Sunday, August 4, 2013

The lost navigation art of Bottom Sounding

     As a kid of 8, in my first year of lobstering  with the Old Timer (who was in his early 70's by then), I asked a lot of questions about the things on the old boat. His new, smaller lobsterboat was his retirement exercise plan. It was a pretty 31' boat with a Detroit Diesel 453, a loud and reliable engine that today, 30ish years later, is still running strong for her owner.
       The Old Timer had been lobstering in Boston harbor since WWII as a second job. He owned gas stations and an auto body shop, so the boat was always his refuge, but with 50 years of fishing experience, the guy knew his shit. The new boat had a VHF radio (never turned on) and a bottom sounder (turned on once when new), and that was about it for electronics. No LORAN (the nav system of choice for lobstermen- a radio-based almost-grid system that gave numbered coordinates instead of lat/long in the days before GPS), and chart plotters hadn't been invented yet. It did, however, boast of an expensive compass that was annually adjusted by a professional compass adjuster (yes, that's a thing!).

    In summer fogs, the old guy preferred to stay in, and this was a bummer for yours truly. Occasionally, though, a fog would spring up when we were working, and we'd get socked in. At those moments, the old timer would pull out his watch and clean the mud off the compass, and figure out where the nearest navigation buoy was. Using the compass, rough knowledge of the direction of the tide, and his watch, the old guy would run to the channel marker, do some math in his head, and either head for the next marker on the way home, or to the next set of gear to be pulled. If there was a Groaner or a Bell Buoy nearby, we'd fish around that area before going home. Channel markers with an audible signal were our breadcrumbs, and knowledge of the bearing and distance between channel markers would let him know when he was in the neighborhood od

 In the next 10 years, only once did I see the old timer miss a mark. He was about 75 at this point, and, in running for home, we missed a buoy. He looked at his watch, did a round turn, nothing.
    With a sigh, he went into the little cabin and came out with a sounding lead and some knotted rope.

 For those of you not in the know, a sounding lead is a heavy weight with a hollow cup in the end, made of, you guessed it, lead. It is kept on a rope that has been marked at certain intervals- fathoms, in this case, or 6 foot increments. It looked like this, only smaller.

        When the lead strikes bottom, you read the depth of the water by reading the marks on the rope. This was how ancient sailors checked the depth of water. The cup in the end of the rope was filled with tallow- this picks up any pebbles, shell, mud or sand, and lets you know the bottom type. Even today, navigation charts list the bottom composition, for exactly this reason, though this is a lost art now, and the bottom composition is mostly used for figuring out where little boats can anchor.
It's in there. There's a whole book ("Chart #1") that helps you read charts, so don't sweat being confused .

     Anyhow, as you might imagine, there wasn't any tallow to be had on a little lobsterboat in the 80's. There was plenty of ale grease, though, so a plug of that stuff went in the cup of the lead, and over she went.

 The old guy read off the depths and showed me the sandy mud in the grease. We ran for 30 seconds in one direction, and he read it again. With the bottom composition and a general idea of where we were, plus the depth info, he figured out where we were more precisely, gave up on Arming the lead (loading it with grease), and had me turn and steer a compass course slowly until the depth of water rapidly increased, at which point we were in a shipping channel, and he had me turn quickly, giving me a direction to steer, (up the channel) and pulled up the lead. A few moments later, a channel marker came in sight, and the old guy went back to his compass and stopwatch and we headed home.
      After, all tied up at the dock, he told me that that had been the 1st time in 30 years he had used a lead to navigate, but that he got caught in the fog more frequently when he was younger, and had become fairly adept at getting around, and without the pressure of relying on fishing for his sole source of income, he never saw fit to buy a LORAN.  The ideas made perfect sense to me. Knowing the general area, bottom type and depth you can figure out where you might be. Using the changes in depth and bottom composition, you can refine where you think you are. Each factor can be used for rough navigation with local knowledge or a chart. Combining them increases reliability of any position fixes you might make.
Just another tool in the toolbox. In our modern era of multiple GPS, plotters, ECDIS, ARPA and AIS, many old skills go by the wayside. Some are preserved- celestial navigation is done for traditions' sake more than anything else, though it is still useful and important skill for emergencies. Others, like quadrants, the 3-fathom curve, bottom sounding... those are passed into history, but that makes them even more important to me


bigsoxfan said...

Another one of those skills that aren't worth diddly, unless you use it on a regular basis. See my second book in the series of sailing in Casco Bay; "running blind with Dad".
Say, what is ale grease? Some Massachussets thing, like calling soda, "tonic"? Fine piece of writing, Paul. Put me pack in cockpit with dad. I will have nightmares.

Third News said...

Loved reading this for the sake of understanding a little of the art in navigation.

I'm confused as to why 30 seconds in distance would change the soil composition

Paul, Dammit! said...

Third news- it doesn't, necessarily, but if it does, you know that you're very close to the transition point, usually coming with a change in depth, as well. If you've got a mental picture of where that break is, you now know you're on x side of the break. It would have been just as worthwhile to wait 1, 2, 3 minutes, but a 100-yard jump is sometimes all it takes if you know an area really well.