How Big a Kayak Do I Need?
Kayaks are probably the most custom tailored of any boats. In fact, if you’re building a traditional skin-on-frame kayak, then the dimensions are directly based on your size. While other kayak designs aren’t quite that customized, when it comes to kayaks size does matter. In this article, I’m going to focus on the volume of the kayak that you need rather than on the length, or width, or style of kayak, which we’ve covered in a couple of our other articles.
Now before getting into too many details of how to pick the right sized kayak for you, let’s take a minute to look at how and why a boat, any type of boat, floats. In it’s simplest form, a kayak is just a hollow shell. That hollow shell has a weight of it’s own and it also has a volume of empty space (well actually it’s air) inside the hollow shell. Of course water has weight too, so when you put the empty kayak in the water it pushes an amount of water out of the way that is equal to the weight of the kayak. The amount, or rather volume, of water that a boat “pushes out of the way” is the “displacement” of the boat.
Illustration of how an empty kayak displaces just enough water to equal the weight of the kayak hull. As you put more weight into the kayak, either yourself or gear, then the kayak sinks lower in the water until it has displace or "pushed away" enough water to equal the weight of the kayak and all of it's contents.
Since all that empty air inside the kayak doesn’t weigh nearly as much as the water underneath the kayak, you end up with a ‘light’ kayak floating on top of the ‘heavy’ water. As you put more stuff into the kayak – whether it’s yourself, the dog, or your camping gear – the kayak gets heavier and “displaces” or pushes away more water until the amount of water that the kayak has displaced is equal in weight to the weight of the kayak and all of its contents. If you want a more detailed scientific you can look up Archimedes Principal of Bouyancy.
I introduced the concept of a “design waterline” when I talked about Kayak Hull Shapes, Length, & Width. The design waterline is where the designer intends for the kayak to sit when it has the proper load in it. That load could just be you, or it could be you and bunch of gear. The good news is that you don’t have to be exactly on the design waterline, anywhere within a reasonable range will let the kayak perform well. This is why most kayak designers provide a recommended or “optimum” load range for their kayaks. For example the Endeavour Sea Kayak has an optimum capacity of 150 – 260 lbs (68 – 118 kg). As long as you are using your kayak within the optimum load range, then it will handle the way the designer planned it to.
Illustration of how an overloaded kayak has to displace so much water that it sinks well below the design waterline.
On the other hand, if you overload the kayak, it will sit lower in the water than it was intended to. This will give the kayak a longer waterline, probably give a wider beam, and reduce the amount of rocker. All of these factors will make the kayak feel sluggish in the water – possibly to the point where you’ll feel like you are paddling a barge. OK, so now that we’ve looked at why the size or volume of the kayak matters, how do you pick a kayak that is the right size for you? This is probably one of the easier decisions you get to make when choosing which kayak to build, because it has everything to do with weight, and nothing to do with esthetics or style. Start by thinking about who is going to use the kayak and what they are most likely to be using it for. If you are building a recreational kayak for playing around at the cottage, then you just need a kayak that is big enough to carry the paddler and maybe 10-20lbs (5 – 10 kg) of fishing equipment. On the other hand if you are buiding a sea kayak for some weekend or longer trips, then you’ll need a something big enough to carry the paddler and maybe as much as 100 lbs ( 45 kg) of camping gear. The folks at the Newfound Woodworks help to remind you to consider the weight of you gear when they give the recommended weight capacities for their kayaks. For example they say that their Explorer hybrid kayak will “work nicely for 130-175 lb paddlers on trips with gear or for 175-225 lb paddlers for day trips.” So what’s the worst thing that will happen if you build your kayak and then decide you picked a design that was the wrong size? Well, I guess the really worst thing would be that you could sink your kayak, but most likely you will just have to go and build another one!
April 25th, 2010 at 5:29 pm
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