I like inventor but for my ski design I used autocad. Heres how I drew mine.
1.)First off I drew out a construction line the length of my ski (I work in millimeters)
2.) From there I find the center point of the ski (I built mine for mounting true center) and I draw a line parallel to the construction line that is the length of the ski. The length of this line will be the waist width of the ski. If you're ski will be mounted up so many centimeters back from true center, I move this line back that number of centimeters so the waist is right underfoot. Place this line by clicking on it, and clicking on the center grip, and moving it to the center of of the construction line (you will need midpoint snap to be on for this to work)
3.) Determine the tip and tail widths and do the same as step two where you place them on your center line but move them back from each end about 5 centimeters. If your skis aren't perfectly symmetrical, keep track of which one is the front and which one is the back.
4,) Draw out your tip and tail, you can move the line in step 3 back and forth some if you need to, my tip and tail are not perfect circles, they are 3 point curves that I have experimented with to make them my own nice tip shape, however you can just use a circle and then use the trim command to remove the other half.
5.) Use the Arc command and you will want to use the three point curve. Make sure your endpoint snaps are on and start at the tip, click on the end of the line, go to the waist click the line endpoint, and then go to the tail and click the line endpoint. Do the same for the other side and you should have a ski.
If you have never worked in cad before then this will be very confusing, but for making refined ski shaps I prefer cad over inventor because inventor has constraints and all lines and whatnot are dependent on each other. When drawing shapes in autocad, lines and arcs aren't constrained to eachother, so its much easier to finesse your shape.
Heres a picture of my skis (still haven't built the real deals yet) with some labels to clarify things. Its abit confusing but if you know how to use cad, then you will understand. If you need me to I can draw your ski profiles out for you on cad, then just email you the file.
secret fucking SNOWBALL mission...