July 22, 1959 Beach Abort capsule being prepared for flight
Capsule Construction
The 1/17.44 capsule is constructed in an identical fashion to the earlier 1/24 version, with the capsule skin vacuum-formed over a master created from .020" and .015" styrene. Robert Blaske's shroud calculator was used to lay out the necessary dimensions for the capsule master.
Like the prototype, the shroud master is very simple. The most significant detail is a round access hatch detail, with 24 individual bolts. There are also a pair of umbilical hatches and a camera hatch.
After forming the shroud over the master on the vacuformer (here's a video of a part being formed), the part was cut from the sheet of .015" styrene and rolled into the completed conical shape. The entire process of cutting the shroud, joining it with medium CA glue, and sanding the finished joint took less than ten minutes. If you're interested in learning more about producing your own vacuform parts, George Gassaway offers a great primer on the process. Tip: use a fresh #11 blade (I like the Testor's Model Master blades, which are expensive as hell but have a groovy Zen vibe) to cut out your vacuform parts, and mark the line to be cut with a pen before cutting.
The recovery section was fashioned by wrapping an appropriately sized tube with .015" styrene sheet, then adding details made from pieces of .080" half-round rod. Cutting these items to length was made much simpler by using a "Chopper II" from Northwest Short Line. A shoulder was added using masking tape, and the part was placed inside a mold box made from Lego pieces borrowed from my daughter. (Scratchbuilder's Tip: 90% of what is needed for most scratchbuilding projects can be found in the model railroading section of a well-stocked hobby shop.)
Once the mold boxes were complete, the interior of the boxes and the masters were given a spritz of mold release (I prefer the Crown wax-based stuff intended for epoxy; it was the only thing on hand years ago in the midst of an earlier project and it seemed to work fine), then the mixed mold goo was poured in slowly around the master.
Construction of the antenna section shroud master started by laying out the dimensions for the major structure using Robert Blaske's shroud calculator (again, this is an incredibly useful tool for a scratchbuilder). Once the shroud structure was completed out of .015" styrene sheet, the locations for the stringer details were laid out on a piece of scrap material, and the process of gluing on the 48 stringer details was begun. You never would have guessed that I like working with styrene, would you?
Above, we see the results of a minor "reboot" procedure involving the molds. I wasn't pleased with the molds produced using the Synair stuff, so the much softer Expert's Choice product was used. The first picture shows the poured molds for the recovery section, antenna section, and escape motor aft closure. The center picture shows the recovery section mold with a thin layer of Polytek resin in place, and the right photo shows the finished part popped free from the mold. You may notice a few stray fiberglass threads in the last picture, as a layer of 3/4 oz. glass has been added to the interior of the part for a bit of additional strength.
At this point we are able to stack the parts for the first time, primarily as a sanity check...
The heat shield is incredibly simple to do, and this technique may be applied to any prototype with a spherical heat shield. First, a bit of math determines that a scale heat shield for this beastie should have a radius of 4.58". A quick trip to the local MegaLowMart produced a kiddo's play ball (featuring SpongeBob Squarepants, specifically) with a diameter of just over 9", which is close enough for a component that the judges won't bother to measure. A sheet of .020" styrene was secured in a vacuform frame, heated in the oven, and pulled down over the ball. Bingo, a perfect heat sheld!
The shield part was trimmed to a slightly-oversized shape, then glued to the base of the capsule shroud with Tenax plastic adhesive. After a bit of trimming and shaping with an assortment of sanding sticks, it was time to test fit the components. Things are beginning to fall in place!
Next up is the addition of 24 individual bolt details to the circumference of the capsule hatch, helped by a raiding party on the railroad section at King's Hobby, resulting in the purchase of some ready-made bolt & washer parts from Grandt Line. The bolt/washer detail parts are simply snipped off of the sprue, dropped into a hole drilled on the surface of the capsule skin, and glued into place with a touch of Tenax. The handle detail was fashioned by heating a section of .040" styrene rod over a candle, then bending the rod over an appropriately-sized form (which turned out to be one of the jaws of a micrometer that was handy). The photo on the left above shows a formed handle part 'tween thumb and forefinger, with a similar part already installed on the capsule behind. In both of these photos you can catch a glimpse of the BT-60 airframe material inserted into the capsule. The Beach Abort version lacks the internal airframe tubing as it will be a static, non-flying model.
Cutting the Heat Shield
The Little Joe model will be flown in a two-stage configuration, with a motor buried in the Mercury capsule intended to simulate the operation of the escape tower. It's not a prototypical simulation of the tower event (the tower nozzles are just too small), but it will still provide a reasonably accurate effect. As the staging motor will protrude through the aft end of the capsule, we'll need to cut a hole in the heat shield. The challenge facing us is to find the exact center of the heat shield, which is complicated by the fact that the component is a section of a sphere.
Just by coincidence, I learned that the center pivot of my Micro-Mark yardstick compass fit into 3/8" styrene tubing like a bullet in a rifle barrel, so I whipped up a quick jig that would center the styrene stock in the capsule's BT-60 airframe tube. The jig was then inserted into the capsule, and the center pivot was then dropped into the jig. The pivot placed a small dimple precisely in the center of the heat shield!
With the center point of the heat shield accurately marked, an Olfa compass cutter can be used to cut the motor exhaust hole. The resulting hole is precisely located in the center of the heat shield.
Motor mounts were fashioned from short sections of 18mm airframe tube and standard BT20/BT60 centering rings. Kevlar line has been anchored around the capsule motor mounts, and the motor mounts have been glued into place in the aft end of the capsules with Titebond. I prefer an aliphatic resin adhesive such as Titebond for any paper-to-paper surfaces that need to be stuck together.
At this point the capsule is effectively finished, save for the addition of lift eyes on the recovery canister, followed by some paint and decal work. The lift eyes will probably be done in photoetched metal, as I wasn't pleased with the resin eyes used on the Beach Abort model.
On to part 2: Escape Tower assembly...
On to part 3: Transition Shroud 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...