Mini 6.5 or Mini-Transat boats: Minis for the Max
The Didi - a radius chine plywood Mini 6.5 you can build yourself
Mini 6.5 or Mini-Transat boats attract great interest worldwide. Tiny but costly offshore yachts, they give spectacular sailing, but are generally beyond the ability of most amateur builders. The Didi Mini was commissioned by a client who wanted to build a Mini for himself and is our input toward reducing the cost of these boats.
The Didi Mini has no pretensions of being the latest and best in the Mini 6.5 class. It exists primarily to give motivated sailors the method to build a reasonably competitive Mini at moderate cost. The concept and detailing is based on a series of radius chine plywood designs that I have developed over the past 10 years.
It started with the Didi 38, which I designed and built for myself in 1994/5 as a test for the concept. That produced a cruiser racer of 4 tons displacement and 50% ballast ratio on which I crossed the South Atlantic three times. She was followed by the Didi 34 cruiser racer, Didi 26 performance trailer-sailer and Didi Mount Gay 30. The Didi Mini draws on the lessons learned from those boats in fine-tuning the construction method and hull shape within the limitations of a sheet material.
Simple construction was a priority for these designs. They are aimed at owner-builders, to provide a way to personally build a boat of good performance without the need for advanced boatbuilding skills. Most guys learned some woodworking in school, so have the basic skills needed. Hull shapes are uncomplicated and require no lofting skills, even if building from offsets rather than the optional Mylar patterns. There are also no materials in the structures more exotic than conventional ambient temperature curing epoxies.
The Mini hull is built with stringers over permanent bulkheads and skinned with plywood. Approximately 2/3 of the hull surface is skinned with a single layer of 6mm plywood and the other 1/3 with two layers of 3mm. The deck is skinned with 6mm plywood and stiffened with doublers where needed for hardware loads. A plywood backbone interlocks with the bulkheads to help with setting up and forms a box structure to carry keel loads. Full size Mylar patterns of the backbone components are included in the plans, as well as patterns for rudders, daggerboards and ballast bulb. Patterns for bulkheads are also offered as an option.
Structural design with the 6mm skin is to ABS and will give the lightest weight. Those wanting a bit more flotsam resistance can increase the hull skin to 9mm or add a reinforcement layer to the outside. However, the 6mm skin is very strong in the impact zone due to the structural grid that is designed into the building method.
The hull shape is near enough to round bilge that most people cannot see the difference. It is also fast, with efficient planing surfaces for hard downwind sailing.
The initial design was for a fixed keel, which is an aluminium fabrication with lead beavertail bulb. There was much pressure from builders for a canting keel option, so that came later. It uses the same structure as the fixed keel version, with some mods to accommodate the water box of the canting keel. The fixed keel version has a daggerboard in the cockpit and the canting keel version a forward board.
To date we have sold 41 sets of plans for the Didi Mini to 22 different countries, of which 5 have been with kits. Our plan prices are US$450 to build from plans and offsets. We also offer optional Mylar bulkhead patterns for $225 extra. Not all boats are for racing, some are being built as little fast cruisers with the alternative short rig and I will be drawing a shorter cruising keel as well.
A comprehensive kit from CKD Boats in South Africa is approximately US$7,000, including all plywood panels pre-cut except for deck doublers. The CKD kit also includes pre-finished stringers and all other timber, epoxy, fillers etc. A kit from Jordan Boats in the UK is ?2,280 and comprises all plywood components pre-cut for bulkheads, hull and deck construction but not the interior.
The completed cost of an amateur built boat to a reasonable sail-away standard will be about US$25,000.
Dudley Dix Design: www.dixdesign.com
CKD Boats: [email protected]
Jordan Boats: www.jordanboats.co.uk
