Brief:
The Emerson Electric XM47, aka Little John (Honest John's baby brother), was the smallest nuclear-tipped missile in the Army's arsenal from the '60s. It had a fairly limited range of only about 11 miles and was retired from service in 1969.

I was looking for a quick and easy scale project to knock off one of the EMRR 2008 Challenge requirements, and found the basic information for this online at Directory of U.S. Military Rockets and Missiles" website, which included a very easy to paint test round in solid olive green with white lettering. From there, a little more research unearthed decent scale data in Peter Alway's Scale Bash booklet. This excellent guide is out of print but highly recommended if you happen across a used copy.

For purposes of the challenge, this is to be a clone of the old Estes 0819 kit and a (1:2.66) downscale of the current Madcow 2.6" kit. However, that kit only includes 1 Army decal, not the 2 called out on the Alway drawing.

Construction:
The link above to the RockSim file should provide sufficient component specs and sizes, including fin pattern. The parts are pretty common:

• 24mm nose cone (4:1 ogive, can be bashed from several Estes kits such as Comanche-3 or the NC-50 nose cone pack)
• BT-50 body tube 7.64" long
• 3/32 balsa for fins
• 18mm motor mount
• CR 50-20 centering rings (2)
• CR 20-5 centering ring/motor block
• metal motor clip
• Kevlar® shock cord
• 12" plastic chute
• clay nose weight

Once I got the basic RockSim design work done, which took about half an hour, the construction was a snap. I had the model ready for paint in under an hour.

The motor mount is standard BT-20 tube with a pair of centering rings and metal hook. I anchored 150# Kevlar® to the forward ring, then glued the finished assembly inside the BT-50 main body tube.

The fins were cut from 3/32" balsa, although I would imagine 1/16" basswood would be more scale-like. I sanded down scale tapers on mine though, which would certainly be a bit more work with the basswood.

You'd think with 4 fins instead of the usual 3 that this would not need much help for stability, but they are very small span fins and are very long. As a result, flying on anything more than an A or in any significant wind is going to push this unstable. I simmed it using C6-5 motor and up to 15 mph winds, and found that I'd need about 20 grams (0.7 oz.) of nose weight to ensure stability.

The resulting CG should be no further than 7.5" aft of the nose tip fully prepped and loaded with the heaviest motor you'll fly.

Finishing:
I didn't bother with spirals and grain as I was up against a deadline, so I just shot everything with a light white primer coat. I followed up with a little 400 grit sandpaper to take the scuff off the primer and two light coats of semi-gloss white. The rocket is supposed to be olive green, but I didn't have white decals or adequate stencils so I optioned to lay a white foundation, then cut out the "U.S. ARMY" on masking tape and mask off the lettering. I then finished up with a couple coats of olive green and was done.

Flight:
For the first flight I went with a B6-4 in light winds of 5-8 mph. The rocket weathercocked a fair amount and deployed just after it had arced over. Overall, it was a nice, stable flight.

For the second flight I went with a more ambitious C6-5. This time the weathercock was much more pronounced, but it still got to pretty good altitude. It deployed just a hair late, and I could barely pick out the chute against the sun. Unfortunately, I blinked for a second as it was coming across the sun and somehow lost it trying to pick it back up. I have no idea how I could have lost this in clear blue sky, but it must have been blowing a bit harder up there than I'd thought as I did not come across it even later in the day chasing down modes of similar altitude and descent rate.

Recovery:
It flies fine although it's a bit overstable and I could have backed off a bit on the nose weight. It surprised me how quickly it got up there, given its weight.

Summary:
If you're looking for a nice, easy scale candidate, this could be your project. It used common materials, has an easy paint scheme (although the lettering was a bit of a pain), and can be built in one evening.