Sunday, October 8, 2017

Locked Up

September 22, 2017

The only memory I have from my high school physics classes is the Ripple Tank study.   I recall clear tanks of water the size of small, shallow aquariums where we studied wave mechanics.   Somehow we would set the water in motion, waves would hit the end of the tank, come back on one another, and create waves over waves.  I liked that part.  We soaked the class I’m sure.  We were expected to observe wave structure (crest, trough, wavelength) and if I remember correctly, velocity (speed), angles of incidence (the wave travelling towards the wall), reflection (the waves bouncing off), and interference (when two waves meet).  I struggled with the formulae measuring those angles, wondering what the sense was of studying waves in such detail and where the numbers belonged that described all of the wave phenomena.  I should have paid much more attention to this theory of Wave Interference: when two waves meet, the combined height of the new wave is double the initial height of the original two.

After crossing Lake Ontario in mid September, I drove our boat into our 65th of 74 locks in the past three weeks.  We were in the Erie Canal system in Northern New York State, having motored through the Canadian Trent Severn Canal system north of Lake Ontario.  Craig and I have the lock passage routine down pat. 
- Motor up the chute to the entrance of the lock. 
- Radio the lock master. 
- Wait for the steel door to bang and rattle open and the green light signal from the lockmaster. 
- I drive the boat into the lock structure (concrete or rock walls) and up to within inches of one of 10 or so cables or ropes along the lock wall. 
- From the bow, Craig grabs one of the ropes/pipes with a boat hook, ties it up, and runs to the stern to tie to another one. 
- Once he signals to me, I hurry down to the inside helm and shut down both engines. 
- I run back out to the stern and grab the line wrapped around the cable. 
- Craig returns to the bow and hangs on to the rope.
- Water raises or lowers.
- Doors bang open, I run back in and start the engines, Craig pushes us off the wall and out we go.

The height of the lock can be anywhere from 3 feet to 47 feet and the last five locks of the Erie Canal (called “The Flight” because they are only a few hundred yards apart) at the town of Waterford take us down 140 feet of elevation.   The lock steel doors slam shut and we begin the push-me-pull-you dance with the ropes as the boat squeezes against the lock wall or swings out into the lock.  Sometimes it is uneventful and we stand for 10 minutes or so as the lock empties or fills and we rise or fall.  At other times, we push the boat off with all of our might or hang like Tarzan to keep the boat from swinging into the middle of the lock.  Sometimes as the water empties and the boat lowers, freshwater mussels living on the wall squirt water into our eyes as we are holding the ropes. 

By lock 65 (#9 on the Erie Canal), I was getting smug.  I usually steer the boat slowly into the lock and let it drift towards the wall.  This time I roared us in, thinking I could hurry things along.  Our speed brought the boat wake waves into the lock with us and the waves banged against the forward wall of the lock.  Angles of Incidence.  The waves came back and rocked us against the wall.  Angles of Reflection.  Not a problem, except that the back lock doors were closing so there was nowhere for those waves to go except to keep running into and over one another.  WAVE INTERFERENCE We found ourselves sitting in a giant wave tank as my smugness rolled back and forth under us, waves over crested waves, rocking us against the wall.  It took several minutes for the waves to subside.  Velocity.  Craig did not need to say I-told-you-so. 

Another interesting type of lock is the Lift Lock, of which the Trent Severn Canal system has two.  The Peterborough lift-lock elevation change is almost 20 metres (65 feet) and the original was built in 1904.   It is the world’s highest hydraulic lift lock, and operates on a balance system.  There are two large pans of water that balance one another out as one lifts and the other lowers.  We just float into one of the pans and enjoy the panoramic views of Peterborough as we are lowered.  It can be somewhat harrowing pulling the boat up to the edge of the pan at 65 feet and it takes only a couple of minutes for the lock to lower us into the bottom river.

Peterborough lift lock
View from the top of the lift lock

2017 was a great year to travel the Trent Severn and Erie Canal systems.  With Canada’s 150 celebration and the Trent Severn operated as a national park, we did not have to pay the fee of several hundred dollars.  
Lock attendant in Trent Severn opening the gates with a hand turning gear system.
They walk in circles pushing the handle and the gates open or close.
We were pleasantly surprised to find the same fee waiver as the Erie Canal system
celebrates its 200th year.  Horses or mules pulled the barges from shore through the canals of the early 1800’s and the animal paths can still be seen along today’s canals.    

We finished our last lock with a four day respite in Waterford, New York.  Only a 20 km bike ride from the state capital of Albany, we had the chance to ride up and down the Hudson River from Troy to Albany knowing we would soon be on the Hudson and heading to NYC.

Albany: Best doughnuts 
SUNY on the Hudson River

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