How to Use a Plastic Welder to Fix a Cracked Kayak Hull

    There are a lot of things that can go wrong in life when dealing with your kayak's hull. Take for instance, a recent "upgrade" I tried to do with my kayak.

The story:

    About three years ago, I had an Eagle Cuda 350 (Sonar/GPS), a small, gray scale, entry level fishfinder with GPS. It served me well for about 3 years during the day, but I mainly used it at night to help me find my way back to the boat launch area. But, there came a time when I needed it the most, and it failed to start - even after I had just finished charging the battery.

    So, I finally caved in and got a Lowrance Hook 5 DSI fishfinder/chartplotter/GPS. It was like stepping into the future with this new unit. It has a much larger 5" viewing screen, color display, a micro SD card with 6000+ lakes pre-loaded for all 50 states, and a state-of-the-art GPS system. It also came with a much larger transducer measuring in at 2" wide and 4" long - way bigger than the previous version. The way I had my transducer set up, it shot through the hull. This setup provided protection from the rocky bottom and other underwater obstructions that couldn't be seen by my eyes -  day or night. The transducer sat in 2 foam spacers that were doubled up together and affixed to the inside of the kayak's hull using Marine Goop. I would fill the spacers with water, then press my transducer in slowly to squeeze out the excess water and air bubbles, to give me a solid reading every time. But, with the bigger transducer, it wasn't going to fit my spacer setup. So, in order for me to make a new spacer, the old spacer setup had to come out.

    I figured I would use a scraper first, to see how that goes, then switch to something heavier duty later. I knew Marine Goop was pretty durable, but instead, it was harder than a rock. The fact that the air temperature in my unheated garage is around 30 degrees doesn't help. The scraper just wasn't cutting it. So, I switched to a heavy duty chisel, and a small ball peen hammer to help scrape away the spacer blocks. At first, it was going pretty smoothly, but then the inevitable happened - I thought I was making headway, but I ended up driving the chisel completely through the bottom of my kayak, tearing a 3" gash in the hull! While I'm usually patient at doing things to my kayak, I'm pressed for time for an upcoming saltwater show in early March, so my impatience led to me trying to cut a few corners, and it cost me by compromising the hull.

The solution:    

    But, being a former auto body technician, I have a remedy to this unlikely situation. While most people would've freaked out, and possibly thrown away their damaged kayak in the garbage. There is a cheap alternative that will save you a ton of money and it's called a Plastic Welder.

So, let's get started:

    If you've never heard of a plastic welder, they're usually used in auto body shops to repair front and/or rear bumper covers on today's newer cars. Some plastic welders can cost several more dollars, but this one that I have costs around $17, and it's a decent 80 watts, more than enough to get the job done. It was purchased at Harbor Freight. 

    The nice feature about this model of the plastic welder is the flat triangular head that makes it act like a very small iron (much like its big brother that you use to iron your dress shirts with). This will enable you to smooth out the plastic better.

    Because I've already sealed the crack in my Hobie kayak's hull, I'm going to use a scrap piece of plastic that I found at the transfer station. The piece in question came off an old Honda Quad (a fairing vent, I think). 

    

    Anyway, let's pretend that this is a crack in the kayak hull. Yeah......., it looks pretty deep.

   

    Above photo: from the front.

    Above photo: from the back.

    Okay, after assessing the damage, you want to get a screwdriver, and from the back (or, bottom of your hull) you want to press the raised edge back in so that it's "level" again. The nice thing about a kayak's hull is you can flip it over to work on it.

    Then, once you get it as close to level that it was, you take a razor knife and slice a thin piece off the exposed raised edge. This should form a "valley", or a V-like channel that you're going to fill in.

    Above photo: Prepping the "valley" for a fill in.

    Using the previous piece of plastic that you trimmed off earlier with that razor knife, you're going to use that piece to fill in the crack. Lay the trimmed piece in the valley, and with smooth strokes, melt the piece into the valley. 

    You'll know when the plastic welder is hot enough when the plastic begins to melt under the head of the iron. 

    (As seen on the Plastic Welder's carton in the above photo)

* DO NOT, FOR ANY REASON, TOUCH THE CHROME AREA ABOVE THE HANDLE! *

    * Note: DO NOT leave the iron in one spot! Keep moving it around so it doesn't burn through!

    Above photo: Melted plastic piece inside the valley.

    If you need more plastic to really completely fill in the damaged area, you can use an old milk crate. It's made of the same material as your kayak. But, instead of stealing a milk crate, you can buy one here (to match your kayak's color): The Container Store - Milk Crates

    To get the plastic shavings you need, you can use different size drill bits make the shavings you need. Small drill bits will make thinner and stringy shavings. While larger drill bits will make thicker and longer shavings. Color shouldn't be a big concern. You're filling in a crack that nobody will see.

    

    * Tip: In the photo below, when filling in the valley with the desired plastic, to keep the plastic "clean" and not to have it discolor the area by turning black, you should use the small wire brush (provided) to clean off the iron's head frequently. As the plastic melts, the built up melted plastic will burn on the end of the iron's head causing it to turn a blackish color, further discoloring your damaged area.

    Above photo: Patched area discolored from a dirty iron's head. Clean the head with a wire brush frequently, so as to do a nice clean patch job.

    To strengthen the back (or, inside hull) of the damaged area, repeat the same process.

   
    Above photo: After the welded patch is complete, you have a nice weld that is waterproof inside & out.

    When you're finished, unplug the plastic welder and set it on the angled metal rest provided, (preferably on top of a piece of scrap wood board) and keep it away from anything flammable while it slowly cools down.

    Above photo: Using the metal rest provided, this will make it easier to keep the iron clean.

    If you need more practice, use some old milk crates. Pretty soon, you'll be plastic welding everything in sight - helmets, kayaks, bumper covers, water jugs, etc.. Be sure to save the scrap milk crates when you're done cutting them up. You never know when you'll need them. I have lots of containers with scrap & colored shavings from all kinds of "donor" plastics, such as ATV/Dirt Bike fenders and scrap milk crates. So far, I have shavings in the following colors: Red, Yellow, Orange, Black, Grey, and Olive Green.

    I hope this "How-To" article is helpful to you and your friends in making the right decision to save money on a simple fix, rather than to spend several hundred dollars on buying new equipment. That way you'll have more money to spend on better fishing equipment.

    As usual, keep those lines wet and tight! - J