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Kayak Cockpit Placement Rule of Thumb

cockpit placement on the Siskiwit Bay

Siskiwit LV sea kayak study planIf you’re working from a set of sea kayaking plans, figuring out the kayak cockpit placement is easy. You just consult the diagrams. But, if it’s a historic replica or one of your own designs or if the plans didn’t include drawings of the cockpit area, finding the best placement becomes a challenge. This is a hurdle I faced when building my Siskiwit Bay and Siskiwit LV designs. After a day or two a research, I ended up coming up with several rule of thumbs for sea kayak cockpit placements. Any homebuilder could use these and come up with a good cockpit placement.

Sea Kayak Cockpit Placement Rule of Thumb

For homebuilders that don’t want to calculate the perfect kayak cockpit placement based on their body and the boat, these three rules of thumb will help with locating the cockpit. This is for a standard keyhole-style cockpit, such as the one found in the free Keyhole Sea Kayak Cockpit Plan. If you’re having a hard time deciding what kind of cockpit to build, check this out: What Kind of Kayak Cockpit Should I Buy or Build? With an ocean cockpit, I’d still plan to have the back rim of the cockpit 3.5 inches away from your back to make room for a backband or foam padding. After you figure out your placement and build the boat, you should also figure out outfitting: How to Adjust a Sea Kayak

Rule of Thumb One = The aft of the cockpit opening should be positioned 3.5 to 4 inches from the back of the paddler when the paddler’s Center of Mass and the kayaks Center of Buoyancy are aligned. Or for most paddler’s 14 to 16 inches behind the Cb.

Rule of Thumb Two = For a good kayak cockpit placement put the coaming of the cockpit 15 inches behind the longitudinal center of buoyancy.

Rule of Thumb Three = Have 55% of the cockpit behind the Cb and 45% in front assuming a standard keyhole-style cockpit.

Any of these rules of thumb will get you close and probably close enough.

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Center of Mass

kayak cockpit placement
This is the placement in the example.

If you want to be more exact, you can find your center of mass and align it with the boat’s center of buoyancy. To do this, you’ll need to create a balance board. Essentially, a balance board is small scale teeter totter. Take a 1×10 or 1×12 board and put a pivot point in the center. A 1×1 board in the center works fine as a pivot point.

You’ll need a friend to help you with the next part.

  1. Get on the board and sit in your normal kayaking position with your legs forming the shape of a diamond, also known as the frog position, and your back sitting up straight.
  2. Then move forward or back until you are balancing on the board with all your weight supported by the pivot point and both ends of the 1×10 or 1×12 are in the air.
  3. At this point, have your friend move a framing square up against your back and have them mark where that square meets the balance board. This mark shows where your back is in relation to the pivot point.
  4. Measure the distance from you back to the pivot point.
  5. Add 3.5 to 4 inches to this measurement to find the point where you should have the inside of the cockpit riser. Add your riser’s thickness to this measurement to arrive at the cutline. For example, if you want 4 inches and your riser is 1/4 cedar strips, then where you start your cut is 4.25 inches plus the distance from your back to the pivot point.

At this point, you can decide how much distance you want behind your back for a backband and your seat. Ideally, you’ll pick a distance that will easily work with a spray skirt, such as NRS’s Drylander Shock Cord. That way, you won’t have to have a skirt custom made. Usually, 3.5 to 4 inches is what you want.

For example, after balancing on the balance board and running the framing square to my back, we found that my back was 12 inches away from the pivot point. My skirt is designed to fit about 3.5 inches away from the coaming and one of my favorite boats has that distance as well. So, I added 3.5 inches to 12 inches to get 15.5 inches. If I was using 1/4-inch cedar strips for the cockpit risers, then I’d add another 0.25 inches to arrive at 15.75 inches.

Aligning the Center of Mass to the Center of Buoyancy

After you find your center of mass, you need to align that measurement to the kayak’s center of buoyancy. To do so:

  1. Find the measured center of buoyancy. For PaddlingLight’s drawings, this will either be included with the drawings or found on the kayak’s webpage. It’s usually taken from the stern.
  2. Mark the center of buoyancy on the kayak.
  3. Measure the distance that you calculated in the above steps back from the center of buoyancy towards the stern.
  4. Mark that point.
  5. This is where the rear most cut should be and where you’d place the stern of the cockpit plans if you are using one.

For my cedar-strip kayaks, these rules have worked well for me. Hopefully, they help you determine your kayak cockpit placement as well.

4 comments

  • Hi Bryan,
    1-Is Cb the Center of Balance and the Center of Gravity?
    2-How does a non engineer calculate CB?
    Thanks
    Rick

    • 1. Cb is the center of buoyancy.
      2. There isn’t an easy way. You could cut out the profile of the kayak, fold it multiple times along the length and then try to find a balance point using a pin. Then scale to find the CB on the full-sized version. Many plans or drawings include this information.

  • Hi, I got myself a Dragon kayak(http://dragonkayak.com.au/), and its cockpit placement is a bit off from your diagram. Will that make any difference? I mean, I’m enjoying my rides and haven’t experienced any problems yet, but now that I’ve read your article, I definitely need to know more about it. Thanks in advance!

    • This is more about people who are building their own kayak. A manufactured kayak should already have this figured out before they build the mold, etc.

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