but it can't accelerate, not indefinitely - otherwise it would either hit light speed or be travelling in circles. if speed and direction are constant then forces must be in equilibrium and there is, by definition, no acceleration.Because an I-14 has a net movement to leeward. That means that it is being accellerated to leeward, and thus the force vector to leeward must EXCEED the force vector to weatherThanks for clarifying Mark
OK - I see where you are going with this. There actually are THREE effects here that you are conflating. The board will see the normal AoA initially and that will change as it lifts out of the water because when angled the AoA changes. But that's not really the issue here.
The way to think about this is with a notion engineer's call a "Force Couple" - which is a fancy way of describing two forces acting in opposite directions at the opposite ends of a seesaw (ie with a pivot in the middle). In the case of a sail and a daggerboard you have
- A force acting at the Center of Effort (CE) of the sail pushing the sail directly to leeward.
- A force acting at the Center of Lateral Resistance (CLR) in a direction that in the vertical domain (as opposed to fore-aft) is a vector opposite of the leeforce - and with the blade down, this acts from below the waterline
- The "righting force" generated by your weight on the trapeze.
#1 and #2 create a Force Couple http://en.wikipedia....uple_(mechanics) that rotates around the hull (slightly below the waterline). this Force Couple rotates the boat mast to leeward and the blade upwards. This is Effect #1
Effect #2 is the "righting force" - which is a second force couple that is the force of gravity acting on the Center of Mass of the trapezed crew being off centerline of the bouyancy of the hull. This Force Couple rotatates the boat Mast To weather and the blade upwards to leeward.
When Effect #1 and Effect #2 balance each other, you have a ZERO effective set of rotational forces acting on the sails and the blades.
In this balance of couples you still have the difference in the MAGNITUDE of the vectors of #1 and #2. on a Moth, it turns out that when heeled to weather, #2 is GREATER than #1 and the Moth climbs to weather. In an I14, the balance is close at speed but #1 is still slightly greater than #2 - so the boat makes leeway.
sorry. i don't get this. how can, what shall henceforth be referred to as forces no 1 and 2, be anything but equal and opposite? (the couple being counteracted by no3)
And it does.if a moth had a net force to windward, would it not accelerate in that direction proportionally to the net magnitude/mass.
similarly a standard i14 with it's force to leeward would accelerate to leeward, presumably until relativistic effects limited it at the speed of light?
I'll see about drawing a picture with labels - which should help.
And Moths are NOT "apples and oranges" - the fact that moths can generate enough lift force to weather to accelerate to weather does not mean that I-14s boards are not generating lift to weather. It just means that the net balance of forces is different, but the forces involved are the same (if you exclude the vertical elevation lift forces).
maybe i'm being dim again