fuel range of my Targa

[ianainge]

anybody got a idea to the range of my targa 31. 2x VP 41b 200hp.tank holds 120 gallons of diesel, cruising at about 26 knots.?

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[Guest]

We worked out that our AD31B's are doing an average of 1.5 litres per mile between them, so around 3mpg. Your engines are 33% more powerful, so you can assume you'll burn proportionately more fuel - 2mpg at a guess, so...

Assume bottom 20% of the tank is unreachable = 96 usable gals
Assume 25% safety margin = 72 gals
Assume 2mpg at cruise = 145nm

Which is about the same as us, and your tank is 33% larger, so that should be about right. We managed Falmouth to Christchurch on a single tank, which is 145nm or so.

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[Observer]

Assuming only 60% usable tank capacity a bit over-conservative surely? No need for both allowances.

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[Guest]

I thought so, too, but someone wiser than me pointed out that depending on the tank design, in any kind of sea you may not be able to reach the bottom 20% - you really don't want the fuel pickup sucking air as the fuel surges in a big sea.

The 25% is just the 'normal' safety margin.

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[tcm]

hm, i think it a bit overconservative; remeber the thing picks fuel off the bottom anyway?

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[Deleted User YDKXO]

2 mpg sounds about right to me but the boating rags quote cruising range at tank capacity less 20% which makes the range about 200 nm. But fuel consumption can rise significantly in rough sea conditions so your more conservative calculation could be wiser

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