I am not sure I would feel comfortable to implement free-turning front fins. I do not want to take the risk to turn a model that is stable in theory to a fast moving pointy object that is unstable in practice
I also do not have access to a machine shop and live in an appartment that is already over crowded. The kitchen is also the painting/sewing/gaming/model building workshop
I will restrict my builds to carboard and balsa for some time since my launch field is a small park.
Umm... you don't have to make these parts out of METAL... in fact, it's basically against the safety code to do so (no "substantial" metal parts, which granted is a bit open to interpretation.
If I were building a rocket with pivoting fins, I'd use a pen tube or other plastic tube going through the body tube as a pivot 'bearing', and a SMOOTH hardwood dowel for the "axle" upon which the fins pivot. Cut and glue the pen tube through the body tube so that basically it JUST protrudes a bit on either side. Fit the wood dowel so that it doesn't bind in the tube, but isn't floppy either. It should rotate smoothly and evenly. The dowel should be long enough to stick out about between 1-2 inches or so for the forward fins to be glued onto it, on either side. Cut the forward fins to the desired shape, and then cut notches into the root edge toward the center of the fin for the dowel pivot rod. These notches, ideally, should be as FAR FORWARD on the fin as possible, while still maintaining sufficient structural strength to hold the fin together... IOW, maybe the 1/4 chord line of the forward fin, IOW, about 1/4 of the way from the root edge front tip towards the back tip. If one is concerned about possible "binding", add a plastic washer (available at practically any hardware store) to the axle before gluing the fins onto the dowel pivot axle, to create a small gap between the fin roots and the body tube. Just make sure no glue gets into the tube and dowel, locking the dowel axle in place inside the tube.
It's not like these things have to be on ball bearings or bronze bushings or whatever... it's not THAT critical... the fins aren't going to move much at all in flight, actually. It's just that they have to be FREE to move; IOW, if there's an aerodynamic force that starts acting on the forward fin, they have to be ABLE to swing a little to negate or damp that force out, rather than transferring it into the body tube, which would affect the stability of the rocket.
That's really all there is to it...
If in doubt, experiment a little... read up on the technique, see what works and what doesn't, build some "test rockets" (make a Big Bertha "Wasserfall" or something with forward fins, something big and slow and with a blunt nosecone) and test your methods, and then when you're comfortable with it, build your bigger/faster/heavier/pointier version of whatever interests you...
Good luck! OL JR
