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Boat Wake Wonder
glassy wav(k)es
David Hooper
10/29/17 #22124
Looking at the thermometer yesterday morning, I decided to wait til the sun was warm before paddling. I went to launch around noon. Heather was just returning from her “slowest paddle ever” with her dog in the foot well, with some mention of hitting 7 mph, which is more like my fastest paddle ever. Most others were packing up boats from their morning paddle. I headed south, nursing a tweaked lower back, just happy to be out moving in the sunshine, though a bit grumpy about having forgotten to change back to my recently repaired weedless flatwater rudder. On the way back from Chuckanut Island, just north of “the tunnel”, I encountered a big set of wakes, heading south. I paddled through them, then decided they might make for a quick surf. A bit of fun on an otherwise flat day. I turned, paddled into them, and got an awesome ride. No Lipp Units, but smooth, cresting, carveable 2 footers that carried me a couple hundred yards, at which point I found myself in front of the whole set. So I looped around back through them, caught up with them again, and got another equally awesome ride. I was able to repeat this about 8 times, ending up all the way back down at the south end of Clark’s Point – over a mile of glassy surfing. At that point, the wakes finally began to peter out. I never saw the ship that made them, but I had a much bigger smile on my face the rest of the paddle back to Marine Park.
Maybe some of you who know more about wave physics than I do can help me understand something: how is it that I can enter a set of wakes from behind, apparently stay on one wave the whole time, but then end up in front of the set? I know that waves are water moving in circles, but I’m still perplexed (though happy).
Dave H.
Tom Swetish
10/29/17 #22125
Not sure if this image of a duck will embed in my post, but I think it is a nice illustration of a boat wake. As you can see, the wake is a series of parallel waves radiating outward from the duck. If you are able to get on the peak of one of the waves and then point directly at the duck, you will get an infinite ride. But typical boats are faster than ducks, so you end up going straighter down the wave face and eventually running off the outside of the wake. But then if you wait and let the subsequent waves pass you, you can paddle in from the inside of the wake and do it all again. During the summer the Victoria star comes by the post point buoy at 5:15 every day and you can chase a 13mph duck.
Reivers Dustin
10/29/17 #22127
noun: precession: the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope.
In open water you can see it better. The wave you are riding gradually subsides and rises in front of or behind you. Boat wake is doing the same except not. The composite boat wake waveform continually shifts back while the wavecrest you are riding precedes ahead - thus placing you eventually at the leading edge, then past the whole series of the boat wake.
https://arxiv.org/abs/1608.04241
Swell is not the same. These are maintained wave energy and theoretically you could ride one for a looooonnng time. But that takes some high energy to get and hold the right position.
further reading for the student:
https://en.wikipedia.org/wiki/Wave
David Hooper
10/29/17 #22135
Hey Tom,
Thanks, that helps a lot. I also like the idea of an infinite ride on a duck wake. Badass duck. Anyway, what it sounds like from your description and the limited additional reading I just did is that the directional motion of the wave is actually the same as that of the duck, correct? So, while I might tend to paddle perpendicular to the wave front (steepest drop), the wave is moving more in the duck’s direction. Is that right? Otherwise, I don’t see why I wouldn’t just travel along with the wave.
Even the terminology in Wikipedia lost me pretty quickly on this one!
Dave H.
Tom Swetish
10/30/17 #22136
I’m already talking out of my a—, but here’s what I think I think. The duck waves are close to perpendicular to the direction of travel - but as a boat moves faster, that angle changes. So to go the same direction as the boat, you need to angle on the wave face to go the same direction as the boat. If you can manage to do this, I find that you will stay at the peak of the wave and never wash off the wake. So I guess this means that the waves are traveling the same direction as the boat, but are not traveling perpendicular to their faces? Kinda weird. And maybe totally wrong…
Tyler Irwin
10/30/17 #22137
It seems like the wave would travel perpendicular to the shape of the bow of the boat (or duck, in this case).
duncanhowat
10/30/17 #22138
Tom I think your about right. I've taken my boat (23' with a lot of heavy HP) out and gone at least 3 miles behind it by staying on the first wave, not directly behind the boat but to the side and pointed the same direction as the boat. Big rudder on ski to hold in there and some tapping along with paddle. With even more skill and bigger boat I think it just takes some leaning and carving. Would go further, but my boat driver always (Gail) gets bored. Speed anywhere between 9-11 mph once settled in. I think thats about the same speed as those surf wave making ski boats with water tanks in their sterns go when their sound system is so loud you can hear it down town from lk whatcom and their buddy is riding the wake on a surfboard with out being towed. Big Wave
Nicholas Cryder
10/30/17 #22139
Best wake I ever road behind a mega yacht from Lake Union out to Lake Washington. It was a 150’ catamaran hull and the wake was unreal. Surfed back and forth on a stern wheeler sized wake for 10 miles with my paddle on my lap, and the owners offered to throw me some beers. Eventually I got bored and turned around when I saw another yacht going the other way (free ride both ways).
All this to say that hull shape, draft and the stern shape make a big difference in how one surfs behind another’s boat.
David Scherrer
10/30/17 #22140
Ah yes, the transfer of radiant power or . Man thats a lot of HP.
D.
