07-02-2023, 01:10 PM
Time to make some composite rocket parts!
the most common composites used in rocketry are fiberglass and carbon fiber. they are similar weights, carbon fiber being a bit lighter, and similar strengths. fiberglass is a bit cheaper, and it is transparent to radio frequencies (unlike carbon fiber), allowing you to send telemetry from the rocket to the ground station.
carbon fiber is great for body tubes, but fiberglass is better for nose cones since you can send radio signals through it. the very tip of the nose cone is made of chunk of solid aluminum, since that takes the brunt of the aerodynamic heating at higher Mach numbers.
for the purpose of the current rocket i'm working on, the entire airframe will be fiberglass since it's cheaper. some future high performance rockets will have CF body tubes though.
This rocket is called "risky business" and it'll be my first rocket to go over twice the speed of sound. it has a top speed of just about 1,700 mph. it is mainly being used to test avionics and structures under extreme G-forces, as this rocket accelerates at almost 95G on takeoff (peak thrust/weight for this rocket is 91.2).
the body tube will be pretty simple to make - I put about 1.5 wraps of 4mil Mylar around a cylindrical mandrel, which is given a thick coat of laminating epoxy. while the epoxy is workable, i add 4.5 wraps of 6oz fiberglass cloth, making sure to let the epoxy soak through the cloth. finally, 2 wraps of PeelPly (release cloth) is added to remove the excess epoxy and make for a smooth surface finish. the epoxy is allowed to cure at 80 degrees fahrenheit for 24 hours. once the epoxy is cured, the PeelPly is peeled off, the rough ends of the tube are removed with a miter saw, and the tube is sanded with 180 grit, 220 grit, and then 320 grit sandpaper, with the tube being cleaned between each sanding.
the nose cone will have a 3D printed mold for everything except the very tip, which is given 4 wraps of 6oz fiberglass cloth and one wrap of peel ply.. the nose cone tip is also the anchor for the kevlar shock cord, and is added later. once the peel ply is removed and the nose cone is sanded and cleaned, the shock cord is attached to the eye bolt, which is stuck through the forward end of the nose cone, and the aluminum tip screws onto that.
the fins are tacked onto the body tube with JB-Weld steel reinforced epoxy, after which they are given a fillet at the root using thickened West Systems epoxy. then, after sanding and cleaning the surface of the fins, they are given a 2-layer tip-to-tip fiberglass layup (with the 6oz fiberglass cloth rotated 45 degrees between layers), followed by a layer of peel ply. as usual, the epoxy cures for a day at 80 degrees F, the peel ply is removed, and it is sanded with 180, 220, and 320 grit sandpaper, being cleaned between rounds of sanding.
the method for making this rocket if you made it from carbon fiber instead of fiberglass would be the same, assuming you used similar density carbon fiber cloth, and a high quality epoxy.
the most common composites used in rocketry are fiberglass and carbon fiber. they are similar weights, carbon fiber being a bit lighter, and similar strengths. fiberglass is a bit cheaper, and it is transparent to radio frequencies (unlike carbon fiber), allowing you to send telemetry from the rocket to the ground station.
carbon fiber is great for body tubes, but fiberglass is better for nose cones since you can send radio signals through it. the very tip of the nose cone is made of chunk of solid aluminum, since that takes the brunt of the aerodynamic heating at higher Mach numbers.
for the purpose of the current rocket i'm working on, the entire airframe will be fiberglass since it's cheaper. some future high performance rockets will have CF body tubes though.
This rocket is called "risky business" and it'll be my first rocket to go over twice the speed of sound. it has a top speed of just about 1,700 mph. it is mainly being used to test avionics and structures under extreme G-forces, as this rocket accelerates at almost 95G on takeoff (peak thrust/weight for this rocket is 91.2).
the body tube will be pretty simple to make - I put about 1.5 wraps of 4mil Mylar around a cylindrical mandrel, which is given a thick coat of laminating epoxy. while the epoxy is workable, i add 4.5 wraps of 6oz fiberglass cloth, making sure to let the epoxy soak through the cloth. finally, 2 wraps of PeelPly (release cloth) is added to remove the excess epoxy and make for a smooth surface finish. the epoxy is allowed to cure at 80 degrees fahrenheit for 24 hours. once the epoxy is cured, the PeelPly is peeled off, the rough ends of the tube are removed with a miter saw, and the tube is sanded with 180 grit, 220 grit, and then 320 grit sandpaper, with the tube being cleaned between each sanding.
the nose cone will have a 3D printed mold for everything except the very tip, which is given 4 wraps of 6oz fiberglass cloth and one wrap of peel ply.. the nose cone tip is also the anchor for the kevlar shock cord, and is added later. once the peel ply is removed and the nose cone is sanded and cleaned, the shock cord is attached to the eye bolt, which is stuck through the forward end of the nose cone, and the aluminum tip screws onto that.
the fins are tacked onto the body tube with JB-Weld steel reinforced epoxy, after which they are given a fillet at the root using thickened West Systems epoxy. then, after sanding and cleaning the surface of the fins, they are given a 2-layer tip-to-tip fiberglass layup (with the 6oz fiberglass cloth rotated 45 degrees between layers), followed by a layer of peel ply. as usual, the epoxy cures for a day at 80 degrees F, the peel ply is removed, and it is sanded with 180, 220, and 320 grit sandpaper, being cleaned between rounds of sanding.
the method for making this rocket if you made it from carbon fiber instead of fiberglass would be the same, assuming you used similar density carbon fiber cloth, and a high quality epoxy.
Local rocket man