Aside from the glue spill (on carpet... oops), my skirt's coming along great for a first attempt. Might even be serviceable! We'll see tomorrow, when I cut open the deck and glue on the tunnel.
I'm working on it from Bob Putnam's directions over at wwslalom.org. What I noticed when I sat down to think about it prior to starting construction was that he doesn't explain how to make the "mandrel He also used aluminum sheeting - I went the cheaper route and used some heavy art paper of some sort that's been in my room for ages. Worked surprisingly well, at that; cones are pretty sturdy structures, apparently.
As to how I made it... I decided to do some websearching on how to construct cones in general, and found out the term for what you need: a truncated cone (since a true cone comes to a point). And I found the following site, which explained the geometry, that I'd forgotten, which allowed me to figure out exactly how to get the arcs right on a flat surface to make a cone.
http://jwilson.coe.uga.edu/emt725/CarlC ... lCone.html
Long story short: I taped the paper to the floor, found the center of one side, taped a string perpendicular to that side (86" away), and swung an arc in either direction. This was repeated at 69" (to make a 14-15" tunnel, with a couple inches overlap with the deck). The paper was cut at those lines, then measured along the new edges to find where to draw straight lines between the two arcs (shorter arc, 13" to either side of center; larger arc, 16" to either side of center), then cut along these lines (well, one of them; to allow overlap when rolled up and taped together, just made it easier).
This'll probably go into the FAQ, soon as Adam and I sort out what's happening with it, but I figured I'd post it here and get some feedback. How else are you supposed to make a cone? Easiest way, according to one site (http://www.ex.ac.uk/cimt/res2/calcs/calcone.htm), is "by cutting a sector out of a circle and then folding it around so that the two cut edges meet." So I figured the easiest way to make a truncated cone was by cutting a truncated sector out of a circle; and since that circle is gonna be awfully large (that 86" referenced above is the radius), you just have to do some maths to figure out all the measurements so you only have to actually represent the circle on a small portion of itself.
My name is Brett, and I'm a math freak. But hey, the math lets me make things for paddling, so it can't be all bad, can it?
Homemade skirt
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Well see, my initial intuition would've led me to just take a rectangular sheet and bend it into a cone. Probably would have figured it all out after trial and error, but I actually enjoyed the geometry; ironic because I hated the class when I took it. What I'll probably do for the FAQ is just link to the page that ultimately helped me; it's simple geometry, but it's been ages since I did any at all, and I had to look it up. Though that's assuming I update that page before I forget.
Alternatively, I could've just asked one of my engineering-inclined friends. But that would've made too much sense! (And I didn't think of it...)
Alternatively, I could've just asked one of my engineering-inclined friends. But that would've made too much sense! (And I didn't think of it...)