Select to expand quote
JakeNN said..wongaga said..
I love my nice semi-full keel 55% ballast ratio, 14 SA/D old man boat!
Cheers, Graeme
Just keen to learn here ... What is a semi-full keep 55% ballast ratio, 24 SA/D?
Does it get planing? Wouldn't it be nice to get planing, switch on the auto-pilot and enjoy the ride with a beer?
Hi Jake,
The ballast ratio is a percentage of the ballast compared to the dry weight. The higher the number, the more ballast is carried compared to the overall weight, which means more resistance to heel. Graeme's 55% compared to my 36% means as the weather gets a bit fresh Graeme is enjoying a nice cup of tea with full sails up as I am scrambling to downsize sail area to keep the boat on her feet.
The SA/D is a comparison of your total sail area to your displacement. Upwind I run a SA/D of 34'ish, downwind it jumps to about 65. Graeme's SA/D of 14 means as the weather gets fresh he is now enjoying a nice nap after his cup of tea, still with full sails up, as I am hanging on grimly as the boat charges off like it's been possessed

. We start planing at about 15kn TWS and as the wind comes behind about 80 deg TWA.
To answer your question, yes its the best feeling in the world to sit back when the boat is trimmed, on the plane and it' s effortlessly soaking up miles. For Fusion, the lower ballast ratio is offset by a wider beam which lends a lot of hull form resistance to heeling, so gusts tend to be soaked up by the hull shape rather than put you over on your ear. That sort of thing isn't reflected in your SA/D or Ballast ratio, which is why there is a bazillion other calcs naval architects use to typify a boats manners.
So while a higher SA/D is enormously rewarding, you can't be lazy. Speed is fun, but if the comfort level goes way down to achieve this it gets a bit naff pretty quickly.
To apply this to the real world... Graeme and I are headed for same harbour and its been a bit fresh. Graeme may get their a tad later but he'll be dry, comfy, sporting a big smile and a hairstyle like he stepped out of Vogue magazine. I might get there a bit quicker, but I'll be soaked, tired, counting bruises, sporting a HUGE smile and a hairstyle like I stepped out of Just Mechanics.
Cheers!
SB