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Is there a future for automotive power for unlimiteds?

By Doug Ford
Reprinted from h1unlimited.com.

There has been a lot of chatter lately about the potential of an automotive powered unlimited hydroplane--and for good reason. They are loud. They would clearly be a fan favorite. They attract an entirely different group of potential sponsors such as automotive products, motor oil, spark plugs, etc., and the general public can more easily identify with a Chevy, Ford, or Chrysler engine similar to what they drive at home rather than something powered with a turbine.

In the past, automotive powered Unlimiteds were only marginally successful at best. Today, however, modern engine technology and the adoption of rules involving a higher minimum weight for turbine powered boats with a lower minimum for piston powered boats, it appears that automotive power could come into its own as a competitive option.

A supercharged automotive V-8 with aluminum block as used in high performance cars (e.g., dragsters) weighs approximately 500 pounds, or two of them about 1000 pounds. Today, a turbine boat must weigh a minimum of 6,575 lbs. empty, so the hull and systems must weigh roughly 6,000 lbs. without the engine, although this may include some fixed ballast weight.


However, empty weight of a modern technology hull can be much lighter than what is required to make minimum weight for turbines. A race ready hull without engine could be built for much less, say, 4,000 pounds maybe less with modern construction techniques. I used to do the official weighing of these boats long before the minimum weight is up to what it is today. You would be surprised at how light some of the boats were then, prior to the current minimum weight restrictions (remember the first Pay 'N Pak turbine boat, or the Sutphen Spirit? - VERY light!). With that in mind, a twin supercharged automotive engine powered boat could easily be built to weigh in the neighborhood of 5,000 lbs. dry. So, making the 5,775-pound minimum weight for piston powered Unlimiteds is not a problem today. Further, twin supercharged automotive engines can produce a combined horsepower approaching that of the T55-L7C under the current turbine fuel flow restrictions. So, in theory, the resulting horsepower to weight ratio could produce a very competitive boat.


There are negatives. A turbine engine theoretically operates like a "constant horsepower" engine when held at full throttle. That means, when the output shaft is lugged down, torque increases to keep the horsepower constant. Of course, in reality they really don't operate exactly like that, but close. A piston engine on the other hand will lose horsepower and torque when the output shaft is lugged down to the point where the engine falls of the torque curve. So, the engine, gearbox, and propeller, and the hull design for an automotive powered boat would need to be optimized such that the engine RPM can be maintained at a level to produce the horsepower and torque needed to remain competitive, especially in the corners. Ed Cooper has done this very well with the aircraft piston-powered U-3.


An automotive powered Unlimited would also need to carry a lot of fuel to complete a warm up and five lap heat, perhaps even twice as much as a turbine powered boat. Note that a Top Fuel dragster burns about 20-25 gallons of fuel in the warm up plus a quarter mile run. An automotive powered Unlimited wouldn't burn fuel that fast, of course, but will burn it much faster than a turbine boat. Regardless, even with the extra fuel the "wet" weight of one of these boats could still be considerably less than the turbine boat fueled and ready to race.

The main downside to the automotive technology today is cost; the cost of the engines themselves and the cost of development of the engine-boat combination. I gave a talk on Unlimited Hydroplane Aerodynamics and Hydrodynamics to the Engineering Society of Detroit at the Gold Cup this year, and several people from the automobile manufacturers were present, and showed significant interest.

Now, if the automotive manufacturers got involved, that would really be something.

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Comment by James Michael Dickinson on February 25, 2012 at 12:22am

In my opinion there is a great potential for Automotive power in unlimited Hydroplanes. In the last few years absolutely unbelievable advances have been made, everything from engine management to electrical valve operation to refinement of "old technologies".

I think we need to look to the car circle track racing for our inspiration. Drag racing is a static function , huge power on for a short time, at the end of the run the engine is close to being destroyed, they cannot live long enough to make even one lap. Nascar also is in this authors opinion, not applicable, the asphalt track is a fairly constant source of traction, if the driver decides to spin their tires, both tire and engine life are drastically shortened, making the vehicle a loser. 

The closest comparison the oval course boat racing in the car world is dirt oval track racing. The Hydroplane power plant is subjected to varying loads because of the inability to keep a constant bite on the water due to the surface conditions. Similarly the dirt track racer encounters varying track conditions due to ruts, slickness, and traffic. As a former open wheel racer, I often came out of the corners with my rear tires spinning and then to have them suddenly grab and literately launch the car. You can here similar engine loading of the older Piston Boats as you can in dirt track Sprint Cars, every summer Saturday Night, all over the U.S.

I am in process of designing a system using multiple racing specific V8 aluminum block Sprint Car engines. These engines can be produce over 950 HP each for what most Hydroplane Piston Engine Racers would call an "extended" period of time. Small blocks can be pushed out to 470 cubic inches and still breathe! No these are not hopped up car engines, they are purely racing motors, thousands of these, (albeit under 410 CI) perform on dirt tracks on any given summer weekend.

Further we do not need super or turbo chargers of any kind to produce this horse power, it is done with simple mechanical injectors and alcohol fuel, fuel use will be similar to the old aircraft engines.

No, it won't sound like a Merlin, it will be different, but to my take, a lot better than the whoosh of the Turbines.

Jim Dickinson, the dreamer who just bought the un-restored wooden Squire Shop.

Comment by William Black on April 9, 2011 at 7:43am
Doug: Great Idea.  This sport is Entertainment....and there is currently an unused resource to fill in at the races...that being several "race ready" vintage unlimiteds including a couple of the dreaded Detroit boats that have the potential (with sponsorship) to put on a great show with a lot of noise.

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