Over the weekend I did a bit of research into how the full sized Lifeboats were built, and to find out whether in fact a layer of Calico was placed between the layers of planking. I found that back in the 1970’s, the RNLI Journal contained a series of 10 articles entitled “Building a Rother Class Lifeboat”, which contained all the build information you could possibly want! I knew that these boats used the ‘Double Diagonal’ hull construction method, and had assumed that there were 2 layers of planks. However on reading the description, it transpires that actually there was a longitudinal layer between the 2 diagonal layers, so 3 layers in total. And there is no mention of any Calico being used, so I assume by the time these boats were built, the use of Calico had been phased out. This is how the process is described in the Journal:
The 37' Rother class lifeboat is of cold moulded wood construction; which means that, instead of solid timber, her hull is a skin made up of three layers of thin planks, laid at different angles and bonded together with glue into one immensely strong laminate moulded to the boat's shape. The first skin is the thickest. These planks are 8 mm agba, about 4" wide before they are shaped. The planks are laid diagonally across the longitudinals and timbers of the boat's frame, bottom aft to top forward, at an angle of 45 degrees. Once all the planks of the first skin are laid, it will probably be necessary to do a little fairing with the plane in way of the solid wood members of the frame, particularly the longitudinals, to make sure that this first skin is quite smooth, with no high points. Now for the second skin—a thinner one, of 6 mm agba, which will be laid straight fore and aft. Each strake of the second skin is bonded to the first skin with resorcinol glue and fastened with silicon bronze staples. The third skin, also of 6 mm agba, is once again laid diagonally, but this time on the opposite diagonal to the first skin: top aft, bottom forward. It is glued in the same way as the second skin and fixed with staples. Now that the three layers have been built up, the completed skin is finally fastened through to the solid timber longitudinals with 12 gauge screws at 3" centres.