Avionics Bay Assembly

a step by step breakdown of assembling and manufacturing the avionics bay, as well as key design decisions that were made.

• Sand Paper

• Filers

• Phillips screw driver

• Drill and drill bits

• Respirators (when filing fiberglass)

• Epoxy (JB Weld ColdWeld ™️ Steel Reinforced Epoxy)

• bulkhead jig (designed to correctly place bulkhead and keep level

Procedure

Unfortunately for this assembly/manufacturing process to epoxy the avionics bay into the airframe became more inconvenient due to the need to epoxy the door nuts to the airframe. As a result, we must assemble the av bay in the airframe tube layer by layer. The components once within the av bay will no longer be accessible, apart from the sled and electronics mounted on it.

Prep work

• Confirm you have all required materials including tools

• Sand down the PLA and Wooden bulkheads to allow the them to more easily slide into the tube

• Sand down sled to allow for it to more easily slide into the bulkheads

  • you want only enough clearance to allow for easy removal, while still maintaining enough friction to hold the sled in place securely during flight.

• File down aluminum bulkheads to ensure they can slide down the tube

  • NOTE: Make sure the bulkheads are properly dimensioned before attempting to assemble, or you run the risk of getting them stuck even with filing for 4+ hours

• Sand down the inside of the airframe tube that you will be epoxying to

  • NOTE: sand down enough to remove the first layer but not enough to break down the fibers of the fiberglass

  • Make sure you are wearing a respirator, gloves, and long sleeves

• Using a handsaw or sharp dremel bit, cut the threaded rods to length

  • Note: if using a dremel be aware that the rod can heat up, wear thick gloves on the hand holding down the rod

• Using 5 minute epoxy, glue the PLA bulkhead and wooden bulkhead together for the top and bottom sections of the av bay

  • Allow this to set for at least 10 minutes, you can place a weight on top to hold each subassembly together while it cures.

  • Be sure to prevent any excess epoxy from pooling out from the sides of the seam (this will change the physical outer diameter and make it more difficult to slide into the airframe tubes)

• Drill out the holes of the PLA and Wooden bulkheads once the epoxy has cured to ensure the wires can pass through them easily

• Align the Aluminum Bulkheads with the PLA bulkheads and drill out the holes once again to ensure wires can pass through the assembly easily

Aluminum Bulkhead Manufacturing

• Insert the U Bolts into the Aluminum Bulkhead and attach the nuts on the other side

  • take care to make sure the nuts are level

• Add epoxy to the underside of the bulkhead between the nuts, ubolt, and bulkhead

• Add epoxy to the top of the bulkhead at the interface of the ubolt and the holes

  • allow that to cure

Assemble the AvBay for Test Fit

This is done so that we can be assured of the fit of all components before we assemble the av bay within the tube

• Begin first with the sled and work from the "inside" outwards

• PLA bulkheads around the sled on the top and bottom

  • this is a great time for any final filing to ensure the slide can slide in and out smoothly

• Slide the threaded rod past the first bulkhead, and add 2 nuts

• run the threaded rod past the second bulkhead and add an additional nut on the exterior side of each bulkhead

• adjust the nuts so that the assembly is secure against the surface of each side of the bulkhead (the nuts serve as placeholders)

  • check that you can slide the sled in and out easily and tighten or loosen the nuts as needed

• add an additional nut ~1 inch away from each of the most exterior nuts on the threaded rod

• repeat for the second threaded rod

• add the aluminum bulkheads to each side

• adjust the outer most nuts as needed to ensure the aluminum bulkhead is level! and the ubolt is gently touching the wooden bulkhead

• add the wingnuts to the exterior of the aluminum bulkheads to hold them in place

• make a final check that the sled is still able to slide in and out of the assembly and that all the nuts are properly tightened

  • then you take off the wingnuts and the aluminum bulkhead

  • leave the rest of the assembly together

• Test that you can slide the assembly into the tube and file as needed

• Place the assembly into the tube and mark where the epoxy for the first bulkhead will be placed

Assembly of AvBay within the Tube

Note that this is especially difficult and limited for BFO specifically because of the accessibility and mounting requirements of the av bay

1. Epoxy in the first bulkhead

• Begin epoxying procedure using JB Weld: https://docs.google.com/document/d/1DCgi2xNbCKLSVA-2AojZUtkCFQReliQGcxFavwJx-4g/edit
• The procedure for the first bulkhead is the airframe standard for epoxying bulkheads into the airframe tube

• The first bulkhead (put in place prior to the sled) can be done normally, with two precise fillets on either side done by hand.

  • The specific epoxy will depend on the material of the bulkhead and the material of the airframe.

  • in this case we have a fiberglass airframe and an aluminum bulkhead and are using JB Weld Epoxy

• INSERT SLED INSERTION PROCEDURE

• For the second bulkhead, Make a ring of epoxy on the inside of the airframe, pull the bulkhead past the ring of epoxy to create a fillet on the inaccessible side (recall we are assembling this av-bay layer by layer)

  • After the first fillet has set, on the remaining exposed side make a standard epoxy fillet

  • let set