boats that are designed with car aerodynamic method?

Discussion in 'Hydrodynamics and Aerodynamics' started by dina, Oct 5, 2012.

  1. dina
    Joined: Mar 2011
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    dina Junior Member

    Hi
    do you know any thing about:
    boats taht they are designed with car airodynamic method??!!!
    please help me:confused::confused::confused:
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    No, it wouldn't make any sense. Cars need to be pushed down into a hard surface at speed. Boats need lift from a liquid that is continuously changing.
     
  3. tspeer
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    tspeer Senior Member

  4. dina
    Joined: Mar 2011
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    dina Junior Member

    thanks tspeer
    that is good
     
  5. Petros
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    Petros Senior Member

    lots of modern racing yachts have aerodynamically deisigned decks/cabins, aerodynamic drag of the hull and deck is detrimental in all points of sailing except going at down wind angles.

    reducing drag and windage of mast, sails and rigging will help when pointing high, and in a reach (reduces heeling forces), but reduces downwind thrust. Seems to a good trade off to me, but there is still much disagreement amoung advanced yacht designers.
     
  6. gonzo
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    gonzo Senior Member

    That is different from car aerodynamics. Cars need to be pressed down into the road. Boats don't have that requirement. There are high speed powerboats designed as lifting bodies, but that is closer to aircraft design.
     
  7. Petros
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    Petros Senior Member

    reducing drag of a car is always beneficial. actually most cars naturally generate lift, the object is to reduce the amount of lift they do cause to keep tires in contact with the road and reduce induced drag. So the so-called down force is actually the ablity to counteract the lift, which is undesirable in a car.
     
  8. FMS
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    FMS Senior Member

  9. bpw
    Joined: May 2012
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    bpw Senior Member

    Race cars use down-force to increase traction, but you generally increase drag at the same time. Passenger cars are deigned for minimal resistance (windage) and rarely create any sort of down-force, in fact many passenger cars create lift at speed.

    Passenger car aerodynamics may well be relevant to reducing windage in boat design.
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Unless the automobile is moving at 100 MPH or better, the only real concern for aerodynamics is it's drag coefficient. Most aerodynamics in passenger cars is to redirect flow, typically to employ it some how, such as through a radiator or to provide clean, pressurized air for the intake, lower noise or to bleed off pressure for a better Cd.

    High speed power boats do address aerodynamics, some quite effectively, but most pleasure craft don't travel at speeds where it's aerodynamics are of sufficient concern. On sailboats, you can get real anal about windage, but frankly it's just silly, unless you're racing. Removing windage on a racer does have considerable merit, but on most anything else, the fraction of a knot benefit you might gain from recessed roller furlers, below decks shroud and stay tentioners and the other assorted windage reduction tricks, just can't be qualified on a yacht with it's dinghy in tow or enjoying the security of it's railing nets or cleverness of it's radar arch. Large ships can and some are now addressing aerodynamics, but typically this is also a diminishing set of returns, considering the limitations on capacity in these types. Simply put, you can reduce windage on a bulk carrier, but to what end when the vessel is several hundred feet long and several dozen feet high. All the rounded corners in the world aren't going to help a monolithic beast. You might be able to quantify the savings, but amortize the cost of them during it's usfull service life?
     
  11. tunnels

    tunnels Previous Member

    so some one askes a simple question and look at all the strange answers !!!
    the moment a boat gets into the 30 mph and above then aerodynamics are starting to have a effect . 40 mph and you can feel the movements 50 mph and its really starting to get a bit of power to it 6o mph and you well on the way !! remember all those really old plaines used to be flying at 60 mph . Decks, cabins, flat windscreens, big cabin openings facing rear are sucking spray and fumes from along way behind some big boats .
    Designers need to wake up and smell the flowers and unless they get there heads out of that dark smelly place and into 2012/3 you going to be left doing all those old antique designs in reprints !! . aerodynamics makes for much more stable boats when they are travelling in the 30/40/ 50 / mph speeds . we have been bought up to only think about hydrodynamics but with the price of fuel and the speed increases in the modern powerboats its obvious the next major move caars realised areodynamics long time ago and the boating industry is stll wollowing in the dusty past and its progess forward is very slow ! :eek:

    If you want to see where our designers thoughts are read the posts before this one !! they are way behind and may never catch up !
     
  12. tunnels

    tunnels Previous Member

    Cars are cars planes are planes and boats are the things that are left way behind the times . most of our designers are old ,prehistoric and dinosours with preconcieved ideas and dont like change of any sort . . unfortunatly theres a huge gap between them and the computer wizz kids of today that have the new ideas and modern designs !!! some where some how they need to get together (Thats impossible i know ) and do a little sharing of ideas skills and information . :confused::eek::mad:
     
  13. missinginaction
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    missinginaction Senior Member

    I don't always agree with tunnels (no offense) but I have to say that I think he is onto something here.

    You see I ride motorcycles. If you're riding a standard or dual sport bike with minimal faring and no windscreen you really notice the effect of aerodynamics, or more to the point the lack thereof.

    AT 30 MPH no real issue, 40 just a bit, 50 more, 60 start hanging on, 70 and above you want a really good grip on those handlebars. If I'm doing 60 and pull in the clutch I'm down to 40 MPH in a matter of a few seconds. No need for the brakes. Wind resistance is considerable.

    I've often wondered how this plays out on boats. Displacement boats are not a real issue but faster boats might be. I know most boats aren't traveling at 60 MPH. However you can feel noticeable drag at 40. That 40 might sound fast until you consider a boat traveling at 20 MPH into a 15 or 20 MPH headwind. I'm no engineer but my very personal experience with aerodynamic drag makes me wonder.
     
  14. gonzo
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    gonzo Senior Member

    Old Corvettes are a good example of bad design that made them lose grip on the road. At anything over 80mph they started to lift and would lose control unexpectedly. 80's Mustangs are another good example. The Florida State Troopers bought them as chase cars. They found out that at about 90mph they would lift off the road if the windows were open.
     

  15. PAR
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    PAR Yacht Designer/Builder

    You can talk all you want, but unless you've looked at the actual numbers, suggesting aerodynamics are important at 40 MPH is just ridiculous. Can it be improved, of course it can, but is it worth the bother at the speeds normally associated with these speeds, usually not. It has nothing to do with preconceived notions about what you think designers look at, but in fact the return on the concept implementation. If you kill the engine's drive, while in a vacuum, you'll still feel like you've just run into a wall of cookie dough, nothing to do with wind resistance (very little relitivly), just power application. Again, if you look at the numbers, the resistance, compared to the other variables isn't significant at the speeds the average pleasure craft travels. Can you gain a few percent of efficiency, sure, maybe an extra couple of knots (oh boy!), but again why bother, particularly if you have to accept other, less than desirable compromises in order to have your 2.5% improvement in wind resistance.

    Modern cars generally are pretty bad with fairly high Cd's, though much better then 40 years ago, when aerodynamic styling was more important than real aerodynamic improvement (like the C3 mentioned). Like it or not vortice generators on the side of container ships, are going to help enough to offset the cost of installation, let alone their design. Look at the numbers on resistance and compare them to the total of all the resistance that must be over come and you're going to realize it's not as big a concern as it might appear in the big picture, until you get into a full blown gale. So, how many pleasure craft regularly get caught in a full gale?
     
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