Refinishing a sun oxidized kevlar Kayak

Discussion in 'Boat and Accessory Building' started by Water Horse, Jul 3, 2015.

  1. Water Horse

    Water Horse Paddler

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    My son just bought a 2007 kevlar Tsunami 175 pro. The fellow we bought it from had stored the kayak hull up for the past 7 years in the sun. It looked in pristine condition and we thought we got a good deal but when we brought it home we noticed that oxidation on the hull was extensive. The kayak is a red top and white bottom. When we run our hand along the white hull a white powdery substance comes off on our hands. Can this be brought back to life? What is the best approach/products to use? I have never dealt with this kind of problem before - don't know where to start.
     
  2. Astoriadave

    Astoriadave Paddler

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    Hard to say what you have without looking at it. My understanding is that Kevlar demands epoxy in layup, but don't know what the gel coat is. Probably the white stuff is from too much time in the sun. Contact the manufacturer for advice, I suspect. I bet you will need to sand carefully, then renew the gel coat.
     
  3. JohnAbercrombie

    JohnAbercrombie Paddler

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    Is the goal to make the boat hull look 'like new' or is the concern about something structural?

    I'd start with a 'Scotchbrite' or similar scrub pad and give the hull a good scrubbing with detergent and water.
    If only the very surface of the gelcoat is affected, this may be enough.
    Next step would be to try rubbing and polishing compound on a small area (on the bottom) to see if the gloss is restored at all. If that works you can 'do' the entire hull. Autobody shops or the finish shelf in your auto supply store will have what you need; chandlers often carry the 3M Finesse products and similar.

    I'd avoid sanding with anything coarser than 320 and water, unless you intend to do some serious refinishing.

    Also, try to avoid using any polish with silicones. It will interfere with future refinishing work. Removing silicone polish is possible but an extra step and a 'pain'. Silicone-free car/boat polishes are available.
     
  4. Water Horse

    Water Horse Paddler

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    Thanks for the advice. It would be nice to have it look like new again but we were worried about how this deterioration might affect the kayak's integrity in the long run.

    Would a wax like this be the a good polishing compound?

    Meguiar's Flagship Premium Marine Wax

    http://www.canadiantire.ca/en/pdp/megui ... ZgZFWCtmlV
     
  5. Astoriadave

    Astoriadave Paddler

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    I did a search and could not find silicones listed in the ingredients, at least in the MSDS. Unless the ingredient is hazardous, however, it is not required in the MSDS. When you get hold of the container, see what it says.
     
  6. Astoriadave

    Astoriadave Paddler

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    Searched another way. Down a ways under the M subset, they indicate surfaces treated with that wax are not paintable. Context suggests that is due to presence of silicones.

    http://www.meguiarsonline.com/forums/sh ... afe-or-Not

    I'd avoid any wax until you are done reconditioning the surface. Then, consider 303. No silicones in it.
     
  7. JohnAbercrombie

    JohnAbercrombie Paddler

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    Gelcoat is there to scrape off with rocks and barnacles, and then you can apply more. :D
    I wouldn't worry about any structural problems until you start to see exposed glass/resin laminate.
     
  8. Water Horse

    Water Horse Paddler

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    What is problematic about silicons? Is there a difference between gelcoat and clearcoat? Where is a good place to obtain that (I am in Canada)? ...or is it best to have that professionally applied?
     
  9. Astoriadave

    Astoriadave Paddler

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    Don't know what clearcoat on kayaks is. On vehicles it is a plasticized clear paint which protects the underlying finish. Sometimes problematic, degrading ahead of the lifetime of the vehicle.

    On silicones: once applied, they forever make that surface reject all coatings: they won't stick. Unless you physically remove a layer of whatever they were put on. On a kayak, this amounts to sanding off a millimeter or so. Sometimes penetrates into cracks, so you have to grind all the way down to the bottom of the crack to get a layer of gel coat or paint to stick.

    Gel coat is typically a layer of polyester, vinylester, or epoxy resin, sans fiberglass or kevlar, pigmented heavily but having no structural strength. The underlying glass provides the strength. The gel coat prevents UV rays from degrading the underlying resin, and is a sacrificial layer protecting the underlying glass/resin composite from abrasion. Quality boats have a thicker gel coat, so you don't have to renew it very often. Small areas can be patched with over the counter kits, color matching being the tedious, tricky part. A full gel coatcoat renewal is really a job for a shop. Unless you are in the habit of dragging your boat across rocks on landing and launching, only patching should be needed during the lifetime of the boat.
     
  10. JohnAbercrombie

    JohnAbercrombie Paddler

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    +1 on Dave's advice above.

    I don't think your entire hull will need refinishing, but...
    I think that using a good quality 2-part polyurethane paint is easier for most folks than trying to apply/spray gelcoat over the entire hull. (And, paint is lighter than gelcoat.)

    The hull is going to get scratched and abraded; you can repair and 'touch up' with polyester gelcoat indefinitely. A 'mint condition' hull bottom is the sign of a sad, unused boat! :D
     
  11. Astoriadave

    Astoriadave Paddler

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    Waterhorse,

    I did a little Googling on clear coats for epoxy and ran across this article: http://clearstreamwood.com/WordPress/ka ... asion-test

    It may give you a handle on the varieties of clear coat others have used over epoxy. It is a bit dated, circa 2008, but likely the principal choices are not much changed since then. Only one choice he made seems ill advised to me: polyester resin over the epoxy. Depending on the epoxy used in the layup, polyester may not cure. You need to find someone more knowledgeable than I am on that one.

    As John describes, a two part polyurethane, likely one demanding a professional application, is a good choice, for durability, and very good UV resistance. I have worked a lot with System three's WR-LPU, and can not recommend it for a clear coat on the hull of an epoxy boat, unless you are already experienced with it. It is durable, all right, but demands so many coats that you will soon tire of the process. It is also finicky about application. Further, many of the two part solvent based polyurethanes require forced air breathing systems to protect the applicator, and are not usually available on the consumer market. Auto body shops can get it, and a knowledgeable shop might be a good choice if you want to go that way. Here's the bummer: this would be a witch to spot repair.

    I believe most of the clear coat protective top coats on new vehicles are two part polyurethanes, but can't say that authoritatively. Note that some of these fail spectacularly.

    The best solution would be a resin based coating that is easy to renew or spot repair. Note ordinary epoxy, unless it is filled with protective pigments, will not shield the epoxy in your boat from UV.

    If you plan to use a professional shop to do the job, best check their bonafides and see some of their work. Won't be cheap.
     
  12. Water Horse

    Water Horse Paddler

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    Thanks for all your comments and research.

    I have now tried using a dish scrubber on the oxidized part of the kayak. Below are images; the upper right part scrubbed and part left alone (lower section). The difference is obvious. The close up still shows minor blemishes but mainly invisible from a distance. I think this is going to work well. We just need to add some paint to an area at the back where the paint has rubbed off from dragging it on the rocks.
     
  13. Astoriadave

    Astoriadave Paddler

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    My guess those black specks are mold. Hot soapy water should remove them. Sounds like that is what you have discovered.

    The area showing a more or less uniform black cast looks to be a spot where the gel coat has been abraded down to the underlying resin. To protect the resin and the Kevlar underneath, you should build the gel coat back up to what was there when the boat was new. A coat or two of paint is not enough. It will only take a few trips, with normal abrasion dragging the boat across a sandy shore on launching and landing, to abrade the paint off. Then you will have to paint it again.

    If the abrasion reaches the Kevlar, and the boat is used on the water quite a bit, this may eventually compromise the Kevlar epoxy bond.

    The area which needs more gel coat is small, and an easy fix. You could buy a gel coat repair kit from a marine store and try it out in that area to see if it cures. If it does, you are good to go. If not, move on to a kit designed for use over epoxy. The most common kits use polyester resin, which does not cure over most epoxy surfaces.
     
  14. Water Horse

    Water Horse Paddler

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    Yes, I am sure some of discolouration is mold. Sorry the lighting is poor and probably misleading - the dark areas you are referring to are probably the shadows from the straps not worn spots. I sense the gelcoat is pretty uniform (except for a small spot (an inch or so) at the stern were it was taken right down to kevlar epoxy from dragging it on the rocks. I don't think the kayak was used more than a handful of times, it was just left in the sun for years.
     
  15. JohnAbercrombie

    JohnAbercrombie Paddler

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    That's the 'usual spot' for the gelcoat to be 'ground off' with use. Even sandy beaches will do it.
    Most paddlers follow a routine similar to this:
    Hop out of boat, trot to front, grab toggle and lift boat. Pull boat up the shore till the stern (supporting all the weight of boat and gear) starts rubbing on the 'beach'.
    As Dave says, you need to get more gelcoat on that area to protect the Kevlar. Don't be afraid to build up a good thickness - if you use the boat it won't last a long time.