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Welcome to my Level 3 build sheet.
This wiki will document my design and build process for my level 3 rocket. I will be scratch building this rocket using fiber wound carbon fiber airframe, carbon fiber fins with carbon composite tip to tip, and a fiber wound fiberglass nosecone. This rocket will be a 98mm minimum diameter build, capable of flying a CTI pro98 6GXL case.
Length: 8 feet
Diameter: 4 inches
Pre-certification motor:
- Aerotech L1170FJ
- 75/5120
Certification motor:
- AeroTech M1297W
- 75/5120
Balls motor:
- CTI N5800CS
- Pro98 6GXL
I decided to go with four fins for stability and strength reasons. Since four fins have a higher surface area than three, the fins can be made smaller optimizing the strength while still keeping drag relatively low.
drogue: 24" ~55 FPS
Main: 84" Iris fruity Chute ~13 FPS
Dry weight: ~11 lb
Weight with certification motor: ~21 lb
Weight with Balls motor: ~43 lb
The Avionics bay will be housed in the nosecone. This will allow more space for recovery and also a shorter rocket, ultimately decreasing the overall weight.
Tracking and Primary Ejection charges will be handled by a Telemetrum (or Telemega) and secondary charges will be handled with a PerfectFlite Stratologger. All power will be handled by three LiPo batteries, one for each altimeter and one redundant. The apogee charges will be contained in surgical tubing and placed in copper charge canisters. The main will be in a deployment bag and will be deployed by cable cutters.
###Fin design
I first designed my fins in open rocket to develop the shape of the profile of the fins. I balanced altitude and stability by changing different paramaters of the fins, and adding weight to the nose cone. I settled on the profile below.
I used AeroFinSim to model the fins and determine the thickness that is needed for 3.5+ mach.
From the FinSim data, I am going to make the final thickness of the fins 0.2 inches. This will allow for a speed of Mach ~3.75 at 5k ft.
Starting out with 1/8 (0.125) inch plate for the fins, it would require 2 layers on each side of the fin to reach 0.2 inches (.205 actual). Starting with 1/16 (.0625) inch plate, 4 layers on each side are required to reach 0.2 inches (.225 actual). I will go with 1/8 inch plate with 2 layers on each side, since I need to be as close to 0.2 inches as possible. I am also comfortable with the strength of the root edge joint with 2 layers of tip to tip. I will also make a 1/4 in fillet on the root edge joint.