Fiberglass hull with timber deck

Discussion in 'Boat Design' started by Stavbergen, Apr 25, 2019.

  1. Stavbergen
    Joined: Apr 2019
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    Stavbergen Junior Member

    Hello I was wondering if anyoune has ever removed a fiberglass top or deck and replaced with timber deck. I wanted to do this on an existing fiberglass boat. I only wanted to dobtjis for asthetic reasons. I guess you cut the top off and then add some frames for decking. I wonder if the fiberglass at the gunnels would be able to withstand the weight?
     
  2. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Welcome to the forum

    I won't say it has never been done. It does pose significant engineering challenges.

    Wood (teak) deck layed on top of fiberglass is common. Why not leave the fiberglass structure and simply add wooden surfacing?
     
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  3. JamesG123
    Joined: Mar 2015
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    JamesG123 Senior Member

    If you are asking this question here, then you shouldn't. If you didn't have to ask, then you wouldn't. :)

    Blue's suggestion of adding a wood applique deck is the best one. I actually cringed upon reading your post at imagining the amount of work and pain it would entail. And the likelihood that you would wind up with leaky, high maintenance mess that you would never be able to get rid of.
     
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  4. Steve W
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    Steve W Senior Member

    Not a problem at all as long as you have a gunwhale of some sort to attach beams to. Depending on what type of fiberglass boat we are talking about you may end up lighter. I have personally replaced the teak deck on a Cherubini 44 ketch which was built with a solid glass hull with an inward turned flange and plywood decks over laminated wood beams with teak decks epoxied over the plywood. How about elaborating on what you have in mind? No reason not to lay a teak deck over the existing glass deck either but it does require a lot of care, many teak decks over glass have lead to lots of core issues, we are dealing with this on a customers boat right now.

    Steve
     
  5. gonzo
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    gonzo Senior Member

    Older teak decks were screwed on. With modern adhesives it is easy to vacuum bag a teak deck without any fasteners.
     
  6. JamesG123
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    JamesG123 Senior Member

    There are teak (alike) applique decks that don't even need bagging. They just go on with basically contact cement.
     
  7. Steve W
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    Steve W Senior Member

    Almost all the teak decks I have laid have been sprung decks which would be very difficult if not impossible to vacuum bag. We still have not heard back from the OP about what he has in mind, maybe nothing to do with laid decks.
     
  8. Stavbergen
    Joined: Apr 2019
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    Location: Melbourne

    Stavbergen Junior Member

    Thanks for the replys. I will keep it in mind.
     
  9. gonzo
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    gonzo Senior Member

    I have vacuum bagged many sprung teak decks. You simply make the panels on a large table over a template and then transfer them to the deck.
     
  10. Steve W
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    Steve W Senior Member

    Yes I've also bagged down panels, but it takes a lot more force than vacuum can deliver to lay the sprung deck on to the panels. But as you say, vacuum is great for holding down flat panes.
     
  11. gonzo
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    gonzo Senior Member

    The vacuum is not used to spring the planks. However, a average vacuum pump will create about 12 PSI of pressure. Multiply that by the area of the deck to calculate the force applied.
    The planks are sprung and held together by flexible adhesive ( I use SIKA). The whole panels are then applied over the deck.
     
  12. Steve W
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    Steve W Senior Member

    Yes, as you know it take a lot of localized force to spring a teak deck plank and keep the inner edge down so obviously vacuum is not up to the task but as you say, once it is bonded to a sub panel it becomes just another sheet good and is very easily bagged down with vacuum while the adhesive sets.
     

  13. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    I can imagine building a new GRP boat with a wooden deck. GRP makes an excellent hull material, as it takes compound curves rather graciously. The compound curves, to a large extent, make up for the material's low stiffness to weight ratio. Also, hulls typically have very few items bolted on later after they are completed.

    Decks, on the other hand, have little or no compound curves, and have items bolted on long after the vessel is completed. Also, a GRP deck usually needs to be sandwich-construction in order to keep the weight within reason. Adding and subtracting hardware to a sandwich deck requires a number of precautions which are often overlooked. Also, there is the problem of the sandwich construction failing, due to the before-mentioned oversights and or the deck taking a load the designer did not anticipate. Once the sandwich structure fails, it is very expensive to repair. The GRP on either the top or bottom must be removed, as must be the core material. New core material must then be added along with a new GRP surface. And one must hope all this bonds well.

    A plywood deck has none of these vices, however it can rot. But the rot is easier to see in a deck than it would be in a bilge. Once spotted, it can be locally removed and replaced. I also believe it is easier to reinforce locally for heavily loaded hardware such as winches and cleats.

    If I had an old GRP boat with a failed sandwich GRP deck, I would try to repair it. Such may be less expensive than removing it and replacing it with a plywood one.
     
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