Brief:
Conversion to 18mm flight for Hawk (#552-130; circa 1958) and Glencoe (#05103;
circa 1990) 1/48th scale Jupiter C (Redstone/Explorer) plastic models.
Modifications:
If ever a scale model called out for conversion it's the Hawk and/or Glencoe
Jupiter C. This conversion covers both because Glencoe bought and used the
molds from Hawk. The Hawk version is preferable because a) the molds have
warped and the Glencoe models are notoriously hard to put together straight and
easily, and b) the antique factor of the Hawk. I've been lucky enough to locate
two hawk models for $10 or less on auction. I am told they fetch over $100 at
plastic modeler's conventions and even the box is worth the $10. However, the
Glencoe is easier to locate.
Conversion is made easy by the fact that the model is so close to Estes BT-55 diameter that manufactured parts can be used and the fact that the hole where the engine nozzle would go is just a hair over 18mm/BT20 tube size. Plastic cement must be used with all plastic parts and can be used on all paper parts too--it's plenty strong enough. However, plastic glue might be harsh on elastic (although I'm not sure). You might want to use wood glue inside the Estes type folded-paper shock cord mount. Mounting it to the tube will still require plastic glue.
Start by building the major sections of the model but do not connect them: the lower body/fin section (minus the nozzle) and the upper body and nose with Explorer attached. If you choose to use an engine hook, cut a small notch in the base of the fin can so there's enough room for it to open to insert and remove engines (1/4" wide and long is enough).
For the Glencoe version, you'll probably have trouble making the two halves of each section fit together and may have similar problems making the ends of the two sections fit well. All I can say is use plenty of glue and rubber bands. It can be done.
Looking down inside the lower body section, you'll note that the inside base is not round.
Due to the fin can and connecting points of the model, the nearly BT-55 circle is squared off with four flat spaces. The bottom ring of the motor mount will need to be trimmed to fit this. Just trim off some, test fit the piece and repeat as necessary until enough is removed. If you remove too much, don't worry too much as the bottom ring will be glued to the base, so a tight fit against the sides is not strictly necessary. Be sure to note the placement of these flats on your bottom centering ring in comparison with engine hook/notch (if used) so that they line up. You also will need to notch the bottom ring for hook movement. Be sure to notice that the top centering ring will need some, but not as much, squaring off. Test fit both rings and inspect their alignment, marking the rings and motor tube if necessary until you are sure of the fit of all parts. The rounded portions will not start with a perfect fit. The tube is slightly less than BT-55 inside diameter. This is easily fixed by simply running the rings around on their rims while pushing down, slightly mushrooming the edge. Obviously this is best accomplished before starting the squaring off.
Once you're sure of the motor mount fit in the lower body, construct it as you normally would, with good fillets on the motor tube/ring joints between the rings. When its glue has set, put glue on the bottom side of the bottom centering ring and lower it into place. If any glue seeps out through the engine hook notch, remove it immediately. (A Q-Tip works great for this.)
Construct an Estes folder-paper type shock cord anchor, using wood glue to hold it together. Glue it an inch or two below the top inside the upper body with plastic glue. Once bottom and top sections are complete and the glue is set, they can be glued together.
The nose will need to be filled with 2 to 3 ounces of putty plus lead shot or other weighting material. Embed the screw eye (with the shock cord attached to it) within the weight. Do NOT use plastic cement to glue this into the nose. If you trap plastic glue against plastic with something that does not let the fumes escape, it will continue to melt the plastic (that is, after all, how plastic glue works) and you will end up with pits and craters in the surface. If you don't have a weighting substance that adheres to the plastic (I used DAP finishing putty--it's heavy stuff), cut a disk to glue to the inside of the nose, holding the weight in place.
The nose does not sit well on the body. It sits over a shoulder on the upper body, which is only 1/8" high. It may fly OK sometimes but may fall off due to vibration or may separate before ejection. On one model, I glued very thin plastic strips to the outer vertical edge of the nose in 4 places. This worked. On another, I glued scrap pieces of the stems from the kit parts as vertical spars hanging from the inside top of the nose, placed to leave just enough room between them and the edge of the nose for the shoulder of the body. This worked as well even though it was harder to do but didn't ruin the scale. On my next one, I will try the latter technique but build it into the nose weight and bulkhead construction for more solidity.
Construction:
Requires Hawk or Glencoe Jupiter C plastic model plus:
To finish, do a quick balance of the finished model completely assembled with a spent engine casing in the mount. Glue a 2" to 3" launch lug centered on the CG. If you wish to not ruin the scale model, you can easily construct a slip-over ring with launch lug attached. With it sitting on top the fins and going halfway up the body, it will not greatly ruin the appearance of the model on the pad if done in all white .
You could also glue the plastic model's nozzle to an empty engine casing, so that it can be left in when the model is on display.
The instructions are well written and illustrated as well as the same for both versions. The changes in building order won't make any difference to the specifics of the instructions.
<Finishing:
Finishing is preplanned. The color scheme is simple and well described. The
kits contain water slide decals. I dislike these intensely as I can never make
them sit properly. The roll stripes are easily replaced with Pactra or similar
striping tape. The "UE" markings can be done with hand cut or precut
vinyl. If you manage to get the Hawk version, you'll almost certainly need to
replace them, because they'll be 40+ years old, cracked, and all dried out.
Flight:
First tests were done with a previously half-built Hawk model. First flight was
on an A8-3. This was too low. The chute opened only 15 feet from the ground.
Second flight was on a B6-4. This was a very nice flight although it did arch a
bit (probably due more to nose weight than effective engine size). Recovery was
good on a 12" mylar "sport chute" from Aerospace Specialty
Products. An 18" might be better for this engine.
Third flight was with a Glencoe version using a C6-5. Flight was good but still arched a bit on the way up with ejection at apogee and good recovery. The 12" chute was plenty here--the rocket went high enough that an 18" might have let it drift too far. Still, it landed with the Explorer point on the nose striking a very small rock causing it to break off. This can be easily glued. A better thing might have been to paint it correctly and not glue it in place so it could be removed for flight. It's so small that it wouldn't change the flight characteristics either way.
Summary:
The main CON is the fit of the pieces of the Glencoe version. This is not
insurmountable, just an annoyance.
The main PRO is how close the model is to standard sized parts. Any experienced modeler who has ever finished a level 4 kit or at least several level 3 kits, will have no trouble figuring out where to add model rocket construction steps to the plastic model construction. Going step by step, where you have to modify the plastic to fit the rocket is obvious and not difficult.
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