The way I marked the holes to be drilled is to print out the CAD drawing for each bulkhead and lay it directly on top of the bulkhead. This was done on a slide sorting light table to make it easy to align the outer circumference of the drawing with the bulkhead.  I then used some T-pins to put a small hole where each motor tube hole needed to be drilled.  Then just remove the T-pins and head over to the drill press!

The aft bulk plate is actually two separate pieces that will eventually be epoxied together.  These two pieces were taped together and a short piece of motor tubing was used to maintain good alignment between them while the holes were drilled.

Additional holes were also drilled for the threaded rods after the motor tube holes were finished.

Three small #10-32 steel T-nuts will be mounted into the recessed areas on one of the bulkheads.  These T-nuts will be used to anchor machine screws that hold-on the motor retainer plate.

The T-nuts have three small barbs on them that are simply hammered into the wood plate. The barbs prevent the T-nut from spinning when the machine screws are tightened.

A small circle of masking tape is applied over the back side of each T-nut.  This prevents epoxy from getting down into the threads.

This method also allows the center motor tube hole to be drilled a larger diameter in one plate than the other.  Once the two plates are epoxied together, the larger hole creates a nice recessed area within the bulkhead for the aft closure of the motor to fit flush with the aft end of the bulk plate.  The motor retainer plate then fits over that and holds everything in place.

These are all views of the CAD drawings as well as the finished article.

This is a view of the edge of bulkhead B6, the bulkhead that will be used to seal off the altimeter bay.  The edge has been cut back with a router to allow it to fit inside the coupler tubing that comprises the altimeter bay compartment.  This bulkhead forms a cap or lid for the altimeter bay and helps seal it off from the ejection charge gasses.

Another view of bulkhead B6 in a location where one of the threaded inserts will get installed.  I installed six small brass inserts around the circumference of the bulkhead.  They allow #6 machine screws to be used to hold the center section of body tubing to the bulkhead. The body tubing is removable to allow easy access to the altimeter bay.   The brass inserts are from McMaster-Carr and are part number 90016A007.

A small pilot hole is drilled into the edge of the bulkhead and then the brass insert is screwed into place.

Brass insert is in place.  You can also see the small black rubber o-ring that is placed into the edge groove on bulkhead B6 to form the seal with the altimeter bay tubing.

Bulkheads B6 and B5 were also coated with epoxy just to make them a little more durable.  These bulkheads are the two that get hit with the black powder ejection charges and the epoxy just helps protect the raw wood.

Two PVC pipe fittings were screwed onto the surface of bulkhead B6 to serve as  ejection charge holders.  A third threaded PVC fitting was used to create an igniter wire pass through chamber.  The wires pass through the fitting and then connect to the altimeter. Modeling clay is used to seal the pass through.

The motor retainer plate is a piece of 0.1" thick aluminum that is held in place on the aft end of the booster using three machine screws into the T-nuts that were installed in the rear bulkhead.

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