International Hydrofoil Society Correspondence Archives...

Ultra-High Speed Hydrofoils -- The Arguments For and Against

(Last Update 20 Apr 02)

Return to Posted Messages Bulletin Board


A 100-knot Hydrofoil... Why?

100-knot Hydrofoil... Why Not? (below)

[20 Jan 98] Regarding the subject matter, my first question is why? When one looks back at high speed hydrofoils there are interesting motivations behind them. Starting with Forlini, he had a seaplane application in mind. Bell was interested in a high speed record for waterborne craft. Canada's MASSAWIPPI was initially a private venture for a speed record. Starting in the WW II time period the Navy and NACA were interested in the take off and landing application of hydrofoils for seaplanes. It was demonstrated that seaplanes could take off and land in higher sea states by using hydrofoils. This led to Bill Carl's XCH4 which upped Bell's speed of 70 mph to 78 knots. As the US Navy began to phase out the use of seaplanes the related hydrofoil effort was discontinued. The US Maritime Administration's (MARAD's) interest in high speed waterborne transportation was evaluated when Bill Carl's company Dynamic Development and Grumman produced the DENISON, which demonstrated open ocean capability and speeds to 60 knots. In the meantime, the surface Navy's interest in high speed hydrofoil craft continued with an ultimate goal of achieving 100 knots. Under contract with the US Navy, Boeing built FRESH-1. A two phase program was planned with a Boeing canard configuration designed for 80 knots for Phase 1, and Grumman designed a transiting set of foils for Phase 2 with the objective of demonstating 100 knots. The difficulty of stabilization for these high speeds was demonstrated when FRESH-1 had an accident during the Phase 1 trials. Although the AGEH was designed for an initial speed of 50 knots, it had the capability to take additional power and different foils to achieve a much higher speed. However as the US Navy evaluated their hydrofoil craft, it became obvious that military craft up to 50 knots were achievable and fulfilled Navy mission requirements. With this, the Surface Navy lost interest in the very high speeds. In the meantime, other studies directed toward high speed waterborne craft for passenger and cargo transportation also showed that hydrofoils were competitive in time and operating costs with air transportation at speeds up to 50 knots and ranges of up to 150 nautical miles. The only application that I can think of today to use100-knot hydrofoils could be in the drug interdiction and capture of Cigarette boats in rough water conditions. However the PHMs demonstrated their effectiveness in this role at 50-knot speeds. The 100-knot hydrofoil is a tough foil and stability design problem. I think that the problem a hydrofoil designer should pursue today is to design craft in the 40 to 50 knot range that can be built and operated at the per seat costs of the catamaran. The hydrofoil has demonstrated its superiority in rough water ride qualities, but the comparative costs today make the catamaran more acceptable as a business venture. So, I have to ask: why 100 knots? -- Robert Johnston


100 knot Hydrofoil... Why Not?

100 knot Hydrofoil... Why? (above)

[20 Feb 98] In 1955 we designed, built, and tested a 13.5' hydrofoil racing craft in response to many uncontrolled race boat accidents where turning was the cause. Powered by the standard Mercury hurricane 20 it had a wing deck between the two sponsons to create lift to get the hull up off the water and ran between 80 to 90 mph similar to most hydroplanes of that era. The only difference was the skid fin that was modified by the addition of variable incidence horizontal foil used to pivot down (dig in) to hold the craft down on the water on the turning side. The outside was allowed to continue around, giving the effect of spinning around a street sign. Immediately it became apparent that if pitched up instead of down, the foil could lift the craft off the water. Now if you can lift the boat out of the waves with the variable incidence skid fin (hydrofoil) then why not invert the wing deck and use the air to push down instead of up to avoid the dreaded "blowover" and turn accurately at any speed. If you then balanced the downward air force against the up hydrofoil force by controlling size, aspect ratio, curvature, etc. than you should be able to have a balanced system at any speed with the hull out of the water above the waves. In 1972 we founded Hydrofoils, Inc. to produce experimental models and production tooling for the manufacture of high technology hydrofoils that could "turn at any speed." In October 1973 our first US patent was issued disclosing the benefits of these high-speed high control craft. We then produced and tested a number of 16.5', 130 mph boats using these benefits. In 1976 a proposal design for a 28' Patrol Hydrofoil was assembled in response to a "request for quote" from the Canadian Dept. of Fisheries. Russian fishing boats could be fined by the amount of illegal fish that were verified on board when stopped. The Russians knew this and would start throwing the catch overboard when the chase began. So the faster the chase boat, the higher the fine. This 28 foot project was not sold but started the design process towards larger craft. In 1978 we demonstrated a 16.5' 2-man hydrofoil by invitation of the Society of Naval Architects and Marine Engineers (SNAME) at the Advanced Ships Conference in San Diego CA, USA. In 1979 the initial design of 30' turbine powered hydrofoil began. Back to the story. If you can push this boat forward at any speed and it stays in balance, and on the water, than you should be able to put a rocket on it and it will still work. Right? Well, we did and it did. It worked so well in fact, in late 1997 the scaled up calculations went into a larger version, a rocket hydrofoil that can do well over mach one on water! But why, and how do we make this useful? What if we all were directed to drive to work at 35 mph, turnpike, parkway, freeway and all? We did until the cars could go faster. That's what the fastest "fast" ferries do today. The only reason is that they can't go much faster, and if they could would it be safe? There is plenty of room to navigate (assuming control), certainly more than the few feet clearance we give ourselves to pass at 60 mph on the road. Continental US aircraft speeds are limited by the environmental stresses of the sonic boom. When offshore, supersonic aircraft don't just stop at mach 1. They double those speeds-- because they can. Our autos can all far exceed the 60/75 mph US speed limits but we are constrained by lack of control at higher speeds. As the control issues are resolved in the future, auto speeds will increase dramatically to the next BIG hurdle, "G" forces on the human body. Well, if rail, helicopter, and auto normally operate between 60 to 100 mph than what is the marine industry doing to be "intermodal?" The ability to connect seamlessly and effortlessly, carrying similar numbers of passenger, at similar speeds with other forms of transportation is paramount to the survival of marine industry. Air, auto, rail, and bridge technology is rapidly advancing. We can use it or lose it. We need to shake off that "do what you want but not on my watch" restrictive thinking and reach out for a better system. Building safe, high speed boats has not been a problem for many years. Financing them has been the problem. If we want the gold, we will have to get up and go for it. To the polititian or navy officer, why let the other forms of transportation claim most of the funding when most of the earth is water? We don't think bigger slow boats full of people will help the marine industry, do we? True advanced thinking, better terminals and docking, and true high speed ferries and freighters will rejuvenate this industry. Hydrofoils, Inc. currently designing a 75 foot, 30 passenger 100 mph ferry, a littoral water mine map and sweeping device, and we are conducting open water tests of unmanned, radio controlled, extremely high performance, advanced composite hydrofoils with speeds estimated at 1,200 mph. WHY NOT? -- Kenneth E. Cook, CEO, Hydrofoils, Inc. (email: kencook@hydrofoil.com) (website: http://hydrofoil.com)


Return to Posted Messages Bulletin Board

Return To IHS Front Page

Back to Top of This Page


This Page Prepared and Maintained By...

International Hydrofoil Society

PO BOX 51 - CABIN JOHN MD 20818 - USA

webmaster@foils.org