Alphaville does not have an opinion on the political effectiveness of boat parades. Putting a Trump flag in a rod holder and motoring around on the weekend isn’t any sillier than putting a sticker on a car bumper and driving to work during the week. And the Trump flags are, legally, bumper stickers. They represent what the Coast Guard would call a “private signal,” since they’re neither a national ensign or a yacht club pennant, which are used to show origin.
Flags, like hats and bumper stickers and any other private signals, are inherently confrontational. If they heave into view, you cannot avoid them by clicking away. There’s no political science on boat parades yet, but yard signs, for example, do have an effect on the margins if a candidate is already advertising.
Alphaville does, however, have an opinion on how to run a political boat parade: at either very high or very low speeds, in open water, and not in single file. The Trump boat parade on Saturday in Texas failed to do these things, and ended up fighting an opponent more formidable than any Democrat: physics.
On Saturday, inspired by a Facebook page that’s since been deleted, several hundred Republican skippers launched their boats in Lake Travis, a reservoir on the Colorado River just north-west of Austin. According to ABC News, the page instructed boats to meet at Emerald Point at 11:30am, motor about eight miles to Point Venture, then return. (This is similar to instructions also posted to nextdoor.)
At 12:15, the Travis County Sheriff’s Office, which was already standing by for the event, began responding to the first of fifteen distress calls from boaters. Boats were taking on water. Engines had stalled. Some boats had turned right over. Private towing companies responded to calls, too. By the end of the event, five boats were on the bottom of Lake Travis. No one was injured.
The sheriff’s office offered a straightforward explanation: “When the large number of boats began moving together, the wakes generated large waves in areas where participating boats were dense.” Alphaville has no reason to doubt the office, which even has a dedicated Lake Patrol unit.
But we would like to complement what the office reported. It wasn’t just the number of boats on Lake Travis that generated all those distress calls. It was the type of boat, the speed at which they moved, and the way they planned their route.
Trump voters seem to buy boats with planing hulls
In August, Joel Stein in the Los Angeles Timesdistinguished between an “intellectual elite” and what he called a “boat elite,” a group that is “tough, loyal, hardworking, tribal, traditional and focused on wealth. They are so reckless that as soon as they make the most expensive purchase of their lives, they smash a bottle of champagne against it.”
This is propwash. You do have to be some kind of elite to have room on your balance sheet for a boat. But what Mr Stein failed to recognise is that different elites buy different kinds of boats for different activities. Allow us to offer a simple model:
Alphaville has been astonished by the uniformity of hull shapes in the boat parades. Of all the recreational boats they could buy, the skippers flying Trump flags seem to buy an awful lot of the same thing: centre-console, outboard engine, deep-V planing hulls for fishing.
Here’s how a planing hull works:
A destroyer or a tanker or a sailboat or most boats in history have what’s called a displacement hull. It sits in the water, displacing some of it; when it moves forward, it pushes water out of the way, creating a bow wave that spreads out as the boat passes. But the kind of small craft you might buy to fish or take your kids tubing have a planing hull. They’re designed to get going fast enough to surf down their own bow wave:
The above seems to be the platonic ideal of a Trump boat. It was captured at a parade in Florida. Centre console, deep V planing hull for saltwater fishing. Seriously overhorsed, with what looks like three 200hp mercury outboards.
Deep-V planing hulls have a problem though: if they’re not going fast enough to surf off their own bow wave, the bow wave they do kick up is comparatively large.
The Lake Travis boat parade was not run at planing speed
Alphaville was not at Lake Travis over the weekend, so again we have to rely on the float plan as it was described by ABC News. The key detail: The plan was to run at 10 miles per hour. It was good that the organisers wanted to avoid high-speed collisions. But that was exactly the wrong speed for a boat parade of planing hulls.
Hydrodynamic flow is different for every hull, but a common frustration in harbours is that skippers of planing hulls will slow down to just below a plane when they get close to shore, when this is precisely the wrong thing to do. The moment before a boat planes, or right as it settles out of a plane, it is at maximum drag. Which means it’s kicking out its biggest possible wake.
So 5 miles per hour would have been ideal, just fast enough to maintain manoeuvrability. That’s in fact what the Slow No Wake navigational cans in harbours often dictate. At 10 miles per hour, you’re not planing yet. But you are closer to maximum drag, and therefore maximum wake. The Lake Travis boat parade was too slow to plane. But it was fast enough to kick up waves.
The Lake Travis boat parade lined up, then made a tight turn in a narrow channel
The route from Emerald Point to Point Venture follows a narrow channel. According to nextdoor, skippers were advised to wait for 4 parachute jumpers to land, then line up behind flagship boats with flashing lights. So a line of hundreds of boats was moving at displacement speed together, which meant that all these different wakes began to affect each other.
When two waves encounter each other, and they are out of phase, they go through what’s called “destructive interference.” They cancel each other out. This is how noise-cancelling headphones work — they generate a perfectly out-of-phase wave to destructively interfere with what’s coming in from the outside world.
But waves in phase with each other go through constructive interference: they amplify each other. This is how ocean-going vessels can encounter rogue waves in comparatively calm water. Two waves moving through the ocean encounter each other, constructively interfere, and break stuff.
If you line up and motor together, you are making it likely that wakes from different boats will constructively interfere. If you line up, head out, then turn around in a line and head home in a narrow channel, you are guaranteeing that wakes from inbound boats will constructively interfere with outbound wakes.
Which, Alphaville is guessing, is why the first distress calls came in as the boats would have reached the turnaround point at 12:15. And constructive interference produced the unbelievable waves in this now-famous shot from Bob Daemmrich (as a reminder, there shouldn’t be any waves):
No lake boat created a wave that big and that sharp. The peaks? The steep wave face? That’s constructive interference. Compare the Lake Travis parade with another Trump boat parade in Jupiter, Florida:
David Llewellyn-Smith is Chief Strategist at the MB Fund and MB Super. David is the founding publisher and editor of MacroBusiness and was the founding publisher and global economy editor of The Diplomat, the Asia Pacific’s leading geo-politics and economics portal.
He is also a former gold trader and economic commentator at The Sydney Morning Herald, The Age, the ABC and Business Spectator. He is the co-author of The Great Crash of 2008 with Ross Garnaut and was the editor of the second Garnaut Climate Change Review.
