back to earth Posted December 10, 2016 #26 Share Posted December 10, 2016 I would have thought the hydroplanes that lift the hull out the water, and hence totally eliminating any hull drag (except through the air ) would be less drag on the hull than any surface or undersurface shape, man made or animal . producing drag ? Link to comment Share on other sites More sharing options...
Habitat Posted December 10, 2016 #27 Share Posted December 10, 2016 Hydrofoils certainly have introduced substantial gains for certain specialized uses, but there is still the problem of propulsive losses through underwater drives. The Boeing Jetfoil is an attempt to beat that, but it remains a highly specialized application. And of course hydrofoil craft are quite weight sensitive, which means load-carrying is basically restricted to passengers, not any substantial freight load. Link to comment Share on other sites More sharing options...
back to earth Posted December 10, 2016 #28 Share Posted December 10, 2016 How does the problem of propulsive losses through underwater drives and being weight sensitive, which means load-carrying is basically restricted to passengers, not any substantial freight load - effect the fact that when the hull IS out of the water and moving , there is virtually zero water-drag ? Link to comment Share on other sites More sharing options...
Habitat Posted December 10, 2016 #29 Share Posted December 10, 2016 7 minutes ago, back to earth said: How does the problem of propulsive losses through underwater drives and being weight sensitive, which means load-carrying is basically restricted to passengers, not any substantial freight load - effect the fact that when the hull IS out of the water and moving , there is virtually zero water-drag ? propellors are about 50% efficient, and struts and drive elements, rudders have losses, both skin friction and form resistance, your foils also have substantial drag, but it is true that foils, although they have many practical problems, (imagine a collision with a shipping container at high speed, which could be catastrophic to a structure engineered for drag minimization) allow speeds ( look at foiled sail catamarans) that other similarly powered boats cannot achieve. You have to realise that frictional drag increases as the square of speed, so although the hull is lifted clear, to double the speed quadruples frictional drag on what is left underwater. The weight issue is similar to that of an aeroplane, the hydrofoil depends on dynamic lift, and eventually as weight increases, the idea becomes impractical. Link to comment Share on other sites More sharing options...
back to earth Posted December 10, 2016 #30 Share Posted December 10, 2016 (edited) ... so, a large load would create as much as , or more drag , on what IS undersurface , than if it was just a hull undersurface without the hyrdoplane rig ? Those hydroplane ferries ca get pretty big and carry a lot of passengers , do you mean a lot more than that, like a some type of freighter with a LOT of cargo ? Edited December 10, 2016 by back to earth Link to comment Share on other sites More sharing options...
Habitat Posted December 10, 2016 #31 Share Posted December 10, 2016 A large load would require larger foils with more drag, more weight ( the foils themselves are highly loaded, and need robust construction). you get into a spiral where it no longer works. It is extraordinarily power-consuming to travel at high speed through the water, hydrofoils and surface-effect ships are most effective at it, provided weight is restricted, because the vessel is largely out of the water. But we won't be going cruising with on-board ball-rooms in a hydrofoil, the weight kills it. 1 Link to comment Share on other sites More sharing options...
Codenwarra Posted December 16, 2016 #32 Share Posted December 16, 2016 There is nothing new about the Min Min light, it's been talked about since the 1960s if not much earlier. Over very flat, arid or semi arid country hundreds of miles from the sea. Named for the locality called Min Min about 22.778 south latitude, 140.703 long, according to Google Earth, Queensland Channel Country. Link to comment Share on other sites More sharing options...
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