Of all the passages you could dream up, the most difficult is the 4000NM eastbound run from the Marquesas Islands of French Polynesia to Panama. Panama lies dead upwind, with a westerly setting current to make it more interesting. Read on to find out how FPB 64-6 Grey Wolf, Peter Watson, and crew have set out to do something no motor yacht has ever done.
There are three main aspects to this challenge. The first is the ability to motor those 4000 NM with sufficient reserves of fuel. Next comes weather, then current vs distance run tradeoffs. Finally there is comfort – sometimes a longer route is more comfortable. We’ll start with range. Then have a few brief comments from Peter Watson, and finally get into the weather and routing issues.
The FPB 64s carry 12,000 liters/3170 gallons of usable fuel in their internal tanks. Over a number of passages on various FPB 64s, we’ve seen fuel burn rates between 5.1 and 5.7 US gallons/19.3 to 21.6L per hour, at between 9.5 and 10 knots depending on external factors.
These figures require a polished propeller and clean bottom. Even a thin layer of scale on the prop will substantially degrade performance. There is no allowance for adverse current, or the boat being overloaded. On the other hand, performance will improve as the boat becomes lighter at the end of a long voyage. Then there is the real world aspect where the sea, wind, and current may be against you, and maybe the bottom cleaning job less than perfect. Peter Watson and crew aboard the FPB 64 Grey Wolf are keeping careful records of the ambient conditions and auxiliary loads (genset, air conditioning, heating). As Grey Wolf topped off her tanks in Nuku Hiva, and will do so again in Panama, we’ll have a very accurate count on fuel burn and average speed. It should prove interesting.
Right now, two days after departing, we have received the first report from Grey Wolf. This includes data on everything: from alternator amp output, to what high electrical load devices have been run, to the sea state and wind, fuel consumption, speed and distance covered, plus maintenance notes. As gensets are rarely used at sea on FPBs (they have 8kW of power available from their alternator/inverter setup and hot water is served up via waste heat from the engine) there is little added fuel required for these functions.
What we know so far is that after the first two days, Grey Wolf has burned 964 liters of her 12,000L of fuel. She is averaging a speed over ground of a little over 8.5 knots. These numbers are less efficient than indicated by her NZ/Tahiti data and in comparison to the other FPB 64s.
As Grey Wolf had her bottom cleaned and prop re-coated with anti-fouling prior to departing New Zealand, we can be fairly certain the lack of speed over ground is due to .75-1 knot of westerly flowing current.
Now a few comments by Peter Watson:
“We are looking at a combination of the shortest route (by going as east as possible), but taking into account wind, current, and comfort. Our speed at present is mainly governed by fuel rate until we are confident we have sufficient reserve for the trip all the way to Panama. Our target is a reserve of 2000 liters. Right now this stands at 2300 liters. So we are a little ahead.”
At 900 nautical miles from Panama there is a refueling point, if needed, in the form of the Galapagos Islands. But we suspect Peter and crew like a nice even number – and even though the Galapagos are closer, four thousand miles does sound a lot better than three. Going direct without stopping also allows a more favorable approach to the Gulf of Panama in terms of wind and current.
Peter added the following note to his e-mail:
“It’s not till you travel across oceans that you realise how big they really are. It’s wonderful to be at sea away from ‘civilisation’. Grey Wolf is a lovely ocean crossing motor yacht in which I have a fantastic amount of confidence.”
An Eastbound passage to Panama presents tactical challenges. While the easterly trades are right on the nose, and the westerly flowing current costs valuable distance to windward, the ITCZ – aka the Doldrums – lies a few degrees to the north, with lighter winds and possibly a counter current. So a route, like the one shown above (prepared for Grey Wolf by Bob McDavitt), that takes Grey Wolf to the south side of the ITCZ has potential benefits. Here are Bob’s comments:
Here is a map plot of the table for your voyage showing expected weather at Sun 4 May 1800UTC.
Expected position at that time is shown by small red circle (ignore the time code label):
- Showing the surrounding weather when you turn the corner
- Background small arrows are surface current
- Blue/green shading is rain
- 2 line is boundary of 2 significant metre wave height
- 1012 line is an isobar
- Grid of larger arrows shows coloured wind barbs
- Red arrows along path show winds forecast along the way
- One barb is 10 knots and half is 5 knots
Situation and comments:
- So it is agreed that we go NNE at first to get around a zone of counter (adverse) current.
- Turn right at about 01S and head for a zone where the current is with us, but the wind may be a headwind , and we might make more comfortable program by falling off to the north a bit
- Table below keeps us south of ITCZ for as long as possible
- ITCZ is north of 4N
- I’ll email updates or weather quickies when you email me position reports
I am using www.expeditionmarine.com for routing with latest Oceanic and GFS data output. Using VVP file for FPB 64s.
DISCLAIMER: weather is a mix of pattern and chaos. The real world unravels away from the model output shown here. Computer data does NOT do well near a coast or in a trough. In a convergence zone computer gives averaged-out light winds, but occasional squalls can deliver 30 knots for 30 minutes. If your baro strays away from target pressure more than 5 hPa the forecast needs updating.
DECODE: Time HH:MM is hours and minutes in UTC. Lat and Long are in degrees and minutes. hPa is barometer in hPa, wind is compass octant coming FROM and lull~avg~gust is speed range in knots. Crs-Bsp is boat course to in degrees TRUE and speed in knots. TWA is the angle between the wind and the boat course, minus for wind on port. Waves are significant wave height in metres=average of top third, or are exceeded around once in 7 waves or once a minute. Add 50% to get the occasional wave which occurs or is exceeded around once every 10 minutes.
Each turning point or way point is introduced with a line of text; the other lines are extras to fill in the in-betweens.
Departing Nuku Hiva around 5:30pm Thursday= 02 0300 UTC
Timestamp POSITION | Air |WIND |BOAT
|current | waves
UTC- HH:MM| Lat:/ Long: | hPa
Around 1dge 30min S turn to ENE (OK to turn slowly)
And now go almost E
Remainder of table is just an outlook and needs updating
By here we need to turn north
Route distance 4143.20nm, route time 17d 08h 36m
Peter and crew are managing this leg like you would if you were sailing. They are playing a long range VMG (Velocity Made Good) game, changing course depending on local current, sea state, and wind. Check back to see how this is working out.
May 10th, 2014 at 3:37 pm
I have been following Grey Wolf’s communications during their historic trip… what a testimonial to your designs, Steve. Congratulations…I can understand Peter Watson’s desire to take two years to get his FPB 78 home….
March 29th, 2015 at 2:23 pm
Steve, I notice in this photo prop is four blade, others three blades. What is your opinion on difference between these two? I would think/guess that with plenty of clearance between hull and prop on FPB 64, three bladed would be better efficiency all else being equal, but would be nice to hear real facts. What pitch is used with the three blade and four blade props?
April 1st, 2015 at 4:51 pm
Three bladed props are a touch more efficient but noisier. Four bladed props are over pitched by about 10%, so cruise speed is obtained at lower RPM.