Built for Chay Blyth to win the 1978 Round Britain Race this 53 foot trimaran design was later further developed as VSD1.  

She was a fast and in my opinion a beautiful looking boat. GBIV was too delicate in heavy weather because she was built very lightly.  His crew Rob James wrote a book called "Multihulls Offshore" which said she was very fast in light weather but too lightly built so she flexed a lot, and developed leaks. James claimed that there was too much buoyancy in the after ends of the floats forcing the bow to go down in big seas causing the boat bear away with excessive lee helm. Whether that was right or not it was written in the context that he had by then been sailing John Shuttleworth's Britany Ferries which featured very slim low buoyancy sterns to her floats which are not now regarded as a very clever design either. Rob James was implicitly critical of Derek in his book suggesting that the boat was too lightly built and that Derek was casual in his attitude to boat building; he cited that Derek lined the hulls up by eye before final glassing together and that a stay broke a chainplate and similar things. He skippered  Kelsall's GB III and did not like her much either! Rob later worked with Ron Holland to design Colt Cars GB a design that incorporated Robs ideas about trimaran design after racing trimarans by Kelsall, Shuttleworth and Newick -all regarded as top designers, but Rob believed he and Ron Holland could improve on their work. Sadly in 1983 Rob was killed while sailing Colt Cars GB.

Chay took GBIV on the Route De Rhum race but retired soon after the start with self steering issues and she was then sold as Chay went to John Shuttleworth for his next trimaran.  Nicholas Gray campaigned her in 1980 but concluded she was not strong enough to race the Atlantic. GBIV was bought by Alan Toone in 1981 and after strengthening work was apparently a sound but heavier boat.  However qualifying for the TwoSTAR race he and is crew ran into a severe gale in Biscay with 60 knot winds and 30 foot seas. They hove to and streamed a sea anchor from the bow and as the wave passed under the boat she heeled over, went backwards  and buried the aft end of the lee float and fell over in a slow capsize. It sound rather like the loss of Seiko/RTL (ex Three legs of Mann II) albeit she was not laying ahull or from a sea anchor but stopped and feel backwards off a wave. 

However Alan wrote that the sea anchor had ripped to shreds causing the boat to be driven backwards and hence to capsize.  He said he would never again lie ahull or hove to in a trimaran and although the crew were rescued the yacht was destroyed. However, it must be said she was a success because she did exactly what she was designed to do by winning the 1978 RBR.  Others subsequently involved with this boat reported that she was fragile and best in moderate and light weather. There is no doubt that Derek pushed boundaries with many of his boats. With Trumpeter for example in 1970 critics thought she was too lightly built however with modifications that Derek's experiments and lessons with design and construction development showed could improve her she is still sailing the Oceans 55 years later.  She was built too lightly but she achieved what her owner had required namely to win the RBR 1978. Development of the same design further in VSD1 and 2 also showed that the basic design concept was good.