Saturday, April 25, 2015

Oppikat, Tiny Catamaran

Following on my previous post about a big catamaran, here is the other extreme. This catamaran is only 9ft long and primarily intended for use by children. But read to the end to see an alternative use.

I designed the Oppikat for Nebe Boats a long time ago. They were to build it as a fibreglass production boat but didn't even start to build the moulds before closing their doors. More recently I converted the plans to a combination of plywood and strip cedar construction, to make the design more suitable for amateur builders. We have sold plans for this design to builders in 18 countries but don't know how many are sailing.

A new Oppikat is about to be launched, built by Greg Mitchell in California. She may be launched this weekend.
The newest Oppikat, ready for launch by Greg Mitchell.
Greg built it for his children from a plywood bulkhead kit but built the rest of it from the plans.
Strip planking completed, over plywood bulkheads, ready for plywood side panels.
Greg's daughter had input into the colour scheme for the new boat, choosing the colour of the cross-beams. Greg modified the tone of the blue for the hulls to a colour that would not clash. The result is very eye-catching and definitely has a female touch to it.
Hulls completed and other components assembled, ready for the rig.
This little boat is small enough to be car-topped or lashed to the trampoline of a bigger cat when towed behind the family car.
Oppikat built by Frank Nagel in Germany for his children, sailed here by his son.
Although intended for children, Frank Nagel in Germany told me that it has enough buoyancy to sail with him and two children aboard as well.

The Oppikat can be different things to different users. It fits comfortably onto the foredeck or into the davits of cruising catamarans, to serve as a tender and as a toy for both children and adults when anchored. A pair of them on a charter catamaran will add lots of scope for fun activities.
The red image is an Oppikat on the trampoline of a DH550 cruising catamaran.
For more info on this little boat go to and to for our full range of boat designs.

Friday, April 24, 2015

Kit-build Dix 470 Plywood Catamaran

Assembly of the prototype Dix 470 plywood kit by Exocetus Yachts in UK is progressing nicely. This is the second hull, with improvements added into the kit since assembly of the first hull. These photos were sent to me by Exocetus.

Exocetus is able to use more advanced methods than would be used by amateur builders but the kit is set up to allow those with more basic facilities to produce comparable quality. Being the developers of the kit, they have cut all of the components themselves on their own CNC equipment. They also have a large press that they use to join multiple sheets of plywood into long panels or other large components, like bulkheads, cabin soles etc.

Sheets being joined into long hull panels by means of a press.
This long outboard hull panel was pre-assembled into one large piece before installation.
Inboard hull side fitted, with horns for major bulkheads projecting into the bridgedeck area.
Bottom panels were fitted installed.
The side panels were glued into longer lengths for convenient assembly with the equipment available to Exocetus. For my own projects and more primitive methods, I prefer to assemble skin panels in single-sheet lengths. This leaves considerably more scope for adjustment during installation to remedy any possible errors that arise due to builder error. The bottom panels were installed in single-sheet lengths, to allow accurate fitment at the centreline joint.

In the last photo above, the jigsaw joint was aligned using a strip of plywood, wrapped in plastic tape, as a temporary butt-strap. A short screw into each lobe of the jigsaw pattern ensured accurate assembly and held the joint securely until the epoxy had set.

For more info on this and our other designs, visit . For more info on the kit and options, go to .

Thursday, April 23, 2015

Sentinel Explorers Racing

I designed the Sentinel Explorer for Sentinel Boats in 1991. My client was the importer of the Drascombe range of boats built by Honnor Marine but had not been able to sell any of those boats due to the high cost of importing them into South Africa. The brief was to draw my design to a broadly similar concept to the Drascombe Lugger but with sloop gunter rig instead of the yawl gunter rig of the Lugger.

My design was for a much fuller boat, with more volume on less overall length and very different hull section shape, resulting in a boat with more stability and considerably more speed. The UK builders of the Lugger took exception to the design and tried to shut down production, claiming that the moulds for our boat had been made from an existing Lugger hull, which was patently nonsense and no more than bullying the little guy in the playground. It lasted for several years but eventually went away, leaving a very bad taste for the low standard of business ethics displayed by Honnor Marine.

Ironically, Honnor Marine went broke and the company was bought by Bob and Norma Brown. The new iteration of Honnor Marine is now builder of my Cape Cutter 19 design in UK.

Production of the Explorer has been very low key, with small numbers built over the years. I heard a few years ago that there was a fleet of Explorers gathering on Langebaan Lagoon, on the West Coast of South Africa, with owners enthusiastic over their boats. Today I have received photos of this group racing as a one-design fleet in the Sandy Bay Yacht Club Easter Regatta. I have to admit that this is the first time that I have seen more than two Explorers sailing together. The time that I did see two together, I was racing one of them in the Hout Bay Dinghy Regatta, with my late friend Bryan Ferreira as crew.
Explorer start line action. "Dawdle", on the left, won the Easter Regatta.
Explorers dicing to windward in the Easter Regatta.
Explorer #59 being chased by Challenger #20.
It is good to see a smaller sister, the Sentinel Challenger, racing in the same fleet. The Explorer is only built in GRP from moulds but the Challenger can be built from plywood to our plans.

To see more about these and our other designs, please visit