Building the Slug

Based on my wealth of experience in patching two or three cracks in my Element, I decided that I was fully qualified and ready to build my own boat.
The finished product, just 3 short years later

The plan was to design a boat from scratch, because it was becoming increasingly difficult to find production boats that fit me. I liked the Element a lot, but it was just impossible to paddle in a hole, and it was also a little tough on highly concave waves. The long bow tends to hit the water if the wave is really curved. The design I decided to make was basically an Element without a long bow. I decided that I would make it a touch wider, like maybe an inch, and also give it a tiny bit more stern rocker, as well as a shorter and wider stern. I was going to keep the aggressive flared rails. That was where a lot of people raised their eyebrows, since it seems crazy. I was thinking back to the Liquidlogic Vision, which had apparently been acceptable in a hole, despite having some pretty aggressive rails. Of course, the sidewalls on the vision were flared out a lot more, so that the overall shape was still pretty rounded, and my plan was to keep the base wider than the top, but I was the boss.

Everybody that builds a custom boat loves to talk about their design idea, and nobody that's building a custom boat really cares that much about other people's custom boat design ideas. It's because the act of building your own boat is an almost fundamental rejection of other people's designs. You wouldn't be pouring your money and soul into this toxic mess in your garage if you thought the Project X was good enough already, or if Dave's composite boat was a great idea. You're investing all this time and effort because you want something unlike any other boat out there! So I'm done talking about my design.

With Stephen Wright's help, I settled on the name of "the Slug," because I figured that if I tried to give it a badass name and it was a piece of junk, I would look like a dork, whereas if I gave it a terrible name and it turned out to be awesome, people would assume that I just had really high standards and it would be great.

I also was guided through most of this process by the holy text "The Boatbuilder's Manual," by Charles C. Walbridge which is now massively outdated and also out of print. Carl Moser tipped me off to that book. Despite being so old, the book provides a great overview of how boats are made. I found that it was a great starting point. Whenever I had a suspicion that there was a more advanced material out there, I would go google it, but the book gave the framework so that I knew what I needed to google. It showed me what I didn't know. I recommend it to anyone building a boat, and I should mention that any mistakes I made were during the times when I was ignoring the book's advice.

Overall Plan

So here's the scheme I used. It's not the best, but it was cheap.
  • Shape a boat out of foam (called a plug).
  • Coat the boat in something epoxy won't stick to (I used packaging tape).
  • Lay up a top half of a boat on the plug. Peel it off once it cures.
  • Lay up a bottom half of a boat on the plug. Peel it off once it cures.
  • Stick the two halves together. Spruce that up and paddle it.

  • This process is known as making a one-off. The other option (one of many other options) is to use those boat halves as a mold, and build your actual boat in the interior of that mold you just built. The one-off has some benefits and some drawbacks.

  • Looks like crap.
  • Hard to produce repeatable boats that are similar to each other.
  • No silky smooth (and watertight) gelcoat on the exterior - the smooth side is the inside of the boat. (See item #1).

  • Benefits:
  • Faster - only build two big composite pieces.
  • Cheaper (not by much) because you don't pay for a mold.
  • Simpler (good if you have no idea what you're doing, I suppose).

  • So here's how I went about it.

    Shaping the plug

    The plug just has to hold its shape. It's usually made of foam, but you could use an existing boat as a plug (although this is morally questionable). I used that pink styrofoam that you can buy at the hardware store. My original plan had been to lay up the entire boat over the exterior of the foam, and just hollow out leg holes, so I bought waterproof foam. However, this would make repairs difficult, so I ended up switching to the plan described above. If you know ahead of time that your plug doesn't have to be made of watertight foam, you can save a little time and money by getting something cheaper that's easier to sand. Geofoam is an excellent choice, but since I didn't use it, I don't know much about it.

    So there I was, with a bunch of 2 inch thick sheets of insulation foam and a general sketch of the shape of the boat. I drew the vertical cross section of the boat on every sheet (I was able to fit two outlines per sheet) and cut them all out, then glued them together with epoxy, so that my very rough plug was made of vertical stripes of insulation foam.

    Then the sanding began. That lasted about two months.

    It was boring. Boat shaping timelapse from Leif Anderson on Vimeo.

    I used a punch saw and a drywall surfacer to shape this thing. If I had realized how much freaking sanding I would be doing, I would have gotten together a hot wire cutting kit. You can go google that yourself, but it's basically a hot wire, held in tension, and it cuts through foam like a hot wire through butter, leaving smooth surfaces behind, and it does it really really fast. Oh, my wasted life. Also, protip: gluing the foam together with epoxy leaves little epoxy walls in the foam that are harder to sand through, because the epoxy is hard. However, contact cement melts the foam that I was using.

    I cannot emphasize enough how long I spent shaping the plug. It took a long time. Throughout the process, I had a sheet on the wall with my design drawn out, including measurements, and every few hours I would check against those measurements. It took a lot of work. I got very used to wearing a dust mask.

    Eventually, the plug was shaped enough that I decided to move forward. I got 6 rolls of packing tape, and carefully coated the entire plug. I was ready (or so I thought) to start laying up the boat.


    The first layup was a failure.

    My plan was to use 4 layers of fiberglass on the deck, with soric foam core reinforcing key areas (flat spots like the sidewalls). I started laying up by painting on some epoxy, then laying on the cut pieces of fabric. I quickly went into panic mode, because it was hard to get the wrinkles in the fabric to lay down flat. Eventually I got it, mostly, but it took several hours, and I was going nuts because I was worried that the epoxy would cure too early. I rushed the last few layers, and wrapped it up in a mattress bag and stuck a cheap shop vac in there to pump it down to vacuum. This is really bad for your shop vac, by the way, and could potentially burn your house down. BUT THEN I JUST DID IT AND I WAS FINE.

    When I pulled the bag off the next morning, I saw that the deck was a failure. In my rush, I had not laminated all the way to the parting line. There were big sections of the deck that were dry fabric. I think I had assumed that they would get saturated while it was in the bag. Nope. After a lot of debate, I decided that I had to try again.

    Second time around, I had done a little more research. I enlisted Natalie's help, and we mixed small batches of epoxy, just a cup or two at a time. Although the first layer was starting to set up by the time I put the bag on, that's fine. Each layer was bonding to the next, and the overall process can take a pretty long time, with no problems. I went slower and made sure to get the fabric wetted out all the way past the parting line.

    Boat layup timelapse of the second deck from Leif Anderson on Vimeo.

    The one super embarrassing thing I noticed in the video is that we only had one respirator, and I wore it. I feel like I should have been a gentleman and insisted that Natalie wear it. My theory was that I would have my head close to the layup more than she would, and also that since she was helping for part of one afternoon but I was going to be working on the boat a lot, I was facing more exposure overall, which we were trying to minimize. Still, definitely not a great example of health and safety.

    I let it cure, popped it off the plug, and flipped the plug over to lay up the hull.

    For the hull, I had an awesome plan. My layup there was 4 layers glass, one layer carbon, and one really thin layer of glass over the outside of the carbon. However, I also included some foam core, since my hull was super flat. The foam core I used there wasn't the soric stuff, which is basically a thick fabric. No, in the hull, I used a half inch sheet of that same pink insulation foam. It was tough to get it to lay onto the curve of the hull, but scoring it with an xacto knife helped a lot there. I sanded the whole surface ahead of time, so that the epoxy would bond to it (not perfect, but worked ok). Again I layed up fabric to just past the parting line. The hull came out way nicer than the deck, because it was mostly a flat surface. And thanks to the crazy foam core, it was as rigid as... well, let's just say it was really rigid.

    Assembly and Outfitting

    Now I had two halves. If I had planned ahead a little better, I would have put a cockpit rim on the top half right then, while I still had easy access to the interior, but I was eager to have something that looked like a boat. Since I had laid up fabric past the parting line on both halves, I had two overlapping interlocking parts. With a lot of jamming and wedging, I managed to fit the hull half inside the deck half, and once they were overlapping, the shape of the overlapping part held them in place. I then used some 2 inch wide strips of fiberglass to glue the halves together, inside and out. The inside was a bit of a pain, but I could reach everywhere inside the boat without much contortion, so it wasn't bad.

    Real boat builders probably threw up in their mouths after reading that last paragraph. That overlap section was a huge no-no to a pro builder. It makes a void inside the boat, which basically means that although you have the weight of the inside layer and the outside layer (as well as the weight of any water that gets trapped inside there), you only have the strength and waterproofness of one of those layers.

    Also it tends to look like crap. Like, really bad. All knobbly and stuff.

    But know what? I don't care. I used a lot of layers on the exterior seam, so it was watertight, and sure it was less strong and heavier than it could have been, but I wasn't about to go paddle the Slug in the freestyle worlds or anything.

    Cockpit rim

    To build the cockpit rim, I traced out an existing cockpit rim of another boat onto a piece of cardboard, and cut it out, then drew that onto the Slug. I cut out the deck to match that shape, then hot glued a garden hose to the top of the deck in that shape. I used that hose as a ghetto mold to lay up the cockpit rim. A few practical pointers for anyone that is going to do this:

  • Use like 8 layers of glass.
  • Use bias weave strips, and make them relatively short. I describe bias weave in the patching article, or you can google it.
  • Don't try to paint the epoxy on. Roll up the fiberglass strips, dip them in your epoxy until saturated, then unroll the sloppy mess onto the waiting cockpit rim.
  • Do this one half at a time, and turn the boat on edge or on end or something.
  • When you are done, you are not done.

  • What I mean with that last one is that since your layers won't all line up perfectly, you will end up with this horrible serrated skirt-destroying edge on your cockpit rim. It's amazingly bad. Plan to lay up past the final location of the rim edge, then sand it back. Even then, you will basically have a smooth knife instead of a serrated knife. The really awesome finish is to get a thin non-waterproof rope (some little cotton line or something), and saturate that with epoxy and stick it to the top edge of the rim, then wrap two or three very skinny layers of fiberglass over the outside of that, and use like a million clamps to hold it in place while it cures. That gives you something that only does heavy damage to your skirt, instead of instantly wrecking it and also splitting any nearby atoms.
    Here is a rough sequence showing a cockpit repair on El Sinko, using the wrap around the rope technique that I describe above.

    Hip Pads and Seat

    There are a few different options here. Some companies use carbon or glass seats, but I have seen those cause a lot of problems. My plan was a sheet of thick foam glued to the bottom of the boat, with a jackson bean bag seat on top of it. That part worked pretty well (although be sure to use a tall enough seat). My current version is just a very thick piece of foam; about 4 inches, maybe 4 and a half.

    For the hip pads, I had this plan that had a lot of potential. I put in little vertical walls from the cockpit rim to the floor right where the hip pads would need to be. I used more of that half inch foam, with rounded edges, and covered it with a couple layers of glass. I then strapped hip pads around these new pillars. They broke instantly.

    After further experimentation, I have concluded that the idea is fine, but you need about 8 layers of glass. I originally used only about 4. I also determined that these can't be little thin bars, they have to be wider than the hip pad you are going to glue or strap on there. Otherwise the hip pad tends to twist off the bar a little. And furthermore it doesn't hurt to put a little horizontal reacher off to the actual sidewall for extra reinforcement, especially if you used fiberglass instead of carbon for your deck.

    Hot Coat

    Once the rim job was done, I sanded the exterior of the boat and painted on a coat of epoxy, which I then let cure without touching. This gave the final boat a nice glossy finish (not as nice as a true gelcoat, but better than the rough surface from the peel ply inside the vacuum bag). It also helped with waterproofing. I painted a layer of red spraypaint before the final epoxy layer. Not sure what effect that had.

    Getting on the water

    As soon as I got on the water, I started having some doubts. I was only paddling in the pool, but I could tell the slug was wide. Too wide. After getting home, I re-checked my figures on the paper plan I had taped to the wall, and they matched the Slug. But then I checked the figures against the Element, which was my starting point. I had swapped two widths. The width at the rails had become the width at the knees, and then I had added a few inches to get the rail width. So the overall effect was that the boat was about 4-5 inches wider than I had intended. This is an astronomical change. I didn't realize at the time how big of a difference a change by one inch would be. This was way off.

    The other thing I noticed was that I had totally messed up somewhere and the boat was terribly unbalanced. The stern was tiny and the bow was pretty big. This made flatwater cartwheels almost impossible. I could just barely get it up into a bow stall. Of course, once it was on end, it looped pretty well, since there was almost no stern.
    It did flatwater loop pretty well.
    I also couldn't help but notice after two or three loops that I had cracked my stern. Yes, on flatwater. This was because I had a big huge flat area on top of the stern, which was pretty weak. I dried it off that night and laid up a layer of foam core, which has held together ever since.

    Eventually I got the slug out on the water, and it was really hard to do tricks. It was like having a mentally handicapped child. I was fiercely proud of the Slug, but I knew that it was not really going places in the world. Slug ended up living in a woodshed in rural Canada, away from the heckles and jeers of the insensitive public. I would sometimes come visit the shed, and maybe bring out a balloon or some candy, and just spend time in the dark there.

    Then, based on some research with El Sinko, which is a whole different story, I realized that maybe my seat was just too low. So I tripled the seat height and took the Slug out for a paddle. I found that although it was still a far from optimal design, it was far better than my initial impression had been. The Slug was redeemed. It now is moved out of the wood shed, and currently lives in a much larger shed with better lighting. It has many other special kayak friends that it hangs out with.
    One of the first few surfs in the Slug. Incredible speed, incredibly bad tricks.

    Slug returns from Leif Anderson on Vimeo.

    Surfing the Slug with the new seat. Back Pan Am machine!
    Also acceptable at clean blunts.
    I've also learned how lucky I was on my first project. I built a set of other boats that were copies of production kayaks, and tried to make a smoother cockpit rim. Those other boats were fraught with trouble. The cockpit rims weren't watertight, and there were tons and tons of leaks elsewhere in the boats. I think the simple flat surfaces of the Slug made it a little easier to lay up a thick watertight design, but maybe there's some mojo to using spraypaint inbetween epoxy layers or something.


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