Soft spots on the deck.

Discussion in 'Fiberglass and Composite Boat Building' started by LeRi222, Apr 22, 2010.

  1. LeRi222
    Joined: Apr 2010
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    LeRi222 Junior Member

    On my Pearson Ensign the are a few soft spots on the fiberglass deck. I think this is due to incorectly mounted deck hardware that may have allowed water to spoil the balsa core. What is the best procedure to fix this?

    Thanks.
     
  2. alan white
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    alan white Senior Member

    This gets very involved. It's a common problem and the remedy isn't for the faint of heart. To begin with, solid feeling sections of the deck may be completely waterlogged. Sponginess is only the final result of years of water ingress.
    Your only option is to drill small holes from underneath on a regular grid to determine how extensive the saturation. This gives you an idea about the plan of attack.
     
  3. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Indeed. This one is not for the faint hearted.

    Basic procedure: Remove one skin (inside or outside), remove all balsa, install foam, reapply skin.

    Long version:
    -remove all deck hardware, after photographing and measuring where they should return. (if you want to move things around, now is your time. Actually you could do the move first, testsail it (covering drill holes with tape or putty them close, depending on the weather)

    Protect everything that will not be cut up.

    Usually the outer skin is the one that is taken off. Determine if it is worthwile to try and lift it off in several large pieces, as to save the anti skid. But actually the succes ratio of that procedure is low. The easy solution is just to cut around the perimeter with a circular saw, cutting away the outer skin. Then do the same across the deck. It is just like peeling an orange.

    Then remove the balsa. Probably most of it has gone already, but other pieces might need some touching with grit 16 in an angular grinder.

    Clean up the inner skin (grit 16 or 24 is your friend). Be careful, it probably does not have the strength or stiffness to decently walk on it. Create scaffolding, and move around on sheets of wood, laid on the deck.

    very probably there are holes in your inner skin. You would like to cover them with a light cloth, impregnated in epoxy or polyester resin. (I leave the resin choice up to you. Polyester can easily be re-gelcoated, although it is a hell of a job on a deck, epoxy is stronger, has better adhesion, and does not smell). Small patches of cloth will do.

    Now apply a couple of layers heavier cloth or non-crimp-fabric (biax or quadrax). If there were areas that needed beefing up, now is your time, you could add some extra layers in weak spots. Use peel-ply to cover your laminate. (or did you actually like sanding the inner skin?)

    After cure, remove the peelply, and mark the areas where fittings will go. I recommend using a high density foam in those areas. My suggestion is for Airex T90.240 or T90.320, which are very high density, and survive even under a winch. For the rest, an 80 kg/m3 foam will usually do, for instance Airex C70.75.
    Glue that in, using a good quality bonding paste, or mix your own. I like to vacuum down the foam core, but I realise not everyone has that opportunity. Use as much weight as possible to press the foam into the bonding paste. When using a pre-made paste, which is a bit on the "dry" side it is a good idea to "hotcoat" the foam with some laminating resin. Oh, and perforate your foam, so trapped air can escape.

    Once all foam has been applied, you can clean up the foam where needed, fill kerfs, smooth things out, etc.
    Now is the time to also detail the edges, where the (to be applied) outer skin should bond to the rest of the boat. This is very dependant on details on the boat, but generally you would like a generous taper, so loads are transfered smoothly.

    Now apply your outer skin. You were able to see the thickness of the original outer skin. I suggest using at least that thickness, or slightly more. (80 kg/m3 foam is a bit less stiff than balsa, you would like to take that into account). Some test laminates show you the thickness achieved using 1, 2, 3 or 4 layers (or even more)

    Again, use peelply.

    After cure, one can start refinishing in various ways. Sand smooth the edges, so these blend into the original laminate. The rest is up to you:

    -reapply gelcoat (topcoat, actually) and smooth that out, then polish up.
    -apply a teak deck, or anything similar.
    -apply an anti skid paint (I really like the Sicomin / Map Yachting stuff, which is rubbery, and pleasant to bare feet)
    -reapply gelcoat with antiskid texture, using the materials of Gibco Flexmold. (In Europe marketed by Brands Structural Products in Netherlands).

    Remount your hardware. Drilling small holes from below can help determining the right place. And you do have your measurements.
    Drill holes too large, preferably not through the inner skin. Pot with epoxy, let cure. Now re-drill your holes with the right diameter, and screw or bolt through. You could even use bolts in blind tapped holes, if needed.

    Oh, now you also discovered why I do not like balsa for boat decks...
     
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  4. peter radclyffe
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    peter radclyffe Senior Member

    set fire to the boat & buy a steel one:D
     
  5. Herman
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    Herman Senior Member

    Thank you for your most constructive post.
     
  6. mark775

    mark775 Guest

    Poorly installed hardware will ruin any deck, foam faster than anything. Nice instructions save the anti-balsa bias. Herman, you are knowledgable enuf to know better, so I can only deduce that you sell foam.
     
  7. peter radclyffe
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    peter radclyffe Senior Member

    my apologies ,
    i know that when grp goes soft, it can be the start of major defects, which may not be apparent, even when looked at
     
  8. alan white
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    alan white Senior Member

    It;s common to have soft spots in some areas, usually where hardware is mounted of course. It doesn't mean the damage is throughout the deck but it's probable that the balsa core is wet over larger areas. Drilling samples tells you the color of the core (white wood is salvagable even if saturated, brownish or black, replace as rot's taken hold).
    Mapping the damage by exploratory drilling tells you where to cut to remove the brown or black material. Otherwise, the good areas should be drilled more to the extent that the core can be dried and saved. Once any area has been peeled off, the deck no longer has any structural integrity, so supporting from underneath or by whatever means becomes necessary to maintain the original shape.
     
  9. Herman
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    Herman Senior Member

    Listen, Mark.

    Balsa is a great product, and is used in many structures. The only problem with boats is that you will need to protect the balsa from water ingress. For hulls this is not really a problem, but decks seem to be complicated structures for builders, and to make things worse, a lot of hardware needs to be installed, causing many holes into the balsa, that ALL need attention.
    To make things worse, a boat owner might not be aware of the specific requirements that balsa decks need, and might unknowledgable cut or drill into the balsa. I guess boat decks are pretty unique in that. Other structures do not see such extensive rework by owners.

    My advise is not biassed anti balsa. In other structures I might recommend it.

    Oh, and indeed I do sell foam. And balsa...
     
  10. tunnels

    tunnels Previous Member

    Go find the guys that made the boat and put them in the boat before you torch it !!:mad:
     

  11. Herman
    Joined: Oct 2004
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    Herman Senior Member

    why am I being penalised for trying to help someone out? (rep points).
     
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