Don't take your Sportspal Canoe into the saltwater

Discussion in 'Watercraft' started by Jim Wallace, May 28, 2008.

  1. I've used the hell out of my 13' Sportspal square stern canoe since I first got it new in late July 2002, and it has been a fine craft. I use it a lot in the estuaries, and I have taken it into Puget Sound a couple of times.
    If you are unfamiliar with Sportspal canoes, they are made of aircraft aluminum stretched over a form and then strengthened with extruded aluminum ribs. A 1/2" thick foam pad covers the inside of the hull, held in place by the 25 (on my 13' boat) ribs. The foam insulates, makes the hull quiet, and provides floatation.

    I had coated the bottom with Gluvit so I could slide over the rocky riffle sections on streams in low water, as the aluminum hull was really "grippy" on the rocks.
    Lately, I had noticed that the gluvit was getting bubbles of air pockets popping up randomly all over the hull. Were there tiny pinholes in the Gluvit, letting moisture in? I couldn't see any, so I chipped and sanded all the bubbles away, noticing that there were pinholes all the way thru the hull where the bubbles were.

    Uhh-Oh! I deconstructed the boat, taking out the seats, ribs, and foam, and found what I had feared that I would. Sand, salt, and mud had worked its way under the foam and had become trapped down there. The hull was getting corroded thru from the inside. All that sand/salt/mud doesn't just wash out with a good hosing, as the ribs hold the foam tight against the inside of the hull, trapping all that bad stuff, which does its dirty work sight unseen, until it blossoms forth at an inopportune time. Now I am faced with a major repair job.

    I washed and scraped most of the scale out, then polished the rest of the surface corrosion off with a wire brush on my electric drill. I'm over halfway done with this polishing phase. Took some time. There are a few hundred, maybe a thousand, small pits in the thin aluminum, but if I "etch" the aluminum with a mild acid solution (white vinegar) to clean the surface and the pits, patch the actual holes, and coat the inside with something to fill in all those pits, and then refinish the outer hull, I can probably still use this LAKES and FRESHWATER rivers.
    I'm thinking of using "Coat-it" on the inside. Its what I'm using to refinish the outer hull as well.
    I was wondering if there was some sort of polyurethane product which might work, as the stuff is tough and more flexible than Coat-it, but I dont know how well that would stay bonded to aluminum. That "hardened aircraft aluminum" doesn't like coatings. Anyone know anything about this kind of stuff?

    If you use your Sportspal canoe in the salt, this may happen to yours as well. I don't know about you'all, but this sounds like work to that cuts into one's water time. I won't be using this boat in the salt or brackish waters again, once I get it fixed.:beathead:
  2. That sounds like electrolysis ... and it can happen in freshwater as well.
  3. Could be electrolysis, as I don't have a sacrificial zinc anode on the boat, and regularly use Minnkota electric trolling motors on it.:hmmm:

    My next cartopper is going to be wood (if I build it myself) or kevlar/carbon composite or even royalex or polyethylene....looking at the Native Ultimate.
  4. I'm guessing that the problem has a lot to due with your application of the Gluvit. In applying the Gluvit, you probably disrupted the oxide layer on the aluminum - which is the best protection that aluminum can have. Combine this with the foam that doesn't allow you to rinse out the salt on this inside, nor ever really let the inside dry - and you have a real problem.

    I have used aluminum canoes in the salt for decades. I have a 35 year old aluminum sea nymph canoe that has seen lots and lots of salt with absolutely no ill effects. I wouldn't put that silly foam back in the boat if I were you. It does quite the boat, but it's not necessary (there are no loud canoes - only loud canoeists).

    No reason to coat an aluminum canoe with Gluvit or any other product. Yes, they can stick to rocks which can be a problem in class III rapids, but how often do you take a square back into that kind of water?

    Galvanic corrosion can be a problem with aluminum, but as long as the oxide layer is kept in place, it's pretty minimal.

    I've never done anything special to any of my aluminum canoes. I clean them once per year (or more if I want it to look pretty) with soap and water using a green 3M scrub pad. I hose them off after they have been out in either fresh or salt water.

    By the way, I use my 35 year old Aluminum canoe in class III waters and never have a real problem with sticking (the idea is simple - don't hit the rocks!)
  5. Thanks for your thoughts and advice, skirkpat. Yes, the Gluvit was a bad idea, but I suspect the corrosion from the inside would have happened anyway. I was coming to a grinding halt going over the shallow riffles (mainly late summer low water). I was getting hung on smaller cobbles and not boulders, and the hull bottom was getting grooved and scraped. Yes, it was a bad idea.

    However, now I must fix the small holes and coat the aluminum to fill in the pits, or just take a total loss and scrap the entire canoe. I figure i can get a few more years out of it by fixing it. There are a couple of lakes I can drive to that have rough or carry-in launch sites, and I need it for that.

    I have to put the foam back in the boat, or else the ribs won't fit in right, and the boat would be too flimsy to use. I don't have the choice. The foam is also part of the floatation

    I won't ever buy another aluminum canoe.:beathead: This one seemed like a good buy at the time. Great features, otherwise, though. Keep Sportspals out of the salt. They aren't the same animal as your regular aluminum canoe.
  6. I know the theory about aluminum oxide and Galvanic first experience with it doesn't match the common beliefs.

    A buddy's family had a really old aluminum boat that they kept docked at their lake cabin (Twin Lakes, Idaho) during the summer for a couple of decades. It started to leak, and my buddy brought it home to fix. But it turned out that the GV had eaten the transom of the boat until it looked like Swiss cheese, and a particularly holey cheese at that. There were lots, and I mean lots, of little pinholes from the water line down.

    Now this boat had never been sanded, nor had the coating on the transom been disturbed in any way since it came from the factory, yet it was toast. The GV could well have been from a short within the electrical system or because the boat spent four months of every year in the water, but whatever it was, the corrosion had done its job. As I recall, the boat was painted (again as it came from the factory), only proving that the corroding process can be pretty wicked.
  7. I finished wire brushing the inside and after inspecting everything, the blame for the corrosion rests solely on the pad trapping the salt and sand and mud between it and the hull.
    Maybe it was helped by "galvanic corrosion" from running the electric motor, but it is only happening from the inside of the hull where the pad was trapping the salty gunk.

    My Gluvit job was done properly(over 2 years ago), and it is adhering just fine to everywhere there wasn't a hole corroding thru from the inside and causing it to bubble and de-lam.
    Also, the canoe was painted by the manufacturer, and that is holding tight to the hull on all exposed parts, with no corrosion originating on any of it, including the inside near the bow, where the pad does not reach.

    So if you own a Sportspal, you'd be wise to never take it in the saltwater.:beathead:
  8. The saltwater getting in the boat is creating its own galvanic corrosion. You have, in essence, created a battery. The aluminum hull is the anode (metal that will corrode), the foam is the cathode (usually this is a dissimiliar conductive metal, but wet foam will work just fine, maybe even better), saltwater is an awesome electrolyte and there's definitely electrical contact between the anode and cathode. Voila, instant battery and corrosion to beat the band. To stop it from happening again you must eliminate one of these four. The fourth is by far the easiest, aside from never getting the boat wet again. Using it in freshwater only will help a lot, but freshwater will still act as an electrolyte. Just not nearly as good as saltwater.

    In Naval aviation we're pretty aggressive about keeping our multi-million dollar canoes, er, aircraft from corroding. The number one thing used to fight corrosion is cleaning! If that canoe were owned by the Navy, they would require removing the foam on some sort of regular inspection cycle and cleaning the tar out of the hull. Same for aircraft; they get washed and thoroughly lubed every seven days at sea. That's on top of all the daily stuff! You might have to consider doing so on a regular basis; say yearly or something like that.

    Second after cleanliness on the corrosion busting scale is protecting the metal. You're on the right track with coating the inside of the boat. We do this with lots of different chemicals, but aluminum is always treated with a conversion coating chemical. This causes the metal to form an oxide barrier layer. Then, depending on the type of metal, it's primed and painted with up to seven layers of stuff, with only the last layer or two being actual paint. We use a lot of stuff called "Epoxy Paint" that seems to be the bomb when it comes to preventing corrosion. It's used a lot on magnesium, which corrodes if you even look at it wrong. The aluminum exterior skin is usually just conversion coated, primed and painted with a few coats. Interesting to note that exterior paint is "flat" or dull, where interiors are painted with gloss. The flat is supposed to be better camoflauge, but the gloss is better protection against corrosion. I don't know what Gluvit actually is, but it sounds similiar to what we call "epoxy paint".

    For success, you must remove all the corrosion before any coating goes on. Any pockets or cells left will flare up again quickly. And be careful with the wire brush! You should only use aluminum brushes on aluminum, otherwise you can get steel particles embedded in the aluminum. That will lead to a new problem called "dissimiliar metal corrosion". You may not get a problem with that by itself, but if corrosion does get started again by another means the dissimiliar metals will accelerate the process.
  9. Chad, Thank you very much for your explanation. Very enlightening, to say the least.:eek:

    Yes, Gluvit and Coat-It are both 2-part epoxy paints used for coating boat hulls. Mainly used on the bottoms of aluminum drift boats. I plan to apply a couple of thick coats to the inside, and one thick one over the sanded Gluvit on the outside of the hull.

    I'll have to see what's available for a "conversion coating chemical," but i bet the folks down at Englund Marine in Westport can help me find something. Only about 6 miles from here. they carry both Gluvit and Coat-It.

    At this point, I'm almost thinking of retiring the boat and turning it into a planter.:beathead:
  10. Jim,

    For the amount of work you're going to, I think the planter idea has the most merit. Sorry you're having this experience. I've had the same Royalex canoe (Easy Rider) since 1984. I bought it after wearing through a fiberglass one I had previously. What plastic lacks in aesthetics it compensates for in durability.

  11. Chad,

    Could you explain how foam could contribute to galvanic corrosion? Doesn't make sense how foam could act as the cathode. Foam has no electrode potential.

  12. Skirkpat,
    Yeah, I know it doesn't sound right. This is right out of the Navy's Corrosion Control manual:

    A dissimiliar conductive material (the cathode), which has less tendency to corrode than the anode, must be present (a dissimiliar metal may be a different metal, a protected part of the same metal, or conductive plastic).

    According to this the cathode need not be a metal, but can be any material that will conduct electricity at all and allow ion flow from the highly corrosive part (the alumunum) to the less corrosive part (the foam). Depending on what it's composed of, foam could certainly conduct electricity to some extent. Another good example is carbon fiber. This stuff has many metal-like properties and can be highly cathodic and destroy metals attached to it quickly. A key thing to know is that corrosion is increased the more dissimiliar the anode and cathode are, even if the cathode is not a very good conductor. If the cathode is a good conductor and also corrodes at a very dissimiliar rate to the anode (say aluminum and titanium), then things get bad in a big hurry. Jim's boat lasted as long as it did because foam is a crappy conductor. You could also take a swag at it and say the foam had to become saturated with metals absorbed from the saltwater, then it may have become a darn good cathode! That makes it possible there was no galvanic corrosion taking place for a long time, then things got bad quickly once the foam took on those properties. Hard to say for sure; I'm not an engineer, I just read books :ray1:
    astrofisher likes this.
  13. I would not get the Sportspal nor the Radisson if you plan to use it in saltwater.

    The ribs won't fit in right without the foam pad. Its made in Michigan, and those guys apparently don't know salt water.

    You can purchase foam sponsons similar to the ones on the Sportspals, and install them on practically any canoe, pointy ended or square stern. Its an easy job. Cabelas sell them. The canoe store I was in today in Portland, OR had some. They also had a cool wide-transom 3-seater squanoe made from Royalex that weighed in at about 45 lbs. No aluminum on it. Web seats on wood frames. Maybe 14 or 15 feet long. Canadian made and kind of expensive...I'll have to look up the name.

    When i turn my Sportspal into a planter,(thinking strawberries:D) in about three days, as i have decided to scrap the swiss-cheesy hull , I might look for a used tupperware squanoe and install the foam sponsons from the Sportspal on it, to add secondary stability.

    I got the Native 12 in Olive:D

  14. I had a tupperware party a plastic kayoe, ptydptydptyd that stuff ain't cheap!!! and I was looking for a spot to transplant my strawberries ...
    "Here lies a Sportspal 13' Squanoe full of dirt. She served faithfully to the last, and her stern never got wider than the day I brought her home. R.I.P."

    How's that for an epitaph? :rofl:
  15. Those Radissons are very similar to the Sportspals, except their hulls were only 2 mm thick, whereas the Sportspals are 3 mm thick (when I was doing my research 6 years ago. Maybe that's changed?). Thats how Radisson gets theirs to weigh less. It might not last as long as the Sportspal in the salt.

    I saw a huge diesel p/u towing an Airstream trailer yesterday on I-5. It had a large Old Towne sq stern on the roof. Maybe 18 feet long, with a camo paint job. Made out of some kind of polyethylene or royalex. That thing looked like it could hold four people. Heavier, but more durable construction. It was big, and it was a sq stern canoe.
  16. OK, I just looked up the Canadian sq stern. its made by Esquif. Just ggogle Esquif Canoes and take a peek at the Cargo model. Its 17' long with 4 seats, made from royalex. These may be the lightest ones you can find.
    Check out the Heron for a smaller one. I think these may be the best sq sterns available! I don't know. I am not connected with any marketers or sales or stores in any way. Just my opinion. I may have to get one! You can never have too many boats as long as you have a place to store them cheaply.:beathead:

    Now I must leave to paddle my Naive 12 into some secluded backwater. :D It needs to be eddycated.

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