L2 Certification, Rocket Building

Assembly Jig for Attaching the Fins

One of the steps I’m coming up to is the attachment of the fins to the Air-frame/Motor Mount. For a good join and a good rocket build it is important that we:-

  • Sand/score the root of the fins
  • Sand the Motor Mount where they are going to be glued
  • Sand/score the Tang of the Fins for the fillets later on
  • Important that the Fin/rocket do not move for 3 days while it dries
  • Very important that the fins are precisely 120 degrees apart and are perpendicular to the air-frame

The the last two bullet points, we have build up a “jig” to hold everything in place. Below are some pictures of it.

Marking where to cut out circle
Marking where to cut out circle

 

Two pieces of wood assembled so we can cut out circle sections together.
Two pieces of wood assembled so we can cut out circle sections together.
Cut out circle and marking where cut-outs are going to be for protruding fins.
Cut out circle and marking where cut-outs are going to be for protruding fins.

 

Fin Assembly from back. Notice the right-angle bracket to keep it vertical.
Fin Assembly from back. Notice the right-angle bracket to keep it vertical.
Fin Assembly from front
Fin Assembly from front

 

Side view showing how fins are kept in line with two pieces of wood and three bolts.
Side view showing how fins are kept in line with two pieces of wood and three bolts.

 

We want to hold the fins completely still while it is drying. For this, we have used two square pieces of timber and some G-clamps to keep the fins steady. See the photo below.

Fins held in position using wood braces/G-clamps.
Fins held in position using wood braces/G-clamps.