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11 Guests On (EMRR is Off) |
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By Clive Davis
For those of you who know me, you know I like paper rockets. Part of that could
be because I am cheap. The other part of it could be because I like creating things out of nothing. Paper can take any
form, provided one is patient enough. Well, this winter I was making sketches in my rocket notebook, and I was
particularly fascinated with the idea of creating a tube-fin rocket that featured conically shaped fins (see Photo No.
1), with the wider section of the open cone at the top so that the cones acted as "ramjets". In addition to
this general design, I wanted to have two large wing-type fins that were on either side of the rocket, mid way up the
body tube. I put my plans into action and created some templates in MS Word and Adobe Photoshop. After I put together a
mock rocket, I had a chance to observe whether or not I liked the general design. I usually put together a mock design
just to make sure that parts fit. I generally don’t fly my mock constructions (I see them as pre-boilerplates).
The mock design is simply a guide to see if all the parts match and fit. I sometimes use regular paper so that I am not
wasting my Bristol board or other card stock. Well, after looking at my rocket, I decided that I really did not like
the looks of the two wing fins, so I ripped them off. Again, I submit for your reading pleasure Photo No. 1. Another
problem I faced with this design was that I was not accurate in calculating the size of the tube fins in relationship
to the size of the body tube. Thus, I had tube fins that did not fit perfectly around the main body.
At this point, I liked the looks of the conical tube fins, but felt that something was missing from the general design. I liked the looks of my wing design (with tubes at the end for a cool "nacelle" look), but just not all the conical tubes at the bottom of my rocket. My rocket now metamorphosed into a rocket plane with wing-fins while keeping two of the original six conical tube fins. In addition to this, I added two fins at the bottom of the rocket opposite the tube fins. Next, I designed a motor mount for the rocket, then did a Bristol board print. Now I was ready to build and test fly my rocket. After construction, my swing test told me that I needed nose weight. I was not too concerned about this. A lot of unusual rocket designs require nose weight. As long was the weight wasn’t extreme, this was not going to be a problem. In my design of the rocket, I decided early on I wanted my ramjets and nacelles to be red on the inside with the conical tubes blue. The rest of the rocket could basically be grey with a black cockpit printed directly on the main body tube. At one point, I even designed a fire/flame pattern for the nose cone. I added nose weight, then waited for a good day to launch. My recovery system was streamer material. I was interested in flight performance and didn’t want to go chasing the rocket all over the athletic fields where I fly. On all of my flights, the rocket was stable, but there was one slight problem: I had squirrly, roll-type flying with a little bit of fish-tailing. Upon closer inspection, it appeared that my wing fins were not exactly flat, and that one of the wings actually was warped. This became apparent on a few flights when on one particularly robust boost, one of the wing fins sheared right off. I had to return to home and print up more wing fins. When I built my second set of wing fins, I let them dry between two large books ("African Handbook of Birds" and "Stanley in Africa", if I recall correctly). This seemed to do the trick as far as getting the wing fins to remain flat and be identical in shape. I also thought that one of the culprits of the fish-tail flight might actually be the conical tube-fins. I thought about switching the tube fins from wide-narrow to narrow-wide (basically pulling them off the rocket and CAing them upside down) if the wing fin problem was not the cause of the fish-tailing. Photo No. 3 – the first version of the rocket
plane, The launching of the repaired rocket plane commenced shortly, now with straight wing fins. However, there still was some rolling and fish-tailing going on. My original premise that the fish-tailing was due to the warped wing fins was inaccurate. I had to now proceed to the next theory that perhaps the problem was being caused by the conical tubes. I had to go home and remove the conical tubes, invert them, and re-glue them to the rocket. On May 21, 2005, I found myself launching with my club, ASTRE. In between competition flights, I had a chance of sending up the rocket plane, now with the conical tubes inverted. Although the flight was stable and fairly straight, there was a noticeable squirreliness to the flight. I discussed the situation with my fellow rocketeers and it was decided that one of my nacelles on the wing fins was at a slight angle, perhaps causing the twisting in flight. At this point in the game, I made a decision which was unscientific. Not only did I re-glue the crooked nacelle to the wing fin, I replaced the conical tube fins with two regular cylindrical tube fins. Instead of using a process of elimination in finding the cause of the fish-tailing, I decided to make a conservative adjustment to the rocket. Fortunately, I brought along a bottle of CA with me to the launch along with pre-constructed tube fins.
The next flight was spectacular. It was a great boost on a B6-4. The recovery method of using two streamers had been very successful and I decided to keep this aspect of the flight recovery in the "kit". I flew it a couple more times, using a B6-4 again and later a C6-5. Both motors turned in straight, high boosts and good, stable coasts. The delay times seemed appropriate for the rocket. I was now set. I had a rocket-plane that had wing-fins AND tube fins. I was a little disappointed that I did not continue my study of the conical fins, but another idea was brewing in my mind. I decided to hold off on the conical fins for another rocket that I was planning. This allowed me to get the rocket plane off the ground, so to speak, and into the drawing and final adjustment phase of the rocket kit design. Now that I knew what the profile of the rocket was going to look like, I had to make some artistic decisions as to how I wanted the overall rocket to look. That, and I had to come up with a name…. A good name. Up to this point I had been calling the rocket the Simian Space Cruise, or something to that effect. This unfortunate moniker is due most likely to a co-worker who lent me his Planet of the Apes TV series collection on DVD a few weeks ago. For some reason, the word Simian seemed appropriate even though there was nothing monkey-like about the design, except for maybe some of the flight testing.
I eventually settled on a very similar name, the Sirian Space Racer 5, or SSR-5 for short. Next, I opened up the files in Adobe Photoshop and I began playing around with the templates and designs. First of all, the cockpit traveled much further back in the later SSR-5. I re-designed the imagery on the rectangular launch lugs, and I also spent a great deal of time working on the actual shape of the leading and trailing edge pieces of the wing-fins, to make sure that they fit the wing-fin snuggly without any obvious gaps.
In my flight tests, I had some setbacks with the wing-fins falling off during boost. I attribute this to the deformation that I later fixed. I designed some metal, rivited plating that would act as holds and supports for both the smaller fins and wing-fins.
I liked the looks of these since it gave a kind of retro look to the SSR-5. I also ended up removing the fire design on the nose cone and making the nose cone more blunt at the end, since the streamer recoveries caused rough landings for the weighted nose cone. The original conical tip of the nose cone became blunt just after a few landings, anyway. Photo No. 8 - (nose cone battle scars from I added some text to the rocket, including the naming of the rocket, a slogan for the SSR-5 ("to subjugate and protect"), and I even named the commander of the vessel. I also had portholes for any passengers who may be convinced to take a trip on the SSR-5. As I had stated earlier, one of the original decisions was to have the nacelles and tube fins be red on the inside. When creating paper rockets, one generally prints up the patterns and then constructs the rocket. Usually, the designs are only on one side of the paper as the plain side is usually the internal part of the rocket. With tube fins, the inside of the tube was going to be exposed. I came up with three solutions: 1.) One could crayon the other side of the tube fins with red crayon. 2.) One could print up a solid red rectangle on a separate sheet of regular paper and then glue this to the other side of the tube fins. 3.) Or, the simplest and best solution would be to simply print the solid red rectangle directly on the back of the templates that have the tube fins on them. I tried methods 2 and 3 and found value in both of them. In the end, I think method 3 is the easiest. Regarding the color of the rest of the rocket, I had different shades of blue and gray in mind. Depending on the temperament of my ink jet printer, I ended up with interesting interpretations of blue and gray. One last minor change was to make two launch lugs for the underside of the SSR-5 and have them be symmetrical to each other, identical and attached. See Photo No. 9: Photo No. 9 - underside with a view of As with all of my paper rocket kits, I try to come up with some instructions that can guide the builder through some steps which may or may not be apparent from just observing the parts sheet. I like this final part of designing the "kit" because it is like a reward after putting the finishing touches on the actual rocket. I learned a few things about paper rockets when designing, building and flying the SSR-5. First of all, I was really getting annoyed with drawing a line in Adobe Photoshop, only to have a diagonal line be displayed rather crudely, with lots of jaggedness to it. I consulted with a friend of mine who teaches digital art, and was instructed to increase the dpi from the default of 72 to a higher number like 300 or 600. This, of course, means that the size of my files would jump drastically up. Because I was trying to keep things simple, I just left the SSR-5 at 72 dpi. The next rocket that I design, I will probably be more careful about how much resolution I want in my detail. This is one of the main reasons why the flaming nose cone design was removed. It just didn’t look good up close and personal. Another lesson I learned is that if one is rolling identical tube fins for a rocket from a paper kit, one has to be extremely careful to roll them the exact same size and shape. It is very easy for paper to deform, even if one is using a more robust paper like Bristol board. I also learned that the most difficult aspect of building the SSR-5 is rolling the large body tube. The large body tube is easy to crease and it takes patience to glue it just right so that it has a perfectly tubular shape. I found it easier to roll the tube fins and body tubes around dowels and a BT-50 tube to get the appropriate shapes necessary for the SSR-5. Last but not least, it is really important to work with clean hands that are free of moisture and excess glue. Particularly when gluing together the nacelles with the red lining, the color from the ink jet is easily lifted and wants to travel onto your fingers and eventually on to your beautiful rocket. Remember, the beauty of a paper rocket is that there should be no painting involved. Thus, extra care must be taken in all aspects of constructing the final version of the rocket so that there are no visible smudge marks. What I find ironic about this project is that I ended up abandoning the idea of conical tube fins entirely. This was the original concept that spawned the SSR-5 in the first place. The wing-fins were removed after the build of the mock design, but eventually made it back into the final design. I hope you have enjoyed learning about how I design rockets. Please build the SSR-5 and let me know what you think. See you out on the range! Instructions (PDF - 247K) |
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