well balanced catboat

Discussion in 'Sailboats' started by adriano, Jan 5, 2010.

  1. adriano
    Joined: Aug 2009
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    adriano Junior Member

    Hi there,
    Amount of Lead is a rather matter of experiences in boat design, which I do not have much. Nevertheless I would like to design and build a catboat in epoxy strip planking. approx. 5 mt. long and over 2 mt. beam, shallow draft, lifting centerboard, traditional plumb stem and cat rig.
    Given the fact that wide beamy boats tend to have strong whether helm when heeled, lead (CE forward the CLR) should fall in the 10-20% range?!.
    Could anyone suggest what the proper amount of lead should be in this case?
    I appreciate yr help.
    Adriano :)
     
  2. PAR
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    PAR Yacht Designer/Builder

    Without lines and sail plan it's a big shot in the dark and you 10% to 20% range is huge target to hit.

    15% - 20% would be much better with 17% if she's a gaffer or very low aspect Bermudian likely being close. Given your inexperience, you should permit considerable adjustment in the base of the mast step. This isn't especially scientific, but is quite effective.
     
  3. Paul No Boat
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    Paul No Boat Junior Member

    I'm listening as I am still in love with the catboat. Carry on, Gentlemen.
     
  4. PAR
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    PAR Yacht Designer/Builder

    I figured you show up Paul . . .
     
  5. Paul No Boat
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    Paul No Boat Junior Member

    You know me already, PAR
     
  6. PAR
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    PAR Yacht Designer/Builder

    You're a curved butt kind of guy Paul. It's nothing to be ashamed of, you just like big butted babes . . .
     
  7. adriano
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    adriano Junior Member

    Thanks a lot Par, very helpful as usual!
    Definitely she should keep the traditional "gaff cat rig", so you're suggesting to stay on the higher side
    Actually I am a very passioned sailer throughout my life and the scientific part
    of a sailboat has been always attracting my interest.
    On top of that, frankly I cannot resist the beautiful sheer lines of those lovely "century" catboats designed by Gil Smith! This is what I am looking at but in a modern, light composite construction (do hope other G.Smith's lovers will be not too upset), this is a challange/learning process for me. I am sketching/designing by hand tools and once I feel happy with the lines I'll put it into computer data through friends. At that stage I would like to come back for yr kind comments.
    Thanks again
    Adriano
     
  8. PAR
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    PAR Yacht Designer/Builder

    I'll assume you'll compensate in your hull form choices, to account for the much lighter build methods and materials.
     
  9. gonzo
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    gonzo Senior Member

    The later designs were extreme for racing. They didn't handle as well as the early workboats.
     
  10. Paul No Boat
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    Paul No Boat Junior Member

    Yeah, I admit in my younger days I looked for the sleek aerodynamic look but now approaching 60 I like em for comfort, not speed.

    A catboat kind of fits the conditions we have here in the midwest with glass smooth lakes and light breezes. rarely above 10 knts and when we do have winds in November and March they are very predictable.

    In an experimental mood I just can't stop thinking a catboat would make a nice split keel boat. Kinda squat on the shore if I ever did get to tidal waters.

    All the years I lived just off Lake Michigan I wish I had gotten into this stuff sooner. But we do have some interesting lakes and major rivers within driving range.
     
  11. SeaJay
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    SeaJay Senior Member

    Lead for a Cat Rig?...the question I've been to embarrassed to ask! Actually I did ask Tom Wylie and he was kind enough to sketch out a couple of his thoughts but this whole subject of lead is just the sort of black magic that delights me in this age of punch-it-into-the-iphone-app and get an answer.

    Adriano,

    Have a look at Wylie's site

    http://www.wyliecat.com/models/wylie_17.html

    These aren't your traditional cat boats, but I think the update of the rig really deserves more recognition than it has received. Wylie told me that a he heard sailboat owners saying all the time that they wanted simplicty in their sailing lives, so he came up with his Wylie Cats. They are beautiful boats that go like a bat-out-of-hell, but apparently just haven't broken through to the more general boating public. His 65' cat-ketch rigged Derek. M. Baylis, is in my mind, one of the finest modern designs around. I love this boat and if I ever hit the lottery, I commission a sister ship in a heart beat.

    Par,

    I'm planning on a modest cat rig on my 46' motorsailer...SA/D ~ 16. I've looked at Wylie's boats carefully and he was kind enough to take a look at my design and planted the stick where he intuitively felt it should be. I've done the calcs according to everything I've been able to read and don't think I'm too far out of the ball park, but still feel I should leave some adjustment as you have suggested. The problem I have is that I think that adjustment will likely be aft of my proposed starting position which also happens to be at the foward bulkhead of the vee berth. Can you suggest a not-too-complicated way to accomodate adjustment? Keeping in mind that the mast is keel stepped.

    As the cat rigs can have a lot of roach, is there a more accurate way of determining the CE of the sail other than the tradition method of bisecting the opposite sides of the triangle? It would seem to me that a sail with a lot of roach would move the CE aft which is what I think I am after. Any scraps of info on this subject that you could throw my way would be most appreciated!

    Best Regards,
     
  12. PAR
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    PAR Yacht Designer/Builder

    An adjustable step isn't a particularly difficult engineering problem. A longitudinal slot, where a mast heel tenon rides could solve the problem easily enough and retain athwartship relationships. The heavy beams on either side of the partners, should have sufficient room to permit wholesale mast movement, in addition to radical rake adjustments. Consider leaving this portion of the finished decking off the boat, until you dial in the rig's final placement.

    I would strongly recommend against the cat rig on a 46' yacht. A divided rig cat, sure, but not a single stick. Just too much area to have to handle in a quickly building blow.

    Calculate up the area within the roach and see what percentage it is of the total. If significant, add it to the CE calculation, but I wouldn't bother unless well over 10%. Don't get too caught up in the CE, CLP relationship. You're attempt to be precise isn't warranted or necessary. The reality is the damn thing moves around so much (especially on a cat), that it really doesn't matter, so long as you can get the helm to balance with 3 or 4 degrees of rudder incidence in force 4 winds.
     
  13. SeaJay
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    SeaJay Senior Member

    Par,

    I hear what you're saying about the single sail cat rig on my 46 footer. I agree that I'm at the max for a single sail. Wylie's 48' cat has 977 sf (100% SA) and 1295 sf actual (including roach and luff round). So as you can see, his roach is about 25% of his total area. I'm figuring on about 735 sf (100% SA), with a similar cut sail. His displacement is 14,500 lbs, I'm at about 21,000 lbs. A performance sailboat mine is not. I'm happy to drift along where the wind blows kindly. When not, I'll retire to the pilot house and fire up the D-sail.

    I considered a ketch rig, but didn't want the expense, complication, and intrusion on layout that it imposed. I will have to watch the weather carefully and reef early, but I'm not crossing oceans so I can accept these limitations.

    I really appreciate your comments on the probable futility of calculating the optimum fore and aft position relative to CE and CLP. I pretty much came to that conclusion myself but it carrys a lot more weight coming from a pro such as yourself. I've thought about leaving the deck unfinished but haven't figured out how I might accomplish it without a lot of fuss. I will give it some more thought. I think my real problem is that if I think the stick needs to be moved aft, I'm in a bit of a pickle with my accomodations. I could do it but I'm hoping I don't have to. Nonetheless, I'll figure out a way to leave some wiggle room if the thing really develops a nasty lee helm.

    Best Regards
     
  14. PAR
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    PAR Yacht Designer/Builder

    A cat ketch is about one of the handiest rigs of all. I think there are better cruising rigs, but the cat ketch is high up on the list. A 1,000 sq. ft. sail is not a cruising sail. Sometimes you don't have the luxury of reefing early, you just get "caught". This much area in a cat rig is just asking for trouble. Will you use a fork lift to get it on and off the boom? Cruising is the ultimate in realism. You either can do it your self, unassisted and without power or you're probably screwed. Everything about a single 1,000 sq. ft. sail suggests power, lots of it. Divided into a cat ketch, these ~500 sq. ft. sails are still heavy and difficult to manage, but doable.
     

  15. SeaJay
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    SeaJay Senior Member

    Par,

    I'm using a wishbone boom so forklift is optional;) I know this sail is larger that would be found on more conventional rigs, but I am confident that with the proper set up, it will be manageable. My 735 sf (100% SA) is actually a bit less than the Nonsuch 36

    http://www.qsl.net/k3os/ns36/ns36.html

    ...and it is between the sails on the Wylie Cat 39 and Wylie 44. My sailing is primarily on SF Bay. I occassionally poke my head out the Gate and head south to LA, but the weather is generally pretty predictable and steady. If it looks bad, I leave the sail(s) down and motor...I'm not a purist in these matters. Nonetheless, I will take your comments under advisement and keep them in mind when rigging.

    Best Regards
     
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