Thanks for all the input so far. I'm definitely going to experiment with this.
One comment that struck me was the need for a bound log so that pages could not be added. I can see how one would think that would make it more attractive as a legal document (and indeed it might) but on the other hand medical charts can easily have papers added and removed from them and they end up in court all the time. I've never heard of this being questioned before. I'll have to think about that aspect as having them bound would add some cost to an otherwise simple project.....
Faster, your log is partly what I had in mind. Some data is not amenable to graphs and pictures and for that data I would use fill in the blanks, but most of it I'd like to plot on the graphs. The graph makes referencing it in the future faster and quicker to enter more data while sailing.
What I really had in mind though is recording more of the data like the anesthesia record. On Faster's log there is a line for wind and speed. Imagine having an X and Y axis where you could put dots and arrows like the anesthesia record. Dots for boat speed, arrows for wind speed both plotted at 15/30/60min intervals over an X-axis of time. Notice on the record at 8:45 that the arrows start to dip down AND the dots start to rise? The arrows are systolic and diastolic BP and the dots are pulse. Being able to see that trend means the anesthesiologist knows that the patient is leaking too much and needs some fluids added (low BP and high pulse = less blood volume).
Imagine if you could see wind speed increasing on your graph, along with boat speed, followed by more increased wind speed and a DECREASE in boat speed. You might then free-hand on the graph that a reef was put in and you would see the wind speed stay the same but the boat speed increase 15min after the reef. You would have just demonstrated for yourself that reefing at THAT particular wind speed on YOUR boat caused you to gain speed. Might be useful info....
You can also have several different points of data on the Y axis with time on the X like the record above. At the bottom he has drawings for patient positioning for example and above the vitals he has things like how many liters of oxygen he is giving and a spot to put what drugs were given. This way as he changes the oxygen level he can see a trend in vitals. A drug (atropine) might be given (and notated on the graph at the correct time above) and you see a corresponding pulse increase.
You could have lots of fun info on the Y axis like "sailing angle to the wind", engine RPM for when you're motoring, barometer readings. Having it all on the SAME X-axis will reveal a lot about your trip I think. I'll try another example:
You're sailing along hard on the wind in very light air with main and jib but no mizzen (why I don't know, but you are. Maybe you're new to ketches...). You note boat speed and wind speed over time. You notate at the top left (in one of the blank spots)"mizzen hoisted" and on that line you put an "X" at 8:45. Now the wind arrows are staying the same over time but boat speed dots are increasing. You just learned that the mizzen helps you to weather. "strange I thought sloops were better to weather"
Above wind and boat speed you're writing in every 15min your angle to the wind 35deg, 35deg, 38deg. You think that maybe you're pinching (it is a ketch after all) and try 45deg. Since it's light air it takes a while to see the trend but after a couple more data points you see that your speed has increased at 45deg. You WERE pinching. Got a GPS? Plot VMG also.
Finally you get tired of going slow and fire up the engine but keep the rpm low to be fuel efficient. Rpms are noted at the top on the same graph and you continue to plot boat speed. You know that in 8kts of wind, at 45deg off the wind, you can achieve the same boat speed as motoring at 1500rpm (lets say 4 knots).
In the future when you're motoring on a windless day you see cats paws and note that the wind is now 8knots coming from the direction of your destination. From your prior experiment you can make an informed decision as to when to cut the engine and hoist the sails knowing that on your boat, with 8kts of wind you can expect to be able to sail at 4knots, 45deg off the wind.
I also think an outline of your hull with dots for masts drawn without booms would be helpful. Simmilar to the outline of the person on the triage card where you would draw on the wounds. On the boat outline you would be drawing a visual of anything different you did. You could quickly sketch 2 lines for how far out you have your two booms and draw camber in the sails for how much outhaul you have. If you do something goofy like rig a barberhauler you could quickly sketch it.
I would also have 2 pictures of engine gauges with a fill in blank for engine hours next to each. Draw a line on the gauge picture where the gauge needle is at the beginning of the day (and note hours) and draw a line where the gauge reads at the end of the day (and note the hours). Having the line drawn on the gauge with hours next to is will allow you to go back and see that needle really starts to plummet (for the same number of hours) on the bottom half of the tank. Good to know, since you have a "V" shaped tank that there are 30hrs at cruise between 1/2 and "F" but only 10hrs between 1/2 and "E".
Is this making sense? I know, a picture really would have helped the above description....