Didi Mount Gay 30
Tamas Csaba's Mount Gay 30 in Hungary
 This boat has the optional lifting keel
~ Exciting racer

 ~ Build her yourself

 ~ Suitable for IMS racing or club PHRF

 ~ Radius chine plywood construction gives round bilge hull

 ~ Inboard or transom hung rudder options

 ~ Optional lifting keel (add-on to design)
Affordable high performance
Simple plywood construction
It employs the same basic radius chine plywood techniques proven in the Didi 38 and further developed in the Didi 34 and 26, in a mixture of the structural concepts of her larger and smaller sisters. The 34 and 38 are fully framed structures with a solid timber I-beam backbone and laminated floors to support the ballast and rig loads. The 26 is much more lightly loaded and has a plywood backbone tying into the dropkeel casing to carry those loads.

 The Mount Gay 30 is of a size that could possibly accept similar construction to the 26 but it is a much more serious boat. It has to be capable of offshore passages in rough conditions so a requirement of the Rule is that it has to meet the scantling requirements of the American Bureau of Shipping Guide for Offshore Racing Yachts. These boats also tend to be raced hard, with heavily loaded rigs. For these reasons I have chosen to use a fully framed structure with I-beam backbone. The departure from the structure of the Didi 34/38 is that the I-beam ties into a grid of floors cut from plywood instead of being laminated from solid timber. The result is a stiff structure to reduce hull distortion under rig loadings.
For maximum performance, she is designed for construction mainly from lightweight timbers. The plywood is Okoume (Gaboon) marine grade and most solid timber is Cedar. The exception is in the bottom of the hull in the keel area, where Mahogany or Fir marine plywood is used and the backbone structure is Mahogany, to carry the ballast keel loads and improve hull stiffness. This gives a lightweight structure which will bring in the complete boat very close to the class minimum weight of 2300kg. She can also be built from Fir or Mahogany plywood throughout but expect this to increase her weight by about 200kg.

 With most of the structure being plywood, she is well suited to kit construction, much of it self-jigging and most parts epoxy filleted together. Assembly of the hull follows the principles of model aeroplane construction, with stringers slotted into the bulkheads for attachment of the skin. The hull skin is single skin plywood to the sides and bottom and the radius is done in two layers. The radius becomes the strongest part of the hull and is an added safety factor because it is in the region most at risk of puncture in a collision with floating debris. This is in contrast to a conventional chine detail which introduces a potential weakness due to the risk of splitting.

 Deck construction is also over longitudinal stringers which slot into the bulkheads and is all in single skin plywood. The cabintop is designed with a multi-chine skin and is assembled over the bulkheads by the stitch and glue method for a strong, lightweight and speedily assembled structure.

 The entire hull and deck is epoxy coated and painted inside and out. A good standard of finish is achievable with little or no fairing aside from forming fillets at internal angles.
Light but strong
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