Keel strips - what is the covering on NDK boats?

Discussion in 'Boat and Accessory Building' started by Comoxpaddler, Apr 24, 2010.

  1. Comoxpaddler

    Comoxpaddler Paddler

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    I am getting my Explorer ready for a 4-6 week long summer trip. I am going solo so there will be lots of boat dragging. Time for a keel strip.

    I have looked at factory-supplied keel strips on Nigel Dennis boats and they seem to have a slightly rubberised final coating, the same as the covering of the one inch strip between hull and deck.

    Any ideas as to its nature? It doesn't look or feel like ordinary gelcoat and doesn't scratch or flake as easily. Don at Comox Valley Kayaks reckons it is gelcoat but I am not convinced.

    Also, how many layers of fibreglass cloth do forum users apply for their keel strips? I'm thinking two.

    Thanks.
     
  2. Desertboater

    Desertboater Paddler

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    I believe they are indeed gelcoat, however I agree that the surface is different from the usual glossy finish. This might just be a different kind of gelcoat, or something completely different altogether. You can probably use as many layers of glass as you would like, although most are done with just one, maybe with an extra layer at the stem and stern where you get the most wear.
    You might also consider using kevlar. Despite its usual use as making lighter boats, Kevlar was actually developed to be able to withstand heavy abrasion. If you've ever tried to sand it you'll know what I mean. It just fuzzes up and you don't really get anywhere.
    In the past, I have had a Rhinoliner coating sprayed onto the bottom of my boat in the same shape/size/pattern as a regular composite strip. It lasted me at least a full season of guiding, surfing, and general manhandling of my boat before I started to get gouges that went all the way through. Even then, I just filled the small holes with Plasti-dip and it was good to go. When I did it originally, IIRC the guy charged me about $125, I'm needing to have it re-done and recently got a quote from a guy out in AZ (where I live for school) to do it for $80. That might have to happen before this summer. I hope that helps.

    Cheers,
    West
     
  3. Comoxpaddler

    Comoxpaddler Paddler

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    I posted on the Yahoo Group for NDK boat owners and the answer does seem to be that it is just ordinary gel coat.

    Thinking of bedliner material as per Desertboater's post, which I have also seen mentioned on the P&H website, has anyone tried a "do-it-yourself" approach to this? I have found this stuff for $10 a can (aerosol) at Canadian Tire.
    http://www.dominionsureseal.com/product ... 3&catid=35

    I was thinking of spraying it on the top of a glass and gel coat keel strip.

    The advantage would be the ease of touch up half way through my trip (figure eight around the islands of Haida Gwaii).

    Overkill?
     
  4. rider

    rider Paddler

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    My semi educated guess is that the do-it-yourself air-dry single-stage liner won't be near as tough as the 2-part professional product. So frankly I wouldn't bother. If anything, for about 40$ worth of supplies you can add more keel strip the 'normal' gelcoat-and-cloth way.
     
  5. Roy222

    Roy222 Paddler

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    If weight is not an issue, then use "good old fashion" brass quarter round.

    Roy
     
  6. sushiy

    sushiy Paddler

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    I vote for 2 glass tape with graphite powder mixed coat for last coat.

    I read that this man who did Japan circumnavigation had 4 layers and it was overkill. One might wear out while 6weeks of everyday dragging and you have to redo it in a few month. You can see how much you can abuse the rest of the trip when the first one wears out in the middle of the trip!

    From what I hear from someone who used it, graphite powdered coat will help your hull glide on the rock nicely. I've never used it, but Pygmy was selling it, so you might want to ask them about it.
     
  7. Desertboater

    Desertboater Paddler

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    I have used both the spray-on and the brush-on rubberized stuff before both to repair gouges in my keel strip as well as to add a wear-guard on the cap on my truck. It's definitely nowhere near as robust as the Rhinoliner stuff. I thought I heard somewhere that you could get a two-part mix of the rubberized stuff, but I wasn't sure exactly where.

    I've actually been wondering about sandwiching a layer of kevlar in between thin, not-completely-cured, rhinoliner layers...I might see what I can do when I go back to the autoshop.

    Last year in Alaska we were applying keelguards to some of our newer glass boats, and we had this stuff from Seda that was a fabric that had been impregnated with some sort of really tough fabric. I could barely put a scratch in it with a brand new box-cutter razor blade. It was only about 4 feet long and about 4-5 inches wide, with nothing pre-cut into it as a shape/rounded ends. We just drew a centerline on it, and then matched that up with a centerline on the bow/stern, stuck it on, and then with a heat gun, heated it up to the point where it would get malleable (it's really stiff when it's cold) and then fold it over the edges wearing a pair of heavy leather gloves/hotpad pot grips... Once it was on, the only way to get it off/re-adjust it was to reheat it...once it cooled, it wasn't going anywhere. It definitely had a fabric feel/sound to it but it was really really bomber. It might be worth contacting Seda to ask about it. Hope that helps!

    Cheers,
    West
     
  8. Rrdstarr

    Rrdstarr Paddler

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  9. Comoxpaddler

    Comoxpaddler Paddler

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    Thanks for the replies.

    Sushiy, the graphite powder idea sounds very interesting. Anyone have experience of this? Should it be:

    - graphite powder in epoxy as a layer over glass?

    - graphite powder in gel coat over glass?

    - graphite powder in the epoxy when wetting out the glass?
     
  10. Comoxpaddler

    Comoxpaddler Paddler

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    Thanks Rrdstarr. I'm almost getting too many good ideas here!
     
  11. west_coast_russ

    west_coast_russ Paddler

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    When I built my Waters Dancing boat, the kit included graphite powder. After the hull was glassed and covered with epoxy, I put 3 more coats of epoxy with graphite powder, it has stood up very well, a couple surface scratches, but nothing more serious.
     
  12. Stumpy

    Stumpy Paddler

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    Just to throw a spanner in the works, a common keel strip in sof is a 1/4 X1/2" strip of hdpe, available from amazon.com for under $20 for a 1 X2' block, attach to your hull with neoprene tape (sold in auto parts stores as "molding tape"), then drop in a few SS screws to hold it firmly. easy to replace when it gets too beat up, and it actually libricates the dragging part. for longer strips, cut a lap joint in the ends on the table saw, and you can make them as long as you want... just put a screw in the lap.
     
  13. pryaker

    pryaker Paddler

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    Don't use ANY polyester resin at all. New poly will not stick well to cured polyester. Gelcoat is just a poly resin with color, intended to be sprayed first into a mold when a boat is being built.

    For a keel strip I'd use epoxy and by putting the graphite powder in the top coats I think you're protecting the epoxy from it's chief nemesis, UV light. All epoxy needs some sort of UV protectant either paint or varnish with UV inhibitors. From what I remember hearing in the West Systems catalog the graphite is intended for a final coat to inhibit UV damage and to theoretically be somewhat of a lubricant. I think there's lots of info on both the West System and System Three websites.

    So I'd do: wet out with epoxy then final coat(s) with epoxy thickened with graphite. Unless of course you go with bed liner material...
     
  14. nootka

    nootka Paddler

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    I trust new gelcoat will stick to old gelcoat that has been sanded, otherwise my gelcoat fixes should have jumped ship already.
     
  15. Astoriadave

    Astoriadave Paddler

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    I agree with pdxseakayaker that old polyester can be a difficult substrate for bonding, but if you roughen it well (80 grit sandpaper, well sanded to remove all glaze), new gel coat will stick. Epoxy is better, for sure, and if it were my boat, that's the direction I would go.
     
  16. Mark_Schilling

    Mark_Schilling Paddler

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    Barnacles work well too! :twisted:
     
  17. Tootsall

    Tootsall Paddler

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    The CLC solution mentioned by Rick looks interesting but I agree with Stumpy. We used strips of HMWPE (High molecular weight polyethylene) as "skids" for the heavy chain on a continuous elevator that was lifting ag products (sugar beets) up a 40' tall elevator. That stuff would last for months in 24/7 operation while handling a chain with a dead weight of about 10 tons and loaded with sugar beets at a rate of 5,000 ton/hour.

    A bugger to put on right and the weak spot was usually the fastener (that held it to a backing of oak boards) but in a wet, sandy, gritty, dirty, filthy environment it sure outlasted anything else we tried.

    Eventually the elevator was replaced by a bucket wheel but only because the elevator couldn't be upgraded to handle ~8,000 ton/hour.

    If you can get it in the right configuration (half-round?) and figure out how to attach it I don't think you'd be disappointed.
     
  18. gnarlydog

    gnarlydog Paddler

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    I have actually added a keel strip to one of my sea kayaks.
    I used West System epoxy 105 resin/207 hardener (UV stabilized).
    The hull was cleaned, prepared with sanding down the area of the keel strip, masked with tape and then finally I applied the keel strip.
    I mixed the epoxy (1:3 in this case) and then added in the mix graphite powder (West System) to about 15%.
    The graphite does increase wearability and acts as additional UV inhibitor (being black).
    I used a 2” tight woven glass tape for better wear protection and to act as “sponge” to absorb the resin.
    After the initial coat I added another two layers of resin and graphite.
    The job came out really good (shiny without needing to buff) and is way more wear resistant than gel coat keel strips (it was actually very hard to sand down the first coat imperfections.
     
  19. Comoxpaddler

    Comoxpaddler Paddler

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    Thanks to everyone for their advice. I am going to go for glass with an epoxy/graphite mix. We'll see how I get on!