How far can you go?

[ransflyer]

How far can a cruising catamaran motor?

Let's say it is a common model: Lagoon 440
Standard tanks: 325 liters x 3 or 257 gallons (+ 5 gallon can for emergency reserve, but not counted in the range)
Side question: can all three tanks be used by the saildrives or is one tank dedicated to the genset?
Bottom is newly painted and clean.
We are trying to maximize the range so we'll use just one 55 HP engine at 4-5 knots in the doldrums with zero or cancelling winds and relatively calm seas. Boat is fully loaded with gear, provisions, etc.
Flex-o-Fold 2 blade prop (or other, please specify)

Lagoon manual says light displacement is 10,500 kg, Max load disp in theory 13,500 kg with an authorized max load of 5900 kg. Not sure what that means. Maybe someone can help me there.

There are likely other factors that I've forgotten. I'm interested in both the theoretical and real life expertise of the forum. This may help us understand the difference between electric and diesel better, though I admit I'm very seriously considering electric given new battery and solar technology.

Again, this thread is about diesel engine range on a cat. I'm intereested in all brands/models so if you have other actual numbers to share, please don't be shy.

[StuM]

My Belize 43 is quite a bit lighter but about the same LWL as the Lagoon 440. (I figure on about 11,000 kg loaded up for cruising). Two blade fixed prop.

It has a 300l tank and on long trips, I carry 6 x jerrycans giving me at total of 420l. Call it 375l usable plus a 10% reserve.

Motoring on one engine at 2700 RPM in calm conditions, I plan on 6 knots and 3.5lph. That gives me close to 600NM

Throttling back to 2250, I plan on 5 knots and 2.2lph, giving me about 850NM


For your case of a comparatively heavy L440, 54HP motor (4JH4E) and approaching 5 knots in calm conditions, I'd anticipate that would require around 2000RPM and 3.5lph - which should give you around 400NM per tank with a 10% reserve.

[GordMay]

Greetings and welcome aboard the CF, ransflyer.

[dlymn]

55 hp is 36 kilowatts. A standard 140 ah battery can provide 840 watts at 50% discharge, and so you will need more than 40 batteries to operate at full power for one hour. At half power, 2 hours of running. You will need more than 140 square metres of solar panels to collect 36 kw given perfect angle to the sun at all times and bright sunshine all of the time. This array provides sufficient energy to keep the system running all of the time. a smaller array will recharge the batteries over a longer time but this won't help you once you start travelling because the current drain is probably much faster than supply. The solution is to get a suitable genset to keep the batteries fully charged, say a 36 kw unit!!!

[12BCruzn]

We cruised in a Privilege 435, a little lighter than the L440. We burned 0.8 gallons per hour in calm seas at 2400 rpm while making about 6 knots. Consumption rises to 1.1 gph if driving into 4-5 seas and 15 kt wind with speed falling to 4.5 kt. Engines were Beta 38 hp. If you are doing downwind trade winds sailing then you wouldn't have to motor into the wind or waves most of the time so your range will increase. Only you on your specific boat and after multiple trips in multiple conditions will be able to estimate your range accurately.


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[seaskip]

Seawind 1160. I've been told that 1 motor at around 5 knots uses 2 litres/ hour.

So, 2x 160l tanks = 320
320-20% safety margin = 256l
256/2 =128 hours
128x 5 knots =640 NM range.

I haven't had to motor much yet, so I'd love to know if this sounds right.

[StuM]

Originally Posted by 12BCruzn

We cruised in a Privilege 435, a little lighter than the L440. We burned 0.8 gallons per hour in calm seas at 2400 rpm

Per engine? What speeds with one/two engines?

[12BCruzn]

See edited version please. Somehow I posted before being done.
The above numbers were while running one engine.


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[StuM]

Originally Posted by seaskip

Seawind 1160. I've been told that 1 motor at around 5 knots uses 2 litres/ hour.

So, 2x 160l tanks = 320
320-20% safety margin = 256l
256/2 =128 hours
128x 5 knots =640 NM range.

I haven't had to motor much yet, so I'd love to know if this sounds right.

That sounds about right assuming you have the 29HP Yanmars.

[StuM]

Originally Posted by 12BCruzn

See edited version please. Somehow I posted before being done.
The above numbers were while running one engine.

0.8 gal (I assume US) = 3 liters. You're getting a bit better economy that I plan on for a very similar boat. What sort of props?

[12BCruzn]

Volvo Penta 3 blade folding props.


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[seaskip]

Originally Posted by StuM

That sounds about right assuming you have the 29HP Yanmars.

Thanks Stu. Hoping I never have to put it to the test. 😀

[StuM]

Originally Posted by 12BCruzn

Volvo Penta 3 blade folding props.

Shaft or saildrive (I believe that either is an option on the Privilege)?
Regardless, 3 blades would make a difference.

(That's one drawback of the Belize, there's little room for folders between the SD and rudder, so a 3 blade prop would add to the drag when sailing)

[mark_morwood]

Originally Posted by StuM

Shaft or saildrive (I believe that either is an option on the Privilege)?
Regardless, 3 blades would make a difference.

(That's one drawback of the Belize, there's little room for folders between the SD and rudder, so a 3 blade prop would add to the drag when sailing)

Take a look at feathering props. They may need less room.

Mark.

[12BCruzn]

Sail drive.


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