Help: Centerboard Gaff Schooner, CLR vs COE

Discussion in 'Sailboats' started by valery gaulin, Mar 16, 2018.

  1. valery gaulin
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    valery gaulin Senior Member

    I would like to know if anybody as experience with the design and sailing of a Centerboard Gaff Schooner.
    Image 18-03-16 à 11.18 p.m..jpg
    I am trying to locate the COE and CLR. I am not sure if I should have LEAD or not. This is the pictures of my sailboat. The CLR was calculated including the rudder.

    I can provide the full 3D drawing.
     
  2. Angélique
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    Angélique aka Angel (only by name)

    Last edited: Mar 17, 2018
  3. PAR
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    PAR Yacht Designer/Builder

    Each rig, hull form type and appendage configuration will affect the "lead" you might want to carry. On a conventionally proportioned gaff schooner, you'll like about a 8 - 12% lead. Use only 1/2 the rudder's area for CLP calculations, given it's arrangement. Though not related to these calculations, I'd lower the aft portion of the "sheer" in the cabin structure, so you don't dance around on a hook or mooring. This type of hull doesn't like excessive windage aft.
     
  4. valery gaulin
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    valery gaulin Senior Member

    Thank you PAR and Angelique for your input.

    PAR: For the cabin top sheer, I am aware that this type of shallow draft hull does not like Windage. I try to keep my cabin top as low as possible to give me headroom inside the cabin. The cabin top follow the line of the bottom of my hull shape. The inetrior cabin will not have a floor or a bilge. The bottom of the hull will be the floor. I use this option to lower as much as possible the cabin height by keeping interior head room around 6'6" on center line.

    This center board schooner is 40ft LWL 11.5 ft beam, draft of 3.5 ft CB up and 8 ft CB down, 23 000lb displacement, sail area around 1000-1100 sq. ft.

    It is my solution for eventually travelling the ICW, CUBA and the coast of south America diwn to Brazil.

    I am in the desing process, will I be crazy enough to eventually build my sailboat? I don't know but reigh now I am having fun learning and drawing.
     
  5. PAR
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    PAR Yacht Designer/Builder

    A 40' deadrise boat (what it appears you've drawn) is about as big as these were ever envisioned and not the best way, to get the headroom you desire in a 40' boat. Consider using some excessive roof crown to get the additional headroom, which interestingly enough, is typically not as necessary in the companionway area, as you might think.
     
  6. valery gaulin
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    valery gaulin Senior Member

    PAR: You might be right that in the companion way area the height is probably not as critical becayse it is not really were someone actually really stand. It is just an area to get in and out, plus there is the sliding hatch at that location that is usually open when the weather permits it!

    If I understand you suggest to increase the curvature of the roof crown at that location to get the headroom?

    My hull shape is based on the line drawing of Terrapin 42 by Rueul Parker. The hull is curve flat bottom with a V shape starting at a 1/4 of the way from the bow to help cut the wave.

    My intuition is that this hull shape will like to be sailled not too heeled to get descent performance.

    Am i realistic in the hope of getting about 50 degree upwind ability?
     

  7. PAR
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    PAR Yacht Designer/Builder

    The hull performance attributes for this particular set of shapes and rig are fairly well known and it's not a great sea boat, though can make a nice shoal coastal cruiser in good weather. 50 degrees would be as good as it'll get, but don't hold your breath, depending on rig selected and, sail cut, appendage efficiency, etc. Rueul draws up a nice set of plans, though customer service and some building techniques can be easily improved, if not flat out questioned. He also uses the heavily curved roof crown trick to lower some of the visual impact, when putting full headroom cabins on shallow body hull forms. Personally, I dislike this approuch, preferring to slightly raise the sheer line and lower the cabin "eyebrow" to help hide this annoying feature, of course coupled with excessive roof crown. Lastly, don't expect this to be a comfortable ride, in a wet slosh to windward or in a storm.
     
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