Delamination in deck but no mushiness, what to do?

Discussion in 'Sailboats' started by toolgirl, Aug 10, 2009.

  1. toolgirl
    Joined: Aug 2009
    Posts: 1
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    Location: Bay Area, California

    toolgirl New Member

    Hi there everybody.

    First off I'm new and I did look through the forum but did not find anything on my particular problem. I also hope I'm in the correct section and please let me know.

    I am waterproofing a Mariner 36' (New Hampshire) 1979. I'm new to working on boats and there are so many things to consider that I would like some help.

    I have done the stanchions and all was good because the was no exposed core.
    Now I have moved on to the handrails since I know there was leakage, and it turns out that around at least two of the through bolt holes that hold the handrail, the core has rotten away completely. I can pull out a few scraps of wet, rotten wood but now I have done that I can't even see the wood. I have drilled the holes larger to install an epoxy washer as is recommended on the holes where there is still core and did everything as you are supposed to but there is no more core to be found at least in this area and possibly one other that I'm still investigating. I drilled a few holes from below (not going through the top skin) to let the core dry out and find the extent of the damage.
    When I tap the deck to sound it out the area that sounds hollow is fairly large (maybe 2 sq feet) and I know the best solution would be to open it up and replace the core. I am trying to avoid the labor, expense and mess (Hi there everybody.

    First off I'm new and I did look through the forum but did not find anything on my particular problem. I also hope I'm in the correct section and please let me know.

    I am waterproofing a Mariner 36' (New Hampshire) 1979. I'm new to working on boats and there are so many things to consider that I would like some help.

    I have done the stanchions and all was good because the was no exposed core.
    Now I have moved on to the handrails since I know there was leakage, and it turns out that around at least two of the through bolt holes that hold the handrail, the core has rotten away completely. I can pull out a few scraps of wet, rotten wood but now I have done that I can't even see the wood. I have drilled the holes larger to install an epoxy washer as is recommended on the holes where there is still core and did everything as you are supposed to but there is no more core to be found at least in this area and possibly one other that I'm still investigating. I drilled a few holes from below (not going through the top skin) to let the core dry out and find the extent of the damage.
    When I tap the deck to sound it out the area that sounds hollow is fairly large (maybe 2 sq feet) and I know the best solution would be to open it up and replace the core. I am trying to avoid the labor, expense and mess (I live on the boat) of that, the reason I'm even considering avoiding this strategy is that the outer skin of the hull is probably half an inch thick. Therefore there is no discernable difference in the behaviour of the deck (as in mushiness or anything). Also, the leaking has been occurring for at least 13 years (I am a new owner since September and I know the last owner did not fix it) without a repair so it has been going on for a very long time. We have been sailing regularly since we owned it and there is no crazing in the gelcoat or any other indicator of there being a stress problem in the cabintop.
    So my question is: If I dried the area out and filled it with epoxy or foam and I would like recommendations what would be better, would that do the job? The section of the cabintop where this is, is right next to the companionway and a hatch and the edge where the deck bends down from the cabintop to the sidewall of the cabin. So it is a strong section of the deck (not a wide open area). I don't really want to leave it empty since I need to bolt the handrail back in and at the moment there is all this space between the inner and outer skin of the cabintop. The other area with this problem is on the far forward section of the cabintop, again right next to the edge. So not under all that much stress I imagine. (Let me know if I'm wrong.)

    So if anybody has any ideas I would really appreciate the help.
    Thanks
     
    Last edited: Aug 10, 2009
  2. old_sailor
    Joined: Aug 2009
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    Location: Virginia

    old_sailor amateur boatbuilder

    I have seen a number of these problems and the only real solution is to do what you do not want to do. I wouldn't try foam due to the fact that it has no strength value when used in this fashion. Epoxy is too brittle in that thickness. I don't know if anyone has tried it, but look into a product called Flexane by Devcon. It is a pourable polyurathane rubber. It comes in various hardnesses and just might work. I have used this to make rubber shims for my mast step and to make waterproof grommets around the wires that go through bulkheads. It is expensive, but it adheres to things well and seems to have a reasonable strength. I have no idea if this will work in your situation, but it may be worth looking into.
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Sweet lord, here's some advise that actually is correct.

    Yes, you can use foam and yes it will have "strength value" (whatever that means), so it's an option, though I have to admit I too don't think you should use it, but for different reasons.

    I will agree that you're are looking at removal of portions of the decking or head liner to replace some of the core.

    Flexane wouldn't be a wise choice as a core material in this repair either for several, mostly obvious reasons.

    What you need is compression strength and good adhesion properties in a core replacement, preferably one that's fairly light weight you don't end up tripling or quadrupling the weight of your deck (like Flexane would).

    Use the search tool as balsa core replacement is a subject covered here many times and you do have options.

    You have an "end grain balsa" core. This is actually one of the best performance cores available, even though it can rot if it gets wet. I will not go into the reasons, just trust me, it's pound for pound one of the best. So, you can replace the rotted core with more balsa. You also could use other materials, such as foam or one of the honeycomb products. Generally these are more costly, though you can save some weight.

    Since I don't think you care so much about the weight penalty as much as getting back on the water, you're probably best off just replacing the core with more balsa.

    The bottom line is the rotten balsa has to come out. In small areas, you can use hooks and other "special" tools to clean out fastener holes, etc., but when you have wholesale rot, then you have to get serious.

    There are two approaches, remove the deck from above, or cut the liner from below. If you remove the deck (or portions) you need to do some fancy fairing work to hide the repairs, plus paint. If you remove the liner from below, you can hide much of this with fabric headliners or textured paint, making for less finishing work and a stock appearing deck.

    Unfortunately, removing the liner from below means working overhead, which is much harder. This is your first decision after you've decided you actually want to do this. Another mitigating factor is how much stuff do you have to remove to get at the damaged areas.

    Since you're new to boat repairs, this is a hell of a way to get christened. You can do it, but you'll cuss the day you decided to try.

    Log onto www.westsystem.com and www.systemthree.com and have a look at their users guides, to get an idea how to work with epoxy, fillers and other goo related stuff. Then do some searches on balsa core repairs, etc. and pick up the painful truth about what you're in for. Welcome to the forum and Good Luck. You know what BOAT realy means don't you? It means Bring Over Another Thousand . . .
     
  4. old_sailor
    Joined: Aug 2009
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    Location: Virginia

    old_sailor amateur boatbuilder

    From the posts that I have read, Par is right on most counts and is right on the proper way to fix this problem; however, not all of us can Break Out Another Thousand on call. I have not built anything using cored fiberglass because it seemed to me to be too difficult for the amateur to do well, so I freely admit to knowing very little about it.

    Par,
    Perhaps you have some thoughts for this person that might at least be a stop gap. Here is an idea, may not be good, but maybe you can point out the negatives.

    How about punching enough holes and then attaching a vacume pump to reduce or eliminate the moisture, then using one of the epoxy systems that claims to saturate the rotted portion, and then using pourable polyurethane foam to fill the core space where the core has rotted away?
     
  5. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Would it be possible to move and reattach the handrail post to where the balsa core is still solid, and then just use hooks and special tools to clean out the bad spots and then inject/pour something in the space?
     
  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    All the simple tricks, like hooks or drilling over size holes and filling are fine, but she mentioned a 2 foot square (4 sq. ft.) which is way beyond any stop gap measure. It would be nice if a miracle in a can of goo, could come to the rescue, but it will not, unfortunately, mostly because it will attempt to stick to partly rotten, stained and dirty surfaces within the "de-cored" deck. You can't expect much to stick to these surfaces, without cleaning.

    The issue as she knows of it is a large area, likely much larger then realized currently because it's still sealed up. We all know full well what's going to be there when she opens up the deck. A lot more damage then previously believed. I think this is a requirement to any type of repair and not specific to boats. I'll bet she'll find evidence of rot and delamination around nearly every deck penetration and fastener, of course some areas worse then others.

    Given this, some portions of the liner or deck will have to come off, the rot removed, the inner surfaces of the liner and deck cleaned and heavily scuffed, then the new core bonded and the removed panels replaced and faired in smooth.

    Cored structures require complete integrity or they are nearly worthless in load bearing situations.
     

  7. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I didn't notice the 2 square feet part. That is sort of large to rig.
     
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