The easiest way using the Dalton I can see, without getting unduly complex, would go like this:
1. Put windface centre grommet on any convenient round number on the TAS centreline scale, eg 100 kt. Plot the boat's course and speed as a wind cross, eg if the boat's true course is 270 and it's doing 20 kt, you'll plot a cross at 270/20 from the centre point.
2. Say wind is 180 at 30 kt, rotate the ring until 180's at the top, and, starting from the first cross you made, go straight down 30 kts worth of distance (using the original 20 kts worth of wind as a distance reference). Make another cross where you end up.
3. Rotate the ring again until the second cross is at the top and read off the wind (I get about 325 at 35 kt, give or take).
This is just like adding the vectors on a bit of paper, but a bit easier because you can do it on the computer face. The downside is that it's only as accurate as your distance estimate for plotting the second cross, but it should be pretty bloody close.
Now you know the sum of the real wind plus wind due to boat movement, you can easily work out how it will affect the deck using the clock code:
eg, in this example, boat nose pointing 270-ish, sum of the 'winds' 325, that's about 60 degrees off the nose, so I would apply all the wind as crosswind and 1/2 of it as headwind, call it a 17 kt headwind and 35 kt crosswind from the right, assuming I'm approaching up the centreline of the boat from astern.
If you're coming from another direction, just work it out the same way, or if you just wanted it in naval terms, you wouldn't bother with the clock code and say the wind is green 055 at 35 or whatever they say.
Last edited by Arm out the window; 16th September 2012 at 09:00.