| Construction Rating: | starstarstarstarstar_border |
| Flight Rating: | starstarstarstarstar |
| Overall Rating: | starstarstarstarstar |
Brief
The Aerotech Strong Arm rocket is a mid power rocket designed for "E" through "G" impulse motors. It is a sleeker version of the ARM-78 STARM and is on retail for about $70. I found it on sale for about $50, and couldn't resist. This will be my first "real" mid power kit and my first good rocket to get to use reloadable motors on.
Components
The kit comes in one of Aerotech's cardboard boxes. It looks a little small for a rocket of this size, but everything fit in just fine. The parts are also laid out so that the small pieces don’t rattle around inside and damage any of the other parts (and there are a lot of parts). The first thing I did was lay the components flat on a table. The instructions were rolled up in one of the body tubes, and so were the decals, and I recommend taking those out too. Included in the box were:
- motor adaptor tube
- adaptor rings (2)
- "E" spacer tube
- thrust ring
- thrust ring flange
- motor tube
- motor hook
- 4-fin FIN-LOC rings (2)
- centering rings (3)
- Fins (4)
- cooling mesh
- ejection gas baffle
- screw eye
- 8' shock cord
- lower body tube
- upper body tube
- launch lugs (2)
- nose cone
- decal sheet
- 30" parachute
- "F" spacer tube
- coupler tube
- strakes (40
- instructions
Each and every part was of the best quality and durability that Aerotech is praised for. The only problem was a slight warp in the nose cone.
Construction
Building started with a roll call. I wanted to make sure that everything was accounted for and that nothing was bent, crumpled, or damaged. I highly recommend doing this with EVERY rocket you build. You should always check the quality of the components before building so that it can be replaced or fixed. If there is a weak link in the structure, bad things can happen. I don't expect this from Aerotech, but there have been several reports about problems with the nose cones.
Another thing everyone should do before building is to STUDY the instructions. Aerotech has pretty good instructions and the steps are in a logical order, but some of the illustrations could be better.
The actual building started with the adapter (build this first because it will be used to push back the thrust ring and flange). Afterwards, measurements are taken on the motor mount and the motor hook is inserted through a 1/4" slot that you cut. The thrust ring and flange are now glued together and pushed up until it butts up against the back of the motor hook. Aerotech says to cement them in place, but I decided against it since the fit between the ring and tube is so tight and the hook is so long that it's hard to glue anything in place at all.
Now comes the challenging, part-the FIN-LOC rings. They are so tight that the front 1/8" of my motor tube us torn and the layers of paper are separated. To get them into place, I suggest gently tapping them into place with a rubber mallet or small hammer.
What comes next is super important. DO NOT glue the FIN-LOC rings in place until you have test fitted the fins and they fit properly. Slide the centering ring into place and make sure it does not interfere with the fin placement, then remove the fins and glue the FIN-LOC rings and middle centering ring in place. I used Gorilla Devcon 30 minute epoxy throughout the motor mount assembly (because most super glues will deform the plastic and because I had never used liquid epoxy before).
The only problem I came across was the epoxy taking half an hour to set. It runs like syrup. I simply kept rotating the assembly and everything worked fine. In the future, I will use 5-minute epoxy.
Now you make four 1/4" slits at the top of the assembly that are 90 degrees apart, stretch out the cooling mesh, and cement the baffle in place. Unfortunately, I made a stupid mistake and glued in the baffle before I inserted the mesh. After about 5 minutes of wondering what to do, I ended up cutting away the first 1" of the tube, peeling the paper away from the baffle, inserting the mesh, replacing the baffle, and gluing it in place with the front centering ring over that.
Tie the shock cord to the screw eye and screw that into the baffle. The whole assembly is then inserted into the lower body tube and the fins are snapped into place so that the assembly doesn’t move. Now the whole thing is glued into place, and the fins are removed and tacked down, both at the root edge and where the fin tab meets the motor mount.
Then insert the last centering ring and add the launch lugs, and the bottom half is finished!
Now comes the coupler. I highly suggest test fitting the coupler, sanding, and test fitting again until it is snug, but still slides in easy enough so that the glue doesn’t grab before the coupler is in all the way. When all was said and done, there was still a 3/32 gap between the two tubes, so i filled and sanded it down with two-part epoxy clay from Apogee. The rocket was then set aside to dry overnight.
Now is where the strakes come into play. The strakes need to be shaped by hand, and that can be a bit of a challenge. Make several shallow passes with a new razor knife close to the lines that you draw onto the plastic. Then sand down the last little bit and wipe away the dust and any remaining flash. Here is where I found the one, and only, gotcha. There is a wrap (similar to an Estes fin wrap) that marks where the strakes go. The problem is that the launch lugs are already glued on. To avoid this, either use a straight edge, or wait to put on the lugs.
Draw the lines at least 6" past the lower body tube. Now glue on the strakes.
Next tie the parachute to the shock cord and tie the shock cord to the nose cone. The assembly is done!
Finishing
Finishing on this rocket wasn't all that bad.
The first thing that I worked on was the nose cone. It didn't come out perfect, but it could be a lot worse. The first thing I did was wash it (you can use a clean rag) and lightly sand around the seams with 220 grit sandpaper. I filled in the seams with CA and sanded it down again. I repeated these steps until the surface was smooth.
Painting was a breeze. I applied several light coats of primer and sanded with 220 grit. This posed a problem, however. I wasn't using 320 grit sandpaper and the paint on the nose chipped off in several long streaks. I decided to go with it and used 150 grit to get all of the paint off of the nose cone. I repainted it and, from that point on, used only 320 grit sandpaper. Sanding the tubes around the strakes and lugs was easy but it took time to do well.
After a few more coats and some more sanding, I masked off the body tubes and painted the nose cone silver. Two coats and it was done.
Here’s a trick for painting: BEFORE the paint completely dries, remove the masking tape to reveal crisp clean paint lines. Using low-tack tape also helps to keep the paint you masked off from coming off with the tape.
Painting for me took about two days because of the lighter coats, but it was worth it.
Here comes the hardest part of finishing the rocket: the decals. They are not pre-cut and they take time to cut out correctly. I used a pair of sharp scissors and a paper cutter I found in the basement. There were no snags on the decals and they turned out fine. Applying them is pretty straightforward. Afterwards, I applied a gloss clear coat and the rocket is complete!
Or was it...
I was less than satisfied with some of the decals because they weren't staying down. I took the flat end of my razor knife and pressed them down and quickly applied some clear nail polish. It works just like a clear coat, but only for small areas.
Flight
I have flown this rocket once on an Aerotech reloadable E28-4t using the 24/40 casing. One of the great things about Aerotech kits is that no wadding is required. All that you have to do do is to pack in the shock cord and parachute. The motor lit on the first try, and boost was faster than I thought it would be. It probably got to about 550'. The four-second delay is perfect for this rocket, and deployment was at apogee. The parachute opened within the first half of a second after the ejection charge went off.
Recovery
The rocket was was to spot due to the bright yellow 30" nylon parachute. The parachute came out and opened fully without any tangling or snagging on the shroud lines. It seemed to come down at the right speed, but perhaps a little on the fast side. Since there was a light breeze on the ground and no thermals, the rocket landed about 50 yards from the pad, and nothing was broken. The rocket was in perfect condition and flyable as was.
Summary
I love this rocket. It is an easy way to start using mid-power motors, both single use and reloadable. The retail price might seem high to some, but it was worth it. The rocket is built like a tank, and is a pleasure to build. It only takes an afternoon to build and a day or two to paint, so it is the perfect kit if your launch date is soon. I can't wait to fly this rocket again, and will soon buy another kit from Aerotech.
Other Reviews
- Aerotech Strong ARM By G. A. Dean
Brief: Aerotech's take on the often modeled Navy Standard ARM is the "Strong ARM". It's not a particularly close scale rendition, but the result is good looking and well suited to F and G motors, particularly the EconoJets. There's a bit more to build in this kit than in the Aerotech Initiator or Mustang, but not so much that builders new to mid-power should be scared ...
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Flights
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