Our initial idea was to basically add plating to the inside of the tank  walls and hull to create the cofferdam space (about 20 cm wide)  and make this hull inspectionable with an inspection camera like this one from Ridgid .  Making the cofferdam wider to allow access would mean ending up with almost no fuel storage space and rules require you can inspect a cofferdam but don’t specifically say how big it has to be.  But how to keep corrosion at bay and what about not being able to weld this plating on both sides? 

So we started looking at other solutions like a tank we could remove.  To store about 3 to 4 m3 of jet fuel (780-1038 gl.), one big tank would not be practical (how to get it in there?)  Several smaller tanks?  To start with, that would clearly violate the KIS principle.  But then we learned about bladder tanks and we came accross the website of Australia’s Turtlepac and thought, if they can do that kind of stuff with a bladder tank – like throwing filled tanks out of helicopters - it will work for us!  The obvious advantage of a bladder tank in our application is that when empty, you can easily remove it through the manhole and inspect the outer tank!

Unfortunately, there was no information whatsoever available on the Internet about yacht applications approved by a class society so I decided take my case to always very helpful gentlemen of Lloyds Register in Ft. Lauderdale to see how they felt about the idea.  I met with one of their surveyors and the news was good.  Yes, there was a precedent of the use of bladder tanks on (classed) yachts.    But we had to make sure the tank would not collapse while being emptied because they want fixed connections to the tank for filling and venting.  Flexible hoses – not normally visible as they are hidden in a cofferdam – that could  move and possibly allow parts rubbing into each other, resulting in some kind of failure were a no-no. 

Mmm…  a bladder tank that maintains its shape?  How then would we get it at its intended location or remove it for inspection.  But they mentioned there are companies that manufacture a foam specifically for use in fuel tanks (also called fuel cells) that could be inserted into the tank to keep it from collapsing, maintain its shape and allow fixed connections.

A little more Googling and we ran into so-called explosion suppressant foam made by  Crestfoam among others.  To see why this foam is called ‘explosion suppressant’, it’s enough to watch the video below.

Click here to view the embedded video.

So thanks to the helpful advise of Lloyds Register and with a little planning from our side and a lot of ball-shaped foam pieces from Crestfoam it looks we have now overcome the major hurdle to create jet fuel storage that will meet class requirements.

As you can see from the picture below, these fuel cells can be made in any size of shape to fit the particular needs of your yacht.  Of course, they will have to be pressure tested by the class society but the pressure is not that high and as you can imagine, these tanks can meet those requirements easily.

As you can see, the deck extracts almost 3 meters (10 ft.) allowing sufficient rotor tip clearance.  Our situation is shown in the drawing below.  Even when landing partly outside the forward area of the ‘H’-circle  (1/2 D) we’re still OK.

By the way, after a lot of consulting with experts and pilots, the helicopter we plan to have on board eventually will be a Eurocopter EC130B4.  It allows the best guest experience, is silent, safe and has great capacity.

When thinking about the ideal helicopter for an expedition yacht, this is a nice one to have around.  Reliable, spacious and folding blades. The Eurocopter AS 350B2 is a single-engined utility helicopter that can accommodate up to 7 passengers. Development of the AS 350 Ecureuil started in the early 70s under the Aérospatiale banner. The first flight of an Lycoming LTS101-powered machine took place on 27/06/1994. The second prototype was fitted with an Arriel 1A and took to the air on 14/02/1975. Certification (with a Turboméca Arriel 1B turboshaft powerplant) was achieved in October 1977. The single-engined AS 350B2, powered with a Turbomeca Arriel 1D1 engine was certified in April 1989. The AS 350 is marketed in North America as the AStar or SuperStar. The helicopter divisions of MBB from Germany and Aerospatiale from France merged in January 1992 to form the Eurocopter Group.

The three main rotor blades mean it has shorter blades than the Bell Jetranger that can carry only 5 people.  And, they are foldable which is important when you have three main rotor blades ! And as you can see above, we just found a 3D model.

Basically, we plan to create a small platform hinged from the stern to have the required outside-deck-only access to the pump room.  It also gives the chef the option to receive stores at the back when we are at anchor.  And, it’s a place to temporary keep some garbage if needed.  It will only require one watertight door + the access door to the pump room (with a VERY small pomp).

The pump room will have a small approved pump and the required ventilation.  Below an illustration of how we plan to convert our stern diesel wing tanks into compliant jet fuel tanks.

By building a cofferdam in/around the tank we should be able to comply with the rules that require avoiding direct contact between jet fuel tank and the hull and a cofferdam space all around the tank that can be checked on leaks and has an appropriate drainage. In our case, any leakage would end up in the dirty oil tank.

Update: October, 2009: after consulting with a Lloyds surveyor, we decided that instead of building the cofferdam from steel, we’ll create space to install a bladder tank.  Once this tank is put into place, it will be filled with foam to keep it in shape even when empty.  Lloyds Register doesn’t like flexible connections so they’ll be rigid, requiring a bladder that maintains its shape.

Below a view from the rear. As soon as we get the OK for the concept from the Germanischer Lloyd, we’ll design the structure.

Well, start thinking about double walled tanks (cofferdams), special pump rooms, all kind of detection systems, etc. etc.   I have started to look into building a fuel tank inside the starboard stern fuel tank.   Whether it fits depends on the required cofferdam space between the new tank and the existing tank walls.  You need to be able to crawl around for inspection purposes and be able to weld the new tank into the existing tank.  We’d probably end up using like 10 m3 of space to create a 0.3 m3 tank (26.315 /  800 gallons).  Hardly an efficient use of space.  On the other hand, it IS very convenient to have ample storage inside the vessel! 

And what’s the alternative? Put say 400 of these somewhere??   Not really. 

But,  thanks to our ever inventive friends in Germany, land of BMW’s, Weißwurst and other good things that make life better, I ran into a very interesting solution.  Our own containerized gas pumping station!

The gentlemen at Krampitz build an amazingly wide variety of (portable) tank solutions.  This standard 10 ft.  container comes with electronic leak indicator, overfill protection system, transfer pump, switch board, static lead indicator, fire extinguisher, and more.  It’s  CSC approved so any shipping company will carry it. Capacity: a whopping 10.000 liters (about 2.630 gallons).

Amazing huh?  Imagine, going cruising for a few months and know you have all the avgas or jetfuel that you need to fly as much as you want.

A true expedition vessel can’t really be without a helicopter.   If you’re going to the middle of nowhere, you need flexible means of transportation.  Only a heli fits the bill so we plan to make our ship ready for it. 

Obviously, landing a helicopter on a small yacht involves a variety of safety issues.  When I started looking into the rules set up by classification society Germanischer Lloyd, I learned there are basically two things to look at: landing and refuelling.  If you just want to land (and take-off), there’s a variety of rules regarding safety precausions, fire fighting gear, the size of the helipad and surrounding approach area, etc.  If you also want to refuel onboard, you run into a whole set of other rules regarding the safe storage of aviation fuel. 

In this post I’ll start with the landing pad itself.

Below a diagram with measures of what Germanischer Lloyd considers a helipad they would certify.  If  we take a common helicopter like the Bell 206 Jetranger, ‘D’ = 12.15 m (39.2 ft.).  So you need an aiming zone (the yellow H circle)  of about 6 m. and a clear zone of 12.15 m.

Obviously the yacht above does not comply with these rules, not even if they move the Jacuzzi ! 

We’re more thinking into starting out with a Robinson R44 Ravin Clipper with pop-out floats.  It’s ‘D’ is 11.5 m. (37.6 ft.).   More on this in my next post.