Repairing Stress Cracks in a Nonskid Textured Surface

Discussion in 'Fiberglass and Composite Boat Building' started by gjrylands, Mar 2, 2009.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If you add 20% by volume, denatured alcohol to the epoxy, it will create a flexible plastic, much like rubber. If you want, you could wait until the gel stage of the cure and laminate a layer of fabric onto the back of the mold, but it's not necessary unless you plan on many uses. I don't bother with mold releases any more, I use plain old car wax, three coats to be sure nothing sticks.

    "Keying" the mold just makes good sense if the pattern is unidirectional.

    In applications like yours, I would cast the mold to include a "waterway" edge and corner. I can position this as a time saver for some of the waterways, without having to go back and fill dimples neatly.

    The epoxy will have to "lap" into surrounding areas, but it should be a random and smooth transition to be less visible.

    How's it work, well it depends on setup, your experience working with goo, surface prep, etc.

    Try a practice piece on the cracked up portion of the deck that will be removed to fix the rotted core. Will it be perfect as you pull the mold off, probably not, but it will be very close and additional detail work can make it invisible under paint. Wax it first, so you don't have to live with it if you don't want.

    The mold doesn't have to be real thick, but it does have to be thicker then the dimples are deep, plus some for the back of the mold for strength. If you reinforce with cloth, then a 1/16" will work, but might be fragile for more then a couple of repairs. I generally make them an 1/8" if I need to use it several times. I usually don't add cloth and I "flood coat" to the desired thickness, just like coating a tabletop.

    You can safely add a little over 30% solvents to epoxy, before you really start screwing with the ability to cure. Of course it depends on the solvent you elect to use, which is why I recommended alcohol only. Acetone works, but flashes too fast, Xylene also works. I have a few different combinations and concoctions I use, depending on how I want to affect the physical properties of the cured goo. I don't recommend novices try this type of experimentation for obvious reasons.
     
  2. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Just overhearing the conversation, it sure seems like you'd be better off with redoing all the non-skid. For one thing, it's the easiest thing to do if you have several repair areas. For another, you'll have to paint all the non-skid to match the repairs anyway.
    By the way, you'll need to dry out the area around any mushy spot. The balsa should be light in color to keep it at all, not brown. Test samples from inside will tell, in a circle around the mushy area. You need also to test throughout the deck area, especially around hardware. Never redo a deck without making sure no deep work is left to be done.
    My guess is you have some serious issues and maybe some larger areas of wet balsa. The fix is, in my opinion, to drill clear through to dry out wet areas, fan-forcing air through for a couple of weeks. As long as the non-skid is being completely redone (if you so choose to do so), those holes won't matter. Drilling from one side only will take much longer to dry, but will reduce patching.
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've tried drying cores like that before Alan and you sure can make a career out if it. My usual choice is to rip it all out and lay down a new core. It's faster, doesn't tie up the yard and you can work in stages (sections) from one side only.

    I agree, he needs to access how much effort he wants to put into this texture, versus just redoing large portions if not all of the textured areas.
     
  4. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    It is time consuming to drill and dry to say the least. The issue is not so much which way (save or replace core) but whether the shape can be maintained without a lot of extra work. Especially very slight crowning will require careful buttressing before tyhe integrity is temporarily comprimised by removal of the upper skin.
    It's an individual matter, I think, for that reason.
     
  5. gjrylands
    Joined: Feb 2009
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    Location: Chicago, IL

    gjrylands Junior Member

    removing damaged core

    Alan,
    You're absolutely right. Fixing the deck without addressing core damage is crazy, and I have core damage. My deck is crowned slopes to the bow. The core in the bow is totally saturated and has turned to mush. I have removed the lower skin of the deck and removed the core material. I am in the process of replacing the core and lower skin. I’m doing the repair in sections. Once a section is done I plan on wrapping a layer of glass from the under side of the deck to the lower skin of the core. This will create a dam, isolating the new core from the old. This will keep any water in the old core from getting into the new. Any damage in the deck surface will be repaired. Deck plates and hardware will be re-bedded and installed before I move to the next section.

    I know you probably think I’m crazy for taking this approach instead of working from above. Maybe you’re right, but how do you reason with a crazy man. Here’s the crazy man’s logic. I’m not real concerned about how long it takes to finish. Replacing the core and deck is easier and faster when done from above. I live in the north, store my boat outside in the off season, and can’t do the work in the cold. I don’t want my boat stuck in the boatyard while the repairs are being made. I want to do the work in a downtown harbor of Chicago. I can’t have the boat in the harbor if it looks like a major repair project is under way. Cutting the deck open, replacing the core, and glassing the deck is a major repair. Fixing stress cracks or repairing deck damage is minor repairs and is allowed. As long as I work inside the cabin and out of sight there will be no objections and I can work at my own leisure. Anything I can’t do in the harbor can be done in the boatyard later. The more I get done in the harbor the less that will have to be later in the boat yard.
     
  6. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    I am thinking about glassing overhead and well, better you than me. You will need more time, that's for sure. Doing small areas at a time will help maintain the shape, but take care and check constantly for distortion. You can't control shape as well from below. And hopefully, they'll be a minimum of grinding inside.
     
  7. gjrylands
    Joined: Feb 2009
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    Location: Chicago, IL

    gjrylands Junior Member

    Working Overhead

    Your concerns are all well founded. Working over head and fighting gravity is not easy. It is certainly more time consuming and messy. This won’t be my first attempt of overhead glassing. Your point about doing small sections at a time is the key. All stages of the repair require propping while the epoxy dries. The tricky part of propping is to apply just the right amount of pressure so the work is supported without distorting the deck. I plan on using a piece of foam rubber between the props and work to cushion the force. (A wax paper layer keeps the foam from sticking to the work) I’m going to do about a square foot at a time. The size may adjust as the project progresses I would think that once the core is glued to the deck the problem of distortion should be greatly reduced.

    When glassing overhead the epoxy soaked cloth wants to pull away and fall from the surface. Stapling the cloth to the core with Monel staples before wetting keeps this from happening. Multiple layers of overlapping glass can be laminated before propping with the foam. A head liner hides the lower skin of the deck, so the staples should not be a concern and there removal should be unnecessary.

    Inevitably additional resin will be required; there will be a lot of drips and waste.
     

  8. AroMarine
    Joined: Jul 2005
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    Location: Atlantic City NJ

    AroMarine Junior Member

    When you reinstall new core overhead and are using epoxy you can thicken the mixture with fumed Silica "cabosil" somewhere between a ketchup and peanut butter consistency depending on the resin this will be a better bond than original and make sticking it in place much easier. Another technique I have used for installing glass overhead with epoxy is to wet your materials out on a 4 or 6 mill "heavy" sheat of polyethylene 4 or 5 inches larger around the perimeter than your repair then with clean gloves you can handle your glass from underneath. You can bubble roll or squeegee right through the plastic and the resin that pushes out past your material onto the roof will help hold the glass in place. Leave the plastic on overnight and it will peel off in the morning. You need to tape off the area where the resin will push out to.
     
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