Pilot house roof camber.

Discussion in 'Boat Design' started by FAST FRED, Nov 19, 2010.

  1. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Sadly my copy of Skeens is become lost , so the following question.

    Our lobster style boat has a pilot house of about 10ft x 10 ft.

    When built the pilot house roof was done with simple 2x4 lumber.

    There are no loads (except an occasional visit to wash it) but over the decades it has sagged , to the point of leaking.

    I will be using 2x10 or 2x12 lumber to create a new roof , but this time I will be cutting the wide boards to properly camber the roof.

    In 10 ft what would be a good camber to use?

    The lumber will be band sawn to about 3 or 4 inch depth , or less if that is advisable.

    6 overhead beams are contemplated.

    Suggestions?

    FF
     
  2. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Skene:
    C=Crown at B= 1/4" to 3/8" per Foot of B

    BR Teddy
     
  3. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    I generally use 1/2" per ft for decks and 3/4" per ft for cabintops.
    Steve.
     
  4. tom28571
    Joined: Dec 2001
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    Location: Oriental, NC

    tom28571 Senior Member

    Fred,

    Generally I think the crown in a cabintop needs to fit in with the rest of the boat to look right. Some even look right with a roof that is flat across and follows the sheer on the long axis. It should be at least as high as the deck crown though. For strength, more is better but you know that. Put a mock up arc up there and walk around and see how it looks.
     
  5. WickedGood

    WickedGood Guest

    I made a couple of roofs for my little 30 ft Mainship/Alura Lobster Yacht

    they wer 10 ft wide.

    first one had 3 inch higher in the middle with a slope from 5" to 2 inch on the sides.

    not enough. the roof failed in 4 years of people riding on top to watch wales and jumpping on it.

    the second roof was 8 in in the middle with 2.5 inch on the sides and sheathed with 1/2 ply on top covered with 10 oz glass and luan on the bottom covered with 6 oz glass all foam cored which provides floatation and warmth when you have yor cabin heater running..

    Make the inside of your roof Flat and abot 7 feet from deck to roof you can mount Rod Racks up on it to store all your rods/reels ready to go. You can reach them easy and still have plenty of headroom.

    The only difference If I were to do it again wiould be to build in side boxes down both sides to hold a dozzen class I Life Preservers.

    It sheds big waves, rain and 4 ft of snow in the winter. Still going strong.



    I also made it 16 ft long with a 2 ft overhang over the front windshiled into which I built and electronics box and it keeps the rain,waves sun out of the cockpit.


    Built on 1 ft centers using 5/8 plywood frames all covered with resin. whish I had taken photos. Build it like a model airplane.


    Took 4 big guys to lift it up onto the boat and I imbeeded 1" thick Alum plates into the top so I could bolt it to the Alum stantion framework that my buddy welded up.


    run all your wires inside the roof for Red night lights, Nav lights, Spot lights for the deck, Stereo Speakers etc before you close the roof up. You will be glad you did

    oh and one other addidition I wish I had done was to pipe in a Hot/Cold poly water lines for a shower head on the back deck. Nice after a frigid winter dive to come up wash off whith a hot shower and strip out of your wetsuit before dragging all that salt water, urine and fish blood down into the cabin.
     
  6. Chuck Losness
    Joined: Apr 2008
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    Chuck Losness Senior Member

    Scanned a copy of the page from Skene's for you. I could also email it to you. Just let me know.
    Chuck
     

    Attached Files:

  7. michael pierzga
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    Location: spain

    michael pierzga Senior Member

    Also consider that you have camber for strength, aesthetics and interior headroom. Interior headroom, with a bit of air space over the top of your head while standing out on centerline makes a nice summer boat. Camber is a good way to keep the lines of the wheelhouse top low and add head space inside..
     
  8. tom28571
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    Location: Oriental, NC

    tom28571 Senior Member

    Fred said he is going to use 2x10 or 2x12 lumber for the beams and that will not increase headroom. I don't think all that mass of beam is necessary. Laminated beams to give headroom will be plenty strong enough. If combined with 6mm ply top and 4mm bottom, 3/4" foam and 3/4" laminated interior transverse beams, that will be plenty strong and provide both headroom and insulation for northern cold and southern sun. That is the way I design and build crowned cabintops and they work out well.

    If heavy stuff is going to be mounted up there, the top ply and beam scantlings can be increased a bit but not much more will be needed for anything reasonable.

    Fred, I will be happy to email you a drawing of the construction if you are interested.
     
  9. rasorinc
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    rasorinc Senior Member

    Be sure to put a fiberglass layer on the roof--7 pound is good--then cover with UV resistant paint. Good for 20 years.
     
  10. michael pierzga
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    michael pierzga Senior Member

    Ya sure....with correctly framed ,double skin plywood construction, its possible to achieve a very strong, Thin, lightweight structure roof. Worthwhile . also acts as a good heat insulator and hides any overhead wiring and gains light fixture space.
     
  11. Submarine Tom

    Submarine Tom Previous Member

    I used 6 inches over 9 feet with the outer 2 feet (on each side) being straight.
    I also made curved beams out of three laminates of 3/4" spruce screwed and glued on a jig. Spring-back when removed from the jig was almost one inch. I used epoxy and removed all the screws between layers.

    Worked for me.

    -Tom
     
  12. apex1

    apex1 Guest

    If it "hides" wiring you have done it wrong. Wiring should be accessible.


    Tom is right, 6mm top and 4 bottom can make a stron top at this size. Laminated beams add to that.

    And put mineral wool in as insulation. Foam can crumble into pieces after a while, the Wheelhouse always sees some flex and movement in the structure. That high above the sea the wool will not soak with water.

    Regards
    Richard
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Tom that's very similar to my typical roof scantlings.

    Richard, wires should be out of sight, but accessible and retrievable. The cored roof panels Tom mentions is a classic example, the wiring is hidden in a chase, usually PVC conduit and this is accommodated in the core. Naturally a "fish" or leader string is also included with the wire bundle so upgrades can be pulled through the chase without difficulty. I've upgraded many of my wiring jobs and "pulled" new or repair wires though chases many times. They (the wires) don't have to be visible, to be safely accessed or retrieved.
     
  14. Man Overboard
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    Man Overboard Tom Fugate

    I learn a lot of great tips by reading PAR's posts, Thanks.
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Thanks for all the help.

    The beams will be trimmed inside and out to about 4 inches in depth (regardless of the camber), so the weight will hardly be more than the old flat 2x4s.

    This is not a fly bridge deck,just a cabin top , so no party of dancers will be doing the bunny hop.

    There is a need for a rather large hatch (common on lobster boats) to change an engine , but that will probably just be framed in , but not cut till required.

    The covering will be 2 layers of 3/8 ply , with (2) 1 1/2 OZ of CSM in Vynelester over all..


    So far the concept "The Bigger the Better" seems like a good one , so first I'm going to get a 10 wide and 12 wide lumber , carve both as desired and sit and eyeball them in place to see which looks better. Sounds like a beer for perspective at sunset time.

    Some of the reference books that have John Gardner boats show camber fore and aft , as well as from side to side. At this point I'm not sure I want to attempt such perfection of form..


    FF
     
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