The plans show the base as an open topped frame, but I put a top on it. It would recommend others do this too, as it provides a great surface to set up all the frames and girder ready for the glueing of doublers. The girder needs very careful setting up to ensure the fwd and aft sections are correctly lined up. I screwed it to the baseboard, then cut and positioned all the internal framing. The lower frames are bent so I screwed several tapered blocks into the board to hold the curves.
All glued up now. Next stage will be to seal this lot before fitting the other side skin of the girder.
One evenings work to cut the tabs with a Stanley knife and a quick sand of the edges and we're ready for the next step