Project TOTEM - TOwed TEMperature array.
Experimental use of thermistors to measure temperature in a slice of ocean between a start position and an end position.
Contributed by Bruce Hallett & Wayne Bauer.
Bruce begins:-
Thermistors are basically resistors whose resistance changes in proportion to the temperature of the environment that they are in. Generally, in the electronics industry, this is a bad thing! For example, you don’t want the volume of your iPad changing as the iPad heats up in the sun or cools off in the shade. So there is a lot of effort made to manufacture resistors that have the same resistance no matter what the air temperature is.
However, thermistors have their use in electronics, particularly as cut-off switches to prevent damage to a piece of electronics that is overheating – that dreaded little red light on your car dashboard that indicates that the engine is overheating might be triggered by a thermistor.
Thermistors were first used in the 1930’s, but were not very accurate, nor stable nor rugged. By the late ‘50s, they had become more accurate, rugged and stable.
So Graham Lobb devised a test system to use three thermistors to measure the temperature of the ocean at intervals of depth of about 100 feet (as memory serves me) to see if they could be used to ‘map’ the temperature in a slice of the ocean. He was to use the Sir Horace on its return journey from Woods Hole (where she had been doing some work for some other organization) in late summer 1967. The profile (‘slice’) was to be from Woods Hole, Massachusetts to Bermuda, however, circumstances determined a different path – from Sandy Hook N.Y. to Bermuda.
In order to keep the towing wire, to which the thermistors were attached, as vertical as possible in the ocean, he decided to use a ‘paravane’. This is a triangular shaped thing that looks a bit like a stealth bomber (about 4 feet from wingtip to wingtip), but instead of the wings providing lift, its wings were designed to push the paravane (and whatever was attached to it) as deep into the ocean as possible as It was dragged forward. Thus, the wire with the three equally spaced thermistors was nearly vertical as we chugged along at a frightening 3 knots.
As with most things back then, we had to build the paravane ourselves – a steel frame to give the basic shape, then a shell of thin plywood strips bent over it to form the ‘aerodynamic shape’ required, and finally the whole thing was covered with multiple layers of fiberglass. There were a couple of ‘weepholes’ to allow water to get inside it, so that it would not collapse because of the increased pressure underwater. There were two attach points for the towing cable so that the towing bridle could be attached.
T-Boat took the paravane out one day for sea-trials, (without the thermistors attached) to
The thermistors that were chosen had a range of 50 degrees F to 75 degrees F, and an accuracy of about .1 degree F. The thermistors came with a chart that cross referenced their resistance to the temperature. Outside that range, there was either zero resistance (below 50 degrees), or the resistance became huge and meaningless (above 75 degrees).
Brian Turner and Leon Ingham designed and built an electronics box to measure the resistance of the thermistors once a minute, and print out the data. Once the system was up and running, the 'scientist on watch' had little else to do but ensure the system kept running, and change the paper on the printer when necessary.
Wayne Bauer continues the story.
Thermistors are basically resistors whose resistance changes in proportion to the temperature of the environment that they are in. Generally, in the electronics industry, this is a bad thing! For example, you don’t want the volume of your iPad changing as the iPad heats up in the sun or cools off in the shade. So there is a lot of effort made to manufacture resistors that have the same resistance no matter what the air temperature is.
However, thermistors have their use in electronics, particularly as cut-off switches to prevent damage to a piece of electronics that is overheating – that dreaded little red light on your car dashboard that indicates that the engine is overheating might be triggered by a thermistor.
Thermistors were first used in the 1930’s, but were not very accurate, nor stable nor rugged. By the late ‘50s, they had become more accurate, rugged and stable.
So Graham Lobb devised a test system to use three thermistors to measure the temperature of the ocean at intervals of depth of about 100 feet (as memory serves me) to see if they could be used to ‘map’ the temperature in a slice of the ocean. He was to use the Sir Horace on its return journey from Woods Hole (where she had been doing some work for some other organization) in late summer 1967. The profile (‘slice’) was to be from Woods Hole, Massachusetts to Bermuda, however, circumstances determined a different path – from Sandy Hook N.Y. to Bermuda.
In order to keep the towing wire, to which the thermistors were attached, as vertical as possible in the ocean, he decided to use a ‘paravane’. This is a triangular shaped thing that looks a bit like a stealth bomber (about 4 feet from wingtip to wingtip), but instead of the wings providing lift, its wings were designed to push the paravane (and whatever was attached to it) as deep into the ocean as possible as It was dragged forward. Thus, the wire with the three equally spaced thermistors was nearly vertical as we chugged along at a frightening 3 knots.
As with most things back then, we had to build the paravane ourselves – a steel frame to give the basic shape, then a shell of thin plywood strips bent over it to form the ‘aerodynamic shape’ required, and finally the whole thing was covered with multiple layers of fiberglass. There were a couple of ‘weepholes’ to allow water to get inside it, so that it would not collapse because of the increased pressure underwater. There were two attach points for the towing cable so that the towing bridle could be attached.
T-Boat took the paravane out one day for sea-trials, (without the thermistors attached) to
- a) determine the exact configuration of the bridle to get the maximum vertical-ness without too much strain on the towing cable,
- b) see how much the paravane ‘danced around’ (like a bat kite on a windy Good Friday!), and
- c) determine how much cable needed to be paid out before the effect of this ‘dancing’ was negligible – i.e. how far up the cable from the paravane the thermistors needed to be placed to avoid being dragged back and forth sideways.
The thermistors that were chosen had a range of 50 degrees F to 75 degrees F, and an accuracy of about .1 degree F. The thermistors came with a chart that cross referenced their resistance to the temperature. Outside that range, there was either zero resistance (below 50 degrees), or the resistance became huge and meaningless (above 75 degrees).
Brian Turner and Leon Ingham designed and built an electronics box to measure the resistance of the thermistors once a minute, and print out the data. Once the system was up and running, the 'scientist on watch' had little else to do but ensure the system kept running, and change the paper on the printer when necessary.
Wayne Bauer continues the story.
A paravane on a shipping pallette.
A paravane being deployed.
Above 2 photos courtesy of Royal Australian Navy.
The Vane that Graham Lobb designed and built was similar, but lacked some of the aeronautical design shown here. Posted Apr. 2014 . --==oo00oo==-- |
As an assistant working with Marvin Drake in the summer of '67 I had the good luck of going out on my first project shortly after I arrived there. Exactly what the "project" was I don't recall, but it was significant because we encountered some rough weather. I guess on previous projects, some of the "assistants" had trouble with seasickness which proved to be a deterrent to them accomplishing their "tasks". I suppose I surprised everyone by never getting seasick on the trip, and as a result I was “loaned” out to some of the other scientists when their projects went to sea. One of those projects was Graham Lobb's trip that took us to Woods Hole that you and Gerry Ryan mention in the interview. And as he mentioned and I’m sure you recall, it was “memorable” for more than just the scientific aspects of the trip. The Sir Horace was already in Woods Hole when a group of us flew up to meet her.
Upon our arrival we discovered we would be delayed a few days. Turned out Clem McCann had a sister that lived down on the Cape and he wanted to spend a little more time visiting with her. It just so happened that her husband was a doctor and between Clem and the doctor they concocted a scheme that would have the Sir Horace “quarantined” in port for an extra couple of days. Funny thing was that unbeknownst to headquarters who approved the “delay” the good doctor was a dentist. The return trip to Bermuda finally got underway after a few more “memorable” days spent partying on Cape Cod . As you and Gerry remember, we towed that airplane looking “paravane” back at a rip roaring 3 knots…and all on the tail end of Hurricane Dora. The Sir Horace was bobbing around like a cork, rolling from side to side. I remember you could barely sit in a chair in the instrument room without it tipping over, and the “walks” back to the stern to record the angle of the cable were frightening. As I recall Graham and even Clem had a bout with seasickness on the trip – or maybe it was alcohol poisoning…lol. While all of this was indeed “memorable” there is one moment on this trip that is forever indelibly etched in my mind. After a week or so of this bobbing around, and finally completing the journey, Hurricane Dora had cleared out; we pulled up the “paravane” and headed for home. The sun was just coming up, the ocean was like glass, flying fish were taking off from our wake and there was Bermuda , just glistening in the distance….a mental photograph I will never forget. |
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Bruce continues:-
I certainly heard the ‘story’ that we had been ‘quarantined’, but the truth was that we were delayed because of that fickle female Dora, who was supposed to have died once she encountered land in North Florida, but instead took a right turn and headed back out to sea, passing by Woods Hole a couple of days later as a tropical depression. Once she had safely passed, we set sail, but headed South towards New Jersey looking for calmer water before turning East to head for home. There is a reason that most ships either prohibit or strictly control the use of alcohol while at sea, and Sir Horace was no exception. The reason for this is obvious – nature has a way of making things go horribly wrong in a flash, and you need to be in complete control of your faculties. But when the ship is safely in port, the crew is ashore … The results of the experiment were encouraging. The array deployed with no problems, despite the rough weather, and the equipment worked as expected – despite some initial anxiety that the thermistors were not working, until it was discovered that they had been in water colder than 50 degrees, and hence were giving no readings. I recall that our entry into the Gulf Stream was quite dramatic, with the temperature rising about ten degrees in about five minutes. Once ashore in Bermuda, the data was further analyzed by Graham Lobb and Ants Piip. By mid-'70s, thermistor 'chains' of several hundred thermistors spaced at about 1 foot intervals were being built. Yay for Science at SOFAR!! Bruce Hallett. Wayne Bauer. Dec 2013. |
The thermistors that we used were similar to the 3 large ones at the bottom of the photo.
Once they were connected to the towing cable, they were covered in a thin layer of epoxy for waterproofing. |