How far can you go?

Nghost · 09 July 2003, 12:43

I was wondering about the range of a RIB.
When we did our round the island trip a couple of weeks ago we loaded up the SIB with 50L of fuel in 3 tanks. This gave us plenty of range on the 8 Hp. But should we re-power the boat with a 15 (or even a 25) we will obviously need more fuel. In the Quicksilver that would mean caring 100L of fuel (no room for crew

).
Now most of you guys have engines that would sink the Quicksilver how much fuel do you carry and what is your time/range ?

Brian · 09 July 2003, 13:41

Before anybody else answers, I am going to have a little guess.

Fuel consumption must be largely related to the power/weight ratio of the boat.
Therefore my guess would be, that most of the answers you get will be showing that they fit into the range of .75l to 1.25l of fuel consumed per nautical mile.

Alan · 09 July 2003, 13:41

Well rule of thumb on new hitech 2 stroke (HPDI, Optimax etc) is 1 litre per mile. I achieved around this figure with both a 150opti and a 200HPDi. 'Course you've gottas allow a reasonable % for poor weather and contingency (rough weather can dramatically increase fuel burn). So on a 250L tank gives a ready range of 200nm in good conditions. Mebbe a little less if you want to be more cautious. In rough weather this could be halved.

Of my two RIBS the DS21 had a 40 gallon (180L) tank and the Scorpion (now Richard B's boat Blue Ice) had a 60 gallon (250L) tank. Of course the beauty of a RIB is that this is carried underdeck usually (or at least under console) and thus does not encroach on crew space!

Alan

Garygee · 09 July 2003, 13:50

Hi

Dont forget bigger engine in a bigger RIB means more room for fuel.

100L sounds a lot for a small RIB, but it depends what you want to do. One thing though how long and hence far would to be comfortable doing in a small RIB/SIB.

In my previous 4.8 with a 50HP 4 stoke i used, about 8-12L per hour, and carried about 60L of fuel, so given your speedswill be lower and fuel useage lower then a bigger RIB, do you really fancy spending 10-15-20-30? hours aboard as even with my 50HP I could run for 8-10 hours on 100L.

The other thing is fuel in a small boat is diminishing returns, 100L is about 90KG the weight of a extra big person how would this affect speed, sea keeping etc.

I currently carry 270L in the main tank (underdeck) plus another 240L in flexi tanks 2 off, plus another 40L reserve in cans stored under deck lockers, total 550L. But his is a 7.8M RIB and I dont think this fuel load in unusual, and it takes no deckspace sway from the occupants.

This I work on 400-450 miles range allowing a 25% reserve to allow for bad conditions etc.

In flat calm I get about .85L per NM dropping as conditions get rougher.

Hope this helps, but i am not sure if you compare like for like in our cases.

Regards Gary

MarkWildey · 09 July 2003, 14:02

Hghost

Just to up the size of tank a little, I have a single under floor 550lt tank. As the other guys suggest I get around 1lt/nm when the tank is full. As it empties it improves the consumption.

Cheers

Mark

Alan Priddy · 09 July 2003, 15:05

In SOC our 3500 litres will give us 1400 nautical miles.Our last Atlantic boat (7.5 Ribtec Open) had a fuel capacity of 750 litres and this gave us a range of 750 nautical which was 35 miles short of what we needed to get to Iceland from Greenland! Alan P

thewavehumper · 09 July 2003, 15:16

AP,

If you need to borrow some Jerry cans for your next trip feel free to ask.

Ng

In answer to your question it depends on the weight of your boat/thepower of your engine and the length of your throttle arm.

Our Ribtec 6.5 , heavy boat with a 130 (underpowered methinks) gives us about 40 knots for 50 litres per hour

Our Scorpion 6.5 , Light boat with a 150 Opti give us the opposite 50knts at 40 LPH

The Avon 4.7 with a 70 gives us broken bones at 4O knts, but I have no idea of the consumption as I am enjoying myself too much too worry about it .

The easyway of improving those figures is too slow down but I missed that day in school

regards Stuart

Charles · 09 July 2003, 15:36

Quote:

Originally posted by THEWAVEHUMPER

The easyway of improving those figures is too slow down but I missed that day in school

LOL, ditto Stuart.....

I can only manage approximately 160nm with a capacity of 430l, that blows the 1l per 1nm out the window

Alex Brown · 09 July 2003, 16:31

On the back of my 6m Humber, the Suzuki 140 4-Stroke seems to be using around 20litres of fuel every 30miles. That's cruising at about 28knots, 2 people on board, and 90 litres of fuel in the tank (full).
The boat itself maxes out at just over 40knots (43 knots with no tide running), at which point the engine should be using about 33 litres of fuel an hr.
As yet, I see no fuel consumption difference between the new stainless prop and the original ali prop that came with the engine.

On the other hand, my old 5m rib with 70hp two stroke would use 25 litres of fuel for a 20 mile trip, cruising at around 20knots.... this is why I am very happy with the 4-stroke. Although, saying that, you don't buy a big petrol engine if you don't expect to pay out big bucks for fuel - damn that tax man

I have one of them plastimo fuel monitor thingies on the list for a winter project, at which point I should be able to get the best fuel consumption out of the boat.
Looking through the new rib international mag which I got this morning, I'd be interested to see the fuel use now for the new Yamaha 150 4-stroke.... it's 20kg heavier than the 140 Suzuki, and also has a bigger engine block, but probably newer electronics again, so, you never know.

Glad I don't have a boat like Charles' down here - would be on the 2nd loan by now

-Alex

mstacey · 14 July 2003, 08:08

I have 180l tank and I allow for 1 litre a mile when doing my guess-T-mutts of how far I can go. This on my boat gives me a safety margin to take into account rough seas change of plan etc.

GarryGee where did you get the big felxi tanks you carry on deck ?

Upto now I have carried jerrycans if travelling away from land but like the idea of an xtra tank and a change over valve for those longer jaunts.

Charles · 14 July 2003, 08:45

Quote:

Originally posted by mstacey

where did you get the big felxi tanks you carry on deck ?

Contact Paul Lemmer for flexi-tanks - he is the agent for a particular make - 01883622448

Garygee · 14 July 2003, 12:07

Hi Martin

Got a quote through the Avon web site, but think they have passed their flexi tank work onto the link above.

Quote was not bad £350 for two but given cash to spend on RIB at present ended up with two ex MOD air ferry tanks via a "source" I know.

They are OK but at some point I intend to get two that I got a quote for as they would have been made to measure and would lie along the tubes where the tube hull join is.

Regards Gary