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Old 26 September 2011, 07:47   #1
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Can you Solve this Mystery.........

Some of you maybe aware I recently made a crossing to Braye on Alderney from Langstone. What should of been a straight forward crossing turned into an epic 10 hour struggle which eventually seen me run out of fuel and have to be rescued by the French coastguard.
So here is where the riddle begins.
On the return leg, conditions flat calm and for the first hour or so we had a flowing tide pushing us along.
  • Boat - Humber Ocean Pro 6.3m
  • Engine - HOnda Vtec 150hp
  • Crew - 5 Blokes average 90KG per person
  • Kit - 3 x Dive Kit (30kg Each)
  • Fuel - 260l - (260KG)
  • Camping Gear - 50kg
  • Life Raft - 45kg

My boat set up has an internal tank of 160l and 2 External tanks (25l each) with a direct feed into the fuel system.
WE set off with the intention of keeping the boat to about 4000rpm and constant on a direct track (anyone deviates 500m from the track were sacked as skipper).
I had the fuel switch set to draw down on main and the hose was connected to the first 25l. After about 3 hours running across the channel the engine died which indicated the fuel had gone, i then went to move the fuel switch and noticed it was slightly off centre, I moved to all the way to external and tried to start the engine, nothing. Checked the 25l tank and it was empty, so scratching our heads, had teh fuel in this tank leaked out, but surely we would smell 25l of unleaded swooshing in the boat. Anyways swapped the pipe over to the other 25l and siphoned 50l of reserve fuel from 2 jerry cans into the main tank.
So in theory now I have 75l left (50 in the main and 25)
We run the engine and of course we can see home so the engine is flat out and we are doing 28 knots WOT.
External tank runs out and we switch back to main and run that for about another hour which really should be taking it down to about 20l left.
Heres where it gets confusing.
I took the boat out for a trip up the Hamble yesterday and went to fill the engine. Expecting to put in about 140l. But it would only take 50l which indicated 110l left over, which to me is impossible as I only put 50 in after it ran out at sea.
So I couldnt understand how going to Alderney i managed to get through 210l and still run out. Its only 82miles
On the return I actually then only used 150l which is more realistic as we were gunning it.
SO I suppose the question is - how did I end up with 110l after only dropping in 50 on an empty tank?
All suggestions appreciated

Rob
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Old 26 September 2011, 09:17   #2
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Syphoning from the 25l tank back to the main tank the sucking air as the 25l tanks emptyed into the main perhaps?
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Old 26 September 2011, 09:23   #3
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Rob, Sounds like an exciting trip! At least you all made it back intact.

Is it possible that the fuel pick up pipe in the main tank has become dislodged/moved so you can't get the last 60L out?
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Old 26 September 2011, 09:34   #4
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Polwart's suggestion is the only plausible thing I can come up with too.

How much did the French charge you for the privilege of being recued?
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Old 26 September 2011, 10:38   #5
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How about the trim or angle of the boat with weight distibution effecting the pick up pipe.
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Old 26 September 2011, 11:14   #6
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Well I have 2 thoughts
1) as the connector wasnt quite in the position for the main tank, the engine somehow managed to draw down on the 25l and at least 50l from the main. Which in theory is about 3/4 hours cruising. I then topped up with the 50l spare which actually refilled the tank complete.
or
2) I managed to get 3 hours and about 60 miles from 25l (the little external tank) and somehow lost some fuel from the main

How much did it cost for the Coasty - well they lightened my wallet to the tune of 320 Euros.

I actually filmed the events here

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Old 26 September 2011, 12:08   #7
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according to your list you have 260l - according to the tank figures you only have 210l I assume that the list is wrong?

do you have a dipstick for the tank? might be interesting to try again, but dip tank... would confirm theory about not picking up xx last litres...

I would try nearer to land and with a spare tank or two on board though

if only 1nm away - do you have oars? you should have put the crew to work!

Alasdair
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Old 26 September 2011, 14:02   #8
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I went out with 210l but not wanting to make the same mistake on the return leg I then purchased two cheap 25l jerry cans and filled them.

The tank is undert the console and all sealed in so I cannot get to it, but i did go out last night up the Hamble and only ran the main tank, so now when I fill it I will get a feel for the fuel consumption
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Old 26 September 2011, 14:39   #9
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With hindsight my biggest regret of the nite was that I didnt use the oars to row in, as you can see from the video 2 of the crew were in melt down and wanted a helicopter to come save them, I was just annoyed that we could see the lights of Cherbourg but sadly was dead in the water.

Next time I go out with the lads I am going to do a row exercise to just see how hard it would be - would of saved me a ton of cash
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Old 26 September 2011, 15:05   #10
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Quote:
Originally Posted by Polwart View Post
Is it possible that the fuel pick up pipe in the main tank has become dislodged/moved so you can't get the last 60L out?
Pictures attached from the build thread show that the pick up is at the bottom of the tank so a dilodged pipe is unlikley

Is it possible that when you fill the tank the air can not get out of the tank fast enough, so blows fuel out of the filler making you think that the tank is full when it is not, so is it possible that you didn't start with 160l in the main tank?
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Old 26 September 2011, 15:41   #11
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Hi there Ian, (you can tell Jono his old boat is doing the runs it was designed for.
No chance that I could of started with less than 160l as it was empty and I filled it in Langstone, the pump wouldnt let me do more than a 100l so I had to do a couple of payments.
I honestly think the diverter valve that switches between internal and external tanks was between two settings. The engine sucked down on the 25l external tank and then about 50 or litres on the internal before getting some air (which made me think I had ran out)
that in theory would of been 70/80l which you would expect to get through in 60miles (3 hours).
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Old 26 September 2011, 16:30   #12
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How much fuel did it take on the otherside to refuel?
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Old 26 September 2011, 16:48   #13
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I'd be looking at the fuel tap, I never did like multi position ones. If you had an intermitent air leak from either external tanks when either one was exhausted it could have introduced air in to your fuel line and might have acted as if your main tank was empty when in actual fact you still had fuel to burn. I would look at a more fool proof design for future trips, like physicly swapping over pipes when changing tanks.
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Old 26 September 2011, 17:19   #14
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How much fuel did it take on the otherside to refuel?
When we got to within a mile of France we had truly used all the fuel avaialble, so in Cherbourg I bought another 210l for the short hop over to Alderney and then bought the extra tanks and fuel for the return.
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Old 26 September 2011, 17:41   #15
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Is the main tank lower than the 25 litre tanks?

Here's what I think happened-assuming the main tank is lower than the 25 litre tanks.

You were drawing from the main tank 'til the fuel slowly syphoned into the main tank from the 25L tank as the valve wasn't open fully.

You then started drawing air into the lines from the empty reserve tank, creating an illusion of being out of fuel.

<edit> just seen the second page. I think you're right.
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Old 26 September 2011, 17:44   #16
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Quote:
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When we got to within a mile of France we had truly used all the fuel avaialble, so in Cherbourg I bought another 210l for the short hop over to Alderney and then bought the extra tanks and fuel for the return.
So in Cherbourg you had empty capacity for 210L. That would be 160 L internal + 2x25 L external. i.e. your tanks WERE empty.
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Old 26 September 2011, 18:28   #17
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With hindsight my biggest regret of the nite was that I didnt use the oars to row in,
That's exactly what I was thinking of.

We used to do Rye-Dieppe and we broke down just 2 miles off Hastings. We did use the oars, but it only helped us not going further into the channel, until some fishing boats helped us...

You seem to have burnt too much fuel for that journey, 210ltr/82 miles? or am I confused?
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Old 27 September 2011, 02:48   #18
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Have you checked the main tanks breather is clear, was there a whoosh of air when you undid the filler cap. If the breather was blocked, it would create a vacuum that would give the same symptoms as running out of fuel.
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Old 27 September 2011, 04:47   #19
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Rob & Nos have to be Right!

The 25L tank (not in use) was discovered empty after 3 hours running. Obviously it was slowly releasing SOME fuel to either the engine or the main tank via the switch. Once this fuel was gone, air was then introduced to the fuel lines, stopping the engine. The fuel was later found to be in the main tank.

I'l say test the setup again with a full 25L tank and the switch in the correct position. If the tank remains full and the engine runs OK at WOT, you're good. I used a pair of those brass fuel switches for a few years and when I sold them they were 11 years old and they hadn't ever malfunctioned.
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Old 27 September 2011, 06:52   #20
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That's exactly what I was thinking of.

We used to do Rye-Dieppe and we broke down just 2 miles off Hastings. We did use the oars, but it only helped us not going further into the channel, until some fishing boats helped us...

You seem to have burnt too much fuel for that journey, 210ltr/82 miles? or am I confused?
You are right in that I burnt too much fuel, but to be fair the boat was loaded super heavy and the seas were really large, we could only average 8knots and we were at sea for 10 hours. So its more like after 10 hours we got through 210l
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