Tom Wylie Interview in Sierra Club Magazine "Sailing's John Muir"
Wylie Design Group
The Northern San Andreas Project
One of the original goals of this project to map the northern San Andreas Fault was to try to track, and if possible reduce the overall carbon footprint of the project. Also of interest was the possibility that by doing so, we could reduce the overall cost of the project, thus doing more science within the budget we were granted.
As it happened the logistics of the mission favored the use of several smaller vessels as opposed to a single large vessel. The very small port of Fort Bragg California is restricted to vessels greater than ~ 80’ in length and ~ 10’ in draft, making the use of smaller vessels sensible. Beyond that, we chose to use a “green” vessel, the Derek M. Baylis, to purposely reduce the carbon footprint and compare this vessel to other research vessels that might be used. We also used the converted fishing vessel R/V Pacific Storm to act as the mother ship for the AUV “Lucille”.
We tracked fuel usage for all vessels, cars, airplanes etc. that were used in the mission. These data are shown in the pie chart. Some things are very clear from this tracking.
First, the use of a more efficient vessel as the primary survey vessel had a big impact on the total. Although the Derek Baylis is an auxiliary sailing vessel, as we expected, sails were used only about 15% of the time as a primary means of propulsion. This was because of lack of wind, or unfavorable wind direction much of the time. Sails were almost always up however as they serve to reduce rolling of the vessel even in very light or no wind. The main efficiency of the Baylis is through the vessels hull design. Simply put, it is long, narrow and very light. The 65’ vessel weighs only 35,000 lbs due to balsa core/carbon fiber construction. It’s hull shape is an evolution of racing yachts, and is very easily driven through the water. The 100 hp Yanmar turbo diesel can drive the vessel at 9-10 knots using less than 2 gph of diesel. At survey speeds averaging 7 knots for multibeam and 4.5 knots for seismic surveys, the average usage was 1.6 gph, a startlingly low figure. When wind was favorable, surveys could be done with the engine shut down, and the survey equipment running on the 6 kw generator. At other times, sails were partially used, reducing the rpm needed to maintain a reasonable survey speed. In all, the multibeam survey and seismic survey were done over a three week span with a total fuel usage of ~ 680 gallons of diesel, including powered transits totaling ~500 miles at full power.
We also noticed that the use of the engine had a direct effect on data quality. When under power, the effective swath width of the multibeam was a direct function of engine rpm, but not boat speed. Under power, a 10% increase in speed resulted in a 10% decrease in swath width, which was controlled by noisy beams on the outer part of the swath. However, an increase in speed resulting from partial or full use of the sails resulted in little change in data quality up to 8 knots, the fastest survey speed we saw.
Advantages of a sailing auxilliary vessel in this application:
•Faster (more science time)
•Quieter, both for the crew and radiated noise in the water
•Almost unlimited range
•24/7 ops, not common on a 65’ vessel
•Science party of 7, also not common for a 65’ vessel
•Crew of 2
•Improved stability (over a typical 65’ platform) even with no wind, sails reduce roll
•Cheaper (by a factor of ~ 3) Day rate ~ $1800/day
•Very low carbon footprint even under power alone 1.6 GPH
•Easier boathandling with outside helm and science deck adjacent
•Much better platform for small AUV ROV operations
•Crew fatigue low, and it was well, fun!
•Can’t weld things to the deck, have to design composite structures for mounting heavy gear like the sonar pole. This was not difficult.
We are not acoustics experts, but it was clear that the noise that controlled data quality was from the engine itself, from vibration of the hull or sonar pole, or from radiated noise from the propeller, and not from hydrodynamic noise of the vessels passage through the water. Ideally, if we could have conducted the survey under sail to a greater degree, the data quality would likely have been higher, and the time needed for the survey would have been less.
The Bottom line for the green vessel? It was faster, quieter, collected better quality data, and was less costly. We will use it again.
The Pacific Storm, the mother ship for the AUV, used the greatest amount of fuel for the project. This vessel is a typical converted fishing vessel, and burns fuel at a rate of ~ 18-22 gph for a transit, or as low as 12 gph at survey speeds in good weather. In total, the Storm used ~ 3300 gallons of the ~ 4900 gallons for the entire project. Although the vessel operated at low RPM as a mother ship, several long transits were needed to position the vessel for the project, and to return it to its home port in Oregon. Overall, Pacific Storm used diesel at about 8 times the rate of the Derek Baylis.
Other points of note: The rental Prius was the obvious car winner, followed by a Chevy Aveo rental car. We had a number of long airline flights to transport investigators from the east coast and Hawaii to the project in northern California. Long airline flights are as bad on fuel economy as one might think, averaging ~ 45 gallons per person for these flights per person, although the impacts are high as the greenhouse gasses are injected directly into the stratosphere. Also it is clear that short haul airlines using turboprop aircraft are more efficient than jets. While this is well known, and isthe reason the commuter airlines use them, the efficiency is something passengers rarely think about.
Total fuel usage was ~ 4900 gallons. This number seems quite high, but to put the whole cruise in perspective, if the project had been run on an intermediate class ship (like OSU's Wecoma), the total fuel burn would have been in the range of 30,000-40,000 gallons. Clearly, using two smaller “right sized” vessels was a great savings over doing the three components of the project serially on a larger vessel.