The data:
So I took the liberty of a looking at each interval on
@Bruce's inreach ( Propless) and recorded speed. I also did the same for my inreach ( Yonder ). For mine I also had 2 minute intervals. I started the first observation east of port everglades and stopped at the last observation before making temporary stop outside Bimini Sands. The 10 MI ( minute intervals) I tried to match them as closely as possible between the 2 boats based on proximity of the coordinates.
Boat similarities:
I also included some key metrics which in my opinion show that both boats had more or less the same weight load.
Why go through the trouble?
After Bimini there was some discussion about fuel consumption and how we could explain the variability between someone running out of fuel 10 miles prior to Bimini and other using less than 70% of the fuel supply. The top 5 attributes seemed to be:
- speed
- steady hand
- weight load of the boat
- new engines Vs. old engines
- tabs vs no tabs
How did examine each attribute?
- speed = speed from inreach explorer ( line 1 on the table)
- steady hand = standard deviation of speed ( line 2 on the table)
- weight load of the boat = (lines 5,6,7 on the table)
- new engines Vs. old engines = lines 8 on the table
- tabs vs no tabs = I asked and we all had tabs deployed 100% for the majority of the trip.
Observations:
- clearly the average speed between the 2 boats is very very close. This makes sense as both boats where part of same group. Speed on its own does not seem to explain the difference in consumption.
- the variability on speed between the 2 boats is 1.6% ( 2.76 vs 2.72) which indicates that the speed variability between the 2 boats was very similar. These results will not support the "steady hand effect" as a explanation for the variability in fuel consumption. Furthermore,we can say 70% of the times the speed of the boats was between 11.77mph and 17.29mph
- Given the size of the boats and occupants and baggage I want to say that both boats were very similar. Hence, the weight on its own is not explaining the 15 gallon difference in fuel.
- clearly here there is a difference on the engines. I would have a hard time believing that the newer engines are 44% more efficient than the old ones, let alone believing that the older ones are 44% more efficient than the new ones. Although, statistically someone could attribute the difference in fuel to the engines I disagree. Further soouport on my argument is that @swatski has the same new angines as me and consumed less than 40 gallons.
- I had my trim tabs ( 12x12) deployed 100% for about 95% of the trip. As fara s I know @Bruce has the same metrics. From what I recall Swatski ( 9x16) had the same metrics
Conclusion:
In my opinion the only consistent difference between Yonder and Propless way that I took waves and the way that Bruce did. I recall that the first hour of the trip my fuel needle was moving rather fast and the remaining 3 hour it was rather steadier. Given the results results that I am seeing here, I am more and more inclined to believe that I was battling the waves while Bruce was skimming them. Especially given the second part of the trip where I was hitting clean water. I am sure for the seasoned this conclusion is obvious, but for me I needed the data. And so far the data cannot disprove it.
Footnote 1: I touched my throttles very very few times. I deliberately avoided touching them that is why I was not 100% sold on the "steady hand" ( I am sure there is argument to me made here that steady does not equal do not touch the throttle) and that is why I was itchy to see the st. deviation on speed.
Footnote 2: notice that the st. dev on speed between 2 Minute Interval & 10 Minute Interval on the Yonder !!!! The difference between boats is 1.6% whereas the difference within Yonder is 12.6%. I would expect to this difference to increase but by a 10 fold it just too much. Given this info, someone could argue that I have not disproved the "steady hand effect". My come back will be that the 10 MI interval between the boats are random and therefore representative. The this other person will say that I am full of sh!t and the only way to proof anything is to run an experiment in 2018. To which I will agree 100%
Final note for the newbie who is making the 2018 crossing. No matter how comforting Emma's life jack might look 50 feet in-front of you,
put some more space between the lead boat and your boat.
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