Definition of Planing

Discussion in 'Hydrodynamics and Aerodynamics' started by Leo Lazauskas, Nov 2, 2012.

  1. tunnels

    tunnels Previous Member

    I have 2 jobs hanging in the breeze .one will start very soon the other later in the year , China you have to play a waiting game nothing happens in a hurry !!
    Its absolutely amazing that companies can buy a set of crappy old moulds from overseas and start making boats ,yet know nothing about them what so ever !!
    Every time i visit the lakes i see smaller boats speeding along with there noses buried in the water and the outboards tucked in as far as they will go ,always !!,Not one driver uses the power trim !!!! never !!
    The cruisers we made a simular thing , never saw anyone ever use the trim tabs so as we took off the 48 used to bury its stern way down to the point of water pouring over the boarding platform and pushing heaps of water and with all it 750 plus hp it gradually climbed out of the hole and up over the hump to get going !
    In two years plus i never saw one person push the trim buttons on any of the boats we made .
     
  2. daiquiri
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    daiquiri Engineering and Design

  3. W17 designer
    Joined: Oct 2010
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    W17 designer Senior Member

    Have to say … I was rather surprised to see such a long debate on the definition of planing! Anyway, thought I might add a little historic background from my UK background, for interested readers.
    As a naval architectural student in the 50’s, I grew up with the understanding that it was simply “an expression of the effect of net positive hydrodynamic lift, that permitted a hull to be somewhat lifted and therefore lower total resistance and run faster”. We used to talk of ‘partial planing’ or ‘full planing’. That was certainly the framework of understanding when listening to provocative Uffa Fox in a tavern in Cowes, UK as a starry-eyed teenager! We always knew we were in the company of someone pretty special in the field, as Uffa had taken a development first created for wartime seaplanes at nearby Fairey Aviation and then applied it to sailing dinghies, to go down in UK history as the first to do so – initially for his International 14, Avenger.
    He later became involved with Fairey Marine for the construction of 1000’s of hot-moulded Fireflies, Albacores & Jollyboats etc, to develop the first known ‘mass production planing dinghies’.
    To avoid using too much space here, I’ve posted the rest of my thoughts on this subject at my website. Feel invited to visit for more on ‘planing’.
    http://www.smalltridesign.com/Trimaran-Articles/design/planing.html

    Happy hiking guys ... mike
     
  4. tunnels

    tunnels Previous Member

    This is possibly the first post that has made any sense and the trimaran articles are definitely well worth reading and saving for those rainy days :D.
     
  5. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Now do we have to go ahead and find out at what point of the plane is most efficient? Is that not what the reason is to make a boat plane, to get the best performance?
     
  6. tunnels

    tunnels Previous Member

    Just over the hump !!

    Ah step 2 !!
    Every boat to get on the plane after digging a hole for its self goes over the hump and is running freely over the surface of the water ! some where at that point also all motors have a rpm at which they run best at!, they are quieter because the only doing a minimal amount of work and at that speed are economical as well , the boats rides comfortably and with out pounding and thumping, Tracks beautifully and is a pleasure to drive .:D

    By playing with the power trim at say 3000 rpms its possible to finds the sweet spot to trim to !!
    trim in and the bows down and motor working , The spray coming out the side is forward of the drivers position , gradually trim up and all begins to change motor sound is different , boat moves better and has a better feel , spray has shifted aft a little , rpms just come up a wee bit
    trim up further , now things are really starting to change motor rpms up almost 3100 and the spray is back to the drivers position .
    next step trim up further spray behind the driver now and rpms 3200 and motor is quieter nose has come up and speed has noticeable increased and boat feels really alive so to speak .
    I have practices this a thousand times and once the 3200 has been reached that's it for my boat ,its at its sweet spot !!
    Puss the lever all the way down at 6400 rpms on the tacho its flying almost , the needle on the speedo is off the dial , the boat still feels comfortable in a small chop and really smooth riding . Back off to 4250 and it will cruise comfortably there all day and really covers some ground .

    My motor has 450mm of step back and makes my trim very sensitive to the touch of the button ,at 3200 where the sweet spot is if I trim up the bow lifts and its noticeable the sound of the water is louder and rpms have dropped a little . spray has gone back even further out the side
    trim a tad further and the water begins to thump and rpms dropped to under 3100 at that point it will sometimes begin to porpoise and increasing power does nothing sure goes faster but porpoises even worse !!, trim back and its all over and smooth quiet and comfortable again .
    Know your boat and what IT likes !! They all different !!


    I know its not the answer you looking for !! what you want is all kinds of formulas and pages of figures with graphs and the like ! all boring stuff that no one can ever agree with anyone else and so the debate will rage on for another 6 months and go nowhere same as before then some one will write a really good reply that puts everything into prospective and all makes sense !!!.:confused:
     
  7. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    I am quite happy with..when a boat rides over the top of the pressure wave and continuously falls forward with the pressure wave (like a surf rider) that suits me for an economic form of transport.
     
  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Tunnels: if you only have negative and asinine comments, why don't you stay off this thread. You keep on disrupting a very positive and creative discussion.
     
  9. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Actually, for each cg location of a planing system, there is a most efficient planing speed that matches that location. To put it another way, for each speed you want to travel at, there is a cg location that results in a minimum drag. If the cg is more forward than the optimum location, there is more wetted surface area, and therefore higher drag. If the cg is too far aft, the planing angle is higher and the drag is higher. So you see, there isn't a most efficient speed that you are on a plane, there is a most efficient speed for that specific cg location. If you want to optimize fuel efficiency, you would place the cg forward, and slow down and that would be more efficient than running faster with a more aft cg, but your average speed would be lower.

    For a flat planing hull the optimum angle is different than a v hull, so the deadrise angle also is part of the equation.
     
  10. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    I can agree with most of those comments .Can you compare a surfer to a boat on the plane? the surfer travelling free with no energy input for forward motion. A boat must make use of it`s pressure waves the same way.
     
  11. gonzo
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    gonzo Senior Member

    Not really. They are two completely different things. A surfer is falling down the forward face of a wave. A boat planing is using its own power to overcome resistance.
     
  12. El_Guero

    El_Guero Previous Member

    :)

    After 46 pages, are we anywhere near take off?

    C'mon! Strap on a couple of Pratt & Whitneys in about the 3,000 hp range with 5 bladed props, and get that on a real plane ....

    And then it doesn't matter if you are falling down, or can't read straight (won't mention any of our people by name), or have a really small outboard, 6,000 hp will get you on a plane, even if on just a surf board ....

    I hope ya'll were ready for a little comedic relief.

    wayne
     
  13. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Either on a plane or to the sea bottom - which is also a kind of final solution to this problem... :p
     
  14. tunnels

    tunnels Previous Member

    why are you missing the point they are both planning !!the surfer is using his own body weight to make the board plane !! and the boat is using it motor to power it !! confused are we ??
     

  15. El_Guero

    El_Guero Previous Member

    I bet we cross the 700th post tonight?

    See you at the bottom of this ....

    :D
     
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