Cruising Bilge Keeler

Discussion in 'Boat Design' started by lewisboats, Feb 11, 2008.

  1. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Sometimes I hesitate to show a possible design because of the percieved impression that it is simply a "pretty picture". I do consider more than the skin when showing something that I have done although I may only be able to display it with a "pretty picture". I am currently working on a 20 ft bilge keeled cruiser for two (+) and am past the "pretty picture" phase and on to weight calcs and accomodations, along with sail and keel placement. It should displace around 2500 lbs with a max displacement of 3000lbs and a dry trailer wt of 1700 lbs. I would still like some first glance impressions of the "pretty pictures" just for shits and giggles. Many folks have commented on the "unconventional" shapes of some of my stuff but I think this will manage to get close to fitting into most folks idea of close to conventional. While the pictures don't show the details, I have drawn on paper a 12.5 ft cabin interior which has a 6.5 ft+ Vee berth forward, two 7 ft quarter berths, a small galley with a folding table and some cabinet space and plenty of storage under the three berths and a possible enclosed or partially enclosed head. There is also a folding 4 person cockpit table which stores adj to the cockpit seats. The 7.5 ft cockpit sole is self-draining and has quite a bit of storage aft of the Q-berths. There is room for flotation in the transom area and forward under the Vee berth and plenty of storage in between. At 7.5 ft beam and 1700 dry wt the boat is quite trailerable and designed to float in 2+ ft of water and ground on the level for stable semi-beaching in wadeable waters. Sail configuration is Bermuda sloop (200 sq ft) or High peaked Gaff sloop(225 sq ft) with Jib and/or Genoa. I hope to have a detailed set of plans for this boat available in the next 6 months (give or take a year or so). The different profiles are due to the developablility of the panels and the portions that aren't so developable. The bulkworks are added after the panels are in place :) . As of right now I am simply looking for initial impressions of the purpose vs suitability of design and build. The boat is designed to be built with 9 mm plywood... with S&G West style being the most favored method of construction. The keels are of Steel plate as is the skeg/rudder protector/third leg. The keels are of two 3/4" or three 1/2" plates welded together and the Skeg is of 1/2" to support the aft when grounding. Total steel ballast is in the order of 800 lbs or so and is easily obtained locally (most places will cut up to 3/4 " with a laser... no problem). A flange is welded to the keel fins which conforms to the hull and bolts to an interior flange and frame which spans the width of the hull and provides transverse stability. Each fin is demountable for repair/replacement.




    Oh...btw....the boat is called H (subscript) 2...OBO)(H2OBO) or Water HOBO

    Steve Lewis
     

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  2. Kay9
    Joined: Oct 2006
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    Location: Central Coast Oregon US.

    Kay9 1600T Master

    Just an opinion here. It looks a bit top heavy. Once you put a mast on I would be worried about the stability of this shallow of a hull. I suppose you could use water ballast to try to keep it light on the trailor.

    K9
     
  3. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    The overly asymetrical waterline will make downwind control difficult, prone to broach, and hull balance poor. Filling out the foreward waterlines would help a lot.Rudder and skeg look good, but a slight traditional rake on the rudder would make a self steering vane simpler and more effective.
    Otherwise she looks good .
    Brent
     
  4. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Thanks for the replies. There are a few designs out there that have similarities that are successful (Vagabond 20 comes to mind), so I don't think I'm breaking any new ground here. The total ballast should run around 700 lbs and construction is of 9mm ply, it only sticks out of the water 4 ft and has a waterline beam of 6.25 ft so it shouldn't be overly top heavy. As to the waterline...in the picture look at the second line, not the outline and you will see that the forward waterline is fuller than it appears at first glance... see picture of bottom below.I'll look into that rudder.

    Steve
     

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  5. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    Calculate the centre of buoyancy when the boat is heeled 25 degrees. If it moves aft, you have poor hull balance, and will have poor directional stability.. If it stays the same or moves slightly foreward as the boat heels , you have good hull balance and with that good directional stability.
    Brent
     
  6. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Applying your suggestion I find that adding more waterline beam forward wasn't enough but by adding a wedge which creates a 3rd chine for about 1/3 of the length of the hull forward of the stern I can reduce the buoyancy aft and move the CB forward while only minimally affecting the internals and maintain the ability to easily use plywood.

    Steve
     

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  7. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    Looks good
    Brent
     
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