A fin can or metal fin attachment can be made in a day for about $25. This design is not likely to survive extreme flights. It should work fine for common flights into low supersonic speeds.
The fins are rough cut from 0.80 inch thick 6061 aluminum sheet. A general purpose table saw with a carbide tipped aluminum cutting saw blade works fine. I use an Oshlun Aluminum and Non Ferrous blade.
Rough cutting the fin
Next, all the fins are clamped together. The fins are ground on a belt sander until they are the same size. This step is identical to the old Estes method of sanding balsa fins. Sanding aluminum proceeds remarkably fast.
After the fins are equal, an airfoil can be ground using the same sander technique. The airfoil is optional. I just eyeball the angles. The results are accurate enough.
Grinding the shape
The fin attachment bracket is made from 3/8" x 3/4" rectangular aluminum.
A slot is cut in the rectangular aluminum using the aluminum cutting sawblade with a rip fence.
Next, holes for the pins are drilled. I'm using a 1/4" countersink drill bit. The head of the 6x32 screw fits in the hole. The smaller portion of the drill bit penetrates through the mounting bracket.
|The location of the fin attachment is masked and roughed-up with sand paper.|
JBWeld glue is applied. The glue is smoothed with a tongue depressor, wooden dowel, or metal rod.
At this step, the fins are attached to the mounting brackets to get accurate placement of everything.
|Another angle - Remove the tape when the JBWeld is half cured. The tape will not come lose if the glue has completely setup. The time to half cure is about 4 hours.|
The picture below shows the mounting brackets, pins, and internal speed nuts.
Obviously internal speed nuts will not work on a fin can. Instead, additional pins are used and the holes threaded. A threaded pin attachment is not as strong as an internal speed nut. It works fine, however.