Ontong Java I and Ontong Java II - Tuamotus Pahi(s) built by Hans Klaar

Hans Klaar's first boat, A lateen rigged Wharram catamaran ketch

Some photographs of Mareva (the first Ontong Java). First four photos are after boat was sold, remainder are from before that

For a higher resolution of the above photograph, please use this LINK

The 2020 extensive refit of Mareva in Auckland New Zealand

All following photographs are of Ontong Java II, built 2012

The first and third photographs are from Seahorse Magazine, August 2020

Hans Klaar 2022

Hans is now in Portugal. He has a new sail, a Gaff/Gunter sail. It is made from three sails stitched together over four days. Notice the gaff jaws on upper and lower spars. There seems a new block for the mainsail. He has crossed the Atlantic seven times over the last four years

'Ontong Java' Pahi built by Hans Klaar

Ontong Java is a large Pahi built in Africa by Hans Klaar. It is made of solid thick timbers and not epoxy coated. Cost was much less (a small fraction) of the equivalently sized modern high tech catamarans. Maybe it is not as refined, but it does work. Hans has sailed countless tens of thousands of miles in this boat. Boat life may be limited does to lack of epoxy, maybe only 30 or 40 years, however if your boat costs a fifth of that it does to build a 'modern' design then is that really bad economics, it sure sounds good to me.

There is some information on the Wharram owners website, some from Woodenboat forum, some from Youtube, and some from August 2020 digital version of Seahorse magazine. One photo was emailed to me directly by Hans. I found some information from a New Zealand magazine Issuu by Sun Media July 2012 about the refit of Mareva, the first Ontong Java. My understanding is that Hans built a Wharram inspired catamarn with two masts and crab claw sails first , and then Ontong Java was built in west africa to a more traditional design but with a low aspect main and jib.

Sealing of the planks (caulking) I think was done with rubber soaked in petrol to soften it, then hammered into the gaps between the planks then nailed on, simple but effective. Building the boat is west africa makes sense as the cost of labour is just so low, and high quality timber can be had for very low prices. The downside is that its not all shiny white and gleaming and may only last 40 years, but that cant be all bad, at least you get a great boat for relatively little money. My understaning is that Ontong Java was modelled on a Pahi craft from the Tuamotus Islands based on sketches from 1845.

Note that one hull is slighly smaller than the other, this reduces bending stresses on the crossbeams. Note that the rudders are lashed to the main hull and are known as quarter rudders

Ontong Java is a very impressive boat, especially when you consider it probably cost a fifth of what a modern large catamaran would cost. There are a few videos floating around on YouTube of this boat, I have included one below though I know there is a much longer YouTube video of this boat sailing but cant recall where I saw it, apparently it can self steer by linking the rudders to the jib sheet?

A near identical version of Ontong Java being built early 2013 and called Ontong Java (2). It seems Hans was very happy with Ontong Java so he has built a new similar boat. The first Ontong Java was sold in New Zealand around 2012 , it had a first refit in 2012 and a second more extensive refit in 2020 and now goes by the name Mareva

Overview of Hans Klaar's boats

  • Hans Klaar's first boat was a lateen ketch rigged Wharram cat in plywood/epoxy
  • Ontong Java 1 (now known as Mareva) and the new Ontong Java are very similar. One difference is in the paint work. Mareva has a large red area on the hull, whereas the new Ontong Java has an all black hull. The second Ontong Java is a fraction larger
  • In 2007 Hans built the first Ontong Java in Senegal
  • Ontong Java was sold in New Zealand approx 2011, and now goes by the name Mareva
  • Maerva undertook a 15 month refit in New Zealand in 2012
  • In 2012 Hans built Ontong Java II in Gambia in West Africa
  • Mareva undertook an extensive second refit in 2020
  • Hans is currently in the Carribean

Details about Mareva

  • Built in Senegal in 2007 from two large Okume logs
  • Came out of the water weighing 11 tonnes, went back in drier weighing 10 tonnes
  • Planking is Adzed and is 450mm to 350mm wide and 45mm thick
  • Ontong Java was sold in New Zealand approx 2011, and now goes by the name Mareva
  • On reaching the crab claw rig gives 90 percent more driving force than the Bermudan rig
  • The rig may be tilted straight up in light air to reach for the stronger air aloft, or in a fresh breeeze angled down to keep the center of effort low

Details about Mareva edge on edge planking

  • Here is some information from Josh Lutz. Josh is currently refitting Mareva. Josh writes

    "I'm helping a friend restore the first boat this guy built. Amazing wood, but held together with steel rebar rods inserted into the edge of the planks and then the next stuck on top. The gap then filled with tar and a strip of conveyor belt tacked over with copper nails. Unfortunately every area of steel has rusted damaging the wood."

    I find this very disappointing. The best way of doing edge on edge planking is via many small wood dowels, as per the Indonesian method of boat construction. Perhaps Ontong Java II uses stainless steel instead of non stainless

The extensive 2020 refit of Mareva

  • Boat owner and head of refit is Hamish Mcgregor Murray
  • Refitted in 2020 in Auckland New Zealand
  • Low aspect wood crab claw rig replaced by high aspect bermudan rig with large aluminium mast
  • Hull now epoxy encapusalted, with 400L of epoxy and a lot of fiberglass
  • Wooden hatches replaced with commercial aluminium hatches
  • Solar cells added
  • The hulls were painted yellow

Details about the Newer Ontong Java

  • The hull decks are plywood. The bridge deck between the hulls is covered with wide planks secured by fishing line
  • The sails are made from a tarpaulin. Total rig cost was $2000
  • The jib is there to improve balance
  • Upwind there is a big loss in performance, but for the long distance passage making this may be made up by gains in reaching and running
  • The crab claw is simple to handle, cheap to build and easy to repair
  • the planks in the hull are overlapped and bolted together using stainless steel bolts, washers and nuts. The hulls are strongly V shaped. Between the planks are strips of rubber taken off an abandoned conveyor belt. There is also a sealant made of melted car tyres and plant oils, and some other strange things.
  • Theoretical hull speed is 17 knots but Ontong Java rarely travels that fast. 180 to 200 miles a day is the norm, and that happens with barely lifting a finger. The boat more or less sails itself. Hans reads a lot and carries a lot of books and a lot of surfboards

  • I can now say, yes in its extant it took me 4 years to dream up, 6 months to build (from 2 bare tree trunks 4 foot diameter and 27 feet long), 2 months for the rig, crab claw naturally, a very refined version, asymmetric hulls, built along the line of the Anaan, Tuamotuan canoes as seen by both Commodore Wilkes and Admiral Paris (approx. 1845)
  • Here are the dimensions: starboard hull is 71 feet LOA, 8 feet beam, 6 feet deep; port hull is 57 feet LOA, 8 feet beam, 6 feet deep; draft over all is 2 feet. Deck platform 42 by 21 feet, beam over all 22 feet, 7000 kg plus/minus looking at the weight of the dried wood used.
  • Tacks like a dream all one way, no hanging back at the last moment, and takes off once through the eye of wind almost at once, holds a good 50 degrees on the wind and leaves a nice straight wake aft. I can handle her totally on my own, self-steers very well. Something funny goes on with this one mast that seems to make it possible. One example is 400 miles in 40 hours, jib to tiller steering (controlled surfing if one can call it that) with fully reefed main in 28 knots of wind.
  • Will head out for the Pacific come January, are at the moment in Brazil on our way to Trinidad-Tobago. Hope you like the lines and that all is well in Devoran.


  • The owners of Mareva list dry weight at ten tonnes. Hans says Ontong Java weighs 7 tonnes unladen
    (I suspect this is low, will explain later). Explaining the discrepency is not easy, it may well be that the newer Ontong Java was built with thinner planking than the first build which used 45mm thick planks, however I have my doubts. It may also be that Hans weight is an estimate, whereas the weight from Mareva is more accurate from the scales of the boat lift in New Zealand. I have been in contact with John Caprani, who helped with the 2012 build of the second Ontong Java. His recollection that planking thickness was similar to the 45mm thick planks of the first boat. Now the second boat is a tiny bit larger than the first, hence I suspect weights to be very similar. Thus I suspect the weight to be close to 10 tonnes, the 7 tonne estimate is just that, a rough estimate made without benefit of scales found in a boat lift

Character of Hans Klaar

  • This is difficult issue. I respect the sailing skills and boat building skills of Hans, yet there are some issues that need to be addressed. I have recieved emails from two separate people which were not complimentary about his character. Hans was convicted of a serious crime in South Africa and served jail time there. Is hard for me make a judgement about the character of someone I have not met. I have put this information up here for others to make their own judgement

Much more information can be found at the atom voyages website   LINK 1
Lots of building photos at this   LINK 2
More information here also LINK 3
Information about the 15 month refit of Mareva can be found in this LINK

Youtube video Sailing Ontong Java, 2 mins 30 seconds.

Building Ontong Java II - Timelapse Video, extremely good

Additional videos

Hans explaining the boat. LINK
Ontong Java, British Virgin Islands 2015 LINK
Ontong Java, Panama 2016 LINK