Free Flight: Indoor
PROP STRUCTURE BASICS. Prop-wobble due to structural variations is the hardest problem to spot and fix. Last time, we covered the problems of geometry (blade angle, twist, and alignment), and problems of repairing working props so they remain wobble-free. So, how do you get a wobble-free prop to begin with? The lighter you want the prop, the harder it is to make it wobble-free. A Pennyplane (P/P) prop is usually sturdy to handle the high power required to drive a three-gram model. However, the prop on a world-class FAI Stick model typically will have much higher relative stress on the prop structure. Here is why: a typical Pennyplane prop may weigh .021 oz. and be driven by .066 oz. of rubber, which is a ratio of over 3.1:1. The FAI prop may weigh .0065 oz. for a rubber weight of .036 oz.-5.5:1 ratio. Both rubber loops may be similar in length, so the P/P launch torque could be twice as high as on the FAI in an unlimited-ceiling site.
Free Flight: Indoor
OUCH! Twenty-twenty hindsight! After checking what I've said about prop wobble, I think I need to stress one point again. Indoor props don't wobble because of a weight imbalance-at least not for any reasonable amount of static imbalance. The problem is caused by structural or aerodynamic mismatch between the blades, and all reasonable care to match blades will pay off. This is because the amount of energy dissipated by the prop is much greater than the wobble force caused by a weight mismatch. A vivid example is the Easy B with one prop blade broken off. You can static-balance the remaining blade, but you won't do much for the wobble. Because of air loading on the single blade, the only way to demonstrate that the prop was balanced would be to run it in a vacuum!
Free Flight: Indoor
A SALUTE! Once a year, I try to remind you how lucky you are if your club has a newsletter. I get many club newsletters each month, and many of them show a strong labor of love. Even the smaller ones which report local club news, announce contest and meeting dates, and report contest results appear faithfully. The more elaborate (spell that thicker) newsletters carry plans, design and theory articles, philosophy, nostalgia, safety articles, and whimsy. Club newsletters are informative, timely, funny, and enjoyable; they are published on a shoestring, appreciated by the members, and seldom supported by contributions. And, those readers who don't contribute are the ones with the most suggestions about which topics should be published!
Free Flight: Indoor
HOW DID THAT HAPPEN? About this time last year, I reported that AMA had made an extraordinary effort to get Nats planning input from Indoor fliers. Then I tracked the effort through a few evolutions to the point that it seemed that the 1986 Indoor Nats would be a great meet. Well, things kind of fell apart. First, AMA couldn't get solid clearance for the big Coliseum in Lake Charles, so the meet was shifted to the Municipal Auditorium downtown. We thought we had dibs on this site, but this turned out not to be true due to a communications problem. So, the meet had to be shifted to mid-week in conflict with the Outdoor events.
Free Flight: Indoor
RULES PROPOSALS. We are halfway through a new rules-making cycle. If you noticed, all the Indoor rules proposals which will be considered during this cycle were published in the December 1986 issue of MA (in the "Competition Newsletter"). I hope you contacted your District Indoor CB member and told him your feelings about these proposals before his deadline (December 1, 1986) for mailing in his Initial Vote ballot. Otherwise, he had to vote without your guidance! If that was the case and a proposal you favored is eliminated by the Initial Vote results, don't complain! After the Initial Vote results are published, please try to do better by helping the ICB decide which of the surviving rules should be adopted.
