Dellenbaugh angle

Discussion in 'Stability' started by willfox, Oct 2, 2009.

  1. willfox
    Joined: Oct 2008
    Posts: 79
    Likes: 1, Points: 8, Legacy Rep: 22
    Location: southampton

    willfox Junior Member

    Is it that gives the amount the vessel will heel at 1pound per square foot of pressure?
     
  2. TeddyDiver
    Joined: Dec 2007
    Posts: 2,564
    Likes: 113, Points: 73, Legacy Rep: 1650
    Location: Finland/Norway

    TeddyDiver Gollywobbler

  3. Paul Kotzebue

    Paul Kotzebue Previous Member

    Dellenbaugh angle is useful for comparing the sail carrying ability of similar boats. It has too many assumptions to accurately predict heel angle or to compare different types of boats. Comparing Dellenbaugh angles of a heavy displacement cruising boat and a light displacement racing boat would not be meaningful.
     
  4. willfox
    Joined: Oct 2008
    Posts: 79
    Likes: 1, Points: 8, Legacy Rep: 22
    Location: southampton

    willfox Junior Member

    Thanks for that Paul.....so is there any better ways to accuratly predict the heel angle of a boat? If i kept the dell angle constant only varying the wind pressure, sail area and heeling arm. Would this be acurate in saying that the heel angle is constant?
     
  5. TeddyDiver
    Joined: Dec 2007
    Posts: 2,564
    Likes: 113, Points: 73, Legacy Rep: 1650
    Location: Finland/Norway

    TeddyDiver Gollywobbler

    Yes, and Dellenbaugh angle isn't for that purpose at all.. It predicts somewhat tendernes/stiffness in small angles of heel not the actual heel..
     
  6. Çemberci
    Joined: Apr 2007
    Posts: 127
    Likes: 6, Points: 0, Legacy Rep: 133
    Location: Istanbul/Turkey

    Çemberci Senior Member

    dellenbaugh

    A small excel program for dellenbaugh angle

    Oktay Çemberci
     

    Attached Files:

  7. Paul Kotzebue

    Paul Kotzebue Previous Member

    Predicting the actual heel angle is difficult. When the heeling moment produced by the sails is equal to the righting moment at a given heel angle, the vessel is in equilibrium. The righting moment at various heel angles is not difficult to calculate, but the heeling moment is.

    Most stability criteria involving wind heel assume the windage is projected to a flat plane at the centerline of the vessel. Sometimes a cosine squared function is used to account for the reduction of heeling arm and projected area as the boat heels. This gives an approximation of the heeling moment, but it is not accurate enough to predict the heel angle in real world conditions.

    A designer has to rely on experience and careful comparison of stability data for known boats to reasonably predict the heel angle of a new design.
     
  8. dskira

    dskira Previous Member

    Paul, pretty cool:)

    [​IMG]
     
  9. Paul Kotzebue

    Paul Kotzebue Previous Member

    Thanks Daniel.

    I think boats should be cool ... like this one of yours:

    [​IMG]
     

    Attached Files:

  10. dskira

    dskira Previous Member

    I agree hundred per cent. Thanks
    Daniel
     
  11. gonzo
    Joined: Aug 2002
    Posts: 13,726
    Likes: 419, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The problem with many of those formulas is that they use formulas for static conditions. At different speeds the wave form changes. When the trough of the wave is in the middle of the hull (around hull speed) it decreases the floatation of that area. It means that the hull stability decreases. Tank testing and experience on a hull type usually prevent boats that become too tender at speed.
     
  12. dskira

    dskira Previous Member

    I agree Gonzo, but we have to start somewhere. The formulas are not the answer, but are a guide. We can't start by sailing, then designing, we have to start with the design.
    I agree that experience by sailing on other hull is necessary, if you don't be to comfortable with your experience and just repeat the hull over and over, as do to many designer. The fear of mistake, well documented.
    A "formula" by experience is as detrimental.
    Cheers
    Daniel
     
  13. gonzo
    Joined: Aug 2002
    Posts: 13,726
    Likes: 419, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I agree. But there are few really radical designs that work well
     
  14. dskira

    dskira Previous Member

    I know what you mean Gonzo, and yes radical design are not always succesful.
    I was mostly talking designing boat out of the production line type, plain vanilla, boring with the same two triangular sail, no sheer, nothing to stop the eyes. Just corporate stuff, where nobody wrong, nobody right, nobody to take responsability.
    A sea of white crap with blue biminis, this is the sight of marinas today. No difference, no feeling, just the bad smell of bad barbecues the Sunday.
    That what I meant by lack of diversity, challenge and creation. Not automaticaly radical design, but different.
    Cheers
    Daniel
     

  15. gonzo
    Joined: Aug 2002
    Posts: 13,726
    Likes: 419, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    You can thank CAD for a lot of the crappy looking designs.It made the job of designing look-alike boats too easy. When you use a pencil and splines, being creative is part of the job.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.