MBY.com upcoming changes

[ChrisJefferies]

Hi all,
Just a quick heads up for those of you who read MBY.com on a regular basis.
You may have noticed a few changes to the website design over the past few weeks - this is a work in progress, so we'd welcome any feedback and suggestions you have.
One specific change that you'll see from next week onwards is a newsletter sign-up gate on some articles (mostly boat reviews).

You will need to put your e-mail address in this box to unlock the whole article.
This will sign you up to the monthly MBY e-mail update, but no marketing messages (unless you opt-in).
Unfortunately, those of you who are already on our mailing list will need to enter your e-mail address again, but you won't receive multiple e-mails.
This should be a one-time inconvenience for loyal readers such as yourselves and will hopefully bring more passing visitors into the conversation.
Thanks for your understanding and let us know if you have any feedback or suggestions.
-Chris
(MBY Digital Editor)

 

[Deleted User YDKXO]

Dunno about MBY.com but I see that in the magazine version, mpg (should be nmpg) has made a welcome return in the boat tests, or at least one of the tests in the last edition. Maybe that was just a dreadful copy editing oversight but I hope nmpg is back to stay

 

[Whippersnapper]

Surely the appropriate metric is l / Nm

 

[Deleted User YDKXO]

Surely the appropriate metric is l / Nm

Not for me it isnt. Of course I'm capable of converting litres to gallons but traditionally nmpg has always been the most widely used indicator of fuel efficiency in the UK for boats for many years. Mpg is also by far the most popular measure of vehicle efficiency for cars. Nobody in the UK uses the contrived European measure of litres per 100km so I dont see why we should use something similar for boats. It also helps that many boats in the popular 30-50ft range have a fuel efficiency around 1 nmpg which is a lot easier to assimilate than 4.5 litres per nm

 

[MapisM]

Nobody in the UK uses the contrived European measure of litres per 100km so I dont see why we should use something similar for boats.

That's only because it's hard to teach old dogs new tricks (let alone when they are seen as contrived by the EU, heaven forbid! ), not because it isn't logical.

We all grew up with the habit of measuring fuel burn in terms of "distance/fuel" rather than the other way round, but it's a nonsense to use a measurement unit which decreases when what you are actually measuring increases, and vv.
Btw, what we have always been used to with boats (as opposed to cars) is actually different, i.e. fuel/time, rather than distance/fuel.
Which is a bit pointless in some ways, but at least has the merit of a consistent logic.
When adopting a new measurement unit which considers distance rather than time, why get rid of consistency?

And that's leaving aside metric vs. imperial, where it's crystal clear that it's only a matter of "old dog and new tricks", so to speak.
Everyone survived the swap to metric afaik, in all the Countries who dared adopting it...

 

[Deleted User YDKXO]

Btw, what we have always been used to with boats (as opposed to cars) is actually different, i.e. fuel/time, rather than distance/fuel.

Fuel/time is even more pointless in a boat than in a car because in the end it still comes down to distance. Knowing that your boat consumes fuel at a rate of 100 lph is of academic interest only. The only critical thing you need to know on a boat is whether you have enough fuel to get to where you want to go and for that you need to know distance/fuel. It is useless knowing your boat does 100lph unless that is related to speed and if you relate it to speed, that is distance/fuel

And as for old dogs and new dogs, it may have escaped your notice but instead of being a colony of Europe, very soon we are going to become a colony of the USA where they still use miles and gallons, albeit we will need to teach them exactly what a gallon is

 

[MapisM]

It hadn't escaped my notice, but for some reason your statement reminded me now of a famous song:
...did you exchange a walk on part in the war for a lead role in a cage?
With all due respect for Syd Barrett (RIP).
If he could look at his Country now, he might well think that his own insanity was nothing, in comparison... :ambivalence:

Back to your first paragraph, I agree with everything but your last conclusion.
Of course it makes sense to relate fuel burn to speed (hence distance) rather than time alone, even if sea conditions can affect that MUCH more than anything like rain, wind, or whatever when driving.
But the point is, why invert the measurement?
The most logical change is from fuel/time to fuel/distance, not distance/fuel. :encouragement:

 

[Deleted User YDKXO]

If he could look at his Country now, he might well think that his own insanity was nothing, in comparison... :ambivalence:

Well you know very well I agree with that

The most logical change is from fuel/time to fuel/distance, not distance/fuel.

Not in Blighty it isnt. Its mpg for cars and nmpg for boats

 

[MapisM]

Not in Blighty it isnt.

Well, that doesn't mean it isn't the most logical...

 

[wellf100]

+1 for nmpg. Was glad to see it back on one review and hope it returns for all!

 

[oldgit]

GPH. for me.

 

[jfm]

I’m litres/nm and have always been in my boating life .

 

[AndieMac]

I’m litres/nm and have always been in my boating life .

Agree, just seems so logical when the fuel you load on is in litres and your trip is in NM.

 

[petem]

For me, it's got to be litres per xxxx. I know the cost of a litre of fuel in our marine (€1.28) and I know the tank holds 592 litres. The only time that an mpg is useful is for impressing or shocking your mates down the pub.

Regarding nm or statute miles, I'll say this quickly before retreating to my nuclear bunker, I often do passage planning on Google Earth which of course is statute miles to litres per statute mile kind of works OK for me. Of course this all falls down a little when one measures speed in knots (it would be sacrilege to do anything else).

 

[Andrew M]

I often do passage planning on Google Earth which of course is statute miles .

Any reason for keeping Google Earth in statute miles Pete ?? I use GE as well for mucking about at home on routes but alter the units to NM.

 

[petem]

Any reason for keeping Google Earth in statute miles Pete ?? I use GE as well for mucking about at home on routes but alter the units to NM.

Apologies, to be precise I use satellite images from Google Maps which I don't think allows the units to be changed.

 

[Portofino]

I use what I have .

L/ hr
Time to target if I set up the plotter which I do on longer unknown trips .

Visual of the tanks sight glasses , although up to now the gauges are accurate enough , but I would never wholly trust them before a long trip.

I then know if I need to seek refuel before , during ( If coastal) or after the trip and plan accordingly.
With a bit of mental agility you can work out the total used if your bothered .

I feel like most planning boats there’s a plateau with range perhaps with a insignificant slight incline once up on the plane .Then a steep semi exponential ramp on the far RHS , the last 10 % of available rpm .

So if you ease back 5 knots and the L/hr drops the total burn is about the same as 5 knots quicker because the journey lasts longer and the extra time consumes the perceived saving .

There’s also a steepish ramp at the higher end where the extra speed from more throttle seems to consume a disproportionate amount of extra fuel for a few extra knots , the final 10 % of rpm available.So I tend to stay out of that As I can cruise @ 30 knots without entering that zone .

28 knots consumes 180 L/ hr is near enough 20 % off WOT

Another ball party number is estimating 30 miles / hr in distance calls .It know 28 knots is more but that’s an error on the right side .
So I have old fashioned dividers set at 30 miles from the paper chart scale and tell “ crew “ - “ it’s about an hr to here “

I’ve tried cruising in company down at 22 /23 knots it’s doesn’t really work for us .
We seem to be at the far LHS of the plateau, as said any savings on L/hr evaporate when the extra time at this lower consumption is added back .

I just set the throttles as I think they ( the designer / engineers from MAN , the gearbox ratio calculator + prop trial team on hull #1 etc ) have set it up and enjoy the boat as is and stopped worrying about fuel consumption a long time ago .It feels dynamically more stable too going faster .1760/1780rpm makes 28 knots .

Having said all this recently with enormous discipline we cruised about @ D for about a week 9.5 knots 55 % load , 875 rpm , and 18/20 L hr per side .
Tick-over is 7 L/hr per side at the dock by way of comparison.
Conditions were dead calm stability wise and a heat wave of mid thirties ++ air temps so the prolonged artificial breeze was welcomed.

 

[bluetooth]

Having said all this recently with enormous discipline we cruised about @ D for about a week 9.5 knots 55 % load , 875 rpm , and 18/20 L hr per side .
Tick-over is 7 L/hr per side at the dock by way of comparison.

A week at displacement - that is impressive discipline ! But also impressive diesel cost saving. Would you do it again ?

 

[Portofino]

A week at displacement - that is impressive discipline ! But also impressive diesel cost saving. Would you do it again ?

Yes .

I think we did 4 hrs in one stint before anchoring up for a swim as it was hot even by SoF standards + lunch .covered about 45 miles as opposed to near 140 !

Interestingly the two main tanks are 800 L and I have a reserve ( added bespoke extra ) of another 600 L .
I was in two minds as to fill em all up , brim then before we set off .

The two main where at about 40 % on the sight glasses .so say est 300 L in each .
In planing mode that’s 3 hrs or 100 miles .
So I topped them up adding near enough 1000 L in all 2x500 to 800 .Left the reserve empty .
When we returned the tanks are at 60 % so over 500 L left , ie more in then when I left due to the 18/20 L/hr being gobbled from each one for 5/6 days .
In other words I under estimated it all .
Never mind it’s sat there for next time .
I did the last 20 mins / 10 miles a P speed to blow away any carbon .
EGTs at D were about 400 , at P 570 degrees with 80:% load doing 28 knots

 

[Elessar]

Not for me it isnt. Of course I'm capable of converting litres to gallons but traditionally nmpg has always been the most widely used indicator of fuel efficiency in the UK for boats for many years. Mpg is also by far the most popular measure of vehicle efficiency for cars. Nobody in the UK uses the contrived European measure of litres per 100km so I dont see why we should use something similar for boats. It also helps that many boats in the popular 30-50ft range have a fuel efficiency around 1 nmpg which is a lot easier to assimilate than 4.5 litres per nm

When did you last buy a gallon of diesel?

L/NM the obvious measure for a boat as far as I’m concerned. It equates to £/NM which is what matters to me.
It also quickly tells me how many litres I need to get somewhere.
I don’t know how many gallons my boat takes. I can work it out but I don’t know or care.

Completely agree though l/h pointless except for craft not intended for passage making, eg a jet ski or wake board tow boat.