Didi Mini Mk3
Radius Chine Plywood Mini 650

Didi Mini Mk3 radius chine plywood Mini 650 boat plans
Didi Mini Mk3

Low budget performer

~ Economy of plywood

~ Modern radius chine hull with topside chine

~ Stitch & glue cabintop & topside chine

~ Developed from Didi Mini concept

~ Round bilge from sheet material

~ Amateur or pro builders

~ Fixed or canting keel

~ High performance racing on a tight budget

~ Kit suppliers North America & elsewhere

~ Build photos ~ Flickr Album



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In the 10 years that we have offered plans for the Didi Mini, we have sold plans for 90 boats. Apart from a redesign of the aft deck and a continual expansion of build options, it has remained the same basic boat sold as the Didi Mini Mk2. Now we introduce a major redesign, as the Didi Mini Mk3. It has some major changes from the earlier versions while retaining the same basic structure and detailing. It remains suitable for amateurs to build economically but performance will step up a notch or two.

Introduced in the Didi Mini Mk3:-

~ Updated hull shape with broader stern and topside chine

~ Extended cabin roof, forming protected cuddy over front of cockpit

~ Easier access between cockpit and interior

~ More power from broader and flatter stern

~ Water ballast of fixed keel version further outboard

~ Bow and stern ballast tanks in canting keel version

~ Tacking daggerboard in canting keel version

~ Redesigned foam flotation, cleaner interior

~ Inboard chainplates for tighter genoa sheeting

~ Larger square-head mainsail

~ Carbon or aluminum spars

Overall, these changes produce a boat that will be more powerful, faster, more weatherly and more comfortable to sail.

Now also added to the drawings (Oct 2018) are twin daggerboards and composite chainplates.

Didi Mini radius chine plywood Mini-Transat boat plans Didi Mini Mk3 radius chine plywood Mini 650 boat plans
These views show the hull and cabin changes clearly.

Detailing is based on the series of radius chine plywood designs that started with my DIDI 38 "Black Cat", and was followed by the DIDI 34, Didi MG30 and DIDI 26. The underbody has been reworked to allow a topside chine to be added to power-up the aft sections. The chine is formed by stitch & glue methods and fairs into the hull side just forward of the mast, with the bow sections remaining the same as the Didi Mini.

Design principle is simplicity and to the Mini 6.5 Class limits. The design includes options of a fixed keel with conventional port & starboard water ballast tanks or a canting keel with forward daggerboard and bow and stern water ballast tanks. For the fixed keel version the tanks increase sail-carrying power. For the canting keel version the tanks allow the bow to be trimmed down on windward legs for improved windward ability or the stern to be trimmed down for offwind performance in strong winds. The daggerboard can be tacked inside the casing for increased lift. Linked twin rudders are steered by central tiller.

Keels are hollow aluminum fabrications with through-bolted beaver tail ballast bulbs. The fixed keel has optional trim tab. Both keels are supported by the hull structure by means of an internal aluminum box frame. The fixed keel has an integral post to transfer some of the keel loads through to the deck structure.

Didi Mini Mk3 radius chine plywood Mini 650 boat plans
Didi Mini radius chine plywood Mini-Transat boat plans
The sections and waterlines on these views highlight the hull shape.

The deck layout is a fairly conventional 3-winch arrangement. The smaller headsails sheet to the top of the cabin and are led to the cabintop winch. The larger headsails and spinnakers sheet to the cockpit winches. Tweeker lines replace headsail tracks.

Spars can be either carbon for performance or aluminum for reduced cost. If an aluminum mast is used then the ballast bulb must be 10% heavier to maintain stability in the test condition.

Drawings include full size Mylar patterns of the backbone, bulbs, rudders and daggerboard. Optional full size Mylar patterns for the bulkheads are also available. Drawings have been added to the set for composite chainplates and twin daggerboards.

Pre-cut hull, deck and bulkhead kits are available from various suppliers. Click here for supplier contact info. Please clarify with suppliers what is included in their prices.

Click for material list or drawing list of the Didi Mini Mk3.

We continue to sell plans for the Didi Mini alongside the Didi Mini Mk3 because there are builders who still prefer to build the older design.

Didi Mini Mk3 radius chine plywood Mini 650 boat plans

Didi Mini Mk3 radius chine plywood Mini 650 boat plans

Didi Mini Mk3 radius chine plywood Mini 650 boat plans

Didi Mini Mk3 radius chine plywood Mini 650 boat plans

Figures shown are with carbon spars.

LOA 6.50m (21'4")

LWL 6.45m (21'2")

Beam 3.00m (9'10")

Draft 2.0m (6'7")

Displ to DWL 1050kg (2315lb)

Displ light 865kg (1907lb)

Ballast 320kg (705lb)

Waterplane area 9.32sq.m (100sq.ft)

Immersion rate 96kg/cm (535lb/inch)

Wetted surface N/A

Sail area (main + jib) 41.7sq.m (449sq.ft)

Sail Area/Wetted Surface N/A

Sail Area/Displ 41

Displ/length 109

Prismatic coef .53

Block coef .34

Fineness coef .67

Righting Moment @ 30 deg
886kgm (6408ft.lb)

Righting Moment @ 60 deg
965kgm (6980ft.lb)

Righting Moment @ 90 deg
670kgm (4846ft.lb)

IG 8.62m (28'4")

ISP 11.62mm (38'1")

J 2.585m (8'6")

P 10.435m (34'4")

E 3.7m (12'2")

Mainsail 31.36sq.m (338sq.ft)

Solent Jib 10.33sq.m (111sq.ft)

150% Genoa 16.67sq.m (179sq.ft)

This design is dimensioned in both metric and imperial measurement systems.


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This page was updated 23 October 2018

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