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Thread: Tongue and Groove Instead of Plywood

  1. #1
    Join Date
    Jan 2002
    Location
    Washington DC
    Posts
    17

    Post

    I need to replace the previous owners botched ply and fiberglass coachroof repair. I am considering Western Red Cedar tongue and groove covered with canvas. The coachroof was origionally 1/2" plywood and I am not sure what it was origionally covered with.

    Am I asking for too much trouble varying from the origional design for plywood?

    The boat is a Cheoy Lee Burmuda 30. The coachroof is in two parts, roughly 5'X8' forward, and 6'X6' aft. Roof beams, 1-1/2"x1" are placed 10"oc and have a good camber.

    I know that the tongue and groove would need to be thicker than the plywood. Maybe laterally strengthen the roof beams around the mast? ...is this is more complicated?

    If I did go with toungue and groove, what should the plank width be? Is there a reason the width should be narrow (2") or wide (4")? Or is this solely a matter of taste? Is there a "for the sake of tradition width?"

    Thanks,
    Whenever in my bunk, I look at the hardened epoxy drips, checked fir plywood, missed screws partly angled out of the beams, exposed plywood seams, and think how nice tongue and groove would look.

  2. #2
    Join Date
    Feb 2001
    Location
    Dana Point, CA, USA
    Posts
    379

    Post

    Sure it would look nice, but the designer of the boat designed the coachroof with plywood in mind. it has tremendous strength for the application. The ply is usually glassed (or dynel or canvas) for rot resistance.

    Using tongue and groove would seriously underine the strength of the coachroof, and cause it to flex no matter how thick it is. Since ply derives it's strength from multiple layers of opposed grain wood glued together, it is hugely strong for stuff like decks and cabin tops.

    IMHO, put the tongue and groove between the deck beams on the underside for that pretty overhead look.

    Also, it was probably built originally with two pieces of 1/4" not a single 1/2" piece. Usually they sandwich two layers in. My boat has 5/8" forward, 1/2" on the doghouse made up of two layers.

    [ 05-27-2003, 06:30 PM: Message edited by: Adam C ]

  3. #3
    Join Date
    Jul 2001
    Location
    Seattle area, Washington State
    Posts
    2,825

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    What I've done is buy the sheets cut to look like paneling, about 3/16", and put that down first, prefinished. Then laminate a couple sheets of 1/4" (or 5-6mm if fancier than fir) over the top and glass. It's very easy to work with the thin sheets, and very strong once the three of them are glued together. You can use an electric or pnuematic stapler and 9/16" staples (I leave them in- GASP!!) to put the whole thing together. A layer of 7-10oz. glass over the top should keep the water out for a long time.

    The cedar really isn't very strong for this application, especially if covered with canvass. Glass and epoxy would be a better choice, but ply is best. Yeah, I know, they used to use it for small boat decks, but most larger boats used fir or teak which are much stronger, especially compared to the fast growing young cedar you're most likely to find these days. |Have fun! [img]tongue.gif[/img] [img]smile.gif[/img]

    [ 05-27-2003, 07:12 PM: Message edited by: Conrad S. ]

  4. #4
    Join Date
    May 2000
    Location
    Cummington
    Posts
    4,518

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    The Bermuda 30 is the Choey Lee version of the LFH H-28. The H-28 is drawn to have house beams 3/4x1 1/2 on 9" centers with the house deck being t&g pine 5/8 or greater 2 1/2 or less wide, canvas covered.
    The reason for the narrow plank is to better follow the beam camber and to minimize the effect of movement in the pine. The canvas covering is an important structural element as well as being a water repelling agent. Your beams are heavier and slightly farther apart, evening out the difference. If a deck is to be walked on much a thickness of 3/4" or more would be expected by LFH. The t&g works to keep the planks fair, protecting the canvas.

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