When an arch is to be built without mortar, the fit has to be perfect. Not an easy job for a group of amateurs.
We began by cutting the ply sheets into 400mm strips. We made a simple jig and cut the pieces in pairs, but then the pieces got shuffled. A trial assembly this moring showed a very poor fit so we had to try again.
I made a new jig about 2mm smaller than the original. I spent some effort setting up the saw and we screwed the pieces together in pairs, then recut all eleven pieces on both mating edges.
To allow for any slight misalignment of the saw (it is VERY difficult to get the blade set vertical) we alternated the direction of the pairs. Carefully lining up the pieces produced a much more encouraging result and gave our first clear impression of the size of the finished job.
That took all morning, but at the end we had an arch that fitted.
Tomorrow I will need to re assemble it and set out the end angles for the abutments. I guess it will take an hour or so to get that to the state where I can relax and actually cut it.
From there on the job should be much easier, but watch this space. The Chaplains would like to use the unfinished bridge on Monday at a freshers induction then finish it and finally use it for the service on 9th October. I hope to get a video of the final assembly. whether it can be displayed here is another matter.