on an airplane, to provide lift.) In front of the ram wing is usually a separate airfoil, with a canard wing on its trailing edge whose angle can be adjusted by the driver via a foot pedal.

Since the canoes and the ram wing may be built separately, there have been cases in recent years where they have been separated and one or the other replaced. A few years ago the Budweiser team sold a center section to another team and built a new center section to fit between existing canoes!

The driver sits in a reinforced safety capsule with onboard oxygen and radio, covered by a hinged canopy made from F-16 units rejected by the USAF (but safe for boat racing) and with an escape hatch in the bottom. He drives using a steering wheel and a right-foot throttle pedal not unlike a racing car, but of course there is no brake. His left foot operates the pedal for the aforementioned canard wing.

The engine is (with the exception of one turbocharged Allison V-1710 V12 piston engine) a Lycoming T55-L-7 turboshaft engine rated at 2650 SHP, fitted in recent years with a speed output (N2) sensor and a fuel flow valve to try and equalize equipment and save on repairs. Although the boats have large exhaust pipes, these serve only that purpose and provide negligible residual thrust. The engine is actually installed backwards from helicopter use, with the drive coming off the front of the engine (as it's installed) and going to a gearbox underneath which is connected to the long propeller shaft. The prop is a three-bladed, hand-crafted, steel unit which is incredibly small, about 14″ in diameter, and it spins at about 14,000 RPM. The fact that only half the prop is submerged is what causes the tall "roostertail" of water behind the boat at speed. When out of the water, the prop is usually covered, in part to protect anyone who might walk into its sharp edges, and in part to hide any secrets a team might have come up with! A well-heeled team usually has several slightly different props, to adjust for different courses and conditions.

Two other items stick down into the water. One is, of course, the rudder, which is attached to the transom (aft end) of the hull. The other is a large metal blade attached rigidly to the left side of the hull immediately aft of the sponson. This is the skid fin, which is what allows the boat to turn left. Since a hydro must corner flat and cannot lean into a turn like a conventional boat, it actually skids through the turn, with the skid fin acting as a pivot point. (Announcers will sometimes refer to this as "hanging it on the hook.") This will cause a second roostertail to appear in the corners. Since all the weight of the boat is concentrated on the skid fin in the turns, they and their internal support structure have become increasingly massive with the increased cornering power of the newer boats. As a result of this design, hydros turn left just fine but can't turn right worth a darn!

Skid fin at work

The last feature of note is the large rear wing assembly, which all the Unlimiteds have, and which is substantially unchanged from the design Jim Lucero first put on the Atlas Van Lines "Blue Blaster" way back in 1977. The horizontal is readily adjustable in the pits but cannot be altered by the driver. For transport, the horizontal wing and the diagonal struts can be removed and the vertical fins, which are hinged at the bottom, can be folded flat. At one time, the boat's identifying "U-number" was usually displayed on the sponsons, but with the desire for more advertising space that can be viewed from the shore, the number is now usually placed on top of the horizontal, where only the referee in the helicopter can see it (but then, that's what is important).

Well, that basically describes the boat, but how is it transported? The boat is towed on an open trailer behind a support truck that is basically a shortened, one-piece big-rig. The cargo box has both side and rear doors and carries the team's tools, machinery, spare engines, wings and other parts and computer gear. The roof is reinforced to act as a viewing platform; once in position in the pits, handrails, a ladder, and sometimes a canopy can be erected so that team members and friends can watch the racing.

The boat trailer is a custom-made unit with a unique feature. Since, at 14 feet, a hydro is too wide to travel on the highway when horizontal, the boat platform is hinged on one side and can be elevated using a hydraulic ram by about 50 degrees, thus making the rig legal for over road travel. The boat is secured, the prop and shaft (and usually the engine) are removed, the rear wing is detached as described above and stowed under the platform, the canopy is covered with a cover, and the boat is elevated to travel position.

While the boat is exposed to the elements as it travels, it makes a heck of a rolling billboard! Most teams also have a "display boat" which consists of a truck-trailer rig like this fitted with a non-running boat, either an older hull that has been retired, or even a fake replica which looks enough like the real boat to be convincing. These will be set up in shopping centers or other public venues to raise interest in the race, the team's sponsor, or both.


Unlimiteds run on a variety of courses: rivers, fresh-water lakes, and salt-water bays. The one thing they all have in common is that they are ever-changing—not just from race to race but from lap to lap. Tracks on the land will change during a race, but gradually, and cars can be adjusted accordingly. On the water, though, the course changes constantly, and the best drivers are the ones who can react quickest to the conditions.

It is interesting to note that when conditions roughen, drivers will not slow down much, since the boat actually rides smoother the faster it goes. This is because the bigger tunnel of air under the boat at higher speeds puts it higher up, and less likely to hit the wave tops. Of course, too much air can be problematic, also!

The rivers have the reputation of being the roughest, but that is open to debate. The big problem on the rivers is seen as the wakes caused by the boats rebounding off the shores and coming back onto the course as rollers. (Due to the way they ride, a single hydro will not cause much of a wake, but put six on the water at a time, and the water can really get churned up.) This is usually not a problem in short preliminary heats but can cause headaches in the longer finals.

While lakes may have a theoretical advantage regarding rollers, this can be cancelled by other conditions. In Seattle, for instance, a "log boom" set up along the backstretch, to allow spectator boats to tie up and watch, causes wakes to rebound much as they might on a river.

The biggest problem on lakes is wind, especially cross-winds. At Syracuse, the water was usually smooth most of the day, but it seemed that the wind would pick up substantially just before the all-important final heat. As a result, I saw boats blow over in the final heat two years in a row. In San Diego, there is an island that runs down the middle of the Mission Bay course. While this island doesn't seem to cause much roller conditions, it does seem to shield the course from winds that can suddenly appear when the boats reach the end of the island. In an oft-televised moment from 1988, a sudden gust at the end of the backstretch caused two boats to blow over simultaneously!

San Diego is a salt-water course, and that causes other problems. In the piston-engine days, the boats had to be hosed down between heats, but drivetrain performance seemed relatively unaffected. When the turbines came along, they had all sorts of problems with ingested salt gathering on the compressor blades and causing the engine to stall. A number of intake designs were tried before the present dorsal scoop was adopted.

Even that wasn't a complete answer, especially when the boat was starting from rest, when it kicked up a lot of spray which could still be ingested. Some teams tried a hinged flapper door, which the driver would keep closed until the boat was up on plane and the threat of salt ingestion was minimized. (An auxiliary inlet at the back end of the scoop provided air for the engine in the meantime.) The eventual answer was to add an extension to the dorsal scoop, which puts the intake well forward of where the spray flies on startup. This extension is usually attached to the top of the canopy and moves with it. It works, but adds nothing positive to the boats' appearance!

Now, most of the courses are symmetrical ovals. At the beginning of the modern era, 3 mile courses were common, but they were later shortened to 2-½ miles and then to 2 miles. This was done mainly for safety, as the length was taken out of the straightaways to minimize top speeds. This is in part why cornering speed is so emphasized nowadays. Today's circuit consists mainly of 2-mile courses, with some 2-½ mile courses still used where room permits it.

Even on courses of the same length, proportions vary. River courses, naturally, tend to have longer straights connected by tighter turns. There are some interesting variations, though. Evansville has a dog-leg on the frontstretch, which makes it look like the land-based track in Phoenix. The course used in Barrie, Ontario in 1999 wasn't even an oval at all: it was a triangle, with 3 distinct corners, like the Pocono Speedway! And there can be obstructions, also. San Diego's island has already been mentioned; at Madison, Indiana, the course passes under a highway bridge, though that hasn't seemed to have had much effect on the racing. It makes an interesting vantage point, though!

The famous course at Detroit, which celebrates its centennial in 2004, is interesting. It runs in a branch of the Detroit River between Belle Isle (where CART has raced in recent years) and the mainland. While it is an oval, it is anything but symmetrical. The north, or Yacht Club, turn (the Detroit Yacht Club is adjacent) is the tightest and slowest corner in the entire series. The south, or "Roostertail," turn (adjacent to the Belle Isle bridge) is conversely the fastest corner in the series! This makes the optimal setup for Detroit devilishly difficult to find.

Perhaps the most unusual course used by Unlimiteds was the tiny oval at Firebird Lake in Phoenix. Listed, perhaps optimistically at 1-½ miles, this course was really intended for drag boats and limited hydros, but saw Unlimiteds run several times during the 70s and again in the mid-90s. Because the course was so tight, only 2 boats could be raced at once, so the race was done drag-racing style, with a series of elimination heats. One strange moment came in 1995 when Miss T-Plus had a failure of a skid-fin support during practice. The boat slid off the course, rode up the bank, and wound up sitting atop the berm surrounding the course looking like a beached whale! Fortunately, no one was injured and even damage to the boat did not keep it from racing in the event. This scenario is unlikely to be repeated, since the race has now been moved to an orthodox course near London Bridge at Lake Havasu City.

Miss T-Plus, 1995


While it is not that unusual for a racing driver to switch vehicles during his career, usually he leaves one series before starting another. For instance, Didier Pironi's career-ending injuries in Formula One eventually led him to turn to offshore powerboats, where unfortunately he lost his life.

That has happened in hydroplanes, also. "Wild" Bill Cantrell drove in a couple of Indianapolis 500s in the late 40s, without success, before starting on a longer and much more successful career in Unlimited hydros. Chip Hanauer drove sports cars during his first retirement from hydro racing, and Tom D'Eath dabbled in motor sports after leaving the big boats.

But Unlimited racing is the only speed sport I know of where drivers raced while at the same time also racing other types of vehicles! Actually, "racing" isn't the whole story, because I believe Russ Schleeh was racing hydros successfully during the mid-50s while still a test pilot in the U.S. Air Force. Later on, Russ flew at least once in the Reno Air Races, though this may have been after his hydroplane career had ended.

Mira Slovak, the charismatic Czech defector, is unique in holding national championships in 2 very different "Unlimited" classes. In 1964, he was the first national champion in the Unlimited class of the new Reno Air Races, flying an F8F Bearcat. Two years later, he won the Unlimited hydroplane national title at the wheel of Bill Harrah's Tahoe Miss. Slovak raced on both the water and in the air for a number of years, and even today performs at airshows flying—appropriately—a Czech jet trainer.

David Walther was nicknamed "Salt" which fit his career in hydros, but not his other racing career, in the Indy 500. In both cases the vehicles were often owned by his father and sponsored by his dad's Dayton-Walther company. His hydros were named Country Boy and carried number U-77; his IndyCars, not surprisingly, carried number 77.

Salt's career in both seemed rather ill-starred. He started in 7 Indy 500s during the 70s, with a highest finish of 9th, but he also finished 33rd and last on 3 other occasions. His hydro races were no better, with a best finish of 3rd at one race in 1974. He is probably best known, unfortunately, for a serious crash at the start of the disastrous 1973 Indy 500. But he survived all his racing experiences, which is more than can be said for some of his contemporaries.