With the completion (sort of) of the main assembly, time to integrate it into some fiberglass airframe.
I had some 4” airframe sitting around so I pressed that into service for this module. It was just about the perfect length to start with!
A bit of measuring and thinking and CADing, then the 3D (FDM) printed drilling guide was slid over the tube. The 35mm holes were drilled using a hole saw, and the pilot holes for the mounting screws drilled. The mounting holes were drilled out to final size and countersunk after the drill guide was removed.
The edges of the holes in the filament-wound fiberglass ended up with some loose filaments of f/g around the edges so they were glued with the usual Loctite 401 and then taken to the final size and dressed lightly with emery cloth.
The airframe was a bit longer than needed and had a test hole I had drilled in earlier that had to be amputated. I dropped it into the lathe and attempted to use my dental drill as a toolpost grinder. Progress was a little slow so I switched to using the cordless angle-grinder and made a nice clean cut.
A length of coupler was inserted in to the correct depth and glued in with the usual West Systems 105/206.
Holes were drilled at the top to accept the NC and at the bottom to mate to the Velociraptor I am using as the test-bed for this project.
A coat of plastic primer and white paint tarts it up a bit. I will add some decals as a roll pattern sometime before launch.
To close out the bottom of the assembly to the parachute compartment from the ejection gases I took to SolidWorks and sketched up a bulkhead incorporating an O-ring, connectors for battery charging, eMatch connections, charge canisters, and breakwire for switching off the VTS when ejection occurs. This was printed in “flexible” material on the SLA printer.
- BulkheadCAD1resize.png (235.42 KiB) Viewed 3112 times
- BulkheadCAD2.png (124.58 KiB) Viewed 3112 times
Charge canisters were machined up to suit and the wiring connections to extend the interface to the VTS module were fitted.
The bulkhead was fitted to the coupler on the airframe. There was a bit of shrinkage on this 3D printed part (the flexible material seems to suffer from this problem) so the diameter was boosted a little with some Kapton taped wrapped around the boss. Also, the holes were drilled in the fiberglass airframe and the bosses in the bulkhead were drilled, tapped, and fitted with Recoil thread inserts to hold the bulkhead in place
So that is the completed airframe, sans VTS module, and also yet to be fitted with an M6 eyebolt to tie everything to the recovery harness.