Fuel Consumption, with a twist...

[big_si]

Got back from the Channel Islands on Saturday night and here is a little bit about out fuel consumption for the trip, with a little twist at the end...

Left Gosport with a full tank went to Weymouth and filed up - £9

Left Weymouth with a full tank went to Guernsey, went to Jersey and filled up - £22

Left Jersey went to Cherbourg and filled up - £60 (i think) but bear in mind they tax their fuel.

So at the moment we have done a fair few miles on very little fuel. The economy the Merc 1.7Tdi has given us so far has been astounding. I mean Shelley and I have been MEGA impressed!

So we leave Cherbourg with a full tank, given previous trips we sould get back to Gosport with well over half a tank left. Marvellous!!

However, it didn't quite go to plan.

20 Miles off IoW the swell swelled. 10 miles off it must have reached 3-4m, thankfully it was relatively far apart.

This really had an effect on the fuel consumption, more than we could have ever realised as 5 NM off the IoW we ran out of fuel. In what was now 2-3m swell.

Called the CG and got towed in to Sandown Bay by the Sandown lifeboat.

The RNLI appreciated the fact we were caught off guard with regard to fuel consumption given the weather conditions, they were also very impressed that we were wearing lifejackets and our flares were to hand.

75 ltrs of diesel later we were on our way with a valuable lesson learned and another chunk of appreciation for the RNIL.

A donation that would more tha cover the cost of fuel was sent to Sandown as was a bit more so the guys could have a beer or 2.

 

[Whitelighter]

75 litres sounds like a very small tank! I have concerns our tanks on the 24 are only 130 litres, so are having bigger tanks fitted.

What size is the boat again?

 

[adrianb]

Si - Bloody Hell - I didn't realise when I spoke to Shelley that you actually ran out of fuel - or needed a tow.

The forecast was a F6-7 can't remember the direction now, and I tried calling you am Saturday morning, but you were in the dead area, probably mid channel by then I guessed.

Adrian

 

[djefabs]

Glad you are both OK. Its amazing what a bit of rough weather does to fuel consumption. Saturday was a bit rough for a channel crossing, we only went down the Solent to Swanage and had a few 'over the top'. I seem to remember hearing Solent Coastguard asking for assistance for a boat out of Sandown Bay. I think it was about 1.30/2.00 pm as we were passing Cowes. Wonder if that was you??

 

[Chas25]

Have to say I'm shocked by some of those figures and thats coming from someone who used to own a very similar sized boat with the same engine as that (as you know!)

One thing I did have for a short period was trouble actually getting a full tank of fuel in, the pump would click off way before the tank was full, never did find out why but it seemed to sort itself out! Are you sure on each of the fill ups that the tank really was full?

How many litres did the £60 equate to? and how big is the tank?

Main thing is you made it back safely, albeit with a little assistance!

Look forward to seeing the pics, we've identified a possible long weekend we might be able to go accross for so fingers crossed /forums/images/graemlins/smile.gif

 

[michael_w]

Foaming; leading to a false assumption that the tank is full?

75 litres is feeble for a cruising raggie let alone a MoBo.

 

[jhr]

Reading between the lines, I suspect the 75 litre thing is a red herring - I'm assuming it happened to be what the lifeboat had available, rather than the capacity of their tank, but I'm open to correction.

I'd expect a boat of that size to have maybe 150 - 175 litre tank capacity, with perhaps 130-150 litres useable in normal conditions? £60 worth of fuel at French prices (€0.80 to the litre?) does equate to about 75 litres put in at Cherbourg, but I'm assuming the tank was nowhere near empty at that point.

A sobering tale, come what may. Glad it had a happy ending.

 

[KevB]

The Chaparral web site says the 215ssi has a 212 ltr fuel tank?

 

[Deleted User YDKXO]

SiandShelley, I'm not saying these figures are wrong but I wonder whether your tank was 100% filled each time because the mpg figures you are getting are so variable

Let's assume diesel costs £0.50/litre in the UK and €1.20 (£0.82) in France

Gosport-Weymouth (say 50miles) £9 = 18 litres = 4 gals = 12.5mpg (!!)
Weymouth-Jersey (say 100miles) £22 = 44 litres = 9.7 gals = 10.3mpg
Jersey-Cherbourg (say 40miles) £60 = 73 litres = 16 gals = 2.5mpg
Cherbourg-IoW (say 60miles) - ran out of fuel 5 miles short so 55 miles run on 75 litres = 3.4mpg

For sure rough seas make a difference to fuel consumption but to go from 12.5/10.3 mpg to 2.5/3.4 mpg is just too big a difference. If you average the fuel consumption from Gosport to Cherbourg, it comes out roughly at 6.4 mpg which I think is more realistic. Possibly you did'nt 100% fill the tank in Weymouth and Jersey?

 

[CaptainMike1970]

When we had our petrol SeaRay 225WE we used to estimate fuel consumption at 25l/hour for passage planning, however on a rough trip from Hamble to Poole fighting the wind and tide our speed dropped and the average went up to circa 35l/hour.

I know 10l/hour doesn't sound much of an increase but it is over a 50% increase and that knocks a big hole in your passage planning fuel calculations!!!

 

[jhr]

50-ish gallons; sounds about right. My 22 footer has a 40 US gallon tank (about 35 Imperial) and I've always felt it's a bit on the small side - particularly for a thirsty 5.0l petrol engine.

Even in perfect conditions it's unlikely they'd be able to make use of all the fuel in the tank, but in the swell they describe, I bet there was a fair amount of unreachable fuel. Still scary to see the extent to which adverse weather can use up additional fuel.

 

[big_si]

Jez, the 75 ltrs was not a full tank, just a get you home. Our tank is about 200 ltrs

Derek, i beleive that call was for us!

I can check the prices and amounts for the fuel we bought, as these were 'off the top of my head' figures!

At the time, the sea was going north, and the wind was coming from the east. This weather prevented me traversing west to get in to more sheltered waters as i felt it was too dangerous. I felt it was safer to go with the sea that fight the wind and subject the boat to a beam sea.

Funnily enough, i felt far safer once we had run out of fuel and just was left bobbing about!

 

[[2068]]

My initial reaction is that there is something "up" with your gauges and filling system, and for whatever reason, maybe you didn't leave Cherbourg wth a full tank, or there's a large chunk of "unsuable" fuel due to the tank/pickup.

I was amazed at the fuel consumption my new S24 was getting, right up to the point where the gauge went from 1/3 to way down the bottom of the red section within 2 miles. Somehow I didn't run out, and the faulty sender was replaced.

The thing is, a 1.7DTi will use maybe 20litres an hour at a fast cruise. That should give you 8 hours endurance, whatever the conditions, and whatever the speeds. Did it really take you 8 hours to run out? Or were you continuously powering up the waves using full throttle?

Something doesn't stack up!

dv.

 

[big_si]

"The thing is, a 1.7DTi will use maybe 20litres an hour at a fast cruise. That should give you 8 hours endurance, whatever the conditions, and whatever the speeds."

I disagree (as does the RNLI), as our speed was dropping to 6kts going up the swells. I just cant beleive that the engine will just carry on using 20Lts per hour, irrespective of variables.

I do agree with what you say about leaving Cherbourg without a full tank.

The fuel gauge was broke, but each time we filled up we waited for the filler nossle to cut off. 'Foaming' has been mentioned, this may have been a contributable factor but the weather was THE contributing factor.

 

[Chris_d]

I think you have missunderstood, a Diesel engine will have a maxmium fuel flow rate for a given rpm at max load. So say 20L/h at 4000rpm gives 8hours running at max load, this may of course drop but it won't be any higher. Thats the worse case scenario you should use to calculate your passage. Of course your speed will change due to the weather and hence your mpg, but thats not the same thing. All passage planning should be done in l/h, gph or even gallons per mile at the worse case consumption.

 

[[2068]]

>the engine will just carry on using 20Lts per hour
I think it would, or therebouts: but because your speed drops dramatically, it's the litres per mile or miles per gallon figure that would change.

dv.

 

[dpb]

Fuel consumption apart I am more interested in the actual trip. Some would be nervous in a boat twice the size! I have mentioned the possibility in our 21 footer to my wife who's reaction at present is only if escorted by a lifeboat and helicopter!!!
So tell us more about the crossing!

 

[[2068]]

It's all about the weather.

In a flat calm, you could do it in an 18ft bowrider, but there would be no contingency if the conditions changed.

In the S28, we ended up having to slow down to 16kts and going crash bang wallop for a couple of hours when the swell came up.

dv.