Cracked seam repair

Discussion in 'Boat and Accessory Building' started by paddlesores, Feb 6, 2018.

  1. JohnAbercrombie

    JohnAbercrombie Paddler

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    Dave:
    Why do you use 2 layers of glass tape?
    And, are they the same width, or a wider tape over a narrow one?
     
  2. Roy222

    Roy222 Paddler

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    It looks like good work.
    But, I would check it for water leaks with an air compressor as follows:
    Use compress air to locally compress the suspected inside surfaces while applying water to the outside.
    This is probably a 2 people job. Any leaks will show up as air bubbles.
    I worked in a car factory and we used this method to locate hard to find water leaks on car bodies.

    Back to your boat:
    I would not use fiberglass tape to fix the seam. Woven tape doubles the amount of glass, because only 1/2 of the glass threads are spanning the crack. 9 oz. glass tape will soak up a lot of resin and adds a lot of weight.
    I would make strips of cut at 45 degrees ( cut no the bias ). To keep the glass from fraying use masking tape on the edges of the cuts. I would use 2 layers of 4 oz. glass cut on the bias. (should be stronger then 1 layer of 9 oz. tape and probably 1/3 the weight add.)

    Anyway keep up the high level of craftsmanship.


    Roy
     
  3. JohnAbercrombie

    JohnAbercrombie Paddler

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    Roy-
    Are you suggesting pressurizing the compartment?
    I'd be careful with that.....
    Or do you just mean to direct air from an air gun?
     
  4. JohnAbercrombie

    JohnAbercrombie Paddler

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    All the tape and resin to bond the hull and deck on both sides probably doesn't add up to that much weight (a few pounds), so I don't get very concerned about it, when I build or repair. but I've never managed to build a 25 pound boat, either! :)
    I have seen the argument about using bias-cut fabric (strands crossing the joint at 45 degrees, etc.) but I haven't seen any 'real-world' test data on the strength difference between standard tape and bias-cut strips. The huge disadvantage of bias strips in a 'straight line' application (especially for a beginner) is that it's tricky to control the strip width when working with the strips. (If Doug needs to reinforce the skeg box-hull joint from the inside, bias strips are definitely the way to go as they conform to curves so well.)
    If weight is a concern, woven tape is available in different weights (thicknesses). Probably the most effective way that I have found to keep the weight/waste down on a seam tape job is to compress the tape and resin composite while it is curing, by using peel-ply or taping plastic tightly across the seam. It reduces the amount of sanding required to smooth the selvage edges of the tape, and gives a smoother surface for subsequent gelcoat or pigmented epoxy (or paint) application.
     
  5. Astoriadave

    Astoriadave Paddler

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    First, in response to Roy's suggestion of using bias tape: the weight difference is small. Bias tape is a PITA to cut yourself, especially in the lengths needed for a full length seam. Yes, bias is stronger, no question, but not worth the trouble.

    Second, I use two layers of same-width tape (4 oz tape would be better than 6 oz, if you could find it) because I aggressively fair in the first layer at the edges to the hull profile and roughen it thoroughly for a better bond to the second layer, so that the second layer is needed for added strength. OTOH, Doug has prepped the seam with what looks like a thick, strong bead (perhaps a little proud?) which should fair in well, and a single layer of tape on top may be enough. Any gel coat on top adds little strength.

    I don't think it makes much difference whether the first layer is narrower or not, if the seam is going to be faired later anyway.

    One versus two layers: does it matter much? Maybe not. For me, the prospect of having to go back and redo a hull seam for lack of the added layer pushes me to two.
     
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  6. paddlesores

    paddlesores Paddler

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    Weight isn't an issue with this boat. More concerned about it being solid and dry. The epoxy I put in the seam dried with a little concave shape to it but it will be fine for the pool sessions. Once I strip all the old gel coat from the seam I plan on filling the groove with epoxy first and fairing it out so I do have a smooth surface before taping.
    I bought 6 oz,, 1" wide E-glass seam tape for the job. I'm hoping after filling the seam groove with epoxy, one layer of this tape will be strong enough. The reasoning being it had nothing before so it has to be better. Roy, I know if I cut the tape the way you described I wouldn't be able to make a clean job of it. I think I'll try to keep it simple for myself the first time out. If all goes well I want to do keel strips on this boat and my Anas Acuta next.
    I'm heading out to the garage right now to put water in the compartment and see if I can find the leak.
    Doug
     
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  7. JohnAbercrombie

    JohnAbercrombie Paddler

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    Good plan, and good work!
    If you are going to do keel strips later, you might as well start using gelcoat on the side seam job (after the epoxy and taping, etc..). It will save the expense of epoxy pigment (if you haven't bought it already). Gelcoat isn't very hard to work with, it's just a different 'concept' than epoxy. With gelcoat you can vary the amount of MEKP catalyst to control the speed of reaction; with epoxy it's a strict ratio of resin:hardener always.
    Also, unlike epoxy, gelcoat and especially hardener needs to be fresh, so buy from a place like Industrial Plastics that has a good turnover of stock - not the 'kit' that's been on the shelf at CdnTire for 2 years.
     
  8. nootka

    nootka Paddler

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    and keep your MEKP in the dark during storage.
     
  9. paddlesores

    paddlesores Paddler

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    Looks like the water is coming in from a pinhole at the front corner of the skeg box.

    IMGP7277.JPG

    It is just gel coat around the skeg box and a lot of it is coming loose.

    IMGP7270.JPG

    So, initially I'm thinking of opening up the pinhole area slightly and get some thickened epoxy into the space. Hopefully that will keep the hatch dry and then I will scrape away the loose gel coat inside and fiberglass the box itself after the pool sessions are done.

    Doug
     
  10. Astoriadave

    Astoriadave Paddler

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    Sounds good to me. Old gel coat only area was less than an inch? An inch is good, especially since, as you say, the internal glass on the seam carried the load well. Good on ya, Doug!
     
  11. Astoriadave

    Astoriadave Paddler

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    John, I have very little experience with polyester gel coat over epoxy/glass laminates. As I recall, correct surface prep allows the use of MEKP catalyzed resins over well cured epoxy. Has this worked well for you?

    The WEST System folks have some detailed information out there on this:
    http://epoxyworks.com/index.php/applying-polyester-gelcoat-over-epoxy/

    The video at the end is very good for an overview.
     
  12. Astoriadave

    Astoriadave Paddler

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    That should be good. Nasty place to work. I would also add some milled glass fibres to the thickened epoxy, glass fibres first, then the thickener. If that fillet is resin-rich, you can usually put the pre-cut glass directly onto the fillet immediately while the resin is fresh. This will draw excess resin into the glass, stabilizing the fillet cross section, and preventing sag. Underdecks, no UV exposure, hence no need for gel coat followup.

    This rear compartment should be really good when you are finished!
     
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  13. JohnAbercrombie

    JohnAbercrombie Paddler

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    Doug-
    For the pool session, I'd probably just put some tape over the area with the hole, or tape over the skeg slot completely. Afterward, you can clean off any tape adhesive residue and get started with the epoxy work.

    I'd do the inside work first - scraper & wire brush to get any loose gelcoat off, then sanding with coarse sandpaper.
    It's a tricky place to work.
    If you start filling from the outside yo could end up with drips/resin 'icicles' on the inside and they can be a pain to remove with sandpaper on a stick.
    I had to repair a couple of WS Pro (170 & 180) kayaks with leaks aft of the skeg boxes, so I 'feel your pain' . :)
    Speaking of sanding, a drywall sander (swivel pad on a broomstick) makes a good starting point for a DIY sanding tool. Using PSA (sticky) sandpaper on a shaped foam block also works. If you can reach and work accurately a Dremel with a small sanding drum or flap sander is also useful. Use every trick you can think of to prep the area well!

    I'm assuming that your water test got any salt residue out of the inside. If you aren't sure, just let the boat leak at the pool and rinse it there! :)
     
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  14. LAM

    LAM Paddler

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    Ha ha ha... Dave when I pulled hard on the strap the other night and Doug heard the long loud crraaackkk he smiled with glee at the prospect of getting into his shop to do some new work!! That's enough apropos rewards for him!! Don't want to spoil the guy!! LOL

    Lila
     
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  15. JohnAbercrombie

    JohnAbercrombie Paddler

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    For laying in that fillet, load your epoxy mix into a ziploc (sandwich) bag and snip the corner to use like a cake decorating bag. It really helps when working in an awkward space.
     
  16. AM

    AM Paddler

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    Good grief. I thought Nootka's gel-coated skeg box was a one-off.

    Luckily, you have the expertise of John and Dave to guide you through your repair work. BUT...the fact that you have to do the work in the first place is ridiculous. Yesterday, prompted by this discussion, I checked the skeg box on my Wind 535 and was relieved to see actual glass surrounding it. But then I checked a neighbouring Greenland and it looks the same as yours: the skeg box is held in with gel coat. And get this: that Greenland is a Zegul, which is supposed to be the premiere line from Tahe Marine.

    Cheers,
    Andrew
     
  17. Roy222

    Roy222 Paddler

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    Is that a water drop I see in the upper right corner dripping off an upper deck bungee cord attachment.

    I did not suggest pressurizing the hull. I should of explained the process more clearly. You simply direct pressurized air at suspected seams, that air finds any openings and will be visualized as bubbles on the opposite side. I did not see any water leak witness marks at the seam between the top and bottom hull and suspected the leak was coming from elsewhere - like bungee cord attachments and other attachment holes in the hull.

    Myself, I would not gel coat the seam between the upper and lower decks. It is a lot of work and you will still need to color match the gel coat ( hard to match a faded color ) and/or paint or cover the work with color stripe.

    But in the end when your boat next hits the water it will be a better and safer boat and you will have the satisfaction of having done the repair. That satisfaction is the best reward.

    Roy
     
  18. JohnAbercrombie

    JohnAbercrombie Paddler

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    I agree that colour matching is 'not fun' - I'm not very good at it.
    Even if Doug doesn't tape the hull-deck seam all the way round, it's still not a very big job to re-coat the seam area with gelcoat. (Mask, sand, re-mask, apply gelcoat). And if the whole seam is done, no colour matching is necessary. Using neutral gelcoat and pigment, the 'sheerstripe' could be made any colour.
    Anyway, epoxy cannot be left exposed to UV so it will need some sort of protection - gelcoat or paint (and gelcoat hides a lot more flaws than paint, and is easier to repair).
     
  19. paddlesores

    paddlesores Paddler

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    The plan is to tape the whole seam and then gel coat. Not worried about color matching at all. If Lila doesn't want the white that was there we may pick a completely different color for the seam and keel strip. Why not personalize it a bit if we're going to all this trouble.
    John, thanks for the tip about the ziploc, that will come in handy.
    Doug
     
  20. JohnAbercrombie

    JohnAbercrombie Paddler

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    I forget where I first saw that idea, but it is an excellent technique. There are videos at youtube and more info online:
    http://www.epoxycraft.com/using-piping-bag-epoxy/

    To emphasize couple of hints that are mentioned online :
    Put the empty plastic bag into a paper cup or similar container, and fold down the top to make it easier to 'load' the epoxy into the bag.
    Use a piece of pipe or a plastic squeegee on the outside of the bag after the epoxy mix is loaded, to work the epoxy into the corner of the bag. Snip the corner off the bag just before you are ready to apply the mix to
    the work area.
    Don't mix too big a batch - fillers make epoxy cure faster (they slow down the heat escape from the curing mix and the reaction rate increases). I generally use about 4-6 'squirts' from the WEST pumps, which makes about 1-200 mL of epoxy mix (?? - I'm guessing here- it's about half a 'sandwich' bag).
    Get your mix out of the bag and on to the work fairly promptly - once the epoxy is 'spread out' the heat can escape better and the cure rate won't accelerate so much. Once you have applied the mix, you can go back and shape the fillet. Try to avoid using your fingers or thumb for shaping. Sometimes as a 'final step' I use a dry chip brush with the bristles trimmed back to gently smooth the fillet surface.

    Although I don't follow his method exactly (I just snip the corner of the bag and don't add a 'piping tip'), this video shows a very good selection of filleting tools:


    I use tools that are much shorter (mostly cut from plastic Bondo spreaders or plastic jugs); it can be awkward swinging a longer handle inside a kayak.

    You could use the bag to apply the thickened epoxy to the side seams as well. It's a great technique that minimizes slop and wasted epoxy. If you are trying to fill voids, brushing on some straight epoxy first can help.