Building a Perfect Kayak: Part Ten

cedar strip kayak with rubber and plastic hatches
cedar strip kayak with rubber and plastic hatches

cedar strip kayak with rubber and plastic hatches

Last episode, I wrote about Free!Ship, and now with version 2 out, I’ve been able to recalculate by hydrostatics using the Free!Ship program to provide me with numbers that I had to calculate and figure by hand in the third episode of this builder’s log. With the new numbers, I’ve come up with some more realistic numbers for Resistance, and the like. Opps, I forgot to account for long tons when using FREE!ship. My calculations via hand and mind were actually closer than I thought. Here are the updated numbers:

Design Name: Siskiwit Bay

  • Length Overall: 17′
  • Beam: 21.5″
  • Volume: 11.81 cu. ft.
  • Cockpit Size: 30″ x 15″
  • Coaming Height:
  • Forward: 12 1/2″
  • Aft: 8 1/4″
  • Height of Seat: 1″
  • Weight: 45 pounds (est.)
  • Center of buoyancy: 53.5%
    • Hydrostatics calculated at 298 pounds

    • Lwl: 14.945′
    • Bwl: 19.728″
    • Draft: 5.16″
    • Displaced Volume: 4.693 ft3
    • Block Coeff.: .4443
    • Prismatic Coeff: .5510
    • Midship Coeff: .80631
    • Wetted surface area: 21.041 ft2

      KAPER

      I made an opps, and forgot that displacement in tons is in long tons, so my original calculations for 295 pounds in KAPER was incorrect. These are now the correct numbers:

    • 2 knots .906
    • 3 knots 1.883
    • 4 knots 3.479
    • 4.5 knots 4.842
    • 5 knots 7.116
    • 5.4 knots 9.673

    These KAPER numbers compare closely to the Chatham and Romany Explorer. They are slightly better than the numbers for those two kayaks, but close enough that in usage, they probably won’t make much of a difference. These numbers are much better than the Chatham and the Romany Explorer. At 4 knots showing an 11% gain over the Chatham and a 4% gain over the Explorer. I guess, I’ll see soon.

    Kayak coaming being clamped in place.

    Kayak coaming being clamped in place.

    Finishing the Kayaks Cockpit Coaming Lip

    With the cockpit cutout and the riser mounted and glassed, I could move on towards the coaming lip. If you remember last episode I used thickened epoxy to form a bead around the riser and the hull so that the fiberglass would be able to conform to the curve better. This worked, but it is ugly. Next time, I would ignore this advice and just glass the riser pieces. Then let the epoxy set up for an hour or so, and come back and push the glass in if needed to make a nice clear joint. I did this on my compass mount, which you’ll read about below, and it worked out great.

    cedar strip kayak coaming and cockpit

    cedar strip kayak coaming and cockpit

    Anyway, with the glass on the rise set and dried, I cut with my circular saw (Anyone want to give me a nice tablesaw? I deserve it. I mean read everything that I’ve gone through on this boat build. Christmas is coming up.) some 1/8″ x 1/4″ strips of mahogany and pine to laminate onto the coaming and form a lip to hold on the spray skirt. On my skin-on-frame Greenland style kayak, I did the same thing. Even without fiberglass, this turns out to me a strong lip that is very easy to make. I ended up deciding on this type of lip, because I didn’t want to have to fiberglass the underside of the lip. I wasn’t worried about waterproofness, because I used a waterproof PU glue to hold the lip pieces together. The thin 1/8″ width of the pieces allowed me to bend the pieces without steaming them, but in several places to get them to bend, I had to use a heat gun. This process started a weeks worth of slooooooowwwwwwwww apparent progress, because I had to wait until the glue dried between adding parts. The glue takes about an hour to get to the point where I could add the next level of the coaming. So, one day was almost shot doing the lip.

    After the glue dried on the last part, I planed, sanded, and glassed over the lip. As you can see in the pictures, the mahogany has beautiful grain, and the single stripe of pine, I think, not only matches my kayak well, but also makes the mahogany stand out even more. Pat self on back.

    My Necky neoprene spray skirt attached to my new and really really good looking coaming.

    My Necky neoprene spray skirt attached to my new and really really good looking coaming.

    The Hatches (Where to Buy)

    I bought my KajakSport hatches from Newfound Woodworks Inc. They were friendly, quick to help me pick the right sizes, and also on the phone they gave me advice on how to mount them in my kayak without me having to ask. On the phone, they told me that they only had one of the bigger hatches, so that the second would come separately. I got the hatches the next week with the note showing that my backordered hatch would arrive almost two weeks later. A couple of days later, the backordered hatch showed up. This was much faster than promised. This is exactly the kind of service that a retailer should provide. Under promise and over deliver. I highly recommend Newfound Woodworks.

    cutting out hatches in a cedar strip kayak

    cutting out hatches in a cedar strip kayak

    Cut Outs

    For my cut outs, I ran a string line down the kayak again and lined the hatch lips up as much as I could. I cut the hole in the deck at the same size as the hatch lip. It turns out that in order to make hatches fit right; you have to cut the openings wider than the lips. In the rear hatches, because my rear deck is relatively flat, I ended up cutting an additional 1/2″ in order to accommodate the hatch cover and have enough room for the cover to fit into the deck easily. For the front, I had to cut this slightly wider. Just about an inch. Before I cut, I used some 2″ masking tape to mark the cut outs on the deck and then drew the openings on this tape. The tape made it easier to see the line and it also helps prevent tear out from the saw.

    The Rear KajakSport Hatches

    The rear hatches were the easiest. After I managed to cut the holes, I only had to make a recess into the deck a 1/2″ to 3/4″ deep. To do this I used plywood. For the oval hatch, I recessed it into the deck using three pieces of 1/4″ luan plywood, and then on the bottom of this recess, I attached a plywood lip to which I epoxied the plastic hatch rim. I roughed up the surface of the plastic hatch lip with 60 grit paper before mounting, and I mixed the epoxy with some wood flour to help glue the lip and fill any gaps that might occur from just using epoxy.

    cutting out hatches in a cedar strip kayak

    cutting out hatches in a cedar strip kayak

    The day hatch, I recessed 1/2″ using the same process as outlined above. I did use a ton of clamps to hold the plastic rims onto the plywood rims. After these dried and before I started the front hatch, I wanted to make sure this would be secure. It is. I can lift the weight of the kayak at this point using the glued in rims.

    The Front KajakSport Hatch

    The front hatch involved much more work than the back. I tried to do this two different ways. The first was using Jay Babina’s use of a wooden rim to make the recess into the front deck. It’s a great idea, and on the kayaks that I’ve seen with it built this way, it looks fantastic, but my woodworking skills weren’t up to the task of making an oval rim that not only fit around the hatch, but also fit into the oval cut out into my deck. I went through a full 1″x8″x8′ pine board trying to do this. The main problem was that in order to make the hatch cover top flush with the top of the deck I would have had to use two stacks of pine.

    When that failed I resorted to cedar strips, and I built a recess by angling short cedar strips down to a plywood lip I would use to mount the plastic hatch lip on. This worked out pretty well, but, I’m afraid that my wood working skill got lazy and the recess doesn’t look as good as it would have if I put more time into it. If I get around to it, I’ll hide my mistakes by making some black epoxy and filling in between the plastic hatch rim and the side of the recess. This will hide the brown epoxy/wood flour mix I used to make the transition from the plywood to the cedar smooth for fiberglassing. Anyway, I glassed the recess, and clamped the plastic lip in. It turned out looking pretty darn good.

    The rear plastic hatch lips are clamped into place on the plywood lips while the epoxy glue dries.

    The rear plastic hatch lips are clamped into place on the plywood lips while the epoxy glue dries.

    This shows the plastic rim sitting on the plywood rim.  I've tacked the plywood into the hull with glue to hold it in place while I build the recess.

    This shows the plastic rim sitting on the plywood rim. I've tacked the plywood into the hull with glue to hold it in place while I build the recess.

    The cedar strips start to form the recess for the hatch.

    The cedar strips start to form the recess for the hatch.

    The front hatch recess is finished and glassed.

    The front hatch recess is finished and glassed.

    Check it out.  A plastic hatch in a cedar strip kayak.

    Check it out. A plastic hatch in a cedar strip kayak.

    A Radical Idea?

    Next time, if I build an other kayak, I’d probably do wood hatches, because they are much much faster and much much easier to build, but if I were to put rubber hatches into a wood kayak, I’d do something completely different. Instead of gluing in plastic hatch rims, I’d build some out of wood. After looking at the plastic rims, I really don’t see anything to would stop this from working. Basically, the build would work the same way as building the cockpit coaming and riser, except in a smaller scale.

    Plastic Hatches the Downside

    The main disappointment with using commercial rubber hatches with plastic rims is the extra weight that it added to my kayak. The oval rubber covers weigh 1 pound 14 ounces each, and the day hatch weighs 11 ounces. I didn’t weigh the plastic rims before I mounted them into my kayak, but my guess is that they add a pound each. If I had used flush hatch covers, I would have used less plywood, so I imagine by using flush hatches my kayak would weigh somewhere around 7.5 pounds less. That’s a lot of weight to add to my kayak. Luckily, when I designed the kayak, I planned on around 45 pounds for the displacement of the boat, but, personally, I was hoping that I could bring it in under 40 pounds. I’ll take a lighter boat any day over a heavier one. Easier to carry, easier to put on top of the car, easier to paddle. But then again, you knew that. That’s probably why your reading this article on the only website completely devoted to lightweight canoeing and kayaking.

    Cedar strip compass cut out.

    Cedar strip compass cut out.

    The Compass Mount

    While mounting the hatches, and becoming frustrated that it took almost a whole week to do so, I decided to complicate my life more. Hip Hip Happy Happy Happy. I decided to build myself a compass mount to put in my Brunton neat-o compass. I bought this compass before I quit working at a sporting goods store, so I got it at cost. I originally planned on putting it into a Chatham 16, but the kayak was going to show up at the store after I knew I would be leaving, so about two month before the kayak got there I canceled it, and had a compass with no place to go. So, when I built my last kayak, I built a mount into the boat for the kayak. When I sold that kayak, I kept the compass, and now I decided to build a mount into this boat. I coat out a opening in front of the hatch, cedar stripped an angle from the deck to the plywood lip, fiberglassed, cut a hole out, and then had to come up with a way to build a fiberglass bubble to hold the compass. To do this, I filled a small square plastic container with plaster of Paris. Then I set the compass into this, and let it set up. After I pulled the compass out, I wet out some glass, and I put that into the newly made mold. I used the compass to compress the wet glass into the mold. After the fiberglass set up, I cut the flange from this part to size and glassed it into the deck using sand to hold it down. I used saran wrap to make sure nothing stuck to my compass, the mold, or to the sand.

    The finished Plaster of Paris mold.

    The finished Plaster of Paris mold.

    Okay, I didn't sand it smooth, but, hey, the compass will hide it.

    Okay, I didn't sand it smooth, but, hey, the compass will hide it.

    Glass wet-out and being compressed by the compass.

    Glass wet-out and being compressed by the compass.

    Glass in the mold after it set up and before I pulled it out.

    Glass in the mold after it set up and before I pulled it out.

    Not the most beautiful part.  I though about using some carbon fiber, but it's not like this part will be ever seen.

    Not the most beautiful part. I though about using some carbon fiber, but it's not like this part will be ever seen.

    I used some sand or concrete or something I found in the corner of the shop to weigh down the fiberglass around my fiberglass part to glass it in place.

    I used some sand or concrete or something I found in the corner of the shop to weigh down the fiberglass around my fiberglass part to glass it in place.

    Inside of the Hatches

    When the rims were mounted and the epoxy dried, I flipped the hull over and fiberglassed the plywood and cedar strip recess. I did this after I used a saw, block plane and sander to cut out some of the extra plywood and smooth everything into a nice shape.

    Inside Seams

    Can we say, “This sucks.” I state it plain and bold and true. It sucked. This was the worst part of building the whole kayak. Trying to squeeze your arms, head, respirator, paintbrush, stick, and headlamp into the small opening of my oval hatches wasn’t fun. Did I say it sucked? It did. Thankfully, it was over quickly, but not before I managed to get epoxy all over my arm and on the back of my neck. I’m slightly allergic to epoxy, so now I have a small rash. It was stupid of me to try to do this without long sleeves.

    Warning: Epoxy is nasty stuff. If you’re not allergic to this stuff, you will be unless you take every precaution that you can to avoid skin contact and breathing the sanding dust and fumes. I wasn’t allergic my first boat, but by boat two I was. I’m not the only horror story, so keep this in mind if you build your own kayak.

    Outside Seams

    Much easier. I sanded the seams, worked the wood around the Layback Lounge (TM Pending), and then measured out the 2″ fiberglass tape. I wet-out both sides very quickly. I’ve noticed that 6-ounce tape is much harder to fill than 6-ounce glass. I wonder if the weave is different. Anyway, this went smoothly, but took all day, because I had to wait for coats to get slightly untacky until I could add the next coat. Even with the heater running in the uninsulated shop, it’s not warm in there when the town is engulfed with fog from Lake Superior all day.

    Bulkheads

    Putting the bulkheads into the kayak, involved squeezing my arms, head, respirator, paintbrush and headlamp into the small opening of my oval hatches again. Luckily, the bulkheads are much closer to the hatches, so this went easily. Some builders use thickened epoxy to build a fillet around the hatch/boat joint. I only did this with the bulkhead behind the seat, which was my worst fit. The others fit very closely, and it seems to have worked out for me.

    Phew, I Need A Break From Kayak Building

    After the bulkheads, I needed a big break from building; luckily, my boat was ready for a trial run on the water. I loaded it onto my car and headed down to the harbor for a test. Since I started this project some 160 hours and three months ago, this was the moment I had been waiting for. Here I was next to the cold blue water of Lake Superior. A kayak I had designed and built would now carry me out into the October waters of the Lake . . .


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    4 Comments

    1. Andrew Belfrage
      Posted December 28, 2008 at 1:24 pm | Permalink

      Thank you for writing such a great piece. What suggestions do you have on constructing a small day hatch for behind the cockpit of stitch and glue kayak? I have recently purchased a Chesapeake 17. I could buy a black rubber hatch (I would go for a Valley Kayak type myself). However then I have three problems
      1)The slight camber of the rear deck
      2)The asthetics of a black rubber hatch on a wood kayak deck
      3) My ability bearing i mind this my first ever wooden kayak project.
      I am thinking that I will probably just make a much smaller version of the hatches that come with the kit. Probably have it held down by one snap over strap rather than two on the full size hatches. I am also thinking of building a small trial piece of deck to get it right first Obviously I will also have to fit an extra bulkhead in.
      Thank you Andrew belfrage

    2. Posted December 28, 2008 at 6:51 pm | Permalink

      Hi Andrew,

      If you don’t want to use a black rubber hatch on a wooden kayak – I actually prefer the look myself – then making a smaller version of the hatches that came with the kit will work just fine. You should be able to make a small plywood flange despite the deck camber.

      From my last kayak forward, I’ll be constructing all my hatches using a composite recess, because it makes construction much easier and drier than any other hatch I’ve made. I detail the process here.

      Valley hatches are also fantastic. If you haven’t used them before, you’ll find them easy to remove and secure. They are water tight.

      Hopefully, this is helpful. Let me know if you have other questions.

    3. Mark
      Posted January 13, 2010 at 10:51 pm | Permalink

      Hello Bryan
      Your coaming and hatch info is PRICELESS.Yor photography is great too. Much less anxiety now that I have a site with EVERYTHING needed to build a one of a kind Kayak! With your very good woodworking skills and extreme patience, I would definitly go with cedar hatches. Or Gaboon Ebony!? Purple Heart? Anyway, I feel WOOD for WOOD. Plastic for plastic. Hatches or anything else.How bout some small rare earth magnets to hold down the hatches, epoxied in. What do you think?
      Thanks, Mark S

    4. Posted January 14, 2010 at 4:15 pm | Permalink

      Thanks, Mark. For more hatch and coaming info, check out one of my other online building journals here and here. For the recess, I like how I did it on the Iggy, for the coaming lip, I like how I did it here on the Siskiwit Bay.

      For rubber hatches, I like the method I used on the Iggy better than what I did here–it was easier.

      I’ve only ever seen the rare earth magnets used on one kayak’s hatches. The magnets held tightly, but the hatches leaked. I suspect that was more a fault of the skill of the builder than the magnets. Even with strong magnets, I’d add external hold-down straps for safety, because I didn’t trust the magnets.