Raingutter Boat Racing - How To Make A Fast Regatta Boat

Understanding Speed Factors

One of the fastest winning times by a sixth grader in our club blowing a 6-inch, 1-ounce boat in a 10-foot raingutter was 2.44 seconds. Amy was a girl! Times under 2 seconds have been recorded for adults.

Which design factors increase your boat's available energy and which ones decrease it. The shape and weight of your boat will either cause it to push water apart to let it pass or cause it to rise above the surface and hydroplane. Knowing which factors cause these two modes of water travel will help you customize your boat design for maximum speed.

Factors That Affect Energy Available for Speed

Increases Speed Decreases Speed
  • Greater force of breath
  • Straighter aiming of breath
  • Shorter time between breaths
  • Lighter boat
  • Up-turned, flat hull
  • Resistance of water to movement of your hull
  • Resistance of air to movement of your sail
  • Friction at surface of water
  • Your boat's tendency to tip (stability)
  • Side-to-side drift in raingutter
  • Adhesive forces at vertical gutter wall
  • Getting stuck under lip of raingutter

Basic Fast Design

Each of these factors must be dealt with in some way in the design itself because they affect each other. For example, if your boat weighs less than 2 ounces, but the front of your boat comes to a point (like most boats you've been in) you may never be able to make it hydroplane.

Here are simple design decisions that lead to a very fast, raingutter regatta boat.

  1. Use a flat hull to distribute the weight of the boat across the width of the water way.
  2. The bottom of the hull is turned up in front so it rides up on the surface of the water.
  3. Make a sail that is right on the deck to reduce forward tipping.
  4. Make the sail from a rigid material that does not allow the air to pass through.
  5. Form a pocket in the sail to catch the air and make it exit backwards.
  6. Balance the boat to tip upward in the front at least a quarter inch.
  7. Make bumpers suitable for the type of raingutter used so the boat won't get stuck at the side.
  8. If the boat weighs less than 2 ounces, a 4th grader should be able to make it hydroplane some.
Find more speed and design information and pictures at www.lastufka.net/lab/boats/.

Why Hydroplanes?

For speed, the best designs cause boats to hydroplane. Motion in the water is limited by the speed of waves. But hydroplaning is only limited by how hard and straight you can blow! Following the basic design principles above will most likely make it possible for a good blower to hydroplane your boat. Even so, among hydroplanes, there is NO single, "BEST" design because the rules of the competition, raingutters and kits used differ from club to club.

Hydroplanes are designed to get out of the water and skim the surface where there is much less drag. These boats win more often given the wide range of participant ability to blow and skill in construction.

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Raingutter Boat Racing - How To Make A Fast Regatta Boat
Copyright © 1997, 2000, 2001, 2004 by Michael Lastufka, All rights reserved worldwide.