Tonke's "Desert Yacht" camper combines classic look with modern solar design


June 26, 2014

The new Tonke Fieldsleeper International

The new Tonke Fieldsleeper International

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The Tonke Fieldsleeper International is one of the latest camping vehicles making its way to the road. Tonke rips out the loud generator and liquid propane systems and replaces them with a full solar array. The motorhome is aimed at providing full comfort on all types of trips, even extended, off-grid stays in hot weather.

The Fieldsleeper International, which was initially called the "Desert Yacht," becomes the largest member of Tonke's Fieldsleeper line. Tonke's smaller Fieldsleeper campers offer solar systems optionally, but the International is equipped with a standard 400 W roof-mounted solar-panel array, 2.6 kWh, 440 Ah AGM battery bank, 3 kW inverter and 1.4 kW charger. A color control panel displays information about the state of battery charge, solar panels, inverter, etc.

The solar system feeds equipment like the 250-liter (8.8 cu ft) double-door refrigerator/freezer, induction cooktop, interior LED lighting and even the air conditioning system. The heater and boiler run on diesel power supplied by a dedicated 30-liter (8 gal) tank.

"We didn't want to use LP or LPG (liquid propane gas) because of lack of availability in remote areas and because of certain dangers involved," the Dutch company explains. "A large solar array provides lots of electricity efficiently stored in large battery banks."

Tonke feels that the 400-watt solar system will provide ample power to reliably run the refrigerator, lighting and cooktop, but of course this will depend on usage, weather conditions and how long the travelers remain off the grid in one place. The Fieldsleeper International's batteries also charge off the engine during travel, and campers can idle the engine at camp for a few hours to charge them. Tonke considers this a quieter, cleaner, more integrated solution than running a separate generator, and it's a strategy that has been employed by other manufacturers, such as EarthRoamer.

The air conditioner can run for short periods with the standard solar system, but Tonke suggests that those that want to run it during extended off-the-grid periods upgrade to the available 600-watt system with 5.8-kWh lithium-ion battery storage. This system provides the added power needed to run the air conditioner for up to about 10 hours.

We're familiar with Tonke's rustic, all-wood campers, but the Fieldsleeper International debuts its new aluminum-panel skin, which covers the mahogany paneling inside, giving the design more of a modern campervan look. Tonke says the aluminum requires less maintenance than the real mahogany body, which is still available as an option. A bit of wood trim on the aluminum shell lets you know it's a Tonke.

Inside, the International is set up like smaller members of the Fieldsleeper series. Its increased length, width and height open up the interior a bit and allow it to sleep and seat up to five people, as opposed to the three-person sleeping and four-person seating limits on smaller Tonkes.

As in other Fieldsleepers, the International's double rear doors open into a living area with fold-down table and cushioned bench seating. The dining area converts into a two-person bed, and two to three people can slide onto the behind-cab bed on the other end of the cabin. The kitchen area is sandwiched between the dining area and the main sleeping area. It includes the 200-liter (7 cu ft) compressor fridge with separate 50-liter (1.8 cu ft) freezer, two-burner induction cooktop, sink with hot/cold tap, and chrome-handled drawers.

Directly across from the kitchen unit is the washroom with shower, sink and Thetford C200 cassette toilet. To support its extended-trip mission, the Fieldsleeper International has two water tanks carrying 68 gallons (260-L), nearly double the water capacity of the other Fieldsleepers.

The new camper is available only on the Mercedes Sprinter 519 CDI 5-ton dually chassis with 190-hp/325 lb-ft 3.0-liter turbo diesel engine and 7G-tronic automatic transmission. The cab has seating for three. While it doesn't look quite as big, bad and burly as some other camping vehicles we've covered, Tonke considers the Fieldsleeper International an expedition vehicle and offers it in 4x4, as well as 4x2. The camper box is built to be separated from the truck in about 10 minutes with the available automated hydraulic system. It can stand on its own, and the truck can be used for other purposes.

Tonke is finalizing its Fieldsleeper International prototype and plans to continue testing for the next few months, starting production sometime after Northern Hemisphere summer. The model will be offered in US 110-volt and European 230-volt specs, starting at US$192,000 with the Mercedes Sprinter base included (about $141K for just the camper). The company told us that it already has a waiting list.

Source: Tonke Campers

About the Author
C.C. Weiss Upon graduating college with a poli sci degree, Chris toiled in the political world for several years. Realizing he was better off making cynical comments from afar than actually getting involved in all that mess, he turned away from matters of government and news to cover the things that really matter: outdoor recreation, cool cars, technology, wild gadgets and all forms of other toys. He's happily following the wisdom of his father who told him that if you find something you love to do, it won't really be work. All articles by C.C. Weiss

New Praga V3S?


IMO, I think that is cool and green. I like how they did the inside of it.


Hmmm did the same thing with my 1979 motor home for 189k less lol

Leonard Foster

While the beautiful fit and finish of the unit is obvious, I see problems with the solar charging system that an experienced RV owner with solar will recognize as problematic.

1 - The solar panels are fixed in position, with no possibility of tilting them to gain the most-effecient 90° orientation to the sun. In addition, the curvature of the roof will exacerabate the problem with half the panels tilted even further away from the sun when the RV is on an east/west axis.

2 - The roof vents will greatly reduce the output wattage by casting shadows on adjacent solar panels when they're opened. Even the smallest amount of shadowing will markedly reduce output.

3 - If this company is building for the European market, the inability to optimize the output wattage by addressing the problems listed above is compounded by the latitude of much of Europe. Amsterdam, for example, is further north than Calgary, Alberta, Canada.

4 - At the quoted price in $US, the Fieldsleeper will have very little appeal to the typical American RV owner unless slide-outs are incorporated.



Thank you Mr. Jones for your comments. Really appreciated.


The loss of output by misallignment with the sun is to our standards acceptable up to 45degrees (!) with 30% loss. It is not simply worth the hassle to allign perfectly, unless you have a solar plant. See: Yes, there is absolutely the problem of shadow, of trees or clouds, but the smaller shadow of a roof vent is no issue: the panels have integrated technology to electrically avoid the shadowed parts of the panels.

Of course there will be situations that the panels are insufficient. If that is the case and there is no hook up available, and you're not travelling the next day, you may run the engine at idle speed for a few hrs (but NOT 24h/24h like a typical genset configuration!) to charge the battery bank. The diesel engine is cleaner and quieter than a genset, does not take any extra space and runs cheaper then a generator.

Kind regards, Maarten van Soest, TONKE, Holland

Maarten van Soest

Might I suggest that, given that the availability of flexible solar panels, you might have either a roll-out or slide out roof with PV panels which could be deployed during extended stays. This would provide weather/shade protection as well as charging the batteries. By adjusting the alignment of the vehicle and the angle of the roof with adjustable poles optimised solar collection could be obtained.


Great suggestion, joeblake! If neither approach can readily be integrated into the body design, it could be stowable, and could be designed to hook onto loops built into the camper along the roofline on the side that has a door, with the outer edge supported by a pole in a sleeve, and support poles at the outer corners, with lines to hold the awning taut going to trees or tent stakes. A tube mounted on the side to roller-furl an awning could be an invitation for damage on a right turn that is too close to a building or a tree. (Check some bigger U-Haul vans, and you will see how often this happens.) Also, there will be more efficient batteries on the market within 2 years. Which brings up my first question for TONKE: what battery specs, form factor and cost per kWh would be sufficient to persuade you (and possibly Mercedes) to make this a full EV, or to use a hybrid drive train from Wrightspeed, getting them to adapt their mid-size truck Route design? My second question for TONKE is, could you include fairings around the cab (or the front of the body, since it detaches), to mitigate the aerodynamic drag from your non-transition from the small cab to the large body? Just like a well-dressed, full-size line-haul truck. My third question for TONKE is, do you have, or could you develop, a diagonal, adjustable cable cross-bracing system for the hydraulic supports, to strengthen them against severe body movement due to impacts, high winds or moderate earthquakes, so people can securely use the camper when the truck is being used elsewhere? Otherwise they could buckle at the bottom of the camper. Together, these changes could make your total value proposition irresistible!

Mark Roest

Apart from the price, the design looks pretty good. I think I could start with a LWB flat tray or cab/chassis vehicle and fit out a shipping container - or insulate an aluminium clad garage - for a cheaper version.

The Skud
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