how much fuel

[ssanzone]

it is time to put in new tanks.

I have (basically) decided on 75 gallons for water and am trying to sort out how much fuel i should carry.

most of the sailing will be gunking down the west coast and then from island to island in the in the carribbean. i can see myself motor sailing in the doldrums and certainly when i head north to seattle from san fran.

i am not constrained by limited space.

thoughts?

-steve

[zeehag]

figureout your longest possible passage.
do the math with how much fuel your bot uses and what the average boatspeed is going to be--figgr 3-4 kts.
then figure ut how much fuel that would be and add 10-20 gallons. that should be your tank size, ideally.

[SVNeko]

You don't say the model or size of boat you have, but my answer is as much as you reasonably are able to.

[ssanzone]

it is a newport 41. about 9 tons.

what do most cruisers have for tanks and do you wish they were bigger or never get close to running dry?

[SVNeko]

Well, I carry about 170 gal in tanks and have about 15 5 gal jerry jugs. The jugs came with the boat to me, which had crossed two oceans by then. Since I bought it, my boat has crossed the pacific and from mexico to california and we used the jugs both times (IOW wished I had more tankage). If you will always be where it is easy to fill up, then its not so critical.

[donradcliffe]

The N41 sails pretty well in light airs, so you should get by with about 75 gallons in the main tank and another 20 gallons in jerry jugs, which will also serve as a way to carry fuel where there are no fuel docks. That should get you a motor sailing range of nearly 1000 miles. Carry too much and your boat won't sail well anymore.

[Celestialsailor]

To me, it depends where the tanks will end up. If you have to saddle them high up, like in the lazarette of an aft cockpit, then they should be kept smaller as the CG would be raised. If they were going in the bilge, you can go higher in volume. My water tank is 75 gallons in the keel as is my 50 gallons of fuel. Being a center cockpit I stow 4, 5 gallon polyethelyne containers on each side. They are well below the waterline. The same goes for 2 Gerry jugs for fuel on each side. So 110 total for water and 70 total for fuel. Now need to fill them up for coastal though. But it is really nice not having to shell out 5 grand for a watermaker.

[rebel heart]

Three days of fuel, cruising rpms, running the whole time, is what I've been happy with. I'd have that include my jerry cans.

[bobconnie]

If ya can keep em low, better to much then not enough!! Just my 2 cents

[roverhi]

We carried 140 hours of fuel on our cruise to SoPac. Went a year without refueling. Sailing in the areas that you plan, fuel and services will never be far away. 72 hours fuel at 5k should be adequate as rebel heart said.

[captain58sailin]

It would be a good idea to take the consumption rate per hour at cruise speed, multiply it by 120 hours, and add 30%. When you get into heavy weather, if you have to motor you will consume more than you anticipate and go slower than expected. The last thing you want to do is worry about making landfall before the fuel runs out if for what ever reason you cannot apply a sail to the equation. There is an old saying which I absolutely loath, but applies in this situation "Plan for the worst and hope for the best".

[Dockhead]

How long is a piece of string? There's no real answer to this.

I have 680 liters. I spend about 90 days on board a year and 50 - 55 days at sea. I heat (in a cold climate; heating can be needed any month of the year) and generate electricity with diesel fuel. I don't have shore power on my mooring so use my diesel generator several hours a day when I'm on board.

I have a 100hp Yanmar which uses anything from 6 liters an hour on up, depending on the speed. However, I am in a windy place, so don't motor very much.

Despite all this on-board demand for diesel fuel, a full tank lasts me almost a year. I last filled up in July, 2012 and still have half a tank left. It is true that this particular year my boat was on the hard with shore power for several months undergoing a refit. But even with shore power, I was heating with diesel.

So is my tank too big? I think it's not good to turnover the fuel this slowly. I guess I could fill it only partially -- apparently all the business about condensation in partially filled tanks is a myth.

But if I were doing tankage from scratch, and had enough space for it, here is what I would do:

1. First of all, a gravity feed DAY TANK. This is the dog's danglies for a cruising yacht, a firm guarantee against fuel problems underway. A good sight tube on it so you can see exactly what you're putting into it, or better yet, it should be altogether transparent. As the name implies, this should hold enough for a typical day's consumption.

2. Working fuel tank, about 300 liters. With sump and dip tube; fittings for ultrasonic level gauge and polishing system. This would be used for normal operation in areas where fuel is readily available. Polish the fuel regularly, and dip the sump to be sure everything is clean before filling the day tank.

3. Passage tank, about 500 liters. For a transat or extended cruise with questionable availability of fuel. Normally kept empty. Sump, dip tube, etc. like the main tank. Feeds the day tank directly, not the main tank (so you can switch in case one tank gets contaminated).

All made out of quality polyethylene, like what TekTanks make.

YMMV, of course, and should be adjusted for the way you cruise and your own levels of consumption.

[seandepagnier]

_none_

[ssanzone]

excellent feedback.

the tank(s) will be located in the lazarette and i have a water maker so i dont need to an excessively large water tank.

at 8lbs per gallon, i am mindful of how many combined gallons i want to carry. i could easily go 50 gallons per and use the water maker more often but i may end up running the engine to recharge the bank that was drained by the water maker.

everything is a trade off.
-steve

[rebel heart]

For whatever it's worth, diesel is usually more in the ~7lbs per gallon range. Seems like a minor thing but 100 gallons is 700 pounds instead of 800 pounds, which is relevant. Good luck, regardless.