Thank you, James, Craig, and Ian for your thoughts.
James, nice to know that the Emek was only twice that of the Atlantic, I thught it was much more. Also important to know that the wobbliness is an issue for both the Atlantic and the Emek arches that needs to be corrected by extra cables or struts
James and Craig,
after several e-mails with the engineer of Atlantic discussing the direction of the pre-tension leg-in or leg-out, I concluded that the leg-out pretention should result in a stiffer and stronger structure than the leg-in pre-tension. This is both due to geometrical and structural considerations, too long to include here but that I would be happy to discuss offline.
So, at some extra cost, I have asked Atlantic to add lateral stiffness to the structure by reinforcing to the forward arch in the same way that they do for the aft arch. That may not still be good enough and I may have to add a strut or cables to the structure. It is not that I plan to carry my dingy on long passages but that I want to make the structure as strong as possible in case we are exposed to bad conditions.
Ipanema SM2K 278