22m cruising cat design concept

Discussion in 'Multihulls' started by Becaris, Aug 3, 2008.

  1. Alik
    Joined: Jul 2003
    Posts: 2,800
    Likes: 184, Points: 73, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    That was North American style, they like it :) In construction now.

    OK, this is another one, 32'. Cabin is sloped, looks sporty but volume of saloon suffer. This one is also in construction, hope to be on water in 2-3 months. We are working on 40' model now (slowly), same style.
     

    Attached Files:

  2. apex1

    apex1 Guest

    Well, this is more the taste of "average joe" here.
    But the US people even buy Nordhavn´s. I would have a problem docking besides them.
    But again, when it comes to individual taste of the average boatbuyer I am worlds away.
     
  3. Spiv
    Joined: Jun 2007
    Posts: 221
    Likes: 16, Points: 28, Legacy Rep: 207
    Location: The Big Wide Blue Brother

    Spiv Ancient Mariner

    Alik,

    The first boat is too narrow for good performance, but has got well thought superstructure.
    The second's ratio is better.
    Both have a flat bridgedeck, on planing cats it tends to slam a lot more than one like Bacari's, concept with double curves.
    I have driven most power cats made in Australia, the best ride was given by the Manta (not in production now) with a wave braker going all the way and round half bridgedeck, like riding on velvet.
    I also found that asimmetric chines (the interal are half way up the external) make it go up on the plane smoothly and break the force of incoming waves more gently.
    Anyway, lets not hyjack this thread for too long....
     
  4. Alik
    Joined: Jul 2003
    Posts: 2,800
    Likes: 184, Points: 73, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    Actually is not, we have studied that using Molland's series. At speeds over 16 kts the interference of hulls is beneficial. The most unfavourable mode for this cat is 12 kts where resistance curve has a hump. Note that design speed of this cat is 21kts. Anyway, limitation of beam originated from Customer's request - they have some restrictions on mooring space.

    I own a planning powercat myself, with flat bridgedeck :) Planning cat lifts up and should not slam (on reasonable wave) if the bridgedeck is high enough - vertical clearance c should be 2-3% of length, so c=(0.02...0.03)L. Also should consider 'air cushion effect' in tunnel that reduces slamming. For overloaded cats with low bridgedeck - I agree, they slam, but this is not a case here.

    Displacement cat needs c=(4...5)L. Displacement cat will start slamming on wave height h double of clearance c (h=2c). This was a guess that is confirmed by simulations and sea trials. So if we are talking about Aleut we should double 3' clearance - we get 6' wave!

    I understand that some would prefer wedge in the tunnel. But in practice wedge is always lower than just flat tunnel. At least, flat and high bridgedeck is my preference.
     
  5. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    Though Alik and his company have reasons to be proud of their boats and designs, this second one particularly is way off topic as it is not even a sail boat. The first one, a sailing cat of the same approximate length as my concept has some merit in this discussion from the windows standpoint and perhaps some of the layout. However, let's not lose track of what the concept is all about. In case you forgot (or didn't want to read), I'm working on the concept for a blue-water cruising sailing catamaran with these features:

    1) Electric motor driven.
    . a) Using new emerging technology batteries, lighter per watt stored.
    . b) These batteries are charged by three methods:
    ... i While sailing running the motors in reverse
    ... ii From sun using 10 kwh solar array.
    ... iii From two windmill type generators.
    ... iv From a gen set running on diesel (last resort).
    . c) In a pinch I'd also like the yacht to be capable of moving via electric motors running directly off the solar array (even if at slower speeds).
    . d) Enough battery storage to power the yacht at about half max speed for a minimum of three hours (more would be nice).
    2) Biplane style sails.
    . a) These would use carbon fiber unstayed power rotating masts with fixed booms.
    . b) Booms will be power self-furling on both of the twin main sails.

    Objectives are simple:
    1) As few ropes, pulleys, winches and stays as possible, none would be great.
    2) As few different types of sails stored as possible.
    3) Using the LEAST amount of diesel fuel as possible, none would be excellent.
    4) Short hand sailing that requires the least amount of exposure on deck as possible.
    5) Interior living space for eight people.
    6) Power sufficient to run watermakers, air, electronics, etc. without budgeting.
    7) Safety in redundant systems (including the mast, motors, etc.)
    8) True positive buoyancy design (including the weight from all the 'stuff')
    9) Efficient sailing design (hull shape, proper length to beam ratios, clearance above water, streamlined cab.

    Things I don't care about:
    1) Cost to build.
    2) Cost to dock at marinas.
    3) Sailing drawbacks of biplane rigs (everything has drawbacks, I know about the drawbacks of a biplane rig and want it for what I consider the positive sides. Others will no doubt disagree, they can build their own boat.)
    4) The joy of sailing. (For me the sails are a means of cheap, self sustaining propulsion, nothing more. The catamaran over the mono hull is a means of avoiding constant 'tilt', and when designed properly, buoyant in case of capsize or hull damage).
    5) The cost of diesel fuel and engines vs. the cost of an electric motor system (and all that comes with it. (I hate fuel docs, and will pay to avoid them at all costs) :)
    6) Having to wait to start my build until the batteries and solar panel technologies reach the commercial market.

    Anyway, those are the goals of this concept for a somewhat new blue-water cruising sailing catamaran, about 20 meters in length.
     
  6. Alik
    Joined: Jul 2003
    Posts: 2,800
    Likes: 184, Points: 73, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    For effect of BCB (beam between hulls CL) on resistance - pls see attached image. 'Base' is BCB=3.33m (case of Aleut), others are marked clearly. Prediction is done by Molland's catamaran series.
     

    Attached Files:

    • BCB.jpg
      BCB.jpg
      File size:
      128.8 KB
      Views:
      294
  7. Alik
    Joined: Jul 2003
    Posts: 2,800
    Likes: 184, Points: 73, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    Electrical propulsion - is a marketing blurb, it does not work with today's level of technology for seagoing cat. Again, there is a lot of brainwash pressure on electrical propulsion, nice concept dream however :D
     
  8. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    I'm not building today. This is a concept, and if you'll notice the last point in my 'I don't care about' section, is waiting for the technology to emerge. It is coming.
     
  9. Alik
    Joined: Jul 2003
    Posts: 2,800
    Likes: 184, Points: 73, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    Sorry to say, but this means that Your concept has no value now :)

    You can calculate windage drag of 22m cat, estimate power required to push it with head wind of 10-20kts (and wave!), and then check required electrical motor and batteries. Then, imagine the cat is passing strait of Singapore with its intensive traffic - how may hours of powering do You need, at what speed? ...

    Without engineering side, such concepts are not worth any discussion.
     
  10. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    A concept may have no value to you. I, on the other hand, believe in planning ahead. I plan to build my yacht several years from now, with that in mind I was looking forward to talking to other designers about a future concept design. In case you're not familiar with a concept, it is usually done ahead of time, and a concept often explores ideas that are not currently available. Take a look at a concept car from any car company this year and you'll get the idea. If concepts had no value, then I'm pretty sure major companies would not waste their time. If you are interested in a thread about building a current cat, well, you can easily start one of your own, but telling me that a concept has no value... well, that's just silly, seriously.

    However, as to your point about the strait of Singapore. Even projecting ahead to better batteries, which means more power storage in lighter weight, there will ALWAYS be a limit to how much stored battery power is available. What I plan for my yacht is sufficient battery storage for most of my motoring needs. I estimate that at about 3 hours or so off the two banks of batteries. If and when a rare situation arrives when I need to motor my sail boat longer than three hours, as stated above, I will turn on the Gen. Set and power the motors off diesel. I hope to not have to do this very often, but the option is always available.

    Now, since you stated that you find this concept not worthy of discussion, that's certainly your prerogative. I did not see anywhere that you were required to post. This was a friendly concept discussion, nothing more. Attacking it is a waste of both our time.
     
  11. apex1

    apex1 Guest

    Well Becaris THAT was not the statement! So, if you argue, argue about the complete statement. In this case that will be a bit difficult, yes?
     
  12. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    As stated, I'm not here to argue with anyone, including you. If you have nothing constructive to add to this concept, I'm done speaking with you.
     
  13. apex1

    apex1 Guest

    The next arrogant bigmouth!
    If you would have the ability to read, you would have noticed that I DID actually contribute to your premature dreams, and without the slightest sort of critic too! But you´re not looking for critical contribution, you´re looking for applause or fight!
    Grow up! Then come back (they will have all the technique you need then! At least I guess so, `cos 20 years can change a lot)


    Do they breed them in thousands at present?
     
  14. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    Classy, now you have degenerated to name calling.
     

  15. Becaris
    Joined: Aug 2008
    Posts: 96
    Likes: 3, Points: 0, Legacy Rep: 46
    Location: Los Angeles

    Becaris Junior Member

    If anyone else would like to get back on topic, there WAS some discussion going on about the slanted windows being an issue in the tropics. There seems to be two things at odds here.

    For example, in several of the Schionning catamaran designs there are a lot of aerodynamic slope to their cab, yet people have made good points that angled windows can add interior heat in the tropics. Is there a compromise? Like double pained glass, the exterior piece slanted for better performance into the wind and the interior piece of glass vertical? Trapping a layer of air between glass supposedly cuts down significantly on heat exchange. Comments? Suggestions? Some other option?
     
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.