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Hydroplanes Explained

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Every year during Hydro week in the Tri-Cities, we're asked questions like:  "What's a sponson?" or "What's a skid fin do?"

So, we thought we'd take the time to diagram the parts of a hydroplane and provide a brief explanation of the parts and what they do.  But, consider this a work in progress.  As we get more feedback, we'll make changes and improve the quality and quantity of the information.  So... we're asking for your help!  Please tell us where we've gone wrong and what we've missed.  We'll incorporate your knowledge into the final document for race fans. 


Send email to HydroInsider.com with any suggestions.


  • AIRTRAP:  The airtrap is the inside of each sponson and runs the length of the hull.  The airtraps and bottom of the ram wing form a tunnel under the hull where air packs, creating lift.
  • CANARD:  The canards are located up front between the sponsons.  Older set-ups included a stationary spar which helps provide support between the sponsons.  Attached to the back of the spar are adjustable flaps.  More mdoern hydroplane have a canard that is fully adjustable.  Drivers adjust the flaps to improve handling by using foot pedals inside the cockpit.
  • COCKPIT:  Just like in an airplane, it's the place where the driver sits.
  • COWLING:  THe cowling is the engineer cover designed to provide maximum airflow over the boat.  On turbine engines, the cowling serves as an air intake for the engine.
  • DECK:  The upper surface of the hull.
  • PROPELLER:  The propeller, or prop, provides propulsion and pushed the boat forward.  At top speeds and attitude, only about half the prop is in the water at any given time.
  • RAM WING: The center, wing-shaped section between the airtraps, providing lift to the hull.  Pressure behind the ram wing, in the tunnel, allow the hull to skim over the water.
  • REAR STABLIZER:  The rear stabilizer is used to control the attitude of the hull and helps determine lift at the rear of the boat.
  • SKID FIN:  A long, stationary metal blade mounted behind the left sponson about the middle of the boat.  The skid fin helps the boat through turns and keep the hull lined up in the straight-aways.
  • SPONSONS:  The two, forward outside extensions of the hull.  The pontoon-like sponsons generate hydrodynamic lift.  When the hydro's at top speeds, the sponsons are barely touching the water.  In rough water, you'll hear people talk about "sponson walking" when the sponsons slap the water frequently.
  • TIPLET:  Small wing-shaped items at the stern, designed to enhance airflow and provide aerodynamic recovery surfaces that stabilize the boat when the bow pitches upward.
  • TUNNEL:  The area underneath the hull, including the airtraps and the bottom of the ram wing.  This area is designed to pack the air under the hull and provide lift.
  • VERTICAL WINGS:  The vertical wings provide directional stability to the hull and are used to elevate the rear horizontal wing.