Boat roof material?

Discussion in 'Boat Design' started by DianneB, Apr 30, 2018.

  1. DianneB
    Joined: Jan 2010
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    DianneB Junior Member

    About 10 years ago I refitted my 1966 Lonestar and added a hardtop over the wheelhouse and the after deck to provide weather protection and shade. The roof takes a step up between the wheelhouse and the after deck. At the time I couldn't figure out what material to use for the roof sheeting that would be 1) maintenance-free 2) have a long life 3) be lightweight 4) not heat up the interior and 5) not brake the bank. Since the refit left my bank account empty at the time, I used 1/4" plywood and the best white paint I had.

    The time has come to replace or repair the roof.

    There are a lot of different materials available now but every manufacturer claims theirs is the best but most of them give no long-term test results.

    Short of adhering sheet metal over the existing roof, what would you recommend to meet the above requirements?
     

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  2. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Ten yrsrs of service, you did it right.

    I am unsure of what the problem is.
    Is there cosmetic paint degradation?
    Is the roof failing structurally?
    If so is it systemic or localised!

    Great pic of windshield. Close ups of problem spots would be helpful.
     
  3. goodwilltoall
    Joined: Jul 2010
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    goodwilltoall Senior Member

    Plywood again with fiberglass/epoxy then paint
     
  4. DianneB
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    DianneB Junior Member

    The plywood has 'checked' in numerous places - it is just regular plywood. One corner is slightly damaged (from being parked too close to a tree).

    I hesitate to do fibreglass over the wood because of the added weight.
     

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  5. JosephT
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    JosephT Senior Member

    Hello Dianne, since you point out the 1/4' plywood you used is worn out I would suggest a couple of options.

    1. Remove the old 1/4" plywood and replace with 1/4" marine plywood. Before re-installing, be sure to apply a layer or two of fiberglass on each side of the wood to ensure it is 100% encapsulated in epoxy. All screw holes should be thoroughly sealed. Finish off with a coat of UV white paint (or whatever color you want). The fiberglass will add strength and offer better flexibility to the wood. The UV paint will protect the fibers and ensure the cockpit/helm area remain as cool as possible.

    2. Consider a cloth roof using a fabric like WeatherMax. This is a tough, water resistant fabric that resists fading. If you know a person who works with boat tops they can order this material in a variety of colors. Provided your existing frame is smooth on the edges the material can be attached in a variety of ways (e.g. tied on, zipper, velcro). WeatherMax 80 is very popular in the boating community and outperforms Sunbrella, canvas and other fabrics.

    WeatherMAX Outdoor Performance Fabric - Marine http://www.safetycomponents.com/WeatherMAX/Marine/index.html

    Best wishes!
     
  6. Blueknarr
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    Blueknarr Senior Member

    I see lots of cosmetic issues.
    I don't see anything structural, but it might be hidden.

    What does the underside look like?
    Possible close up of tree damage?

    I would assess potential rot sites (along seams, at fasteners, under solar ect).
     
  7. JosephT
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    JosephT Senior Member

    Since you have solar panels a layer of fiberglass would be my suggestion. It is actually lighter than you think and will ensure it lasts longer so long as it's got a good coat of UV paint to protect the fibers. Another option would be to fabricate or buy a foam or honeycomb core panel. Talk to anyone who works with fiberglass in your region and they should be able to help. These panels will be your lightest option, but may be more expensive.

    At a bare minimum go with marine grade plywood next time. It will last longer.
     
  8. PAR
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    PAR Yacht Designer/Builder

    It sounds like you used Douglas fir plywood (the stuff the big box stores sell) and this stuff does check, crack and split, if left in the weather, without epoxy encapsulation AND a 'glass sheathing. If the plywood seems in tact, except for some small areas, repair the bad spots, encapsulate with epoxy, including all cutouts, notches, fastener holes, etc., especially the end grain, then sheath (skin) with a minimum of 12 ounces of fabric. If the plywood is really cheap, use two layers of 6 ounce fabric.

    Conversely, there's other materials you can use as a covering, such as 'glass panels, which are available at the big box stores (48"x96") and this can be glued down over what you have. It's waterproof, though has good UV resistance should be painted every few years to keep it from de-oxidizing. Of course, this don't fix any structural concerns, if you have them. Additionally, you can use other panel like products, though most are pretty costly if being used as the actual roof structure (Cossa, StarBoard and similar products). In fact, sheet metal isn't all that bad an idea, assuming the current roof is still solid enough. I'd recommend aluminum, because it'll tolerate the weather much better than galvanized steel. If the galvanized steel was mill finished (left raw) it would do well (20+ years) before starting to rust, but it would need to be glued down, so fasteners would penetrate it. The same with aluminum, glue it down. From what I see, metal would be an easy addition, with some hammering around the edges, especially aluminum, because it's so easy to work with a thumb nail basher.
     
  9. fallguy
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    fallguy Senior Member

    I had a 1974 Starfire 24’ that had to get crushed for core rot. The hardtop was wel made.

    They used a mold and gelcoated and two laminates around a stringer and all that. But what made it so great was by having a gap in it; they were very light and had a great wire chase.

    I am planning a roof build and think I am going with 6mm or 12mm foam with a 12mm foam space and another piece of foam. You would glass one side of the foam; then the other; add the foam spacers/stringers and then glue the other side on and flip it again.

    If you want something special on the edges; you do that all ahead of time on the easy to form foam.

    Personally, I’d skip the plywood or I’d skin the plywood and air gap the plywood, as the air gap can’t be beat for both wire chase and thermal/condensation break.

    If you want to get fancier; you could also use some thin insulation, but not really needed, imo.
     
  10. SamSam
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    SamSam Senior Member

  11. DianneB
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    DianneB Junior Member

    There is no problem with the underside of the roof and/or structure - still looks new. The tree damage was limited to abrasion that exposed the edges of one corner to water causing rot. That section is no more than 12" square and could easily be replaced.

    I like the idea of adhering marine canvas after removing all the 'fittings' and sanding the top. It would give a nice appearance.
     
  12. PAR
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    PAR Yacht Designer/Builder

    Using TiteBond II and canvas will rot your roof pretty quickly. It's a method adopted by a few usually Maine builders and a replacement for lead paint soaked canvas, but it doesn't work well. The reason is TiteBond II isn't water proof, which seems out of hand as an obvious drawback, but they still do it. If you would like to go this route, use "elastomeric roof paint" instead of TiteBond II, this stuff is usually polyurea or polyurethane, which are waterproof. Paint the roof with the relatively thick paint, then roll out the pre-cut canvas into the wet goo. Le tit "kickoff" so the paint "vehicle" can flash off, then paint the surface with the same paint again and let dry. It does take some timing to get it all down, before things start to setup, but working in cooler weather helps.
     
  13. DianneB
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    DianneB Junior Member

    Thanks PAR! I used elastometric paint last fall to protect the roof and I still have 2 gallons left so that is a savings. I have some Sunbrella canvas left from doing new canvases a few years ago but I'll pick up some more in a contrasting colour.
     
  14. PAR
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    PAR Yacht Designer/Builder

    The elastometric paint will saturate and color the fabric. Sunbrella is treated, so I don't think this is the best choice, as it's probably not going to soak in as needed. Regular "cotton duck" is what the use. If you have seams, sew them together (make a hem) and align it down the centerline. A flat felled seam is the usual one, but difficult to make in canvas. The nice thing about the elastometric paint is you don't have to paint it afterward and it last for several years, so pick a color you like. When applying the canvas in the wet goo, stretch and bend it around the edges of the roof and staple it along the edge. You can cover the staples with a piece of trim.
     

  15. DianneB
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    DianneB Junior Member

    I have had correspondence with the manufacturer of Sunbrella and they definitely recommend AGAINST using any type of adhesive because of the waterproofing.

    That being the case, my preference is for light gauge aluminium sheet (similar to aluminium flashing) adhered over the plywood.

    I am thinking of removing all the 'appliances' on the roof, sanding the plywood smooth. and applying a coating of epoxy rosin, then using contact cement to affix the aluminium sheeting and rolling the edges of the sheeting around the 'eves'.

    Does that sound reasonable?
     
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