Dr. Zooch Jupiter-C build thread

Santa left me a Jupiter-C under the tree this past Christmas.



I finally got enough free time to actually build the thing. We'll start with the obligatory group portrait of the kit contents.



The kit consists of a BT-50 main body tube, an 18mm motor mount; a set of parts that will be made into the nose cone (BT3 to BT50 adapter, a short length of BT-5, two 3-5 centering rings, and a short length of 1/8" hardwood dowel); sheet balsa for the fins; a printed cardstock sheet containing the body tube wrap, fin templates, and a couple of minor detail pieces; one the good Doctor's "trash bag" parachutes; shock cords; a launch lug; the most entertaining written instructions I've ever read; and a small bag containing the miscellaneous fiddly bits. This is definitely an "old school" builder's kit.

The prototype had a cone-shaped guidance section topped by a spinning tub that contained the upper-stage solid rocket motors, atop which sat the Explorer satellite.



The kit simulates this with the adapter. The short length of BT-5 fits over the adapter's BT-3 shaft to simulate the tub, and the top of the shaft is then shaped into the cone that held the Explorer satellite, which is in turn simulated with the dowel. The first step is to carve the upper part of the adapter to simulate the "step" visible below the tub. Using a nail file, this went pretty quickly.

Next, the centering rings are glued onto the upper shaft, and the BT-5 fits over those. Note that the centering ring sticks up a bit past the end of the BT-5 to simulate the rounded top of the tub.



Next, using the trusty nail file, we shape the balsa sticking up above the tub into a truncated cone.



After sanding one end of the dowel into an ogive point, we drill a shallow hole in the top of the cone and glue it in.



The nose cone is done, except for the filling and sanding. In the next installment, we'll build the main body tube.

Looks like a fun kit to build!
Looking good so far, nice work!

she is looking great so far!! Great job!!

Looking good... von Braun would be pleased.

I've had a busy summer, but the rocket is finished and I've uploaded the photos from my camera to my desktop. I will finish posting on the build in the near future.

OK, back to work.

The motor mount is of conventional design. The Good Doctor has you glue a cardstock reinforcement around the engine tube just aft of the engine block and the top of the hook. Not sure it's necessary, but I followed instructions. You wrap the hook with masking tape before attaching the centering rings.



Here it is with the centering rings installed. The lower ring gets a notch to clear the motor hook.



The next step is, of course, to glue the motor mount in so that the lower ring is flush with the lower end of the body tube. Now it's time to put on the body wrap. I deviated from the instructions by using a doorframe in my house to draw the guideline, rather than going to my neighbor's house to borrow unsymmetrical dimethyl hydrazine. (Don't worry if you don't understand that last bit, it makes sense in context.)



I cut out the wrap, pre-curled it by rolling it up inside the main body tube...



...then coated it with glue and rolled it on.



All in all, a much more civilized way to decorate the tube than painting, masking, and decaling.

Next, we cut out the fin templates and then cut out the fins. Each fin is made up of two parts, the large pointy bit and the small rectangle that glues on the outboard end thereof. The leading edge of both pieces is to be beveled. I thought about skipping that step, but it went quickly and easily using the trusty nail file.





That "tail" on the main fin piece wraps around under the end of the main body tube and butts up against the protruding engine tube, giving the fin a couple of additional root edges as well as simulating the prototype's exhaust vanes.

I hit the fins and nose cone assembly with balsa sealer, masked off the nose cone shoulder and the fins root edges, and sprayed everything white. I then brush-painted one fin completely black, one black on one side, and a third black on the opposite side. The all black fin goes on the "front side," directly opposite the seam in the body wrap. The all white fin is to the right of that, and the other two go in the remaining two spots with their black faces toward the black sector of the roll pattern.

The instructions tell you to cut the supplied launch lug into two pieces and attach it to the "back" of the body tube. I painted it black and cut a small piece the width or one of the roll pattern stripes, which went up on the stripe. The rest is in the fin fillet below. I used a 1/8" dowel to line them up.



It's hard to see in the photo, but the "rear" fin ended up aligned directly with the motor hook, and I had to cut the "tail" part off so the motor hook would have room to move. (You might have already noticed that one was "bob-tailed" in the photo of the fin pieces above.) In retrospect, I should have drawn my guideline a little to one side of the hook so an unabridged fin would fit.

The elastic shock cord and kevlar are tied together in the usual fashion, with the kevlar mounted inside the body tube with an Estes-style trifold mount.

The black bands on the nose assembly are cut out of the same sheet of cardstock as the body wrap. When I put the horizontal band on, I realized that I hadn't made the "step" below the tub quite deep enough. If I'd been thinking, I would have cut the band out and used it as a template when sanding. I'll have to remember that next time I build one of these.



The upper half of the satellite had a pinstripe roll pattern which is simulated by painting the top half of the dowel black--unless you have a 0000 brush and a lot of patience! I have neither.

The next step is to assemble the parachute. The Doctor gives you a set of high-quality reinforcing rings to go around the shroud holes. After tying everything together and giving the glue on the knots time to dry, I gave it the "belt & suspenders" treatment with small pressure sensitive labels over both sides of each shroud attachment point.



The last step was to paint the lower part of the engine tube white. (I thought about using a medium gray to "simulate" the exhaust plume, but it looked wrong.)

The finished product is a lovely little rocket.



The kit is clever and well designed, and a joy to build. I'm pretty sure I'll do another one at some point.