Are longer kayaks slower?

Advice
#81

Agree highdesert, quick glance at my log. Top entry is a bay crossing. High tide Battery Pt 10:32 @ 2 ft; 72 -85° water temp 60° @ Thomas Pt Lght, 9-18" waves. Wind SE 5-10 mph catpaws evident (up the bay). The *info I think is stop to check current drift. I know any speed over 6.2 mph is assisted by following waves. Haven’t peaked 6.2 mph without current assistance. In 2010. I could pace boats in 6 mph zones for 1/4 mile. I hear about pungos being slow. I can send log entries to disprove that. It doesn’t mean I would tell buyers how fast the Tsunsmi is. I have a 175 entry that is 4.9 mph for 20 miles, but it’s not representative of any characteristic. I can tell you everything about these boats. I paddled with a 17 ft Impex Asseteague for 1/4. He pulled away from me like I was crawling after him on my knees. I doubt he typically paddled that boat more than five miles. He live 20 miles away for years and had never been on the bay. That day, he paddled 2.25 miles from the launch and turned around. It made me weep.

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I spend 15 minutes checking and loging conditions prior to a launch, any travel companion is at least past a point a mile away. And I try to catch them by the second one mile point. It’s what I do.

#82

Talk is cheap regarding speeds.

Only time I can see how fast a particular boat I have is when there’s no tide / currents, no waves, and no wind. Then I’ll take many many runs before I can say this boat does this speed with me in it confidently.

#83

Paddle Dog52 I agree. That log only shows a Tsunami can go 4.8 mph for over 20 miles, which contradicts claims that it’s hard to believe it’ll go that fast. I can tell you it has gained on ower boats traveling in a 6 mph zone for about 1/4 mile. There are ways to compile data to come up with a bell curve. I have other trips that weren’t that fast if you look at the other entries. I also have data of trips with a 240 cm and the same trip with a 250 cm paddle. I would never tell anyone to use a 250 cm paddle. Yet I’ve been told I shouldn’t.I go by my records. That means more than a chart for a person who bought their first kayak.

I can’t do that now. That was when I was only 60. First trip out since my injury was10 miles at 1.9 mph. Sixth trip was 20.65 miles, but it took 7 hrs 20 min. I once could do 38.75 in 8:20. I’ll be honest. It is a slow boat, and anybody would be a fool to give up a good boat for a Tsunsmi. I listen to people talk about their sweet boats. This post is for Tsunsmi and Pungo owners. Telling them to keep shooting for a better boat, but if they have one, get all they can wring from it. Neither boat ever let me down.

#84

For a given displacement, a longer hull not only has a more gradual entry (allowing for slower displacement of the water ahead), it also has lower frontal surface area presented to the water (resulting in less water displaced per foot travelled). An 8 foot boat 3 feet wide displacing 4 cubic feet and a simple diamond profile with no rocker has a frontal area of 4x12x12x12/96x2 square inches, or 144 square inches. At one foot per second forward motion it must accelerate one cubic foot per second to a velocity of 4.5 inches per second. Stretching the same profile to a 16 foot x18" boat we have 4x12x12x12/192x2 or 72 square inches. At one foot per second forward 0.5 cubic foot per second must be accelerated laterally to a velocity of 1.125 inches per second. This gives a 32 fold difference in energy expenditure for displacement between short and fat versus long and narrow at any speed. For simplicity I have ignored varying the draft of the hull for this initial calculation. With the same draft the difference in surface area is quite minimal. Making the short boat the same width and deeper draft would mitigate this to some extent, and significantly reduce wetted surface as well. Specifically, the 8’x18" boat would accelerate 1 cubic foot per second to 2.25 inches per second, for an 8 fold difference in energy. Treating all the displacement as lateral is a gross simplification, the initial deflection is primarily down and the energy is then dispersed laterally, forward, and back by slower movement of a larger volume of water. Incidentally this is part of what increases drag in shallow water: as the downward displacement of water is limited by proximity to the bottom. Further complexity is introduced by using a hull cross section other than flat bottom, and a curved rather than diamond hull profile. Adding rocker increases frontal surface area as well. The work of displacing water is more significant in most cases than the “hull speed” limitation, as evidenced by olympic level paddlers exceeding hull speed regularly in highly streamlined boats

#85

Sorry I cannot fathom a 14.5’ Tusnami doing 4.8 miles per hour for twenty miles unaided by wind and current unless down the Colorado River. I don’t care if the paddler had a 333 CM paddle.

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#86

The strongest determinant of speed in a kayak is the paddler and their strength/endurance. I paddled my Stellar S14 G2 (14.5 ft, 24.5") faster than an well known instructor in a P&H Scorpio which is over 3 feet longer and half an inch narrower (17.7", 24"). But I am well trained, lift weights and work out like crazy due to my chronic illness like over 2h a day on weekdays, more on Fridays and maybe like 5-6 hours Sat and Sun. 95% of my activity is physically active.

The second most important element is length, followed by aspect ratio. So yes a longer kayak can be faster but it has to be long AND narrow, like pencil shaped and sleek. An 18 foot kayak that is 30 inches wide will never be as fast as say a 16 foot kayak that is 21 inches wide for example.

The third is kayak construction. Stiffer means more power put to water and more efficient. So a carbon composite will be faster than kevlar composite which is faster than fiberglass composite which is faster than ABS which is faster than rotomolded all else being equal.

Hull shape is also very important. Flat hulls will be slower due to greater wetted surface area which creates drag and slows you down.

The final element is overall weight. This affects speed very little, there is an equation you can find but yes a lighter boat will always draw less water. But it can also be your gear, paddler weight (go on a diet, get faster!), accessories etc. Not to be excessively roundabout but once you bring about weight another the important element is weight vs wetted surface area so maybe a heavier kayak that has less wetted surface area might actually be faster than a lighter one with a more flat hull.

Also planing counts. I have found that the nicer, higher end kayaks seem to just keep going faster and faster the more in shape I am. With a double I am always faster with a faster paddler. There seems to be no real top speed (yet) as the harder I paddle the higher it seems to sit and the more it wants to go within certain limits. OK an 11 foot pack boat has its limits but with slightly longer boats I have found my speed to grow with time and so has the “planing”. This is a nice feature because when you’re not moving the wetted hull is wider so you’re more stable, but when you get going and don’t need the width for stability it planes and becomes “skinnier”. So there’s that element as well.

So overall speed is really a complex matter. It can be very individual. A lot of people get longer boats thinking they will be faster but the extra weight and wetted surface area and their own potential lack of strength will slow them down.

Said differently all else being equal a shorter kayak will always be EASIER to paddle below its hull speed than a longer one with a faster hull speed. So look below. I am pulling these figures out of my head but just doing it for comparison

A 12 foot kayak with a 3knot hull speed will always be easier to paddle than anything longer up to pretty close to 3 knots.

Once you get to 3 knots a 14 foot kayak with a hull speed of 4 knots will be easier to paddle pretty close to its hull speed than anything longer.

Once you get to 4 knots a 16 foot kayak with a theoretical hull speed of 5 knots will be easier to paddle until you get to its theoretical hull speed.

And finally and 18 foot kayak with a theoretical hull speed of 6 knots will be the fastest overall but the hardest to paddle until you get past just under 5 knots.

So in the end you need to select a boat for the intended hull speed and physical fitness you’re capable of paddling. Stability is also more important than ability. I tried a surfski once that was supposed to be kind of fast and felt I couldn’t breathe without flipping it so you have to keep the stability that your skill level and height/weight can support in mind as well. Certain elements like stiffer or lower weight can make better the same situation but the most important factor is what you can sustain for prolonged periods.

From what I have read the optimal length (also for storage and carrying reasons as a longer boat of same weight just feels a lot heavier and is harder to load, store) is about 14 feet. More seasoned paddlers will likely want a longer boat but if you’re beginner to intermediate most people will be pretty happy with that length giving room to grow yet not being saddled with something too hard for other reasons. 14 foot (and under) boats are also more in demand so will be easier to re-sell later on if you get so good you want something longer/racier.

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#87

My long kayaks are easy to paddle at any speed. When you compare things you can’t have a ton of variables like different paddlers and hull widths if your comparing lengths.

There’s a top speed to anything even light.

So how faster us your SR14?

#88

I have the Stellar S14 G2 not the ski. It’s pretty fast at least compared to mass market and “normal” kayaks not talking surfskis or racier, expedition type boats that are skinny and very long. I am talking compared to anything you could buy say an an REI not a pro-shop. Can comfortably do just under 4 miles in an hour taking a short drink break and slowing down (obviously) to make tight turns around bends or inlets on a pond or taking photos, talking to friends. I was only slightly faster than the instructor it wasn’t like I was speeding away from him but he commented that he was struggling and not really keeping up with me. Again I am not that good of a paddler. Strong yes, not skilled, not steady at all.

I think I can out-paddle my S14 G2 too as I get to the point where paddling harder just feels heavy almost like the paddle is rooted in rubber cement not water. The feeling goes away if I paddle only slightly less hard. I feel like I can go more though and have been told that’s the sign I am going as fast as she will go. But anything faster has just been too tippy for me at this time.

But yes the variables are huge and comparing different boats is never apples to apples. Honestly the only valid comparison might actually be the SAME boat in different layups.

#89

You’ll never detect speed differences of different layups bar paper mache.

#90

Easily is apples to apples when you compare boats properly and don’t throw in other variables.

#91

Paddledog52, I actually take your disbelief as a compliment, but your disbelief doesn’t mean it didn’t happen, or thT it matter, except for another Tsunami owner who wants to know the “potential” or someone who would like to try that course. It would be a bit naive of me to try to convince you.

#92

It may happen but not without currents, tides, and wind.

#93

I can agree with that. The question if you are interested and have the time to explore, is whether the condition were a benefit, a hinderance or a cancel. You peaked my interest to revisit that log to see if there was a statistical advantage or disadvantage. I believe you could assess that by reviewing the parameter in your head.

#94

I know the data from my own gps and the conditions I pick for conditions. I do it over many runs before I say how fast my hulls are.

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