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The "Dillon Mini Tunnel"
GT Pro Racing Tunnelboat
Also Available: Cockpit Plans
Can be adapted to the Mini Tunnel
This 10-foot eight-inch long tunnel boat was designed for racing in the APBA Sportsman class called GT Pro. This class is raced in Minnesota and surrounding states, in races organized by the Twin City Powerboat Association.
In the fall of 2004 I looked far and wide for a set of plans for a tunnel boat suitable for local racing. I found only one: the "Tunnel Mite" from Glen L Marine Design. I built the boat (somewhat modified) and raced it in 2005 with moderate success.
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Length: 10' 8" (3.25m)
Beam: 71" (1.80m)
Bare Hull Weight: ~220 lbs. (100kg)
Max. Power: 35 hp / 120 lbs.
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Then I took what I had learned, in the shop and on the racecourse, and designed my own. My Dillon Mini Tunnel, on its very first test run, was 4 to 5 mph faster than my Tunnel Mite -- same motor, same prop -- with a top speed pushing 42 mph. Rule changes for 2007 increased that speed to 45+ mph, and I expect the upper 40s and maybe 50 mph to be attainable as this relatively new class continues to develop.
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The Mini Tunnel was designed with the 31.8 cubic inch Johnson or Evinrude in mind. This two-stroke, two-cylinder motor was manufactured in 20, 25, 30 and 35 horsepower versions from 1976 through 2005. It is the 35 horsepower model that is approved for racing in GT Pro.
For non-racers, I do not recommend using an engine that exceeds a weight of 125 lbs. The two cylinder, 35 hp OMC that we use for GT Pro of course fits that limit. Furthermore, the 25hp Tohatsu, used with great success by racers in Europe and Australia, would likely be an excellent choice.
About the Plans: I am not a naval architect, or an engineer, or even a draftsman. I am a forester by education, a furniture-maker by profession, and a boat-builder, sailor and racer by inclination. I have built a number of boats over the last 35 years or so: from the 8-foot hydroplane I built when I was fourteen, to a 21-foot sailboat built in the 1990s, and several more since then, including several GT Pro racers.
I have drawn these plans on my computer. As such, they are not, and do not resemble, an architect's blueprints. I also do not have the capability to print out full size drawings. However, it is not difficult for the builder to expand these drawings full-size, right on the plywood. There are no critical curves to draw -- just the dashboard and one small bulkhead. All you need is the patience to do an accurate job. And that patience will serve you well thoughout the building process.
The plans package, available via email or postal mail, includes eleven measured drawings; a scantling list; and some notes on wood and other materials and hardware needed to complete your boat. Also, you will have access to more than 20 web pages of shop notes including more than 90 photos which will guide you through the entire building process. There is also a text-only version of the shop notes which you can print out as a shop manual. Also, I will be just an email away if you have questions.
The plans package costs $45 US. You can pay online through Paypal (you do not need a Paypal account), or you may send a check or money order.
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