Some of you, who have read Patrick O'Brian's work on the Master and Commander series will have come across the HMS Polychrest based upon the Dart and Arrow:
"Hobbs & Hellyer built six vessels to Bentham's design. Dart was the second of a two-vessel class of vessels that the Royal Navy classed as sloops, and she and her classmate Arrow were the largest of the six vessels. The design featured a large breadth-to-length ratio, structural bulkheads, and sliding keels. The vessels were also virtually double-ended"
The picture shown is that of the HMS Project. It demonstrates the overall shape quite well. Being a Butterfly I thought....I can make that!
The basic form is taken from the diagram above, shortened by one segment from the central section, and with a scaled down version as the base. This was sanded into polystyrene and fore and aft (fore and...fore?) decks added.
Going to be slow progress (Brother Handro: "When is it not!") but we will perservere!