L2 Certification, Rocket Building

Practicing preparing and attaching a fin to “Motor Mount”

I’ve purchased some real G10 material to practice on. What I wanted to practice was:-

  1. Learning how to cut it well (even though this isn’t required for this build)
  2. How to sand the Leading and Trailing edges to the profiles I’ve decided.
  3. Sand the root and tang to Grit 80. Also sand other edges lightly with Grit 80 to remove any burs. (But I don’t want to change the shape)
  4. Sanding back with Grit 240 to give it a good finish for painting. I sand it ALL over, except on the tang, and the root where it is glued on the motor mount
  5.  Score the root of the fin (yes, on the thin edge) using a punch and a bit of elbow grease. Did this every cm, in both directions at 45 degrees
  6. Score Tang of Fin that is going to be below the air-frame. I did this every 2cm at 45 degrees in both directions
  7. Cleaning the surfaces thoroughly with Methylated Spirits
  8. Inspect the fins to make sure there is no other dust, grime or dirt.
  9. Perform the following preparation steps
  10. Attaching to “motor-mount”
  11. Test paints – to see how finish is.

 

Preparations Steps

Before I can begin attaching fin, I need to prepare my work area. The “main” steps are:-

  • Clean desk
  • Get Methylated Spirits
  • Get Paper towel
  • Get a clean wood board for mixing Glue and mixing stick
  • Get my Timer
  • Wood blocks
  • Get G-Clamps.

Steps to attach the Fin

We can’t do these steps until the fins are prepared!

  1. Then I mix up equal amounts of J-B Weld black and white on a clean surface for mixing.
  2. I start time for 20 minutes. This tells me how long I have to go.
  3. I apply this to the root of the fin as evenly as possible, and try and avoid it going over the side
  4. Clean off excess J-B Weld off sides very carefully using Methylated Spirits and paper towel.
  5. Carefully lower the Fin into the slot, make sure that the J-B Weld doesn’t get on to the “Air-Frame”
  6. Apply a bit of a wriggling action to get the glue to fill gapes
  7. Make sure the Fin is 90 degrees and use clamps and wood blocks to ensure that the fin cannot move
  8. Leave it for 15 hrs minimum!

Here are some pictures:-

Rounded leading edge.
Rounded leading edge.
V-profile trial sanding.
V-profile trial sanding.
Using a punch to score the tang
Using a punch to score the tang
Scoring on the Tang
Scoring on the Tang
Scored the bottom of the fin.
Scored the bottom of the fin.
Approximately 4cm of glue should be enough for 20cm of root fin with some glue left over.
Approximately 4cm of glue should be enough for 20cm of root fin with some glue left over.
Mixing the J-B Weld glue for a minute.
Mixing the J-B Weld glue for a minute.
Glue carefully applied to root.
Glue carefully applied to root.

 

Using square to get fin at 90 degrees to wood.
Using square to get fin at 90 degrees to wood.
Fin installed in the slot.
Fin installed in the slot.

 

Trying to show fin/glue inside gap.
Trying to show fin/glue inside gap.