As a swimmer, you go fast and easy by keeping your body stretched out for the duration for your stroke. You strive to always keep one hand fully extended in front of you, so that you are as long as possible in the water. The paperwork may not be easy to figure, but length in water equals easy speed.
Is the bow wake the sign that you’re at hull speed?
I’ll answer this one - sort of, but it’s hard to tell in practice. Technically speaking, hull speed is specified as the speed when the boat is moving with Froude number equal to 0.4. Froude number is a non-dimensional measure of boat velocity:
https://en.wikipedia.org/wiki/Froude_number#Ship_hydrodynamics.
There’s a nice diagram on this page that shows the wave pattern on displacement hulls as a function of Froude number:
https://en.wikipedia.org/wiki/Froude_number#/media/File:Froude_numbers_and_waves.png
Since the wave pattern changes gradually, it would be hard to see from the cockpit of a kayak. Also kayaks are undergoing continuous small changes in speed while paddling (due to the paddle strokes), so they are generally not in a steady state.
PS if you read the extended caption for the figure above, it gives a link to a chapter on ship resistance, part of a course at the US Naval Academy. This is a good thorough discussion for those interested and willing:
https://www.usna.edu/NAOE/_files/documents/Courses/EN400/02.07%20Chapter%207.pdf
I can also recommend the well-known and worthwhile book, Harry Benford’s “Naval Architecture for Non-Naval Architects,” used copies are not very expensive.
While the assertions about the F1 are certainly true on flat water, things get more complicated when you’re paddling in waves. Longer boats with overhangs are designed to deal with rougher water and are likely more comfortable and efficient in such conditions. There are practical reasons why traditional kayak designs are typically longer and incorporate features like overhanging or bifurcated ends.
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I have boats that range from 12 feet to 19’-2" and when I have a long ways to go and a short time to get there, it’s not a hard choice. The same goes for when it gets real sloppy and bumpy. Although the 17 footer does a nice job, the big boat just does it easier.
Want to go surfing on smaller waves that the longer boats just ignore, the shorter wider boats give you a nice ride. Paddling upstream inside the eddy line is for the shorter boats.
I have tested my boats with a GPS–not for top speed, but at a moderate cruising effort. As near an equal effort and pace and using the same paddle in exactly the same conditions, the longer the boat, the higher the numbers. In each case, the next longer boat was about a mile per hour faster than the previous shorter boat.
I have paddled a lot of kayaks–enough to know that length is not exclusively the deciding factor when it comes to speed. Some boats are very fast to accelerate, but then hit the wall prematurely. Most boats feel real quick when you first take off in them; after awhile it feels like you’re dragging something. My big boat never feels like that and a couple of times I found out that this boat has no wall to hit. If you’ve got the juice in the right water conditions, this boat will plane. Yeah, I wouldn’t believe it either, but I have done it. Hint: It takes about a one foot chop.
@NotThePainter said:
Just found the Valley Gemini, 14’10" by 21"And yes Celia, full design does matter. We can talk all we want, and hey, I started it, but in the end, you’re in the water in a real boat, not at your keyboard.
Is the bow wake the sign that you’re at hull speed?
The only boat I ever got a bow wake from was a 10’ rental SOT. Only boat they had. Like paddling a log.
Ignoring physics, some of this boils down to:
-Longer boats are generally skinnier
-Skinnier boats require more skill to paddle
-Highly skilled paddlers are generally more fit and capable of going faster than the average person
So basically if you can paddle a skinny boat, its probably pretty long and also pretty fast (if you want to be)
‘Where are all the fast, sleek 14 footers?
Well my Dagger Alchemy is fast and sleek enough for me. When I first started this kayak thing I was all into tracking. Then out in the wind and waves I found myself wishing the boat would turn more easily. To summarize: if it’s relatively calm out I prefer the 16.5 Tempest but if it’s windy and wavy I’d rather be in the 14 ft Alchemy.
Hull speed per water line is a guideline, not a factor set in stone. I have two boats, a Current Designs “Whistler” that is 14’6" and a Current Designs “Storm GT” that is 17’. The hull speed number is based on the point that the faster you move, the longer the distance between the crests of the bow wave, and when the distance is longer than the boat, you are paddling up hill.
Both my boats are the same width, and rated for the same maximum load. Although the length of the waterline is greater on the storm, it has a very narrow hull at the ends. There is very little flotation in the last foot of the stern, so it sinks into wave before the crest passes it, and the effect is that of a shorter boat. On calm flat non-flowing lake water with no wind, my GPS shows that I am able to reach the same speed with both boats, 6.2 mph. (Maximum speed I could maintain for one minute)
The “Whistler” paddles easier at 4 mph. The “Storm” is easier to maintain a straight course when angling into two foot or more waves, and Much easier in two foot following waves.
Hull design is at least as important as length, and a big reason why everyone here recommends a beginner try several boats before buying.
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There are few short kayaks that are really comparable to long kayaks and the difference in resistance at low speeds is often too small for direct noticable results to prove one that longer is not always faster.
But if you really want to know, you could try an Olympic ICF flatwater racing K-1 against a K-2, because these boats are very similar but extremely different in length: a K-1 is 17 feet (520 cm) long and a K-2 is 21’4" feet (650 cm) long.
First paddle the K-1 as hard as you can for about 2 hours and then the K-2 as hard as you can for 2 hours and see how far you get – I am sure you will end up being faster in the shorter boat…
BTW, I just traded my 14’6" kayak for a 17’9" Cetus…
Well in real world terms. I have a Valley Avocet RM and a Tiderace Pace Tour 17. The Tiderace is without a doubt faster on the top end. Plus even paddling slow I can not tell any need for more effort at 3 mph between the two. Same applies for my now sold QCC 700x compared to shorter valley boat.
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I was once told by a kayak design engineer that everything else being equal, an 18’ waterline is about optimal for a fit paddler. Anything over 18’ at the waterline and the friction begins to overtake the advantage of the longer water-line length. There must be other considerations when it comes to skis, because some of them are in the twenties.
Of all the sea kayaks I have paddled the ones that come to mind for feeling fast is the CD Prana, the CD Caribou, CD Nomad, NC 17’-2", NC Expedition, Steller Intrepid, the full sized P&H Cetus and oddly the Sterling Grand Illusion. Keep in mind that I said, “felt fast.” I will admit that some boats do not feel as fast as they are, or until you really power up under the right conditions. I know I left out a lot of boats, but those are the ones that made a good impression right off the bat. I have to say though that my favorite boat–the NC Expedition had me wondering a little until I checked it with a GPS. Even that doesn’t tell the whole story.
There’s an old saying that there are no fast boats, only fast paddlers. It’s pretty much a no-brainer, really.
Long, skinny boats take more skill. Once you acquire those skills, you are faster because of the more efficient boat.
Thin is more important than length but both together is definitely faster.
@DrowningDave said:
Thin is more important than length but both together is definitely faster.
Have you tried my suggestion to paddle a Sprint K-1 and K-2? They are both thin but the K-2 is much longer (21’4" feet ) than the K-1 (17 feet). I am sure you will find the shorter one is faster for you,
I’ve had no opportunity to paddle either. Tracking straight is better in a longer boat and the less back and forth a paddler does the faster he will go. I’m not saying you’re wrong but in my experience the longer boat wins. I see that the Olympic K1 is 17 feet but they’re also powered by the world’s best. That is a class I’m not a part of. Hopefully one day I’ll get a chance to paddle one.
Reviving an old thread. See:
I’m about halfway through it right now…
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I glassed the hull on Qruiser’s boat yesterday. Getting ready to go and do a fill coat. Will be sanding insides tomorrow. Ok, can’t tell? Its a Petrel Play.
Picture before glassing. Fabric “resting”.
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There are many theories regarding boat length and speed. However, try and find a single instance of a flat water race where a 16’ or shorter kayak has won where longer boats were in the race. There must be other factors that are not being considered in the theories cited in this discussion…