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monet · 27-12-2011, 12:48

I am in the process of replacing my wooden mast with an aluminum one, my concern is my spreader location an upper shroud. I have planned on putting the rigging in the exact location as was on my wooden mast. I have been told by an engineer that the upper can go to the top. his suggestion was not to lower it. Have set the spreaders where the were, which is a little under half way up the mast as to to use the same rigging configuration. any thoughts.

psk125 · 31-12-2011, 15:38

The wooden mast was stayed the way it was because of the strength, weight, and bending characteristics of wood. Though no engineer, I would think that attaching the same fittings in the same positions on an aluminum mast would be overkill -- though it depends upon the extrusion, the size of the boat and the length of the mast. There are really skinny, thin-walled aluminum masts that need more support than thick-walled wooden ones. Each mast is a bit different, so calling in an engineer might be worthwhile. You don't want to set up stress points (in the case of the spreaders, a compression point) by attaching fittings in the wrong places. It might cause the new mast to fail prematurely. It's also important that the shrouds and stays be angled properly relative to the chainplates and tangs. (A reason why you should keep things in the same spots...) If the new shroud goes right to the top of the mast, instead of half way up, and the chainplate has been built into the hull at the right angle - both fore & aft AND athwartship - for the old mast, the new shroud would tend to crack it off with the loading and unloading of the shroud. What kind and size boat are we talking about? What you can get away with on a 20' Hobie might not work so well on a 50' ketch.