So then lets start. The basis of creating the shape of the hull is a set of formers at 0.5m, which create a crude female mould. By lining the formers with stringers, the foam core can be laid into and secured. We used CNC cut formers. Do ring around and get quotes as we eventually found a local company who cut the formers for not a lot more than what the 10 8ft x 4 ft sheets that are needed, would have cost.
Remember that sometimes to pay a little more, you can save several days of labour. Accuracy is also paramount and any slight discrepancy will manifest itself in not fair panels and the resulting need to spend time sanding and flattening the panels ready for the final finish. The fairer you can get these panels the easiest it will become. Even 0.5mm at this stage will show as a greater error later.
So then create a hardback which is perfectly level and even, we used 4” x 2” timber we had laying about and shimmed them up level by using “ packing” shims used in the kitchen fitting game. You can buy a big bag of these on the Auction sites for just a few pounds. You can use any timber though, as even if its not dead level, once you have fitted the formers, its quite obvious by looking along the formers that one or two may not be level and the edges need a small shim to adjust.
Once fitted and “ leveled “ as best as you can, fit the stringers. We used 19mm roof tiling battens as the CNC formers have been cut minus 18mm just for this purpose. 1mm being the outer skin which is layed up once the two halves have been fabricated and joined.
Do use screws which have a cutting edge as part of the screw thread, they are just a few pounds more per 1000 but this will stop the battens splitting and the formers being damaged. We used 3.5mm x 40mm. I can’t stress more to use a cutting screw as from experience we did exactly that, split the former.