Hi,
You are correct. The slot width will dictate CB Thickness up to a point.
If you go to the "Day Sailer Association" tab on the home page and then select "part 3" you can find the exact spec for the CB. There is no min/max thickness measurement for the Board. The oldest DS 1's have only a 7/8" slot, and some of the newest boats Have on that is nearly 2". There is a minimum 1 3/8" slot width that the newer boats can narrow their slots to. The older narrower slots can not be modified.
To your question. I would suggest making your CB as thick as your trunk will allow, up to about 1 1/2". The DS has a tendancy to stall the CB rather easily if the board is too narrow. A high point of 30% to 40% seems to work best. At the front of the racing fleets you will find narrow boards and thicker ones. If you sail in a high wind area thinner will work ok. But in light to medium stuff, the thicker the better.
Try doing a search of the NACA 0009 section. I found one site
www.desktopaero.com/appliedaero/airfoil ... metry.html that has a graphic where you can put in the NACA foil name and it will draw the section. Use
' 0 0 09 ' and you will see the section at 9% thickness to cord. Use ' 0 0 10 ' for 10% or '0 0 12' for 12% and so on until you have the foil you want. I did not try to print anything from this site, but it could be a good starting point.
phill