This is an offshoot of Don’s thread [i]Concave Deck? Pros and Cons…
[/i]In that Muzza lists a yacht with a concave hull plus what appears to be stays way down at the gooseneck.
Has anyone done this on their boat(s) as well? Does stiffness at this point offset windage?
Within the IOM rule, those short stays in the above photograph are called checkstays. The rule limits how high they are allowed.
If you don’t have a mast ram, the checkstay can add control to the bottom secion of the mast to resist the forward and twisting forces of the boom/vang.
I built my first boat in over 30 years; an IOM. In my ignorance, I built a flush deck and deck stepped mast. Without a ram or checkstay, the bottom of my mast flexes under the pressure of the boom, allowing the boom to lift a little. That in turn allows the upper leach of the main to twist off (uncontrolled). As a result, my boat loses power and is not competitive. My next boat will have a raised foredeck and skiff aftdeck to allow an effective mast ram.
I must admit to being inexperienced in IOM rules. I didn’t see it, but it may be there. Why attach the boom to the back of the mast at all? Have a gooseneck attached to deck behind the mast - so when running downwind, camber is induced in the sail as the boom swings out to the side. Kind of like a radial jib boom.
As I said - I’m not “into” IOM so perhaps this is illegal in their rules. The offset of the boom attachment in relation to the rear of the mast allows camber in main as boom moves to sideof boat since clew difference is less when running than when close hauled.
This would not be legal in the IOM rule as the goosneck is a mandatory fitting on the mast.
I use a ram on my IOM, but used this method on my old Victoria (deck stepped mast). I was using a very thin walled and light aluminum mast and the lower side-stays did the trick perfectly.