I am a flat water Kayak paddler. For the past year, I have been paddling a Necky Manitou 14 (14’ 4" x 24", 49 lbs.). A couple of months ago I picked up a Manitou Sport (10’ 11" x 26.5", 44 lbs.) so that I could leave it at an alternate location. The funny thing is that as far as I can tell I paddle the Manitou Sport at a faster pace than the Manitou 14 when in calm flat water. I have verified this with a gps speedometer. Seems about 1/2 mph difference (4 vs 3.5). The 14 tracks better and is better in chop and crosswinds (it has a retractable skeg). The Sport is sportier and likes to turn. It’s a bit of a challenge to go straight without compensating with stroke and edging, although that seems to work out pretty easily. The Sport looks like a scaled down version of the 14, and it could be that the 14 was a scaled up version of the 13? I just find it curious that the shorter boat seems to go faster. Why???
FYI I am 6 foot tall, 180 pounds. I actually like both boats for different reasons.
Speed for all types of propulsion is always a matter of Power to Resistance ratio. Kayaks, Cars, Airplanes, Downhill Skis, and a runners legs ----- all speed, in all forms, is limited to this foundational principal.
The rule of thumb is that a longer kayak is faster then a shorter one, but it must be remembered that the only way a longer kayak can be the same weight as a shorter kayak is to make it from lighter material or make is slimmer, or both.
So if longer was the only thing we needed to go faster why are we not seeing 30 foot long racing kayaks? Easy answer, the drag of that extra length can’t be overcome by a human being enough to find any benefit.
I am sure that if we had 4 kayaks all of the same type and all being 22" wide that the theoretical hull speed of the longest would be faster then the shortest. But the “engine” is a human being and to gain speed on a very long hull it’s necessary to also increase the power that propels it. So depending on the power available in a given persons body there is going to be an upper limit on the Sq. In. of dragging (wetted) surface that can be a benefit and at some point the power is going to run out and the extra length and weight is going to be slower.
“Perfection” is not achievable because to gains anytime in physics you need to give up something in exchange.
So you may find that the resistance of the longer (larger) kayak is simply greater then your strength is able to overcome. It can also be related to design but no matter what the issue is, it WILL be a matter of Power vs Resistance.
Could be because you’re focusing on making the shorter kayak go straight, so you’re using more powerful/efficient/measured strokes.
How you paddle the two, waterline L/W, hull characteristics, skeg use, boat weight.
Since both kayaks can go faster than 3.5-4 mph I think you’re saying that the shorter boat feels more effortless (more efficient) at your normal cruise speeds. Short boats with low wetted surface area are often very efficient from a dead stop or at low speeds. Maybe your shorter kayak is actually more efficient up to around 4 mph, or maybe you just like the way it feels better. Short boats with low surface area cruise like water bugs…they shoot forward with every stroke (and then slow down) and feel like they have no resistance (making them seem playful) and just require a fast cadence to make speed but with the longer boat you may be more aware of the muscle required to move the boat.
Some boats perform better than their specs and some don’t…and in the canoe world some short boats can be driven past their theoretical hull speeds pretty easily whereas others feel like they hit a wall.
@Coaster, the discussions about boat width/length and wetted surface go round and round. The shorter boat is wider, but if it is actually 5 lbs lighter as you described, it displaces about 1/2 gal less water. Although the shorter boats might have a very slight edge at slower speeds, the longer boat will have an advantage as the speed increases, ironically, around 4 mph. The hull speed chart shows that neither boat is approaching the point where either boat will begin to labor as it attempts to climb out of the trough created by the bow wave and the following wave.
As you surely know, the 10’ 11" kayak will not make headway as easily as the 14’ 4" kayak when going into wind drivene waves, so enjoy each boat for what it offers. It would be interesting to try these paddling experiments.
Paddle both boats at the same location to see which boat can reach the highest speed the fastest, then see how long you can remain at the maximum speed.
Also, see how close each boat gets to the theoretical hull speed, and how long it can stay there.
Next, invite someone to go out in the other boat. Then with both of you paddling at maximum effort, see which one hits the highest speed and stays out front the longest. Then keep the paddle with the boat and switch boats, as you repeat the exercise. Compare performance and discuss impressions. It might not be scientific, but it might help you gain some insight that you can share.
Have you kept records of how long or how far you can paddle each boat at 3.5 and 4.0 mph. Set a fixed distance of 5, 10, and 15 miles to see if those speeds are sustainable as distamce incresses.
How are you comparing speeds on the GPS? Instantaneous speed readings are not accurate, they bounce all over. Instead look at average speed moving over the same course.
Agree, measure time over distance and paddle both boats over the same distance course. Then using the same distance for both boats, calculate the time to see if it matches the average speed of your GPS. All you can do is control for conditions and use some unit (accurately record time over the same course).
When revording maximum speed, I only use a a speed reafmding that I can sustain for several seconds, rather than an instant spike. Apply the same standard for both boats. If you paddle many miles using a GPS, you should recognize consistency vs spurious spike. “Use the same standard for both boats.”
If you don’t know the GPS or don’t trust it, then just take a will guess? As I said above, paddle side by side with another person on the same course, use the same distance and record how long it took for each to finish, then switch boats. Repeat that for 1 mile, 3 miles, 5 miles, 10 miles, 20 miles . . . At some point, each paddler will reach the breaking point. See if it happens in the same place for both paddlers or if one boat gives each paddler an edge. I have a set course and relynon the GPS. Some paddlers would rather rely on a wild guess.
Optical illusion.
Seems the easiest way for me to verify will be to paddle and time a known course in similar conditions in each boat. Ideally in slack tide and calm.