A Day on the Lake

or, Why a Wake Boat Offset of 500 Feet Won’t Work on Small Lakes

The narrated animation below illustrates a typical summer day on a small Vermont lake. It demonstrates the normal and traditional uses of the lakes people enjoy as a natural shared resource. It introduces a single wake boat to show how its surfing affects these other lake activities. It illustrates why a wake boat offset of 500 feet from shore is inadequate to protect and preserve the traditional uses of our public waters. A 1000 foot offset, as proposed by RWVL, would keep wake surfing off our smallest lakes, and keep them far from shore on the largest.

(The transcript of this animation is included below.)

Once you have viewed the animation, ask yourself these questions:
– What would be the effect of a second wake boat operating on this lake? 
– What would be the effect of two or three more at the same time? 
– What if instead of a half-dozen traditional users shown, we saw 25 or 50 of them as may be common on summer weekends and holidays? What would happen to them?


This animation is based on the more than 100 years of science, from Lord Kelvin’s equations that describe the shape of a boat’s wake, to the more recent research of Jeff Marr at the St. Anthony Falls Lab in Minnesota, and that of Yves Prairie of the University of Montreal at Quebec and others who have measured the power of wake surfing waves at various distances from shore. The triangular wakes shown in the animation are drawn to scale, but the boats themselves are not; they are drawn larger than normal. The animation is based also on the eyewitness accounts of dozens of Vermonters. (For further details, contact Jim Lengel at jim@lengel.net)

Transcript of Animation

A summer’s morning on one of our Vermont lakes.
The wind blows gently from the southwest.
The boaters and swimmers still asleep, their craft resting on the shore or on the docks.
First to emerge is the angler, out at dawn to land a big one.
Out goes the angler, onto the lake, and begins casting.
The anglers know that they haven’t got the entire lake to work with.
The area along shore is studded with docks and floats and moored boats and shallow spots, shown here in pink, that they must avoid.
Next out is the waterskier, who needs the morning calm with its flat water to enjoy the sport.
The waterski boat produces very little wake, and as it circles the angler, all is well.
Paddling out from the southeast shore we see the canoeist starting to cross the lake.
The green kayaker emerges from the opposite shore.
The paddle board follows.
By now the wind has risen enough for the sailboat to venture out onto the lake.
As the sailor continues his run, he greets the swimmer stroking across the water.

By mid-morning, many of our lakes look like this, Vermonters and tourists alike enjoying their traditional watery recreational pursuits.

Out motors the red wake boat.
When its pumps engage and its stern begins to sink, the others begin to worry.
The wake boat is filling its ballast tanks for a surfing session.

Now under the proposed Use of Public Waters Rule, the wakeboat must surf within the area 500 feet from shore and 20 feet deep.
As the wakeboat throttles up the engines and engages the surf rudders, it raises a four-foot wave in its wake.
The wave expands behind the boat as a train of waves.
This triangular train is drawn to scale here, 500 feet wide at its base.
Within this triangle, the wake ranges from 48” to 9”, and at its ends carries 3500 joule/meters of energy.
Enough to swamp the most of the folks on the lake today.

The angler has seen this before. Quickly he skedaddles to shore. He knows what’s in store.
So does the canoeist.
The swimmer is breathing on his right side, and fails to see the wake boat.
The kayak speeds up to avoid the surfing run.
The paddle board makes its way back to shore.
So does the waterskier. No more skiing until the wake boat goes back home.
The wind has died, however, so the sailboat is stuck in the middle, unable to move.
The wake boat begins the surf run, staying within the allowed wake sport area. 
But notice how the wave train triangle extends half-way to shore, and half way to the middle of the lake.
At the end of the run, the wakeboat slows, loses its wave and its surfer, turns around, and takes another run down the southeast side of the lake.
Staying always within the zone, but spreading its wave train far and wide.

The net effect of all this is to restrict the small craft to a narrow strip of safe water between the pink along the shore and the edge of the wake boat’s triangle. 
This strip is shown here in green.

And that’s with just one wake boat operating. 

What if there were two? Three? Five?

What if at the same time there were dozens of swimmers, kayakers, water-skiers, and paddleboaders trying to enjoy the lake? What would happen to them?

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