Included here is a collection of printable model rocket fin cans. The actual types included here as .stl files are only a sample. A large variety of fin configurations may be generated by changing parameters in the OpenSCAD file (see note below).

The basic fin shape is fixed - a trapezoidal planform with spanwise taper and tapered leading and trailing edges. Fully filleted.

The options you have for altering it are to change the fin span and root chord. You can also choose to include a filleted 1/8" launch lug in a fin root. You also have the choice of any number of fins, though 3 through about 12 is the practical range (though it also allows 1 and 2).

The basic fin can is intended for a 24mm body tube, which also has a single fin span of about 40mm and a fin root chord of 100mm. You can shrink or enlarge the span by a scale factor, and likewise shorten or lengthen the root chord (and the overall can length) with another independent scale factor. Practical values of scaling are from about 0.5 to 2.0. Note that the fin thickness does not scale.

There is also the option to scale all of it, up from a 24mm tube to a 29mm tube. One of the fin cans in the included photos is a 29mm upscale that fits very well. A scale factor is included for a 38mm tube, but you're on your own, I haven't tried it. Note that the launch lug, if used, scales by the same factor, so the 1/8" @ 24mm lug will be 1/8 x 29/24 on the 29mm tube - probably not practical.

I've included a bunch of cans as an example of how the scaling can be done. My file naming convention is like this:
FC = Fin Can
T = Trapezoidal
24 = 24mm
-3 = 3 Fins (-4 Fins, -6 Fins)
xS1.0 = Fin Span Scale = 1.0
xR1.0 = Fin Root Scale = 1.0
LL = Launch Lug exists

Example: FCT24-3xS0.75xR1.5LL would be a fin can with trapezoidal fins, for a 24mm body, with 3 fins, the span is scaled 0.75 (so 30mm) and the root is scaled 1.5 (so 150mm), and it has a launch lug.

UPDATE 9/14/18: Upon request, I've uploaded a greater variety of pre-made .stl files. These include 24mm cans without the launch lug, and some more 29 mm cans. I'll probably add in a few 38 mm as well. Additionally, I've run everything through Netfabb and I'm sure that cleaned stuff up a lot. Also, if there's a particular fin configuration or tube size that you want, and you're not comfortable working with OpenSCAD, just message me and I'll be glad to work it up for you.

UPDATE 9/15/18: I have just discovered the OpenSCAD Customizer (not the Thingiverse Customizer, see below). This allows the use of Windows-style controls to set parameters of the Fin Can. See the included section below on using the Customizer.

(Note. Yes, this would be a potential application for the Thingiverse 'Customizer', but I refuse to use it, as it invariably leads to a profusion of "My Customized Fin Can" Things that muck up Thingiverse worse than it is. Install OpenSCAD, and edit the parameters yourself; it's easy to install and a worthwhile skill. (www.openscad.org)

See my other rocketry Customizer Things at
http://www.thingiverse.com/thing:3133682
https://www.thingiverse.com/thing:3145280
https://www.thingiverse.com/thing:3104666