Changing Width of Sailing Catamaran

Discussion in 'Multihulls' started by Rob Wright, Sep 30, 2013.

  1. Rob Wright
    Joined: Sep 2013
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    Rob Wright Junior Member

    Good Evening,

    I am wondering if someone could lend an opinion on changing the width of a sailing catamaran? I have a custom built wood sailing cat that is 17 ft x 9ft. I've been told the hulls are similar in shape to the 1960's California Beach Cruising Cats before Hobie really took off. I am considering cutting 6-12 inches off the cross beams to make it trailerable. Currently it takes too long to assemble and I need another adult to assist. My question is will this modification upset the overall performance and safety?

    Here are some other specs:
    17 x 9.......soon to be 17 x 8'ish
    approx. 550lbs without passengers
    20ft mast (stayed not stepped, I don't have all the terminology down)
    total sail area 122ft2 (55ft2 jib, 67 ft2 main)
    mast is mounted approx. 8ft aft of the bow
    This is a beach cruiser and even in 15knot winds will not fly a hull
    Lastly it can be a bear to tack, typical cat.

    I'd attach photos but can't figure out how to reduce their size. Any thoughts will be greatly appreciated.

    Rob............
     
  2. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    Reducing the width will reduce the stability but given what you have said that may not be an issue. You could always trapeze ?

    Narrowing the beam should also improve the tacking, but by how much I wouldn't hazard a guess.

    Further if the boat does begin to fly a hull it may be more prone to pitchpoling as the older designs did not have the buoyancy forward like more modern boats.
    That seems like a large jib ? When tacking hold it aback to help blow the bows around before you sheet on.
     
  3. keysdisease
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    keysdisease Senior Member

    "550lbs without passengers" OMG

    I was going to suggest a tilt trailer (like tornadoes use) to reduce the beam for trailering, but at 550 Lbs might not be too easy. Would change multiple operations into one.

    http://www.pbase.com/d30/image/113849074.jpg

    Instead of changing the boat, change the trailer.

    If I remember correctly a Hobie 16 weighs in at about 315 lbs.

    Steve
     
  4. upchurchmr
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    upchurchmr Senior Member

    This boat is relatively heavy and seriously underpowered with a small sail area.
    You could cut the beam and never recognize an issue with safety.

    The Hobie was 315# (maybe more) and about 220 sq ft sail.
    So you have about 75% more weight and almost 1/2 the sail. This makes it extremely "safe" for tipping over the side. Probably the same for over the nose. Nothing tips over the nose worse than a Hobie.

    Cut it and enjoy. Virtually every beach cat I know is less safe than your proposed boat.
    Of course less safe is what makes them fun. Can you get rid of some weight also? Or more sail? Find an old busted Hobie 16 and use the rig.
     
  5. Petros
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    Petros Senior Member

    the original Hobie 18 has a beam of 8.5 ft. I see no reason you could not narrow the beam on your cat. You will probably never even miss the extra ft. and you will defiantly get more use out of it if it is faster and easier to launch.

    Go for it.
     
  6. Rob Wright
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    Rob Wright Junior Member

    Thank you for all your responses. Modifying the trailer and loosing a foot on the beam will greatly increase its use. The idea of snagging an old Hobie 16 rig is intriguing. I'll let you know what I come up with.

    Rob.............
     
  7. upchurchmr
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    upchurchmr Senior Member

    Rob,

    Do you know what kind of a cat this was? Or who the designer was?
    I don't recognize the size as anything I was familiar with.
    Could you post a picture?
    I believe 8.5' width is legal maximum width for trailering in the US.

    I store pictures at Picasa.com . Whenever I attach the link to a message here it always takes it without screaming about size. Perhaps that would help.
     
  8. Rob Wright
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    Rob Wright Junior Member

    upchurchmr, I picked up the cat in february from a home builder in Indianapolis. It was advertised in Wooden Boat Mag. in the free boat section. It was complete and in great shape. I only needed to supply a trailer. He called it a Timber Cat and he was looking to sell them. However, the harsh reality of building a custom wooden boat to a rotomolded world dictated no future. He also has a garage of hand built kayaks and such. So I believe I own the only one. He said he stylized the hulls after trimaran outriggers. As I said in my original post - a guy who lived in California in the 1960's said it was a classic beach cat design - knife edge, deep hulls, lots of boyancy up front with tapering hulls astern. I will try to attach the original flyer I recieved before I committed to picking it up. It will give you a better idea of its configuration. Later I will figure out the picasa thing. It is all cedar, spruce, and marine ply. I think the limiting factor on the rig is the mast is solid cedar and getting a straight length of lumber larger than 20ft may have been a chore for him. The jib is from a lazer 20 and the main from a F18 ???? I think.

    Rob.....
     
  9. nimblemotors
    Joined: Jun 2009
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    nimblemotors Senior Member

    This sounds like the fiberglass 19ft Pacific Cat, of which I just bought one.
    This boat is only 7.5ft wide. Posting pic of one in another thread:
    [​IMG]



     
  10. Rob Wright
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    Rob Wright Junior Member

    Pictures of the cat

    Attached are some photos of the cat. Please note these were the original pictures when I first picked it up. It was not fully assembled. The photo of the guy on deck shows one of the two 3ft x 8ft hard decks. in the middle I run 1/2-in rope but no trampoline. The inside shot shows it in a narrow fishing boat configuration (approx. 6 ft wide). This is how I originally thought I would use it most but sailing is way more fun and I can still use a trolling motor in wide format if needed for fishing. So now I need to widen trailer and get it ready for next season. I will still try to post current photos later.

    Thanks for the 19ft'r photo - interesting boat. How does it sail?
     

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  11. nimblemotors
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    nimblemotors Senior Member

    yes it does look like the pacific cat or p-cat hull shape. I have not sailed one, but my research indicates they worked very well and were fast, so narrowing yours should be no problem.
    I understand Hobie fixed many of the issues with the p-cat, but sailing performance was not one of them.
     
  12. upchurchmr
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    upchurchmr Senior Member

    Are those crossarms solid wood? That would be really heavy.
    More modern boats have shown hard decks are going to be heavy, uncomfortable, and not very useful. A good tight trampoline would be better for sailing.
    The hull shape looks pretty good although a more modern design typically has a wider transom.
    You would do better with two rudders although with as small of a rig you might not actually need them.
    Most forward beams have a "dolphin striker" or bracing under it to allow the beam to be much lighter. Not necessary but lighter.

    Hope you don't mind the comments. Looks like an interesting project, especially for the price.

    Weight is the enemy in a catamaran. That was the major problem with the P-cat.

    I have a set of crossbeams for both a Nacra 5.2 and a Tornado. If you weight yours I can tell you what an aluminum set would weight. I do like the look of the wood though.
     
  13. Rob Wright
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    Rob Wright Junior Member

    Yes the crossmembers are solid wood. They are cedar or spruce. So they aren't too heavy but very stout. The hard decks help keep the whole thing square. I agree it is all heavy but in three foot swells nothing moves. Changing over to modern materials would lighten the load but the greatest compliments come from the bright woodwork.

    The single rudder is ok. There is a single kickup centerboard that mounts right behind the mast between the decks that helps with the helm when coming about. On a straight fast run I feel it just adds drag.
     
  14. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Reducing the demihull spacing can sometimes lead to a slight increase in total
    resistance. Sometimes it will reduce the wave resistance at some speeds
    (technically Froude number) but it can also lead to an increase in
    skin-friction if water tends to well up between the hulls and thereby increase
    wetted area. In extreme cases, for example in shallow water, a bore can form
    between the hulls. Even more rarely, a soliton can shoot out ahead of the boat.
    That would be wonderful to see!
     

  15. Rob Wright
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    Rob Wright Junior Member

    I find the hulls cut through the water very well. But I see and hear a lot of turbulance off the transoms at high speeds. Also the aft end of the cat sits fairly low on the water. Not sure if there is anything to do except move cargo and passengers forward. I dont recall seeing interference from wake forward. However in the narrow fishing setup it is a very wet ride due to waves splashing upward.

    I grearly appreciate everyone's insight.

    Rob......
     
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