This is not quite correct. Even while sailing downwind, the sails are still providing "lift" (if we are calling it that here). There are opposing forces for sa

This is not quite correct. Even while sailing downwind, the sails are still providing "lift" (if we are calling it that here). There are opposing forces for sailing - the Center of Effort (CE) and Center of Lateral Resistance (CLR). These two need to be balanced in order for the boat to sail a proper course - of course if you are just letting the wind push you directly downwind, you could remove your keel/daggerboard, but in practice, you will want to sail on an angle to the wind - on a reach or by the lee depending on the type of boat - so as to create flow over the sails and have a greater pressure gradient than if you just let the wind push directly against the sail. The hull of the sailboat contributes to the CLR, so it is common in dinghy racing to pull your centerboard/daggerboard up partially so as to balance these forces and minimize drag. If you watch Olympic laser sailing, you'll see while sailing downwind, they will heel the boats to windward with their daggerboards about halfway up so as to move the CE closer to being above the CLR, allowing for less rudder drag to counteract the forces and steer straight. Every time there's anything on HN or Reddit about sailing, there's a _ton_ of misinformation and blanket statements that might apply to some types of boats, but are far from general rules. I'm happy to answer any other questions too!