The Spar Strap it a device used to help the spars from springing when the wings are under load. It has to be made around the spars to get a good fit and to allow for some bending under load. Ply’s of clothe are places on the spar and the other spar is put in place and some more cloth is added to tie the spars together. After cure the Spars are pushed apart with a scissor jack. The release tape is removed and the Spar bracket id tidied up. I then refit the spars together to check everything is well.
