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Old 26 January 2011, 03:23   #141
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Quote:
Originally Posted by martini View Post
10 kts on 1 engine = 2700rpm & 28 lph
10 kts on 2 engines= 2200rpm & 24 lph (12+12)
I am lovin the maths behind that phenomena.
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Old 26 January 2011, 04:05   #142
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Distances

Thanks to Mr Garmin, here are some proper nautical distances:

Cherbourg to Le Havre Marina (shortest distance) 70nm
Cherbourg to Le Havre Marine (coast hugging) 90nm

La Havre Marina to Rouen 70nm

Rouen to Paris 130nm

I don't have hi-res chart data for the last leg of the Seine, so have erred on the long.

With Jersey to Cherbourg via Alderney also being about 70 I can see a pattern forming! 5 legs of 70nm, not allowing for river current.

Day 1) Jer - LHM, 150nm @ 30kn, 5h with stop in Cherb for fuels

Day 2) LHM - Rouen, 70nm @ 15kn, 5h

Day 3) Rouen - ?, 70nm @ 10kn, 7h

Day 4) ? - Paris, 70nm @ 10kn, 7h

Day 5) In Paris

To do it in 8 days in all that leaves 3 to get back from Paris to Jersey. Might be possible to ride the current back between Paris and Rouen in one day?

Edit: Sorry, forgot the point, with a total trip distance of around 700nm the fuel used is going to range from 500ltrs to 2000ltrs.
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Old 26 January 2011, 05:24   #143
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Quote:
Originally Posted by malthouse View Post
I am lovin the maths behind that phenomena.
Matt, your figures look a little odd, but I am sure you have checked them??

at 2200 rpm each engine runs at 12 litres an hour

At 2700 rpm this goes up hugely to 28 litres an hour That is some extra fuel flow for 500 rpm
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Old 26 January 2011, 05:25   #144
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Port de I'llon (halfway up the Seine) seems to do fuel, will try to find out more.
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Old 26 January 2011, 05:49   #145
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Quote:
Originally Posted by karlT View Post
Matt, your figures look a little odd, but I am sure you have checked them??
I think he did real world testing, but here is a table from a magazine review of a similar engine:

RPM LPH
1000 3.0
1500 8.3
2000 16.6
2500 22.0
3000 28.4
3500 34.8
4000 41.6
4500 49.6
5000 60.6
5500 72.7

Source: http://www.mercurymarine.com/engines...583.5879323103
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Old 26 January 2011, 06:28   #146
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Quote:
Originally Posted by karlT View Post
Matt, your figures look a little odd, but I am sure you have checked them??

at 2200 rpm each engine runs at 12 litres an hour

At 2700 rpm this goes up hugely to 28 litres an hour That is some extra fuel flow for 500 rpm
It's all about the load!

I've got a website for port d'ilon, its on my google map, can't seem to link it so I'll email you Mart
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Old 26 January 2011, 06:36   #147
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It's all about the load!
Yar, although we accept that you lose about half the benefit of a second engine; at displacement speeds the drag will be much less so the pair will be working well together. One engine propped for planing speeds is going to have to work hard.

Quote:
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I've got a website for port d'ilon, its on my google map, can't seem to link it so I'll email you Mart
Cool, I thought you had mentioned it.
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Old 26 January 2011, 10:03   #148
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Just dug out my powerboat logs from river trips, it seems to me that so long as you are not constrained by both fuel and time then it should be ok.

There will be a speed that suits best, I would guess Martini will be the pace-setter but who knows. In any case there will be a speed that works well, trying to hit the speed limit dead on could be counter productive.

Many moons ago I had a Searay, spent ages plotting fuel consumption at displacements speeds. Darn that thing was thirsty at WOT!
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Old 26 January 2011, 10:30   #149
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Never mind speed limits, if it's quiet & I think I can get away with it I'll be doing 30 knots where I can

Don't think I'm physically capable of doing 10 hours @ 10 knots

Lying in bed last night doing sums in my head, if I leave Jersey with full tanks I need a refuel at somewhere a bit upstream of Rouen, then I'm good for Paris and back with another refuel at the same place which would see me back to Jersey.

So roughly 3 fuel loads @ 600l = 1800l

1 fill up in Jersey @ 80ppl = 500
The other 2 fills could be at 150ppl worst case so they would be 900 each time
Total fuel cost 2300

Don't know my oil consumption at displacement speeds but working on my normal cruising speeds I'm getting 33:1 which makes 55 litres of oil
I think I normally pay around 10 a litre so there's another 550

2850 on fuel & oil thats GJ0KYZ's 3 grand budget gone already!
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Old 26 January 2011, 11:06   #150
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Excellent find Erin, if you want to just translate that and repost it....
This is work in progress to some extent especially the last bit on petrol availability!

I've done my best to intepret it, and I think I've got the gist of most parts. I've ignored bits that don't seem relevant.

Some interesting bits including holiday dates when locks are closed.

PS I accept no liability for anyone relying on it for the trip
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