# Design/ speed question

Given the same paddler and paddle , what would be the speed difference between 14’ and 16’ boats of the same design?

It might depend on what you mean by same design. Speed is part waterline length and width, hull shape, boat weight, boat material. If everything same, then it might just be waterline length/width. When you look at races (8 mile race) on pool stage flat water, I see winning speeds as below. Speeds between 2 ft differences could be around 1 mph avg?

up to 12.5 ft- (4.7 mph)
up to 15.5 ft- (5.5 mph)
up to 17.5 ft- (6.0 mph)
over 17.5 ft- (8.0 mph)

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I meant hull shape. Thank you. I’m considering going from a 14’ to a 12 ’ , both rec boats. Just trying to keep up with another mature paddler. I know what his boat can do so I’ll check the speed of the alternative.
We maintain between 2.5 and 3 mph.

I see. You can keep up with them if they want you to…lol, but if they decide to leave you behind, it can happen at 1 mph or more difference : ). I love 12 ft rec boats…what I use mostly for having fun on flat water rivers.

Using a max hull speed calculation (1.34* the square root of the waterline length in feet) gives roughly 1/2 mph difference, or less. That’s max speed, of course, and at cruising speed it may be less noticeable. Drag would be more on the bigger boat, so it may not be faster at all? Might depend on the design, even if they are the same.

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The hull speed has a fixed formula based on water line length. Specifically 1.34 X the square root of the length of the waterline. So a longer kayak would have a higher hull speed. Here is a rowing site that made the calculations: Hull Speed Calculation and Chart - Ron Rantilla Rowing

But hull speed is not cruising speed for most paddlers. Instead it is the maximum speed one can do before it takes a huge amount of effort to go any faster (usually, through a boat getting up on plane). Sail boats in decent wind can hold their hull speeds, because the power is provided by the wind and the wind doesn’t tire out. An average paddler, though, would tire out if they tried to maintain hull seed, so it more denotes short term sprint speed.

Gets much more confusing to compare boats at below hull speed, the speed range where most people paddle. Even if you had 2 boats that were exactly the same, except for length, once you put the same paddler in each, the shorter one would sit lower (which changes speed calculations) as it needs to displace the same size paddler’s weight over a shorter length. More common is that a longer version of a kayak model would also have some additional modifications to offset for this - often the manufacturers make them narrower, to offset the larger area to displace weight. For example, the 10.5’ Pungo is 30" wide but the 12 and 12.5 are 29" wide. This narrowing would make the boat faster at below hull speeds.

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We both paddle Pungo 140s . Getting in and out is a challenge and I like the freedom of a SOT. I’ve had 7.
I might be a boat nut but I’m in good company here.

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2.5-3 mph is pretty modest and I think there’s a good chance it would be a wash since you’re not at speeds where the hull shape is dominating and the shorter boat should have less skin friction. But like Peter says the devil is in the detail and this is one of those “all other things being equal” questions where all other things are never equal.

And I think the answer depends heavily on your 2.5-3 mph assumption because by 3.5-4 mph the answer may be different.

2.5-3 is a fact by GPS and timed distance.
I’m on the water to see, smell, feel, and hear. Going fast and working hard are past endeavors.

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There’s an old Tasmanian boat builder proverb that says: “Start off slow and then ease up.”

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I was the lead dog until heart surgery, covid, and winter slowed me down. My goal is to regain that position.

Check out Nick Schade’s article on the subject.

Tim

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.5 mph max my guess

I agree with @TomL. I prefer 14 foot over 12, but at 3 mph you probably won’t see a difference in speed. You’d get better results though with a skinnier hull.

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I’m not clear on what you want to do. You ask about the difference between 14’ and 16’ but then you say you have a 14’ and you’re considering going down to a 12’. Splain, please.

In my experience, there’s a big speed difference between 12’ and 14’ of the same model. The Delta 14 is much faster than the Delta 12.10, and that’s only a difference of 1 foot 2 inches. The Eddyline Journey (15’5") was quite a bit faster than the 14’ Equinox, basically the same hull shape.

I found after a number of years that I was willing to give up speed to gain other benefits: lighter weight, less length to deal with, easier to get in and out of the garage and on the vehicle. Also, I think more in terms of glide than speed, meaning distance covered with a light stroke. I’m happier now with 12’ 10" and 13’ 5" than I was with the 15’5". It’s just more pleasurable to have a kayak that’s easy to handle—you’re likely to use it more often and resent it less.

What makes it complicated is that the formula for “hull speed” depends on hull shape:
hull speed in knots can be calculated with the formula S/L*LWL^(1/2)
with the boats waterline length in feet and the Speed/Length ratio from
1.34 up to 1.51 for slender hull shapes and 2.2 for Sprint Kayaks and Canoes.

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I admitted that I’m crazy. And I’ve found a 12’ that Im interested in.

I can tell you the speed difference between my Dagger Charleston 15 and my Dagger Blackwater 11.5 is … it really doesn’t matter. They are identical but different lengths … they have the same cockpit and the same skeg mechanism, etc. Well, I think the specs say the 15 is 3/4" more narrow, but I can’t tell. The designer(s) used the extra length on the 15 to make its entry and exit sharper, so the Blackwater throws water when you paddle quickly and it leaves a wake, but the 15 does not.

The 15 has got to be faster, although I don’t have any data to prove it, and it’s quieter, but the Blackwater just feels a lot more fun - it feels light and responsive, more engaging. Unless I’m going for a very long cruise where the efficiency of the 15 would pay off, the 11.5 is my go-to boat.

Thank you RW. If the weather cooperates , I’ll be test paddling the 12’ next week.

One of hte better answers is hull. A narrower hull is faster and often a longer boat has a narrower hull. I hafve paddled 9’ rec boats, flatwater canoes, whitewater canoes, whitewater kayaks, and sea kayaks, etc.
A plastic rec boat can feel like a pig conpared to a sleek, narrow, composite hull. That is due to less drag/frictionas there is less contact with water. Remember that rocker is a factor, meaning, less waterline contact. A good question to be answered, especially for a tyro paddler.

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