For interest only, I'm doing some research on the benefits and construction of rotating masts and wing masts. I am looking for information on what this means to a cruising sailboat. I got some anecdotal evidence from an experienced sailor friend who had built one for his 27 foot catamaran. He believes it increased his performance by up to 30%. That is until his home made mast came down, fortunately it was insured but the insurance only covered a standard mast so there is no longer an opportunity for testing.
It seems pretty logical to me that in a storm a wing mast can be beneficial, if designed to be the correct size, in that it'll be the substitute for a storm sail. The question I have here is how practical is this in reality? i.e. how much will the mast be allowed to rotate and how to safely handle this in a storm.
Recommended reading, the cruising multihull has some information on constructing a mast and Gougeon Brothers on Boat Construction:
Practical hand construction techniques and ideas for making such a mast in carbon fiber, wood or retrofitting a second hand aluminum mast.