How to make (or where to buy) spring loaded fins for a model rocket?

Firing an RPG-7 The RPG operator or an artillary assistant takes a propelling charge (booster, in image below) and screws it onto the end of a warhead. Basically, this is a stabilizing pipe that has four stabilizing fins that are folded around it with two additional fins at its rear end. A cardboard container encases the back end of the stabilizing pipe. Inside the cardboard container, a squib of nitroglycerin powder is wrapped around the stabilizing pipe and a primer or charge of gunpowder is stuffed into the end of the stabilizing pipe. The RPG operator or artillary person then takes this assembled artillery and loads it into the front end of the RPG launcher so that it lines up with the trigger mechanism. After the RPG operator pulls the trigger, this is what happens: •A percussion cap ignites the primer, gases build up inside the launcher’s chamber, thereby breaking apart the cardboard container and propelling the grenade forward through the barrel of the launcher. In this way, the cardboard container is a lot like the casing containing the gunpowder on a bullet. •The force of the built-up gases throws the grenade out of the tube at approximately 384 feet per second (117 meters per second). The abrupt acceleration of the grenade leaving the launcher triggers a piezoelectric fuze that ignites the primer (pyro-retarding gunpowder mixture). This then ignites the squib of nitro, thereby activating the rocket propulsion system (sustainer motor) to carry the grenade the rest of its trajectory. •As the grenade leaves the launcher, the fins along the stabilizing pipe spread out, which, along with the rocket motor, allow the grenade to travel a long distance at a potential speed of about 965 feet per second (294 meters per second). The grenade moves like a football, rotating through the air; the fins stabilize its flight.

do a google image search for the MLRS munitions. they have springloaded fins, and dont take up much room. i you make a  fin out of soda bottle or a similar flexible plastic, it defeats the point of having fins. they need to be rigid.

You can buy a Hydrogen Fuel Rocket that turns water into hydrogen from your model air craft shop . This rocket has fins that are folded . They are NOT spring loaded . The fins are not used for stability . The Fins are used as a Giro Copter instead of parachutes for Landing safely . Do not cost much and more powerful than puchased rocket motors .

Fins cut from very thin plastic tubing, about the same as the od of the airframe, will fit tightly against the airframe and can be spring-loaded to pop out for stability. See http://www.aeroconsystems.com/rockets/flippitwin.htm

Prfesser

Fins cut from soda bottles (PET) are flexible enough to fold flat and spring back when released.

why not just use flexiable fins that will pop out whenever the rocket leaves the tube? they would just pop out and would be more relaible then spring loaded ones!!!

I agree, but do you really need fins? You can't store them where the rocket motor is, which leaves you with having to put them in the wrong place. Difficult. L