DUDLEY DIX YACHT DESIGN

Didi 34

Radius Chine Plywood Cruiser racer

Didi 34 radius chine plywood boat
"Spoon", the first Didi 34, was built by
Gert Bruwer of Saldanha Bay,
South Africa

Affordable performance

~ Economy of plywood

~ Radius chine hull

~ Round bilge from sheet material

~ Within abilities of amateur builders

~ Easily handled fractional rig

~ Good performance when racing

~ Fast and comfortable cruising

~ Deep or shallow draft keels

~ Kits for hull, deck & bulkheads

~ Sailing photos

~ Design review on SA Yacht Blog

~ Incomplete Didi 34 project available.

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Didi 34 radius chine plywood boat

A compact and fast cruiser racer with good performance which you can build for yourself from plans, this is a smaller sister to the DIDI 38 which I designed and built for myself in 1994/95, as a prototype for the radius chine plywood yacht concept. She is a bit more cruising orientated than the 38, which has more downhill racer in her. In many respects she is also an updated version of my CW 975 , the design with which I won the 1979 Cruising World Design Competition. I built one of those boats for myself and sailed her for 7 years before designing the DIDI 38.

Drawn to be a good all-round performer, the Didi34 will be able to account well for herself in round the buoys or passage races while still being a comfortable small cruiser.

Radius chine plywood simplicity and economy

Construction is radius chine plywood, drawn for ease of construction. I built the first DIDI 38 myself in my garden to prove the innovative methods of construction which I designed into her, to achieve a strong and light structure which could be built by people with average handyman skills and a very modest budget.

Thoroughly modern

Her lines are thoroughly modern, with short overhangs, fine bow at the waterline and moderately powerful stern. Sections are slightly Veed throughout the length. The forward underbody has been shaped to develop dynamic lift to keep the bow up at speed and promote surfing.

Didi 34 radius chine plywood boat

The hull has moderate beam and is well flared to give a narrow waterline, reduced drag and improved comfort at sea. Light and beamy boats are not comfortable in a seaway. After having crossed the South Atlantic twice on my DIDI 38 I can vouch for the comfort of a light boat of moderate beam.

Draft of the standard keel is 1.9m but the drawings also include a shallower option of 1.5m draft for shallow water areas. Stability is similar with both keels but the shallower one is heavier, so performance on all headings is reduced.

Easily handled deck stepped rig

The mast is deck-stepped on top of a post aft of the main bulkhead, structurally the most sound solution for a timber boat. It places everything below the mast in compression rather than trying to force the hull and deck apart, as happens with a keel-stepped mast. It also eliminates the problem of water going below through the mast and collar.

Didi 34 radius chine plywood boat

Comfortable and practical interior

Down below, the layout is based on a feature found in most of my designs, the midship engine. It gives excellent access for maintenance, places the heavy weight at the optimum position to reduce pitching and allows a flatter after underbody because the weight is not having to be supported as far aft. It also allows a good seagoing U-shape galley to be built around the engine, with centreline sinks.

The saloon settees are integral water tanks and the saloon table is a box in two sections. The lower is an epoxy coated plywood fuel tank and the upper is a storage compartment.

The separation between sleeping cabins makes her well suited to small family or two-couple cruising, with the settees serving as alternate berths for bad weather. The aft heads position is prefered by most women. The lazarette is large and has compartments for liferaft, gas and batteries.

Didi 34 radius chine plywood boat

My DIDI 38, "Didi" (previously named "Black Cat") has lived up to all of my expectations in her design concept. The DIDI 34 will do well for anyone wanting such a concept but in a slightly smaller package.

Follow these links to an article on radius chine plywood and the other designs of similar construction, the Didi Mini, Didi 26, Didi MG30 and Didi 38.

Follow these links to print or download a material list for the structure, polar plots, stability curve or list of drawings for this design.

Didi 34 "Spoon" on launch day

Didi 34 "Spoon" on launch day

Didi 34 "Spoon" on launch day

Didi 34 "Wasabi"

Didi 34 "Spoon" galley

Didi 34 "Spoon" interior looking forward

Didi 34 "Spoon" under sail

Click on photos
to enlarge

CHARACTERISTICS

LOA 10,50m (34'5")

LWL 9,60m (31'6")

Beam 3,40m (11'2")

Draft 1.5m (4' 11") or
1,90m (6' 3")

Displ to DWL 4300kg (9477lb)

Displ IMS trim
3600kg (7935lb) deep keel
3830kg (8442lb) shallow keel

Ballast
1730kg (3813lb) deep keel
1960kg (4320lb) shallow keel

Waterplane area 17.07sq.m (184sq.ft)

Immersion rate 175kg/cm (980lb/inch)

Wetted surface 24.4sq.m (263sq.ft)

Sail area (main + 100% fore triangle) 49.8sq.m (536sq.ft)

Sail Area/Wetted Surface 2.04

Sail Area/Displ 18.7

Displ/length 135

Prismatic coef .56

Block coef .43

Fineness coef .66

Righting Moment @ 30 deg 2908kgm (21034ft.lb)

Righting Moment @ 60 deg 3912kgm (28296ft.lb)

Righting Moment @ 90 deg 2952kgm (21352ft.lb)

I 12,24m (40'2")

J 3,62m (11'10")

P 12,50m (41'0")

E 4,5m (14'9")

Mainsail (excl roach) 28,13sq.m (303sq.ft)

Foretriangle 21,70sq.m (234sq.ft)

150% Genoa 38,28sq.m (412sq.ft)

Powering 15-25hp diesel

Headroom aft 1.87m (6'2")

Headroom at mast 1.76m (5'9")

Fuel 150 litres (41 US gals)

Water 600 litres (165 US gals)

This design is drawn in metric and dimensioned in both metric and imperial.


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This page was updated 25 December 2012

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