Posted by Steve Dashew (February 2, 2011)
We hesitate to give out early performance information, but since the preliminary data off yesterday’s runs with Iron Lady are in the ballpark for what was expected, we thought we’d give you an early look. Iron Lady displaces roughly 34 metric tons / 75,000 pounds, in these early runs, as as she has a bit of fuel and water onboard. There were two runs, one up and one down tide, and these were averaged. Speed is from the GPS, fuel burn from the John Deere CPU display. Water is brackish and a touch shallow, both of which retard performance. The engine is a 235HP John Deere six cylinder diesel. At 1600 RPM boat speed was 9.4 knots burning 13.2 liters / 3.49 US gallons per hour. At 1800 RPM boat speed was 9.95 knots consuming 17.6 liters / 4.65 US gallons per hour. Top speed was 11.6 knots. The cruise speed is about 1/4 knot faster at 1800 RPM, compared to the boats without the extension and about eight percent more efficient.Top speed jumped to 11.6 from 11.1. Note, in the real world of crossing oceans, with hydraulic and electric loads plus increased drag from wind and wave, these numbers will deteriorate. Iron Lady is also about six tons / 13,000 pounds light of full load. But for comparison purposes to Sarah Sarah, the numbers give a real world indication of the ocean crossing gains to be expected. Over the next few weeks we’ll get more detailed numbers, and feedback on uphill motion and sound levels, both of which we expect to improve.