The first ones used glass fibre tape and resin to reinforce the joints, following the method developed by Dick Ganderton. In this one I have used 2" (50mm") bandage and PVA glue to perform the same task - a lot cheaper and a lot easier to apply.
The adhesive used is readily available in the UK as Unibond PVA, which is a PVA adhesive supplied in tins for painting onto surfaces.
The original design of board was intended to be used as a flat top, which can be a bit of a restriction when planning scenery. These boards are intended to be used "upside down" and a mockup of a trackbase is shown with risers clamped to the baseboard frame members.
This is also the reason for cutting out all the extraneous plywood sheeting on what is now the underside so that access to the underside of the trackbase can be gained after the layout has scenery added.
The material is cheap 6mm plywood, and the structural strips are 3" (75mm) wide. Construction is very quick, and no great accuracy in joint making is required. The only items requiring some care are the end boards which should be square so that boards will mate well.
Initially, the components are tacked in place using short welds of glue from a hot glue gun. Once the assembly is complete, the additional reinforcing glue is applied.
But on this board, I've decided to experiment with another type of reinforcing glue available in DIY stores in the UK, and called "No More Nails" (possibly the same glue as "Liquid Nails" in the US). This is applied as a bead and can be seen on most of the joints in the picture. I'll know in 24 hours if it has been successful :-)
The reservations I have about this glue is that it does not spread the load at the joint across a large surface area, whereas the methods using tape and adhesive do. The surface of cheap plywood is not all that strong, and the smaller area covered by the bead of this glue may not be sufficient to give strength necessary.
Both boards are 4ft x 2ft (1216mm x 608mm) - the left hand board weighs about 6lbs (2.5kg) and the right hand one, 10lbs. (4.5kg)
The left hand board is very rigid and requires considerable force to produce the slightest deflection or twist. I'll test the right hand board once the "No More Nails" has been given 24 hours to set properly.