Little Joe transition section detail, via Peter McQuillan
Transition Section Construction
Historians will note that the early Type C Mercury capsule and the Little Joe booster share a common diameter of 80". Coincidence? Perhaps, but by the time the Mercury capsule design had evolved to the 74.5" Type D capsule, it was necessary for NACA/NASA engineers to design a transition section to adapt the dissimilarly-sized project elements.
Construction of the transition shroud for our model begins by laying out the flat shroud dimensions, again using Robert Blaske's Shroud Calculator. (If this tool ever goes off-line I'm screwed, as I was a Liberal Arts major in college.) The large radii required by this part are mapped out using a yardstick compass from Micro-Mark.
The outer shroud section is rolled and glued first using .030 styrene, securing the joint with medium CA and accelerator. After cleaning up that seam with sanding sticks, a second shroud layer of .020" styrene is glued into place using Tenax. With a total thickness of .050", we'll be able to add some nifty scale bolt recesses into the surface of the shroud master.
Tip: large sheets of styrene sheet can be sourced from local companies serving the commercial sign production market. I regularly purchase 4' x 8' sheets of .020" and .030" styrene for less than $10 each from Regal Plastics.
To insure that the transition shroud master retains a circular shape during the detailing process, a series of discs cut from foamcore board are cut and glued into place, resulting in a surprisingly rigid part. Next, a drawing is whipped up in Vectorworks to help define the positions of various components on the transition, most importantly the 24 bolt recesses.
With the detail locator drawing in place we can start to add panel lines and rivet details. The detail locator drawing is taped to a piece of formcore board that can be easily removed and replaced as needed.
Once the basic detail is in place, a short section of coupler tube is cut to use as a shoulder to attach the transition to the airframe tube, and the assembly is tested for fit.
Next up, a 5mm strip of .020" styrene is cut to use as a simulated Marman clamp, then glued into place using Tenax. Several 4mm strips are also cut and wrapped around the base of the transition, simulating the section of airframe that extends from station 299 to station 300.
Back to part 1: Capsule assembly...
Back to part 2: Escape Tower assembly...
On to part 4: Boilerplate assembly...
On to part 6: Airframe assembly...
On to part 7: Paint and Markings...
On to part 8: Motor Mount assembly...
