Wanna "Super Size" a rocket? Upscaling (and downscaling, for that matter) has probably been around longer than I care to think. It's not uncommon at launches these days to see big (and small) versions of your favorite model rockets. Most are likely the creations of those flying them. Whether you personally choose to go bigger or smaller, creating a resized rocket these days is a relatively easy process. All you need to start with is an idea and from there "The Sky's the Limit" as the old saying goes.
Even some of the established model rocket companies have marketed resized rockets. The Estes Maxi Honest John and Maxi V2 were introduced in 1974 and were followed by the Maxi-Alpha and Super Big Bertha some time later. In 2007 Estes simultaneously introduced an upscale version of the classic Interceptor as well as an updated version of the original. All are examples of upscales of classic Estes kits originally introduced in the 1960s and 70s. Semroc Astronautics "SLS" (Semroc Large Series) have bigger versions of some classic Centuri kits like the Laser-X, the Hustler, as well as the Estes Sky Hook. In 2008, Qmodeling introduced a 1.65x (165%) Estes Andromeda, joining a modest fleet of other beautiful upscale kits like the Estes Mars Snooper II, WAC Corporal, Nike-X, and the EAC Viper. And lest we forget the awesome Tango Papa upscale Mars Lander kits. These are all just a few examples of commercially produced upscales, many of which are available in 2008.
Body Building
For the purpose of this article, I'll focus on upscaling. Once you've decided on a rocket to resize, you need to determine what body tube diameter to build the larger version around. Research to find out if a commercially available nosecone is available or if you'll have to go custom. Another consideration is whether the upscale will require a serious increase in motor impulse to get the beast off the pad. Motor size will dictate whether you can stick with a thin wall tube or should upgrade to a thicker wall. Not all body tube sizes are available in both versions, however you could choose to use a high power motor tube as your main airframe. Be aware the high power motor tubes (29mm, 38mm, 54mm, 75mm, 98mm) are not the same diameters as airframe tubes so you'll probably have to make a custom nose cone for it.
Once you've selected your upscale body tube, make a note of the exact diameter. Thankfully, body tubes/airframe tubes are manufactured to exact standards, and the diameter is often measured to the thousandths (three decimal places), but some are only to the hundredth or tenth. Get a calculator and divide the upscale body tube diameter by the original diameter. For instance, if you want to build an upscale Estes Alpha (original size: BT-50, .976inch) based on BT-80 (2.6 inch), divide 2.6 by .976. The result is 2.6639 and you can safely round that down to 2.66 or up to 2.7 - it's you choice. That number is your scaling factor and all your future calculations for this upscale will use that number as your multiplier.
Upscale Diameter
-------------------------- = Scaling Factor
Original Diameter
If you have access to Excel or another spreadsheet program that does internal calculations you define, don't hesitate to use it. You can put the simple division formula in a column of cells and use adjoining cells for your original dimensions and have the upscale dimensions appear where the formulas are. Such a tool really does make upscaling/downscaling easier. You can set up a whole page of these simple formulas and start plugging in numbers and see just how big or small a particular rocket will be at a given diameter.
In many cases you'll only have to do one more calculation, and that's for the body tube length. In this case, the original Alpha used a BT50H body tube (7.75 inches long) so multiply 7.75 by your scaling factor and that will be the length of the BT-80 body tube. I'll use the 2.7 scaling factor, so in this case we'll multipy 7.75 times 2.7. The result is 20.925 - your BT-80 will be 20.925 inches long. I often convert the inches to millimeters to simplify the actual measurements. In this case, multiplying 20.925 by 25.4 (millimeters to the inch) and the result is 531.495 millimeters. Round up or down - again it's your choice but I think you'll agree it's much easier to locate 531.5mm than 20.925 inches on a typical ruler that has both inches and millimeters.
If your original design uses a reduced (or enlarged) diameter tube for the upper section (like the Estes Astron Cobra) you might be able to use an upper airframe tube for which nose cones exist. Many possibilities exist with the different airframe/motor tube combinations. If you use a reducer or transition between two different tube sizes, Balsa Machining Service (BMS) will be happy to create a custom piece for you, to your exact specifications. Another option is to use paper transitions you can create using the online Delorie Body Tube Transition calculator/printing program. This nifty program allows you to plug in your diameters and transition length and print out the result. You can even set the smaller diameter near "zero" to create paper conical sections. Another way to save some money with solid transitions is to use a commercially available one, even if it is shorter than the original. To make it match the profile of the original, use the transition calculator to make a longer shroud from paper and cover the solid one with it. Just be sure to modify the length of whatever airframe tube will be partially hidden so you'll preserve the profile of the original. I used this technique on an upscale of the Estes Astron Cobra I recently built and I definitely saved some money versus having to buy a custom balsa transition.
The Pointy End
Hopefully, the rocket you choose to upscale has a similarly shaped nose cone in your body tube size. Unfortunately, not every nose cone shape is available for every body tube size. Unless you make your own custom nosecones with a lathe or other process, availability of specific nose cone shapes often dictates the body tube size you'll upscale to. Sometimes you'll just have to compromise a little when it comes to exactly duplicating the profile of your rocket, but in many cases you can get pretty close.
If you choose to go custom, use your scaling factor here as well. Simiply measure the cone (or take the measurement from a catalog or other resource) and do the math. You'll need this figure if you want to send your data to BMS or another source to have your cone made. I can tell you from experience the BMS custom cones are very nice.
Another consideration is whether or not the nose cone you'll use is a true upscale of the original. Chances are it's not, unless you've custom made it to exact specifications. If the profile of the cone is close to the original you can probably get away with not adjusting the body tube length. However, if your cone is longer or shorter than the original but looks close, you might have to adjust the body tube length to compensate and make the visual effect work. Another way to pull off the illusion is to extend the paint from the nose onto the body tube. I've seen this done on some upscales of Estes Der Red Max rockets. The bigger cone just wasn't quite long enough to match the profile of the lengthy original, so part of the upper body tube was painted black to give the illusion the cone was longer. Just something to think about when planning the build.
Fins
Continuing with our 2.7x (270%) Alpha upscale, lets make the fin pattern. An easy way is to find a copying machine with the capability to magnify the image. Set the copier to magnify the original Alpha pattern by 270 percent. Many machines probably wont go that high, so you may have to do it in two steps. Additionally, you might have to use legal size paper (8.5 x 14inches) to accomodate the longer length of the final image. To make your first enlargement, you might first choose to magnify it by 200 percent. Then you'll have to go up another 135 percent from that to further increase the size to the final size. I made this determination by dividing 270 by 200. I came up with 1.35 and translates to 135 percent of the "new" original (your first, 200 percent copy.) Don't forget to replace the first original with the 200 percent copy when you make the 135 percent copy or your fin will be too small. You can probably figure out how I know this
.Another way to upscale the pattern is to simply extrapolate the existing dimensions on paper. Find the length of the root edge and multiply that by 2.7. Draw a line that long and put the fin pattern root edge straight along that line. Then, keeping the fin pattern lined up, calculate the leading edge dimension the same way as the root edge and draw the leading edge line that long, extending the line past the pattern leading edge. Then repeat the process for the trailing edge and finally the tip. If you made your new drawing on stiff paper, you can simply cut out the pattern and make the fins out of the material of your choice.
If you happen to use RockSim, BMS will accept your ".rkt" file and can produce laser cut fins for your project. The have a varitey of materials to choose from like balsa, basswood, lite ply and G10 fiberglass. Whatever method you decide on, it's probably a good idea to use through-the-wall (TTW) mounting techniques. TTW provides a much stronger bond and you're less likely to pop a fin or two on landing.
The business end
An upscale often requires more thrust to get it safely off the pad and into the air. You can choose to go with a single, higher power motor or a cluster of two or more motors. If you're really talented, you might opt to make your own rings or you can have them made professionally. Thankfully, BMS has the capability to laser cut centering rings to your exact specifications. Find the internal diameter of your airframe, figure the number of motors and BMS can make the rings from a variety of materials ranging from fiberboard to lite ply to G10 fiberglass. They also stock rings to fit a variety of airframes and motor configurations. In either case their work is first rate and the rings fit like the proverbial glove.
Soft as a feather
Typically, upscales are larger, and heavier rockets require beefed up recovery harnesses and heftier parachutes than their little cousins. Kevlar (c) cord in varying weights and diameters is well established as a mounting device, as is braided wire. Whichever you choose, it's a good idea to attach it to the motor mount in some fashion. To bring your rocket safely back to earth, stronger elastic shock cords or tubular nylon or Kevlar (c) should be used to absorb the ejection charge and deployment of the recovery device.
Decals
If you want to duplicate the look of the original and decals are involved, some vendors offer upscale decals and/or custom services. Tango Papa Decals provides both with an extensive line of decals and they'll gladly create super sized decals for your project. If you go bigger than a standard 8.5x11 inch sheet for your custom project, Tango Papa will likely print your decals on vinyl. Be aware this custom service can take a few weeks.
In closing, upscaling your favorite rocket design can be a rewarding experience. Not only will you add another rocket to your fleet, you might learn some new techniques you can apply to future rocket projects. Chances are good that you won't want to stop upscaling after buildng the first...and you might just find yourself building a "super sized" fleet of your favorites.