CL Aerobatics
Frank McMillan, 12106 Gunter Grv., San Antonio TX 78231
When I was out flying one day, one of my friends commented on how someone he knew had released his airplane improperly, and it cost him a propeller. That got me thinking that this was one area I hadn't discussed in the last column devoted to takeoffs.
The irony of this point is that it even comes up at the Nationals, where experienced fliers cause others to have poor takeoffs because of poor launches. The technique is simple, but it requires concentration and focus.
As with everything we do, there are some safety aspects that should be automatic.
I'm going to start with the engine running and the model ready for launch. (I thought about including starting, but decided I'd leave that for a later column.)
The launcher should visually clear the area for persons and obstructions that the airplane could strike on takeoff. He or she should also see that the line connectors are not twisted and that the engine is running steadily. From then on, wait for a clear release signal from the pilot.
The next point is where problems normally arise.
During the release, the launcher should remember that he or she is aiming for a smooth release that will immediately put the model under the pilot's safe control. Has he or she put pressure on the tail, so that it pops up upon release?
The ideal launch on grass and smooth surface is to let the model slide slowly out of the launcher's hands and accelerate away.
There is a potential problem here. This is not a hand-launched Combat model; it shouldn't be thrown! Too many times, launches that are used to put the model into the air cause it to tip over, costing the prop tips at best, an important official flight at worst.
It's the pilot's responsibility to brief the launcher on the way he or she wants it done. The launcher should make sure that the attitude is correct for launch, and let it slide out.
That's enough for now. If there are other points you would like discussed, let me know.
Tech Tips
For some time, I've been using thin aluminum foil as a mask for spraying. It works well, and is cheap and disposable, but it does have some drawbacks.
You have to be careful how you handle the airplane, or you will indent the finish, and the foil will usually mark the lighter colors with a dark smudge. I've tried to remove these marks by sanding lightly with some 2000-grit paper, used wet. That does work, but there is a danger of sanding through thin paint.
I learned by accident that 3M general purpose adhesive cleaner (part #08984), the universal cement remover that I mentioned many columns back, will wipe these marks away with no effort!
This product also works exceptionally well with the Frisket® masking tape and hinge-sealing materials. Just work it on an edge and keep going.
The adhesive cleaner can be purchased at an auto-parts supplier.
I was asked about three-blade propellers and the .35- to .40-size engines. When I was using those engines, I didn't use a three-blade prop as much, because there weren't many choices (the Grish 9 x 6 3B was available).
I remember that the first truly successful three-blade propeller was a homemade wood version that Bob Hunt put on an O.S. .40 FSR to win the World Championships in 1978.
If you look at that setup, you come to the conclusion that the high horsepower of the .40 FSR (at the time) and the extra blade worked well. The success of three-blades is really because of the usable horsepower we now have available. Putting a three-blade on a smaller engine doesn't guarantee good results.
Recalling my experiences with some of the Hunt propellers, the window of useful performance was extremely small. A particular prop would work very well, while a similar prop with minimal measurable differences might not work at all. It was a function of how well the propeller matched the airplane/engine combination.
My best guess is that if you want to try three-blades on the .35- to .40-size engines, you better be prepared for a great deal of experimenting and some very narrow success windows. When it works, I'm sure the results will be good, but I wouldn't recommend the effort until you start to get up in horsepower.
What's New
The winter building season is in full swing as I write this, and news of what everyone is working on is starting to filter out. There is word that a complete, molded composite airplane for a .60 will be available shortly. I'll try to report on this scoop!
Meanwhile, there is continued development on all fronts.
Based on his very successful SV-11/12 series, Randy Smith has a new updated version that he calls the SV-22. It has longer tail moment, enlarged stabilizer area, and a restyled, widened fuselage.
The new series will initially be available as plans only, but you will probably be able to get laser-cut kit sets.
The SV-22's widened fuselage was made to accommodate larger-volume pipes that Randy and Bill Smith are developing. The new series of pipe will be available through Randy. As is normal, Bill Werwagge is the manufacturer and chief tester. If the set is passed by Bill, it's special!
Contact Randy Smith at Aero Products, 1880 Scenic Hwy., Snellville GA 30078.
Windy Urtnowski is getting into the cyberspace revolution with his Web site, windyurt.com, and E-mail, [email protected].
It's hard to keep track of the many new items that Windy produces. Perhaps the best are the interesting videos that he cranks out at astonishing rates. The 1999 subscriber series and the Brodak meet videos are very entertaining.
However, the videos I enjoy most are part of the annual new series on Windy's latest creations. This year the model is starting out as a P-51 variant, Miss Ashley, with the promise of carbon composite moldings to follow. Meanwhile, there are many old and new tips and techniques for builders of all ages. It's fun to follow the evolution of another beautiful work of art.
On the product side, Windy is using his carbon/epoxy molding technology to produce a new line of tuned pipes. They feature very light weight and some unusual features.
Instead of using the high-temperature silicon coupling sleeve as an insulator from the header to the pipe, Windy uses it to simply seal the pipe-header mating point. His pipe is designed to slip over the header tube with a snug fit, then the silicon is not nearly as important in providing a seal. This approach also permits a wider range of adjustment without cutting off ends.
Windy also features molded conical baffles which, along with greater internal volume, serve to broaden the power band and soften the power.
Another product that is gaining popularity is the carbon/epoxy landing gear. Windy has several models available which are designed to fit most popular designs, including the Pattern Master and SV-11 series. They are supplied with aluminum axles and are well-tested.
Also new are the carbon/epoxy bellcranks. These are set up to time-tested numbers, 4-1/4 inches, with hand-laid carbon tower, brass bushings, and music-wire pivot. They can be supplied with leadouts installed. As a special service, custom-made bellcranks are available for an initial setup fee plus regular charge. These are very nice items.
Contact Windy at 93 Elliott Pl., Rutherford NJ 07020; Tel.: (201) 896-8740.
Transcribed from original scans by AI. Minor OCR errors may remain.
