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20231RE: Alluminium mast wall thickness

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  • dougpol1
    Mar 5, 2014
        On Wolftrap 30ft long cat ketch rig I put a 36 ft mast 5 inches in diameter 1/8 inch thick  The bottom 3 foot was buried therough the dack and was 1/4 inch thick and welded together.  This gave me 36 ft above the deck. She carried a perpendicular top yard  2 1/2 inches in diameter and was set another 10 feet higher.  The mast carried a main of 500 square feet. The mast was unstayed. In addition she could carry a 300 square foot flat spinnaker.
      The boat had a full length hollow keel about 12 inches deep with a large centerboard. She was not as stiff as a keel boat I guess.  This might give you some idea about just how strong a 1/8 wall 5inch round aluminum tube is.   I have always woundered if an unstayed aluminum mast might be stronger than a stayed one that does not have lower shrouds.  The lower shrouds keep the mast from and kinking under the compression load of upper shrouds.   I don't know but it may be worth thinking about.  There is no compression load to kink and break an unstayed mast.   Doug
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