Thoughts on Aft Fuel Tanks

I like range.  And I know installing my main fuel tank will be a tight fit though the main hatch.  So as I reported earlier, I installed a temporary tank.  While crawling around inside the lazarette working on the binnacle, and scoping out a future auto-pilot installation, I found myself in the usual situation of sliding down into the bilge.  I have always wanted a flat platform in there but did not want to waste the space.  It suddenly occurred to me this would be an idea location for two fuel tanks. 

In the past there were two triangular boards to contain all the items stored in the lazarette.  While I still want to contain things, a flat platform makes sense, so why not use the space underneath for fuel storage.  It would not be difficult to build two tanks on port and starboard for this purpose.  And since these would be the first tanks, I'd use motoring, once empty they would provide some floatation if this compartment flooded.

I recently received a marine plywood shipment.  This piece of plywood will be a bulkhead cofferdam to isolate the steering compartment from the middle of the boat.  If my steering fails or another boat crashes into the back of my boat, I will be able to survive.

I also plan to install a watertight compartment forward above the waterline, which will be my forward collision bulkhead, with some of this scrap material.

The only question would be the dimensions.  I need enough space to work in there, so two smaller tanks might be appropriate.  I also have to leave space for an autopilot ram on the port side.  I also want to build these so they can be removed easily.

The last question would be how to plumb them in?  I could gravity feed them into my main tank as it gets depleted, or burn off the fuel straight from these tanks.  The issue is complicated by the fact that I must consider what to do with the return fuel lines. It would be too easy to mess this up and have fuel pumping out of the breath hoses and making a mess.  I'd like to make this as idiot proof as possible. 

Finally, I'd like to reuse my temporary 23 gallon tank for either gasoline when in the islands, or diesel when on a longer voyage.  If I had a bladder tank in the cockpit, I could carry 413 gallons of fuel on ocean voyages.  That would give me a range under power of nearly 2500 miles.  That 23 gallon tank could fit nicely on top of one of the aft saddle tanks, be accessible on top of it, and serve dual purposes.

Did you know that a gallon of fuel will make way more than a gallon of fresh water?  It is less weight to carry diesel fuel than water.

Why would I need that much fuel? It is about 5160 miles from the Virgin Islands to the Greek Islands.  Figuring an average of 150 miles a day, I'd need to maintain an average speed of around 6 knots to travel that far in at least 34 days of sailing time--it will be more than that plus time for layovers and side trips.  And it is at least 34 days sail back the other way.  It is important to keep my speed up to cover that distance in a reasonable amount of sailing time.  The longest leg, Bermuda to the Azores could also have a fair amount of light winds and against the wind sailing.  Lots of people run out of fuel making that passage.  I could motor that whole way, and in fact I could motor the entire trip if I refueled along the way.  So there would be no worries about running out of fuel. I could also refuel in places where fuel was cheap like Morroco.

Another reason to carry that much fuel is to run generators--I don't plan to, I like wind and photovoltaic.  I am very interested in heat.  I like colder weather sailing, and this amount of fuel would keep me warm an entire winter.  I like that very much.

At some point I want to sail to the South Pacific.  The longest leg between the Galapagos Islands and the Marquesas is nearly 2900 miles.  Many people complain that they should have brought more light air sails and should not have started the motor until their speeds were under 3 knots.  If I could motor most of this trip, I could do it in 20 days instead of the typical 40 days. Chances are I could motor sail also and have fuel left over when I got there. 

The theme of all this is you can't have too much fuel.  You will eventually use it, it can save you many days of voyaging, help you avoid storms, keep  you warm in cold climate, make power, and make water out of sea water.  While I love to sail.  I also love to get where I want to go in a timely manner with comfort.