Hi, sorry for late reply.
The Gault was a short production run boat made in liaison with Shell Petroleum and patented by Robert Gault who lived at 12 Ranmoor Cliffe Rd, Sheffield S10 3HB in 1982. It was patented in the USA on the 7th December 1982.
The actual designer is unknown, but more than likely was Robert Gault because he was the patent holder.
I have put more on the main web site:
http://www.oldspeedboats.co.uk/gault-folding-boat/ If you have or had a contact, it may reveal more than I ever could. Thank you - BN