... That rivet has made the pole weak in at that point. ...
Really guys, that is non-sense.
I hardly never refer to my myself as a fully schooled mechanical engineer, but I am. And that rivet and hole did not make weaken the pole by any significant amount. That pole is under normal sailing circumstances under compression, ..............BLA BLA BLA........
What an absolute crock!!! In general Wouter, I believe you speak a lot of sense but this is not one of those occasions.
In contrast to you I'm not a certified mechanical engineer but I've been involved in mechanical engineering manufacture for most of my 65 years on the planet and I can state with absolute certainty that the most significant load on the pole is a bending moment. There is a compression loading but this in itself is not significant, but because the pole is not 'in column' while under that load there is a significant bending moment being applied. This is a result of the compression load and the pole being lifted at the middle while the outer end is being pulled/held down causing it to bend and the point at which the bend changes direction, the point of maximum load, is at that saddle. As a result the, while the lower wall of the tube is being compressed, the top is in tension (being stretched) and under these circumstances the rivet hole has a significant effect as it reduces the area of tube wall at that critical point significantly making it considerably weaker.
While I may not be able to back it up with calcs, it's not rocket science, just simple logic. The pole is in essence a simple lever, loaded at the outer end, effort at the saddle, fulcrum at the beam.
Bern
