zoneboy...don't we all have some of those regrets!The calculations on that page are really not that hard - the whole thing is just figuring out how thick it is at any particular percentage of the chord (front-to-back width) of the rudder...meaning, at 1" back from the nose it should be XX thick, at 2" back from the nose it should be YY thick, at 3" back from the nose it is ZZ thick, etc. The "12" indicates that the thickest point is 12/100ths or 12% of the width (chord) of the airfoil - this is where the dimensions you'll get from the Idasailor site come in handy
as the thickness is related to those dims... The formula is actually pretty straightforward, and there are a few places on the internet that supposedly offer a program or spreadsheet to calculate this for you... If you find one***, you could put in the dimensions you need (chord length, NACA design, etc.) and it will plot what that should look like on a piece of paper for you. You could cut that shape out of a piece of plywood or a 2x4 (make a hole shaped like the airfoil), split it nose-to-tail, and use it as a clamshell template for your rudder woodworking (slide it up and down the rudder to find the high spots and such). That and a straight edge to lay along the whole length of the rudder so you keep it straight from top to bottom... Someone with good woodworking skills/experience might be able to offer significantly better options...but I've done this in the past for other contoured items that I wanted to make out of wood. Where's Ken...I hear he has the knack for woodworking... KEN???
If you have a routing table and can figure how to make pass after pass that shapes the board according to a template you have (or make), that's awesome, but just to shape a piece of wood for what you're talking about? I would say you could get away with using a belt sander to do most of the work if you only have hand tools like that...that's all I have, and I have to make-do most of the time, so I get pretty creative...saw cut the big triangles off, then belt sander to shape. But again, I'll defer to the real wood-workers on the site...
One piece of wood and coat it - sure it would work. Can't say it would live forever, but that's not your goal right now...and it might even look pretty since you'll be sanding across grains and such... But I wouldn't use the lightest wood possible (like pine) as you'll have trouble with it popping up (floating) behind the boat - you want something that will be pretty heavy when you're finished so it stays down even when the downhaul is loose (if yours is equipped with a downhaul, that is). Maybe pressure-treated? I don't know the right answer to this one...someone else can help here too... KEN!!!????
***I looked for a good program...not many that are up-to-date, but found one that gave me a NACA 0012 set of dimensions I'll happily share. PM me.
New wheels, got to replace the bunks, and god knows what else lol. And to do all of this, I am going to need to build a stable cradle which I haven't gotten around to yet. I figure in about a year or two, I will see the bay lol. Perhaps in the mean time, I may just buy a little sunfish to play around in