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