One liter per mile - what speed for your RIB?

[jwalker]

Originally Posted by Leapy

All I can say about my own figures is that the measurements are tank brim full to tank brim full and the mileages comes from the GPS. The figures I quoted for that trip are consistent with the figures I've got for the whole of the boat ownership.

I'm happy with their accuracy

Hehe, I wasn't doubting you.

[Channel Ribs]

Summary so far, with estimated 1:1 speeds in bold at the end:-

Zubenelgenubi: 30nm:25L @30kn (90 2/S) = 0.83 lpm 33kn
9D280: 35nm:30L @20kn (25 4/S) = 0.86 lpm 22kn
9D280: 24nm:30L @mixed (55 2/S) = 1.25 lpm 20kn
Leapy: 46nm:26L @20kn (90 4/S) = 0.57 lpm 28kn
Cypman: ?nm:? @30kn (140 4/S) = <1 lpm 35kn
TSM: ?:? @20kn (60 E) = 0.75 lpm 25kn
GordyP: ?:? @40kn (2x 150 Es) = 1.3 lpm 38kn

[Leapy]

Originally Posted by malthouse

Cheers Leapy, will you settle for 25 though as I am trying to adjust to the theoretical speed where 1:1 is reached?

Sorry...misinterpretted your data. You're saying at 30kn/25kn I'd be doing about 1:1. Understand now 30kn is probably nearer the mark but I've never run it long enough to be certain.

[Channel Ribs]

Originally Posted by jwalker

Folk talk about how economical modern engines are, how 4 strokes are better that 2 strokes, how new tech 2s are better than old but they all seem to be around the 1lt/mile.

That was where I started from, it seemed amazing that everyone has the same rule of thumb yet with such a wide range of boats.

It came to a head when someone suggested that an 11m Redbay could not go 200nm without refueling, which if true would be a big departure from said R.O.T.

The key does seem to be speed, which is the biggest variable so long as you have a setup which will cruise without being at full throttle.

In other words, as Jeremy Clarkson would probably say, the bigger the engine the more economical your journey.

[Leapy]

Originally Posted by jwalker

Hehe, I wasn't doubting you.

Yeh, I know you weren't...but life is full of folks making outlandish fuel consumption claims for boat/car... Just wanted to confirm that I wasn't guessing or living in dreamland

[jwalker]

Xxx

[9D280]

Originally Posted by malthouse

Summary so far, with estimated 1:1 speeds in bold at the end:-


9D280: 35nm:30L @20kn (25 4/S) = 0.86 lpm 22kn

Small typo -
the Suz was a 2- stroke Autolube of C.1993 vintage.
Just in case anyone gets the wrong end of some random stick......

[Channel Ribs]

Summary so far, with estimated 1:1 speeds in bold at the end:-

Zubenelgenubi: 30nm:25L @30kn (90 2/S) = 0.83 lpm 33kn
9D280: 35nm:30L @20kn (25 2/S) = 0.86 lpm 22kn
9D280: 24nm:30L @mixed (55 2/S) = 1.25 lpm 20kn
Leapy: 46nm:26L @20kn (90 4/S) = 0.57 lpm 28kn
Cypman: ?nm:? @30kn (140 4/S) = <1 lpm 35kn
TSM: ?:? @20kn (60 E) = 0.75 lpm 25kn
GordyP: ?:? @40kn (2x 150 Es) = 1.3 lpm 38kn

Thanks for the correction.

The average so far is 28 knots to obtain a cruising range of 1 liter to 1 mile.

Which sounds pretty good to me.

[Leapy]

Originally Posted by malthouse

The average so far is 28 knots to obtain a cruising range of 1 liter to 1 mile.

Which sounds pretty good to me.

...and a good fun/£ ratio

[Nasher]

I don't have any examples of actual distances etc to hand, but my set up does about 1.25l per mile at @25 knots.
I've never done any sort of distance at less than that speed consistantly so can't say if I could reach 1:1.

I've a feeling that the only way it's likely to get that low is when its on it's trailer behind the car

RIB is a heavy old Ocean 6.5 with a 1998 Suzuki DT200EFI(2-Stroke).
Considering the amount of hours I get to use the boat, and how little the Suzuki cost me, I can put a lot of petrol in it before it would have been cheaper to buy a more modern engine that would only be slightly better anyway.

Nasher.

[Channel Ribs]

Originally Posted by Leapy

...and a good fun/£ ratio

Is this a good time for me to mention 70p a liter for blue petrol?

[Steve_B]

With the 5.7m Valiant & 115 Opti at 25kts I averaged 1.5mile/ltr

If I recall correctly, it was only when at 32kts+ was it ever getting near 1:1 and that with 4 POB and a reasonably full tank.

Steve

[Channel Ribs]

Summary so far, with estimated 1:1 speeds in bold at the end:-

Zubenelgenubi: 30nm:25L @30kn (90 2/S) = 0.83 lpm 33kn
9D280: 35nm:30L @20kn (25 2/S) = 0.86 lpm 22kn
9D280: 24nm:30L @mixed (55 2/S) = 1.25 lpm 20kn
Leapy: 46nm:26L @20kn (90 4/S) = 0.57 lpm 28kn
Cypman: ?nm:? @30kn (140 4/S) = <1 lpm 35kn
TSM: ?:? @20kn (60 E) = 0.75 lpm 25kn
GordyP: ?:? @40kn (2x 150 Es) = 1.3 lpm 38kn
250kts: ?/? @25kn (115 2/S) = 0.67 lpm 34kn
Matt h: ?/? @? (90 2/S) = 0.84 lpm

Average 1:1 speed is now 29 knots of boating joy.

Not sure what to do with Nasher's data?

[matt h]

yam 90 2/s,

1 person full tank of fuel (71 Litres held)

45 Nautical miles 38L used.

[Channel Ribs]

Originally Posted by matt h

yam 90 2/s,

1 person full tank of fuel (71 Litres held)

45 Nautical miles 38L used.

Thanks Matt, what sort of speed would you say?

[Leapy]

Originally Posted by malthouse

Is this a good time for me to mention 70p a liter for blue petrol?

Your a very nice man...you sold me a very nice Garmin map card thingy at a very nice price...you post very nice photographs of things on the sea bed that I've never seen before and I have no idea what they are.

Your comments on petrol prices, however, suck

[Channel Ribs]

Originally Posted by Leapy

Your comments on petrol prices suck

True, not only that but they are not really accurate. That price is only available to the "big islanders".

Cue a good gloat from Erin....

[Erin]

Time to make a post then I feel

Well, it's varied over the last few years from about 55p IIRC to 62p on my last fill up in October (and it's green BTW down here). Gloat over. But anyway there was a time when your road fuel was the same price as our duty free fuel, so you had it quite good for a while.


A few numbers for you from an Osprey Vipermax 6.5 with Suzuki DF200 (heavy set-up admittedly)

Average fuel consumption over this last seasons 270 miles = 370 litres = 1.37 l/nm (normal varied driving - and yes I'm disappointed that's all we managed mile wise though I suppose it still amounts to a fair few 14 mile trips to France).

Slightly more accurate test over a shorter period resulted in 122 nm = 150 l = 1.23 l/nm

A short isolated/instantaneous consumtion test based on the NMEA engine gauge showed

25knots burning 4.5 mpg
30kts @ 4 mpg
40kts @ 2.8 mpg.

Needless to say I don't cruise at 40+ too often, partly because the other half doesn't like the speed, and partyly because I don't want to damage the French cakes and goodies we normally have on board after our Continental Supermarket dash!

[Channel Ribs]

Originally Posted by Erin

Time to make a post then I feel

Oooo, your such a lurker.

When are you organising a Jersey RIB.net meet then?

[Channel Ribs]

Summary so far, with estimated 1:1 speeds in bold at the end:-

Zubenelgenubi: 30nm:25L @30kn (90 2/S) = 0.83 lpm 33kn
9D280: 35nm:30L @20kn (25 2/S) = 0.86 lpm 22kn
9D280: 24nm:30L @mixed (55 2/S) = 1.25 lpm 20kn
Leapy: 46nm:26L @20kn (90 4/S) = 0.57 lpm 28kn
Cypman: ?nm:? @30kn (140 4/S) = <1 lpm 35kn
TSM: ?:? @20kn (60 E) = 0.75 lpm 25kn
GordyP: ?:? @40kn (2x 150 Es) = 1.3 lpm 38kn
250kts: ?/? @25kn (115 2/S) = 0.67 lpm 34kn
Matt h: ?/? @? (90 2/S) = 0.84 lpm
Erin: 270nm/370L @mixed (200 4/S) = 1.37 lpm 25kn