Weston
Well-Known Member
On this forum, I've read other Sunfish owners talk about the new composite daggerboards and rudders having more 'lift' than the old style foils and can help a fish point better upwind.
I know that sails have lift, just as an airplane wing does, which allows the sailboat to sail upwind. But in my simplistic way, I have only thought of the daggerboard as a stiff board that keeps the boat from sliding. And the only important thing in my mind about the shape of the daggerboard was to reduce its drag by rounding the leading and trailing edge a bit. I never thought of lift. So what is this 'foil lift' that others are speaking of?...
After some research, I found a great Youtube video on the subject by Julian Howarth. Here is a link to the part explaining what foil lift is and how it contributes to the speed and upwind sailing ability of the boat. If I've got it right, under water, the daggerboard and rudder generate 'lift' and can even 'stall' just as the sail can. Due to the greater density of water, even though the daggerboard and rudder are much smaller than the sail, the lift and drag they create is comparable to that created by sail, thus canceling most of the sideways slippage caused by the sail's lift, allowing the boat forward.
Armed with this info, I'm a bit better prepared to try to understand what Kent Misegades is saying on his AeroSouth website regarding a new rudder he has designed that provides greater lift with less drag. Maybe if I save up my pennies, I'll try out one of his new rudders to see what difference it makes.
I would love to hear others' thoughts on foil lift and its impact on boat behavior in various conditions.
I know that sails have lift, just as an airplane wing does, which allows the sailboat to sail upwind. But in my simplistic way, I have only thought of the daggerboard as a stiff board that keeps the boat from sliding. And the only important thing in my mind about the shape of the daggerboard was to reduce its drag by rounding the leading and trailing edge a bit. I never thought of lift. So what is this 'foil lift' that others are speaking of?...
After some research, I found a great Youtube video on the subject by Julian Howarth. Here is a link to the part explaining what foil lift is and how it contributes to the speed and upwind sailing ability of the boat. If I've got it right, under water, the daggerboard and rudder generate 'lift' and can even 'stall' just as the sail can. Due to the greater density of water, even though the daggerboard and rudder are much smaller than the sail, the lift and drag they create is comparable to that created by sail, thus canceling most of the sideways slippage caused by the sail's lift, allowing the boat forward.
Armed with this info, I'm a bit better prepared to try to understand what Kent Misegades is saying on his AeroSouth website regarding a new rudder he has designed that provides greater lift with less drag. Maybe if I save up my pennies, I'll try out one of his new rudders to see what difference it makes.
I would love to hear others' thoughts on foil lift and its impact on boat behavior in various conditions.