Narrowing the beam

Discussion in 'Multihulls' started by Dr. Peter, Apr 1, 2010.

  1. Dr. Peter
    Joined: Mar 2010
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    Dr. Peter Junior Member

    G'day
    I live quite a distance inland and so trailering my boat is a very sensible option for me. I can sail at my local lake, or head 2-3 hours south to sail in Port Phillip Bay, Melbourne or travel even further to the Gippsland Lakes, which is a great sailing location. I'm by no means a bluewater sailor.

    I rather like look of small camp-cruiser type Wharrams. What I don't like is the amount of time it takes to demount onto a trailer, or re-assemble ready to sail. One owner quoted a half-day plus for a 23 footer when I asked the question. To my mind that rather takes the spontaneity out of going sailing, even at my local lake.

    I suppose I could pay for a marina berth, get a swing mooring, store it on a custom trailer on the hardstand, but like many people I like my boat where I can tinker with it. At home.

    Small camp-cruiser Wharrams tend to have their accommodations in the hulls. My idea is to reduce the beam to 2.5m (the legal limit) so that the boat can be launched and retrieved from a trailer, so the only thing I have to do is raise the mast.

    I guess it wouldn’t be right to call the boat a Wharram anymore.

    I know I would have to reef earlier than usual but I do rather like holding onto a low flying a hull if I can (I also have a 14ft Maricat - (surf cat style) which I race around the cans).

    I’ve followed a thread about widening the beam and one contributor spoke of shortening the hulls instead. I don’t want to do that I'd be interested in the thoughts of forum members, especially anyone else who has tried narrowing the beam on a cat to get it onto a road legal trailer.

    Peter
     
  2. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    Good timing Doc, Ray Kendrick has just put his trailerable cat back on the Team Scarab website,
    http://www.teamscarab.com.au/5.6cat/design.html
    You also may want to Google the Goudgeon 32 here on Utube http://www.youtube.com/watch?v=qYmKqu4zIs8
    Just to show how big you can be and still be trailerable !
    The Gougeon 32 was a production boat but I'm sure you could find a designer to help if that was the way you wanted to go.
    Cheers,
    Reuben.
     
  3. outside the box
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    outside the box Senior Member

    Have you thought of folding?

    jamez
    Senior Member Join Date: Feb 2007
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    Location: Auckland, New Zealand

    This has been a most excellent thread.

    Re. Folding cats c. 7 to 9 metre there have been a few different goes at this. This is the one (Ezifold) I've seen most recently which was just posted on our NZMYC website. Anyone know anything about them? (Note: the 8.5 design referred to is not the pod-cabin boat shown in the graphic)

    http://www.multihull.org.nz/image-ga...llery-1005.htm
     
  4. basildog
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    Location: Gold Coast Australia

    basildog basildog

  5. Dr. Peter
    Joined: Mar 2010
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    Dr. Peter Junior Member

    Clarification

    I particularly referred to small Wharrams 'cause I like the look of them. What I don;t like is the time required to demount and / or reassemble them.

    I have seen the Waller 670 and Jaracts but they are trailerable cats and not really the style of boat I am after. I want an open wettish boat that I can camp in overnight.

    The folding beam idea is interesting if such a system can be retrofitted. Any ideas about that? Otherwise, I want to shorten the beams so that the boat can be trailered legally in Australia. That means a width of 2.5m.

    Hope this clarifies my position.

    Peter
     
  6. outside the box
    Joined: Dec 2008
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    outside the box Senior Member

    Hi DR. Peter
    With regards to Ezifold being retrofitted to your style of catamaran.
    The system is retrofit able, we have carbon options for beams and sockets and an option for alloy beams and sockets.
    The system is only available as a ready-made kit supplied with the scantling specifications (undertaken by High Modulus) for the socket reinforcing areas in your hulls of choice.
    High Modulus undertake the engineering for the carbon beams and sockets and the engineering for the alloy beams and sockets being undertaken by our in house engineer.
    If you wish to discuss your design needs further email us on
    ezifold@vodafone.net.nz
     
  7. cavalier mk2
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    cavalier mk2 Senior Member

    Adding length increases stability, if you must be narrow go long.
     
  8. Dr. Peter
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    Dr. Peter Junior Member

    Response To Posts So Far

    I suspect the ezifold option will cost more than the Wharram. I really like the look of the Wharrams but they have another thing going for them - they quite a cheap buy, as a second-hand prospect.

    The comment about going long as possible makes some sense to me. If don't want the lee hull to bury then I need to get some moveable ballast, me. As far from it as possible.

    There's a trailerable cat called a Windrush 600 - it has tramp nets and very basic internal spaces in the hulls. I have sailed against one, it went really well. The guy I know sleeps on the tramp mat in good weather. Has anyone done more than that?

    Peter
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    The native proas had quite narrow beam to length ratios. A wharramesque pacific proa wouldn't bury the bow and a 30' footer could have a cabin in the long hull. A tent on deck works like a tent anywhere else, I've seen them on beach cats but why not sleep in the hull so you don't have to pack it all up ?
     
  10. Dr. Peter
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    Dr. Peter Junior Member

    Hey Cav,
    Thanks for the reply

    "I've seen them on beach cats but why not sleep in the hull so you don't have to pack it all up ?"

    That's the goal. Trailerableand reasonable camping - 'in the hulls'. It will also make the boat open and bit wet.

    You say these proas were narrow. What sort of Length Beam ratio are we talking about here?

    Peter
     
  11. cavalier mk2
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    cavalier mk2 Senior Member

    Very narrow, I'll check my files tomorrow but some were 4/1 to 6/1. I think it had to do with available materials and the fact that they carried large groups on deck so couldn't have big unsupported spans with the materials they had. One craft I'm thinking of is a flying proa from Tonga that had a respectable section hull for the ama, good if you get caught aback. Another common thing is for the mast to be offset from the lee hull so the buoyancy from the lee hull as well as the ama lever arm are keeping you upright. Make some models in the 3' - 6' size range and test them out. You could try outrigger style etc.. and inexpensively figure out what is worth pursuing for your needs.
     
  12. Dr. Peter
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    Dr. Peter Junior Member

    Length : Beam ratio

    Cav

    Assuming an 8 ft (2.44m) beam to stay legal on the trailer

    A length : beam ratio of 6:1 as you suggest is one long boat - too long for a trailerable cat I would suggest. And getting a long way from the spontaneouly launchable boat I was after.

    I ran some numbers for a likely range of trailerable sized boats

    Length : Beam ratio for a

    20 footer = 2.50:1
    22 footer = 2.75:1
    24 footer = 3.00:1
    26 footer = 3.25:1
    28 footer = 3.50:1
    30 footer = 3.75:1

    Are these reasonable numbers. I'm also mindful that as these boats get longer generally the volume of the hulls increase and the actual gap between the hulls could be quite small. I wonder what that means for the boat's sailability?

    You say go long - and I agree with that. But I suspect there is a limit.

    Dr. Peter

    to get a
     
  13. redreuben
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    redreuben redreuben

    Re- How Long, did you look at the Gougeon 32 ?
     
  14. magwas
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    magwas Senior Member

    Corsair F24 is another boat you might want to take a look at.
     

  15. cavalier mk2
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    cavalier mk2 Senior Member

    I think you should establish your max size and work with the variables to get a reasonable compromise. The Gougeon 32 is an excellent example of compromise. The hulls a very narrow to minimize wave generation and interaction between the hulls. If you went to a 12/1 hull ratio there would be minimal wave interference, on a 32 foot hull that is 2.6' wide, room for a footwell and cabin on top. The gougeon hull are narrower, a 16/1 still gives 2'.
    If you want to go the trailer route and don't want to build or want to see how long you can trailer check out the old MacGregor 36' catamaran. Over here they are fairly inexpensive and with good sails very fast. Someone raced one around here recently and they were cleaning up on all the new boats including the Farrier crowd.
    Stability is also a function of weight, the Polynesian approach was a lot of deckhands and I think the G32 used water ballast. Ultimately the simpler your boat is to launch and rig the more you'll use it. The outboard bunch get to launch their boats and turn a key, the closer you can come to that the more time you'll spend sailing.
    I like the F22, another approach with a less expensive folding mechanism is the Horstman Tri-Star 23/25 or the Tri-Star 26MT. They can be folded afloat and you don't get the ama sides near the water.
    The first question should probably be, "How big is your car ?"
     
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