30 SEC­OND BRIEF­ING:

HYDROFOILS

Motorboat & Yachting - - Princess To Norway -

Hydrofoils on boats are noth­ing new. They’ve been around since 1898 when Ital­ian in­ven­tor En­rico For­lanini started work­ing on them. ● His ideas were adopted and de­vel­oped by com­mer­cial boat­builders and navies dur­ing the 20th cen­tury but be­gan to fall out of fash­ion in the 1990s due to high build­ing and run­ning costs. ● Foils have come back into fo­cus in re­cent years due to the ex­cite­ment sur­round­ing the new gen­er­a­tion of foil­ing Amer­ica’s Cup yachts, which are ca­pa­ble of speeds of over 40 knots. ● Foils work like an aero­plane wing. The shape and an­gle of the foil is de­signed to de­flect water down­wards and en­cour­age water to flow faster over the top sur­face than the bot­tom one. ● This cre­ates high pres­sure on the un­der­side of the foil and low pres­sure on the top, which ‘sucks’ the foil up­wards un­til it lifts the main hull clear of the water. ● At a cer­tain speed, the lift­ing force is bal­anced by the weight of the boat, al­low­ing the craft to ‘fly’ at a fixed height above the water. ● Be­cause the sur­face area of the foil is much smaller than that of the main hull, the types of drag and wave re­sis­tance which act on the boat are re­duced, al­low­ing it to cruise faster us­ing less power. ● There are two main types of foil: sur­face-pierc­ing foils like the U-shaped struc­tures fit­ted to Se­abub­bles ,and fully sub­merged T-foils like the ones fit­ted to In­ter­na­tional Moth sail­ing dinghies. ● Although fully sub­merged foils are more ef­fi­cient and less prone to wave ac­tion, they are trick­ier to con­trol and less sta­ble dur­ing turns.

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