Brief:
A Shrox design from the Apogee newsletter, #85; the Javelin is a fantasy research rocket designed to collect high altitude air samples. It’s a quick, easy build, and good diversion from the basic skill level 1 commercially available kits. It’s a nice first step into the build-it-yourself world rather than assemble kits.

Construction:

1. 24mm nose cone (plastic)
2. BT-50 body tube (13.5-inch)
3. 18mm motor tube (BT-20/2.75-inch)
4. (2) 18/24 centering rings
5. 36-inch Kevlar® shock cord (at least 110#, ideally 300#)
6. parachute (8-inch)
7. 3/32 balsa or basswood fin stock
8. clay nose weight (0.25 oz.)
9. decal sheet (download from E-zine archives)

The parts list printed in the E-zine seems to indicate that this is a 2-stage design. The Rocksim file, though, is strictly single stage, which is the way I built this. The free design comes with no instructions, so you’ll have to rely on the Rocksim file and some building experience to figure this one out.

Assemble the motor mount assembly with the BT-20 and centering rings, then mount this into the BT-50. The dimensions for the (2) sets of fins are in the RockSim design file, though I’m lazy and prefer to print the templates using the full version of RockSim. After cutting out the fins, tack them to the body on 3-fin/120-degree alignment.

Add about a 1/4-ounce of nose weight, install the parachute & shock cord, and you’re ready for paint.

Finishing:
The suggested finish on this is a two-color scheme, with a glossy white base and the upper portion of the rocket finished in a light (sky?) blue. I applied a base coat of primer, and wound up with four finishing coats before I got a finish I was satisfied with (eliminating slight runs under the masking tape). I used my ink-jet printer and Avery clear decal stock to print the decals, which include a Canadian Air Force name strip and a couple of Apogee logos. The decals are a very nice touch to the Apogee/Shrox designs, and in my opinion make them stand out from the normal free plans I’ve seen on-line and in other publications.

Construction Rating: 3 out of 5

Flight:
You’ll have to learn simulations in RockSim to come up with a motor selection list, as there were none recommended in the newsletter. I opted for a B6-6, and on a hot summer day with light winds, got just over 500 feet. The delay was a very good choice, with ejection coming just after the rocket arc’d over.

The chute looked a bit small for this, but it did not seem to come down too quickly, and the rocket was recovered safely less than 50-yards from the pad.

Recovery:
No problems at all with flight.

Flight Rating: 5 out of 5

Summary:
If you’re just downloading the Rocksim file, you won’t have much trouble with this plan. If, however, you’re like me and read the newsletter, pulled the parts, then started trying to reconcile the newsletter parts list to the Rocksim plan, you’ll have some difficulty. This was a little disappointing given the many other Shrox/Apogee downloads that are available without this type of issue.

Overall Rating: 4 out of 5