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It seems to me that connecting the outside edges of each blade together would create a stiffer structure with lower stresses and a better fatigue life for a given operating condition.

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    $\begingroup$ The reason is probably different, but joining the outside edges with a sort of ring will increase a lot the m. of i., and the turbine will be less responsive to changes... $\endgroup$ – xxavier Jan 4 '18 at 13:57
  • $\begingroup$ I'd imagine the consequences of a ring failure would be more serious, too. If one independent blade breaks, it (simplistically) just flies away. If the ring cracks, it could take a large chunk of blades with it, creating serious imbalance &c, $\endgroup$ – jamesqf Jan 5 '18 at 4:46
  • $\begingroup$ @xxavier Yeah that makes sense, I didn't think of that. Also, I don't think my question is a duplicate of the one posted. Mine is to do with the attachment points of the blades, not why the blades are loosely attached at the base. What is the proper way to challenge what I believe to be a false duplicate? $\endgroup$ – Jima Jan 5 '18 at 7:50
  • $\begingroup$ Well, this is actually a different question. Long turbine blades, which usually have a short chord, and so a long blade has a high aspect ratio, often are connected at the tips with a shroud. Typically this is done for the last few turbine stages, which are significantly longer than the early stages. And fan blades in early engines sometimes had a mid span shroud, which supported the blade, in much the same way. In both cases this is done for exactly the reasons you mention. $\endgroup$ – Penguin Jan 5 '18 at 11:37
  • $\begingroup$ @jamesqf: If the ring cracked, it would still be held on by all those blades connected to it. $\endgroup$ – Sean Aug 10 '19 at 2:36