My 52m raised deck sloop, question of windage on superstructure.

Discussion in 'Boat Design' started by rlackey, Feb 11, 2010.

  1. rlackey
    Joined: Jun 2005
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    Location: Cape Town, South Africa

    rlackey Junior Member

    Hi all,

    Looking back, it's been 4 1/2 years since I was here! I wanted to reply to one of my old posts, but it's too old. My design is still in progress.

    I've been working on a 52m raised deck sailing yacht, I had thought I was mad until I recently saw pictures of the Rainbow Warrior III. Here's Jim Cooper's last comment on my design (please don't take offense Jim, you make a valid point, I'm just using it to open a discussion) :) .


    Jim, I've remembered your words above ever since!

    I saw this design for the Rainbow Warrior III for greenpeace and I thought of your comments on my design. This is the first raised deck sailing yacht with a lot of built up superstructure that I have seen that looks like my design.

    Someone must have thought it would work.

    Granted, she has a overall lower profile than mine, but maybe then I need to rethink my superstructure above deck a bit. I certainly don't think my design in concept is too far out of the ballpark.

    My design are the two plain grey renders on these attached images, the other two are the Rainbow Warrior III.
     

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  2. rlackey
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    rlackey Junior Member

  3. marshmat
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    marshmat Senior Member

    Hi rlackey, good to see you back here :)

    Regarding RW3 - As with her predecessors, she'll be able to sail, but it looks like she's more motorsailer than sailboat. The powertrain is interesting- a projected 10 knots on the 300 kW diesel-electric system, with a direct mechanical connection to an 1850 hp diesel when speeds up to 16 knots are needed. My guess is she'll sail OK on a reach or a run, and switch to power going upwind.

    Your boat certainly shares some similarities; she could be a very versatile craft but I wouldn't get too optimistic about sailing performance to windward. When the mission is "get to the next port by Tuesday", you'll be firing up the diesel. When the mission is "have fun and attract photo aircraft", out come the sails. The best of both worlds, for the sort of person who can afford a 52-metre yacht.
     
  4. rlackey
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    rlackey Junior Member

    Hi Matt,

    Thanks, glad to be back, and thanks for the enlightenment and reality check. I'm seriously considering getting rid of my enclosed pilot house right on top and making that open.

    I suppose that is the reality of a vessel like this, one makes compromises and so if I make peace with the fact it's a motor-sailer, I'll get further with it.

    Rich :)
     
  5. marshmat
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    marshmat Senior Member

    If you can make peace with it being a motor-sailer, that might make sense. Good windward performance calls for lateral resistance and righting moment, ie. a big, deep keel- not a problem in a 20m boat where the keel might draw 3 m, but in a 50 m boat.... do you really want to draw 5-6 m (15 to 20 feet) or, on the other hand, have a complex/expensive retractable keel?

    Nobody likes bashing to windward anyway; there are quite a lot of successful boats that can sail reasonably well on a reach or run but will start their engines to head upwind.
     
  6. rlackey
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    rlackey Junior Member

    Sounds good, I think I'm going to proceed on the grounds of making it a good motor-sailer rather than a bad sailing boat. I had planned a 5.75m bulbed keel, but this decision will change all kinds of things. Perhaps the expense of such a massive mast and rigging for such a large sloop is also not so practical or necessary.

    Or, I need to rethink the superstructure and keep the bulb keel and sloop rig, but not both.
     

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  7. rlackey
    Joined: Jun 2005
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    rlackey Junior Member

    I suppose I've been also looking at the arrangements of large sloops such as the 56m Parini built "Salute" which has a fair bit of structure built up on top, actually almost all the Perini's of this size. If I lost the enclosed top level, I probably wouldn't be far off the big Parini's... but then I'm not sure. I'd have to superimpose them above their respective waterlines and compare profiles.

    My stability calculations do tell me I have a bit too much mass up top as is. I know that.

    Hmm.... I don't know, what to do, what to do...

    I know at least that the hullform, a radius chine for steel or aluminum construction I am totally happy with, it went through countless design cycles and is exactly where I want it. As a note, the stern looks pointed, like the hull is double ended, but below the waterline up to just above it is rounded.

    I'm going to give this some serious thought, and see if anyone else will respond with some more insight, just to add to the discussion.
     
    1 person likes this.
  8. dskira

    dskira Previous Member

    Very eleguant. Why not going ahead as a fantastic motoryacht?
    Daniel
    [​IMG]
     
  9. Capt JZ
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    Capt JZ Capt JZ

    Yes, that would not be a bad looking motor yacht.
     
  10. dskira

    dskira Previous Member

    She has a "Savarona" flavor.

    Daniel
     
  11. tom28571
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    tom28571 Senior Member

    How does the windage compare to that sported by old 18th century sailing ships? No so bad, I'd think. They did not go to windward at all well either and had very poor keels for that. Large Chinese junks were a bit better and had much better appendages. Much of the sail drive is going to be spent in overcoming the windage though.

    It is way too much money to trust to guesses. Some serious modeling and NA work is in order.
     
  12. apex1

    apex1 Guest

    ...and would probably benefit from having some steadying sails (doubling as a "coming home" propulsion)

    [​IMG]

    Regards
    Richard
     
  13. Capt JZ
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    Capt JZ Capt JZ

    Yes to the masts, for getting home and stabilizing and also to the "Savarona" similarities. The "old style" lines are more fluid and have not fallen with the "dated" look of the Bannenberg stuff.
     
  14. rlackey
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    rlackey Junior Member

    Wow, she is beautiful! This is almost exactly what I envisaged from the beginning in terms of overall style. In my case, not so much superstructure, or certainly not built up quite so high above the waterline.

    I had thought that this classic aesthetic and style with modern build and finishes could be applied to a luxury sailing yacht, but now as this thread is suggesting, I am thinking a motor yacht, or at best a motor-sailer is what I've got.

    I spent months and many design cycles with the current hullform (most of the work went below the waterline) to achieve the desired critical ratios, volume and wetted surface area to suit sail power rigged as a sloop (granted with a large hydraulic lifting keel... but no larger than most modern sailing yachts with record setting mast heights of this LOA).

    As a motor yacht all of that doesn't really matter anymore.

    I haven't had a lot of time recently to put into this, but I am certainly very helpful for all of your input.

    Thanks!

    Rich
     

  15. rlackey
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    rlackey Junior Member

    I'm also hoping to bring a new take on this style, something re-interpreted in a more modern, cleaner way. It's hard to put what I'm seeing in my mind into words. I think some 3D renders are going to say best the design I've got in mind, but there is a lot more modelling to do before I can share more.
     
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