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  1. #1
    Join Date
    Apr 2015
    Posts
    196

    Default Addicted to the fuel burn gauge

    Just took a trip over to N Africa with a d speed buddy..and I have become totally addicted to the fuel burn meter...plodding behind him took my fuel useage down from 220 l per hour to about 18 lol...albeit at a slower speed...but doing the calculation, it's a huge difference. Even an extra knot doubles the fuel burn, so I spent the entire time maximising fuel burn for knots lol...Love driving at 8.5 knots too...saw tons more dolphins etc...and lets face it, never in that much of a hurry to get anywhere.

  2. #2
    Join Date
    Sep 2016
    Location
    SoF
    Posts
    9,824

    Default Re: Addicted to the fuel burn gauge

    I’m also addicted to it
    Neither a Leaver or Remainer be

  3. #3
    Join Date
    Jun 2002
    Posts
    2,820

    Default Re: Addicted to the fuel burn gauge

    We had a coupe of fantastic passages along the east coast this year on hot, sunny days and flat calm conditions. Ran with the tide at displacement speed and the autopilot on - no inclination to burn a load more fuel and foreshorten the experience. To be honest I think it is the future for us as fuel prices will inexorably increase and we near retirement - currently musing whether it will be a yacht (we enjoy sailing) or a displacement mobo, possibly in steel.

  4. #4
    Join Date
    Aug 2009
    Location
    Hamble
    Posts
    1,032

    Default Re: Addicted to the fuel burn gauge

    I would be too, if I had one.

    What I do not understand is why people use litres per hour, which is not really a good indicator of efficiency unless you consider speed as well, rather than litres per nautical mile which is what we are really trying to optimise.

    Other units are available gallons, km, etc.

  5. #5
    Join Date
    May 2001
    Location
    Bucks & St Raphael SoF
    Posts
    1,471

    Default Re: Addicted to the fuel burn gauge

    I don't have a fuel burn gauge so I made a spreadsheet that gives a range of outputs, including cost per NM, which is the most useful. Range is from 3.85€ - 14.00€ per NM, which is quite motivating to keep it slow!

  6. #6
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,182

    Default Re: Addicted to the fuel burn gauge

    Quote Originally Posted by EugeneR View Post
    I would be too, if I had one.

    What I do not understand is why people use litres per hour, which is not really a good indicator of efficiency unless you consider speed as well, rather than litres per nautical mile which is what we are really trying to optimise.

    Other units are available gallons, km, etc.
    I think because consumption per hour will be largely constant where as distance travelled will be subject to currents, wind etc forces. But I agree. When I worked out how much fuel I saved by going 6knts vs 20 knots over a 50nm hop the difference was disappointing in actual £ per hour saved. Would need to be long distance to make significant benefit

  7. #7
    Join Date
    Apr 2015
    Posts
    196

    Default Re: Addicted to the fuel burn gauge

    Quote Originally Posted by EugeneR View Post
    I would be too, if I had one.

    What I do not understand is why people use litres per hour, which is not really a good indicator of efficiency unless you consider speed as well, rather than litres per nautical mile which is what we are really trying to optimise.

    Other units are available gallons, km, etc.
    It's watching the burn going from 18l per hour at 8.3 knots to 36l at 9.3 knots...very encouraging to keep the speed down, as while I realise it's going to get us to the destination quicker...we are only talking about tiny difference in speed = massive difference in fuel used. So the saving in fuel used in a shorter time..is greatly outweighed by the amount of fuel it takes to get there at that speed.

    Just my thoughts...no exact science..it did really help me stop nudging the throttles a little forward lol.

  8. #8
    Join Date
    Sep 2016
    Location
    SoF
    Posts
    9,824

    Default Re: Addicted to the fuel burn gauge

    This morning we moved our boat from itís summer to itís winter mooring. A distance of less than three nautical miles in flat calm warm sunny conditions. 5.1 knots @ 2.8 lph. And thatís with a whole season of growth.

  9. #9
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,182

    Default Re: Addicted to the fuel burn gauge

    Not having a fuel consumption capability I look at my stern wake to judge efficiency. As soon as it gets more than what I see on my 280, 3.5 hp tender I back off. It's probably all in my mind but the thought process goes I cant be wasting more that 3.5hp On my 34 footer that equates to just over 5knts in still waters and about 1000rpm (out of 3900 at WOT).
    I have a figure from the internet (cue unreliable) that I can expect a fuel burn of 4.5 litre per hour per engine at these revs and speed. 9 lph
    At 3200 rpm, (again an internet figure) I am doing 22 knts and a fuel burn of ~20lph per engine. 40lph
    Given on a weekend jaunt I may go 25 miles to an anchorage for a total of 50 return then rough maths makes : displacement burn ~10 hrs x 9 = 90 litres
    planing burn ~ 2.5hrs x 40 = 100 litres
    So where is my Math going wrong?

    edit: these internet figures appear to be born out when averaged against amount refuelled over the course of several trips.
    Last edited by BruceK; 01-10-19 at 10:51.

  10. #10
    Join Date
    Jun 2011
    Location
    Volos-Athens
    Posts
    4,849

    Default Re: Addicted to the fuel burn gauge

    Quote Originally Posted by BruceK View Post
    Not having a fuel consumption capability I look at my stern wake to judge efficiency. As soon as it gets more than what I see on my 280, 3.5 hp tender I back off. It's probably all in my mind but the thought process goes I cant be wasting more that 3.5hp On my 34 footer that equates to just over 5knts in still waters and about 1000rpm (out of 3900 at WOT).
    I have a figure from the internet (cue unreliable) that I can expect a fuel burn of 4.5 litre per hour per engine at these revs and speed. 9 lph
    At 3200 rpm, (again an internet figure) I am doing 22 knts and a fuel burn of ~20lph per engine. 40lph
    Given on a weekend jaunt I may go 25 miles to an anchorage for a total of 50 return then rough maths makes : displacement burn ~10 hrs x 9 = 90 litres
    planing burn ~ 2.5hrs x 40 = 100 litres
    So where is my Math going wrong?

    edit: these internet figures appear to be born out when averaged against amount refuelled over the course of several trips.
    Bruce,

    why don't you do some measurement, I VERY MUCH doubt the dif from 5kn to 20kn is 9lph vs 40lph that's bloody analogous, no way! one of the two lph values is way wrong

    V.

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