S5C Competition Strategies
One thing to remember if you're going to spend months, if not a year, crafting a competitive FAI scale altitude model : Once you ignite the motor, all it is, is an Altitude model !!! Do not begin by "building" a scale model without thinking through your flight strategy! Build numerous "boilerplates" and test fly all aspects of your flight, most importantly staging and recovery techniques. If they should fail, you're DQ'ed and that is an awful feeling after having traveled half way around the world. Test flying and data acquisition could occupy most of your modeling time, but can also be the most fun and rewarding. Select a competitive prototype that can be easily documented for scale. Obscure rockets like the UTE-Tomahawk might be very efficient and adhere closely to established minimum size constraints, but documentation and color photographs may prove extremely difficult to locate. Have the minimum data on a number of prototypes and possibly locate a bit more before selecting the one you wish to model. These "scale" models cannot be built "heavily" to survive numerous flights and still be competitive. Most winning S5 models are altitude models in disguise, they merely appear to be a scale model on the outside.
Begin by designing an altitude model and figure out how to add the detail to it. But, "lightest" is not necessarily better, either. There will be an "optimum" weight for each stage and configuration and that can best be determined using commonly available altitude prediction programs for your PC or Mac. Many European modelers have sacrificed scale detailing to increase altitude potential. By omitting projections on the surface of the sustainer to reduce drag, many times much higher altitudes can be achieved. With proper considerations this can sometimes be an even more than reasonable trade for the loss in static points. There is a saying at the WSMC that "he who places first in S5 static, never wins." It has held for as long as I've been competing. Many times models ranked in the middle third of the static scores will actually win the contest by posting superb altitudes. Your static score should be reasonably good or better, but to win consistently takes a very good "altitude" potential.
Models should be built to be flown as both single and multiple staged. It is not always the highest altitude that wins: if low clouds are present on the day of the competition, you will need to fly just below them to get a tracked flight ! Models should be built to adapt to different competition conditions, modelers should be as open minded as well. A choice of tracking powder color can be advantageous, anything to enhance the tracker's visibility. In clear, sunny skies, Red or a Fluorescent Orange powder shows up particularly well. However, on overcast and cloudy days these colors hold less contrast with the sky. A Black or Navy Blue powder will have higher visibility in these conditions. Tracking powders used are varied but commonly consist of either snap line chalk (available at hardware stores) copier toner or dry paint. Toner is messy, avoid this if you can. The chalk is highly visible but heavier than dry paint and the weight of the tracking powder is an important consideration for optimum sustainer mass. Amounts and weights necessary should and can only be predetermined by boilerplate flying. Gaining confidence in determining the type of tracking powder for your prototype, or color as sky conditions change is a matter of experience. So, practice flying even in bad weather conditions and expect to loose a number of your boilerplates. Remember, it's ok to ruin boilerplates - the knowledge gained could save you from disaster in a competition that is held only once every 2 years.
Design your second stage to hold the minimum power necessary for visibility and for the 5 Ns allowed in the sustainer. Total impulse of 5 Ns in the booster should be enough to get the entire model off the pad, then stage and drop this additional weight and the draggy large body diameter. Use a piston launcher (with or without a tower) to make the most of your booster motor power. Staging at maximum booster velocity may be difficult, but is recommended. Some model(er)s may need to employ unique staging ignition systems to accomplish this. Weather and tip-off are forces to be contended with if you have a heavy booster like the Bumper-WAC. You may wish to have different combinations of motor impulse and delays available, each suitable for different conditions. In any case, launch the model "as close to vertical" as possible. Basic geometry and algebra tell us this is the only way to achieve optimum results. DO NOT aim for the tracking baseline! Models tracked over the baseline may be clearly visible, but percent closure is rarely within the 10% rule.