MPC Lunar Patrol, Part 6

Today, I finally had some time to resume work on the Lunar Patrol. 
The balsa stock for the glider nose cones has been mounted on the lathe for a few weeks now, while I have been engaged in other stuff - like massive yard work / landscaping projects.  The rest of the Lunar Patrol build is on hold , waiting for completion of these nose cones.

The first step is to turn down the square corners of the pine block to which the balsa stock is mounted.  I will be working in close proximity to this block, and I have no desire to have my knuckles busted by rapidly traveling square corners.

Next step is to bring the stock down to a cylinder.  This is done with a normal woodturning gouge, in a series of very light passes.  Balsa is quite splintery, and it's easy to take out chips and chunks if the work is done too aggressively.

Once the stock is down to around 1/8" of its target diameter, I switch to a medium grit sanding block.
Again, this needs to be done with a light touch.  Balsa sands down very quickly.  I stop the machine often to check my progress with a caliper set to the O.D. of a BT-20 body tube.

Once the stock is the right diameter, I use a pencil to mark out the fore and aft locations of the nose cone shoulder.  Since these nose cones will eventually be glued into the LP glider tubes, I'm only going with a 5/16" shoulder length.

The shoulder diameter is then turned using a straight file, and the nose cone profile is shaped using sanding blocks.  Again, the machine must be stopped often to check the profile with a template.

Finally finished.   The completed nose cone gets separated using a razor saw while the machine is spinning.

A few minutes later:  two completed Lunar Patrol nose cones!

Stay tuned for part 7 !!!!!

The FireFly Re-Visited

Last night, I had a little spare time on my hands, so I sat down at the rocket bench to repair the Firefly glider, which had suffered a broken attachment pin on its May 5^th maiden flight.

As I was gluing the piece back on, I took a closer look.
This little piece of balsa is certainly required to do a lot.

In fact, it’s the prime focal point that takes the brunt of all the glider’s flight stresses.

First, it has to bear the G-forces acting on the glider at liftoff.

Next, it handles the weight of all the drag forces acting on the glider during boost and coasting phases of flight.

Then, it has to withstand any shock forces associated with engine ejection and glider separation.

Finally, it is always the first point of contact on the ground after gliding flight, i.e., the model’s ‘landing gear’.

That’s an awful lot to ask of a little sliver of balsa wood.

I realized that, if I didn’t want to be repairing this attachment pin after each and every flight, some engineering needed to be done to remedy this weak point.

Drawing on pop-pod boost/glider technology, I decided that the best course would be to apply some reinforcing sides on the pylon/pin assembly.

For this, I cut out a couple pieces of 1/32” thick plywood.

After sanding down the dowel pin to match the thickness of the glider’s nose, I wrapped a piece of sandpaper around a ¼ “ dowel and carved out a little hollow in the nose to make a cavity for holding a glob of trim clay.  This will cut down on the amount of clay that normally has to be molded around the outside of the nose for proper flight trimming.

The plywood sides are then glued on, shape sanded, and finished to match the rest of the model.

With this new design modification, it is hoped that the firefly will log many more flights without losing its nose every time!