Rocketry Planet
| Lesson 7: Final finishing and flight results |
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| Tech Tips Series by Darrell D. Mobley | |
| Monday, November 17, 2008 | |
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Page 8 of 8 LESSON SEVEN: Final finishing and flight results Well, it's cap and tassel time in the Rocketry Planet HJ101 Honest John class. The class will conclude with this installation and the results will be displayed for all to see. The class, in my opinion, was a great success and if nothing else, was a real fun time. The results speak for themselves and I think you will join me in saying everything turned out better than expected. When we finalized the previous installment, we finished the construction of the main parachute compartment which resides in the forward nose cone section. That only left the final finishing and application of the decals before final outfitting of the motor retainers, the recovery harnesses and building out the electronics bay wiring harnesses. With the rockets ready for primer, I spend a good deal of time priming and sanding, since the preparation really shows in the final product. I began by carefully sanding the styrene nose cone pieces and the associated fin thrusters with fine grade steel wool. This gets into places where you can't get with sandpaper. It conforms to the various curves and shapes and really gets in the corners. The main airframe received several coats of Duplicolor High Fill automotive gray primer. This fills sanding scratches in the fiberglass well and sands really easy. The nose cone section was treated to regular Duplicolor automotive gray primer because they didn't have the typical sanding scratches that the main airframe did. Once the pieces made it through the "prime, sand, repeat" phase, I covered each piece with three good coats of Krylon's Camouflage olive drab spray paint, which can be found at Walmart, AutoZone and other similar locations. I left the rockets to dry a couple of days before moving to the next step. I hit up Tango Papa for their BT80-sized Honest John waterslide decals. At just $13 a sheet, they provide more than a few extra decals in the event you should make a mistake. Applying the decals took a little orientation to get familiar with the time frame needed to dip the decal into the water, how long to wait before taking it out and then carefully sliding it onto the rockets.  And the results? Well, just outstanding! Here are all three rockets, with the 54mm version proudly taking up the central position flanked by the two 38mm versions. I just hope none of them ever end up in a back alley in Derry, New Hampshire, as they would certainly be confused for the real thing.  The Tango Papa decals really make these Honest John rockets complete, and they worked out well even over an ultra-flat finish like the Krylon Camouflage. You can see in the photos how well the small details came out, which translates into good preparation leads to good results. I didn't paint the couplers, leaving them in their natural finish of sanded CA, meaning I covered the raw cardboard with thin CA and then sanded it smooth, to stiffen and seal the tubing.  Here, the 54mm version is shown with the AeroPack 54mm-to-38mm adapter, and it is just slick. With the 7-1/2" motor mount length, the AeroPack adapter is a perfect fit. With an adapter that fits and works as nice as this one does, the common sense approach is to build the 54mm version and use this adapter to fly 38mm motors. The 54mm version was actually two ounces lighter than the 38mm versions due to the additional weight of the Groove-Lok fin placement system and the foam filling the fin canister used in those models. At any rate, all three rockets are each 3 pounds or lighter.  A closeup of the PML urethane launch lugs, albeit cut in half, shows a clean solution to a tricky issue on rockets that need a rail standoff. They are rugged when used like this, and performed very admirably.  The electronics bays are a lesson in simplicity, combining a compact design in an easy to use configuration that is easily removed for service. Quick disconnect plugs are used to connect the two ejection charge leads while an on-board switch simplifies powering up the device yet keeping the switch hidden. The access hole for the switch is seen in the coupler above, allowing you to switch it on, settle the nose cone into place and stand back. The altimeter of choice is the new Missile Works RRC2-mini, and works like a champ. Small footprint, ease of use, and straight forward connections make it a popular unit. I picked three of them for this project based on these features, and after setting the profile switch for first time use, I used them as they were programmed out of the box, with great results.  On the back side, a Newton's 3rd Rocketry 9 volt battery holder is positioned to tie in with a Missile Works "Z" battery retention clip. Proper positioning so that the "Z" clip used the same #4-40 machine screw and threaded aluminum standoffs as the altimeter mount required drilling an access hole in the top of the battery holder for the other #4-40 machine screw that retained the opposite end of the altimeter. The longer red/black lead in the left portion of the photo has the male end of the W.S. Deans External Charge Connector and connects to the base of the altimeter bay end cover, connecting the drogue charge leads to the terminal block on the outside of the cover. The shorter red/black lead on the right connects to the main charge lead seen inside the electronics bay, and uses Newton 3rd's JST male/female connectors with 22 AWG wire to simplify service.  The leads in the altimeter bay route through the carbon fiber arrow shafts I mounted in the electronics bay for use as conduits. Both ends are sealed with heat-shrink tubing to keep the main charge gases in their proper place. Packing a 36" parachute in a 7-1/2" recovery compartment is a little tricky but it isn't that hard. That room, plus the additional 2" seen above, is enough room to make it all fit. I outfitted each rocket with 12 feet of John Cox's 11mm Kevlar® ribbon cord on each end, which can be found in the auctions here on Rocketry Planet. This resulted in about 15 feet of recovery harness in the back end and the aforementioned 12 feet in the main compartment, with small quick links on each end for attachment to the electronics bay. I used a standard Giant Leap 36" chute that came with my Escape Velocity kit as the main chute, placed about half way on the harness, and I also used the 18" Giant Leap chute from the same kit as my drogue. To get it all to fit in the main compartment, I simply Z-fold the canopy into sections about 5" long and wrap the shroud lines around it tightly. The best way to get good deployment on the main is to orient the ejection charge forward, letting it blow the nose cone from around the parachute. A .3 to .5 charge is sufficient to get the job done, so by placing the ejection charge in a forward-facing position and then feeding the forward half of the Kevlar cord in on top of the ejection charge, it acts as protective wadding. Then place the chute in, and feed the other half of the Kevlar cord into the recess in the forward end of the altimeter bay, shown above. Wire the ejection charge and slide the two parts together. If necessary, add an appropriate wrap of narrow masking tape on the main compartment coupler to make sure the nose cone stays in place until time for the main to deploy. It should be snug, otherwise the main will deploy at apogee.  I took all three rockets to NEFAR's Bunnell Blast held November 8th and 9th. NEFAR is fortunate to have a great field just outside of Bunnell, Florida, at a nice sod farm. Many thanks go out to the Clegg family for allowing us to use their field. In the photo above, the first one to be flown was a 38mm version, on the left, which flew on an AMW Pro-X I170 Tamed Tiger. I tried to capture it on my digital camera at launch, but all I got was a smoke trail. It was gone. The rocket streaked to 3363 feet and landed just a few steps beyond the flight line. The rocket looked perfect after the flight, and I was well pleased. The second flight, I decided to try the 54mm version, shown on the right. So I selected a CTI J240 Red Lightning. I knew this flight would be even more of a bullet, so I was ready for the launch with my camera. But, no joy, as once again, all I got was a smoke trail. And just like a bullet, this rocket was gone! All the way to 7093 feet. I didn't get the nose cone on tight enough and it ejected the main prematurely, creating a nice afternoon stroll for me 2.5 miles due south. But as luck would have it, I found it, and it too looked as good as new. The extended "field trip" prevented me from launching the other Honest John, but there will be plenty of time to abuse it at launches in the future. Most importantly, the results of the class displayed that the upgrades I did were successful in making the Estes Maxi-Brute Honest John into a rock solid model. The fins didn't even flinch, not a stress crack, no evidence of flutter, just bullet-proof performance. I got the look I wanted from the fiberglass fin shells along with the strength needed to take the abuse of larger motors. I hope that you learned a few tricks during the presentation of this class that you can use on your projects, and that you will tune back in during upcoming classes, where we hope to bring you even more great projects, tips and techniques. KEVLAR® is a registered trademark of E.I. du Pont de Nemours and Company in the United States.  Unretouched photo of the 54mm version Honest John sitting on the pad, awaiting liftoff, at Bunnell Blast, November 8th. |
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http://forums.newtons3rdro...com/viewtopic.php?t=3623
I wish him good fortune.
Seriously though, having seen one of Darrell's supercharged HJ's fly in person (heck, was that the original D?), this will be a great article!! The 54mm version sounds way cool!!!!
Guess I shouldn't have sold you mine then I could have built one!
Yeah, the one you saw fly, Greg, was the prototype, which still used the styrene fins shells over plywood cores. Those gave way to flat G-10, and these versions will have the cool diamond-shaped original lines in fiberglass. If I'd get off my butt and make a mold for the fin canister and the nose cone, I could quit abusing these Estes classics.
Good work.
Oh well. In a couple of weeks, I'll start the G worthy one. Maybe a 29mm H?
Len B
You know, I think you're right. But since I have a couple of J90's maybe I need to go 54mm. Hmmm. I'll see when I get it and try a few things but for sure I'll go 38. I have a 54mm Big Daddy that is nearly finished. This would make a nice "companion".
I'll be interested to follow this and work along side your build. I'm curious to know what the final weight of the 38mm version will be.
Len B