Cooper Seabird motorsailor hull modifications

Discussion in 'Boat Design' started by dougseabird, Oct 29, 2004.

  1. dougseabird
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    dougseabird New Member

    I own a Cooper Seabird 37 heavy-displacement sailboat and have decided that its performance upwind is too painful to bear; it won't even tack much of the time. It also makes a lot of leeway going to windward. I love everything else about the boat so I want to try modifications to the hull (full keel, 4' draft) like adding a couple feet of "fin" keel or extending the rudder. I know other Seabird owners have modified their hulls for the same reason, even adding bow thrusters to tack...How do I get started on such a project? Thanks! Doug
     
    Last edited: Oct 31, 2004
  2. PAR
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    PAR Yacht Designer/Builder

    You have a Motorsailor not a sailormotor and you want to get closer winded performance. The very nature of sailing yachts is a large set of compromises, yet you've selected a design that is even more out on the "sailing" limb, a motorsailor, and now are asking if it can be a real sailboat. In short, no. Most well burdened craft (like motorsailors) have too much freeboard, windage, too low aspect ratio, not enough effective sail area, less then adequate lateral plane and a host of other things preventing better performance to wind then a typical sailing yacht.

    You could butcher this yacht into a better up wind boat, but the changes for just a handful of degrees may be more then you or the craft can stand.

    As a general rule, folks will do all kinds of things to their yachts and have wild explanations about the effectiveness of them. Most are shear speculation or folly, not living up to the test of calculations or time. If a bow thruster is needed to tack, you should get a clue about the boat's abilities as a sailing vessel. Most motorsailors are power craft with an assist from the rig to decrease fuel consumption during passagemaking. It's difficult making a Pinto into a Corvette, but it can be done, but will likly make what you enjoy about this yacht, less enjoyable. A gentleman will crank up the engine when going to wind . . .
     
  3. mattotoole
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    mattotoole Senior Member

    PAR, I don't think those "motorsailor" characteristics you mention apply to the Seabird, which is a perfectly normal looking, somewhat heavy cruising sailboat. Just because of hull volume, a heavy boat that size probably can't have an effective keel with a draft of only 4'. So it seems quite possible the boat's sailing performance could be improved by modifying the keel and rudder, and maybe even the hull a little bit. (Forget bow thrusters and all that stuff.) I'd consult a competent naval architect. Or, sell the Seabird, and buy one of Cooper's better efforts, like a Maple Leaf 42! :)

    Seriously, it would be wonderful if such a project could be completed successfully, as other Seabird owners might benefit. I've seen a few Seabirds around BC, and they're attractive boats, as all Coopers are.
     
  4. Bruce Woodburn
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    Bruce Woodburn Junior Member

    How to tack a Seabird 37

    I've had a Seabird 37 for 3 seasons. I had problems getting it to point and tack until I learned to compensate for some of it's design idiosycracies.

    Please note that this is not a "heavy displacement" cruiser or a "motorsailor". With a D/L ratio of 234 and a Sail Area/Disp ratio of 15.3, it is pretty middle- of the road for a cruiser. It doesn't need a bow thruster. Even square riggers can "tack" without a bow thruster.

    Peculiarities: Large rudder that will turn 75 degrees to the centre line when hard over. This will effectively stop the boat dead in the water under sail. Don't use more than half rudder (one turn of the wheel) when tacking.

    Another peculiarity: The ballast is very long due to the shallow keel. This gives the boat a very high moment of inertia. It's slow to initiate a turn, but also overshoots the new heading.

    So, the routine is: ONE turn of the wheel to initiate the tack. Wait. Wait. When the turn begins, start centering the wheel. The rudder should be centered when the bow goes through the wind. Backwind the jib for a few seconds to push her around. Use a quarter turn of helm to slow the turn as she comes up to the new course so you don't overshoot.

    The boat (as supplied) is pathetic to windward because of poor sail shape. To get it to point, you need:
    1) Sheet the genny hard: within 4 inches of the spreader
    2) Boom vang on main (and mizzen) and traveller or bridle on the main
    3) Cunningham on the main
     
  5. Ventured
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    Ventured New Member

    Seabird info

    Bruce - I've been looking at several Seabirds online, and would be interested in talking to an owner. If you wouldn't mind me picking your brain a bit, please email me - my user name is Ventured on ya hoo.

    Thanks!

    Erlin
     
  6. Gerald Wrohan
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    Gerald Wrohan New Member

    Seabird 37

    Hi, I am a long time Seabird owner. My Father had one of the earlier ones built by Cooper in 1978 and passed it on to me in 1980. We have had many adventures! Feel free to e-mail me.
    Gerald
     
  7. Robert Bennion
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    Robert Bennion New Member

    I have a Seabird 37 built by Hardin in Taiwan in 1974 or 1976, rigged as a ketch, w/ a center cockpit and fairly tall aft cabin. My main mast is only 37 ft, mizzen about 24 ft. I only sailed it a few times before I put it up, got divorced and lots of things changed. I dont remember problems tacking and I remember tacking through 90 degrees - isn't memory a great thing !
    But the reason I am posting is that I'm finally re rigging w/ a new aluminum mast and I dont remember or find any notes referring to the mast rake. Seems like quite a bit but I'm not sure if I ever dropped a plumb line. Can any one help me with a starting point. (that forestay would be expensive to do twice) It used to balance sweetly, even when I'd drop the main.
    Another issue, related the the above, is that the hull doesnt float at it's molded waterline. ( the entire hull is molded with lines to resemble a wood hull - are the Coopers done that way? ) Even with batteries and 200 ft of chain, the hull floats about 2" low in the stern. What does that do to my mast rake? Any one else have that "problem" ?
    Also, I was told the boat was designed by Bill Garden, is that so ? I kept the over hanging eye brow that the Garden fishing boats have.
    If anyone will help, Thanks in advance. robert@broadwaytile.com
     
  8. Gerald Wrohan
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    Gerald Wrohan New Member

    My Cooper Seabird has a slight rake aft, which yeilds a fairly neutral helm. She has 200 ft. of anchor chain and a Perkins 4-108 under the cockpit and she sits fairly close to the molded waterline(unloaded)
     
  9. Bruce Woodburn
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    Bruce Woodburn Junior Member

    Hi.

    I'm surprised you have a Taiwan made Cooper Seabird 37. The story I've got is Cooper built them all near Vancouver. After making 58 of them, they sold the plugs and 2 more were made by someone else.

    My Seabird 37 sits 2" low in the stern with 220 ft of chain and a 4 cyl Lehman. Trim is not affected by the tanks which are amidships. I'm going to re-do the chain locker to make it deeper (the chain piles up and jams the winch). I think I'll load 300 lb of boulders in the bottom. It balance is perfect when under way, but the bow gets blown to windward at slow speed in marinas. I think correcting the trim might help this. Until now I've left the mizzen up in marinas and anchorages to counteract this.

    I have some origonal sales brochures with rudimentary drawings of the 3 rigs. I can scan them for you if you send your e-mail address. My rig is pretty "upindicular to the flatizontal". I suspect the balance is quite independant of the rake because of the long keel. The boat tracks well whatever I do.

    Bruce
     
  10. Randy Young
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    Randy Young Randy

    Hi Robert

    I have a raised deck pilothouse Seabird 1982 by Cooper, her designer was Peterson. She also sits low about 2 " at the stern as well. I filled the dinghy on the bow with water and it seemed to equalize things.This turned out to be about 500-600 lbs. I have not added any ballast permanently to remedy this situation.

    Generally , I am very happy with this design for cruising year round out of Vancouver B.C. I still steer from outside under the bimini most times and remain dry if not warm. I have had Rascal for 11 years.

    Randy
     
  11. Bruce Woodburn
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    Bruce Woodburn Junior Member

    I'd like to build a hard dodger or pilothouse for my open cockpit Seabird 37. Do you have a picture of your boat?

    Bruce
     
  12. Randy Young
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    Randy Young Randy

    Pilothouse pics

    HI Bruce,

    Yeah, I've got a hard dodger out of aluminum and a 2 part bimini that keeps the expanding bald spot from burning. I'll find some pics to send you. I 'll start the refinishing of the wood and the removal of the old porthole's in a couple of weeks if the weather co-operates.
     
  13. Bruce Woodburn
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    Bruce Woodburn Junior Member

    In my effort to correct the bow-up trim, I thought I'd put a few hundred pounds of something (? rock, lead?) in the void under the chain locker. Today I moved the chain and cut out the floor of the locker, only to find some one had been there before and filled it with lead bricks. Now I get to glass it over again!

    I'd like to see what your dodger looks like. I was thinking of alluminum. I can't decide how far aft to run it. Extending it with a Bimini sounds like a good idea.

    Bruce
     
  14. Randy Young
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    Randy Young Randy

    Well I've got some pics if your interested but as usual my computer skills aren't up to attaching on this site . Rascal is the pilothouse style if that makes a difference. There are some nice wooden dodgers if you want something to varnish eh ! Whats your e-mail, there are 5 pics , 1 of which is the schematic of the rig and hull.

    Randy
     

  15. DENNIS GALE
    Joined: May 2009
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    DENNIS GALE New Member

    do you know the seabird whinchat ? she had a keel addition.

    do you know of the seabird "whinchat" she had a keel addition in Monterey California.? she is now in Australia.
     
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