Hydroplane (boat) - Hydroplane Design

Hydroplane Design

Early designs of the 1920s were often built by amateurs, who employed the lightest materials available to them at the time, which were often glued timber boarding or plywood on the floor, 4-millimetre (0.16 in) plywood topsides, and varnished canvas decks. Most were about 4 metres (13 ft) long and stepped hulls were employed with a 75-millimetre (3.0 in) step to induce air under the hull, to enable the boat to float on air bubbles. The concept of 'planing' was not fully understood. Thus, hulls were flat bottomed with an upward curve at the bow and the step 2/3 of the way aft. The sheer weight of a 100 hp. engine was enough to keep the bow from digging in. In Ireland the sport was managed by the Motor Yacht Club of Ireland which had a base at the Lough Ree Yacht Club near Athlone.

One of the earliest examples can be seen in the Popular Mechanics issue, Vol. 63, No. 5, May 1935. the story of "Mile A Minute-Thrills of the Water" tells the story of the "No-Vac" by LeRoy F. Malrose Sr. aka. Fred W. McQuigg (pen name). LeRoy was the lead design illustrator for Popular Mechanics magazine, which at the time was located in Chicago, Il. The No-Vac design and build actually began in 1933, when LeRoy Sr. conceptualized an airfoil hull surface design which proved to produce far less drag than conventional "V" style boat hull designs of the time. In June 1933 the No-Vac was put the test with professional racing driver Jimmy Rodgers at the helm. That day the No-Vac set the world water speed record for an outboard powered boat of 78 MPH.

The basic hull design of most hydroplanes has remained relatively unchanged since the 1950s: two sponsons in front, one on each side of the bow; behind the wide bow, is a narrower, mostly rectangular section housing the driver, engine, and steering equipment. The aft part of the vessel is supported in the water by the lower half of the propeller, which is designed to operate semi-submerged at all times. The goal is to keep as little of the boat in contact with the water as possible, as water is much denser than air, and so exerts more drag on the vehicle than air does. Essentially the boat 'flies' over the surface of the water rather than actually traveling through it.

One of the few significant attempts at a radically different design since the three-point propriding design was introduced was referred to as Canard. It reversed the width properties, having a very narrow bow that only touched the water in one place, and two small outrigger sponsons in the back.

Early hydroplanes had mostly straight lines and flat surfaces aside from the uniformly curved bow and sponsons. The curved bow was eventually replaced by what is known as a pickle fork bow, where a space is left between the front few feet of the sponsons. Also, the centered single, vertical tail (similar to the ones on most modern airplanes) was gradually replaced by a horizontal stabilizer supported by vertical tails on either side of the boat. Later, as fine-tuning the aerodynamics became more important, the bottoms of the main hull have subtle curves to give the best lift.