Frequently Asked Questions
Bob Aberle | [email protected]
Full-range 2.4 GHz spread spectrum RC system now available to fly all types of aircraft!
Also included in this column:
- RC flying techniques
- Motor-thrust measurements
- Bob's revised book
- RC pushrod tubing
This is the 36th monthly column in which I try to give you the best possible answers to questions you have written or e-mailed to me. Each new inquiry is given a sequential number for future reference. Many questions and answers have been posted to the AMA Web site at www.modelaircraft.org/mag/faq/index.asp. Unfortunately that posting stopped in August 2005 and will not continue until this section of the AMA Web site is revamped. In the meantime, if you can't find the subject matter you are interested in, drop me an e-mail or letter and I will try to assist you.
Q280: "I built your Scratch-One design that was featured in MA's 'From the Ground Up' series two years ago and is now posted to the AMA Web site. I hate to tell you, but on my first launch the airplane went right into the ground before I had a chance to do anything.
"The damage was slight but it left me kind of shaking. Would you have any suggestions?"
A280: I have a good feeling I know what happened.
Since the Scratch-One is essentially a powered sailplane and has no landing gear, it must be launched by hand. I'll bet you went out by yourself and attempted to make that first flight by launching the model with your right hand while grasping the transmitter case with your left hand. Then immediately after launching (throwing) the airplane, you had to move your right hand to the right-side control stick and apply rudder and/or elevator control as necessary.
The first flight with each model can be different. It might have a bit too much down-elevator trim or it might have been slightly nose-heavy. The minute you launched the airplane, it may have wanted to head straight for the ground. The only problem is that it took you roughly a second to grip that right control stick and command up-elevator.
For that reason I always have a fellow club member launch for the first flight while I grip the transmitter with both hands and have my fingers on the right control stick to instantly apply any amount of corrective control. That has saved a few models for me over the years, and I'm never too proud to ask for some help. It may be hard to get someone out to help you, but you should make the effort. In fact, it is always a good idea to have a helper, friend, club member, or even a bystander next to you while flying. It's not a hard-and-fast guideline, but most fun-flys I attend insist on the "two-person" rule. We do at the SEFLI (Silent Electric Flyers of Long Island) club field on the east end of Long Island and at our annual Northeast Electric Aircraft Technology (NEAT) Fair.
Plans are still available for the Scratch-One design, as is a balsa-wood material package from Aerocraft Inc.: www.aerocraftrc.com/
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Q281: "I keep hearing about the pros and cons of electric-motor thrust measurements, but I'd still like to take some measurements on my own to see if I can correlate any data to my actual flying experiences. My question is, can you recommend an inexpensive thrust test stand for my purpose that is simple to use?"
A281: One of the reasons I love to attend the annual Weak Signals R/C Expo in Toledo, Ohio, is that I get to see a little of everything offered in our hobby. With modern digital cameras I usually take 500 or more photos during the several days I attend the show. After reading your question I realized that I had seen a simple and inexpensive electric-motor thrust-measurement stand at the BP Hobbies booth in Toledo.
The stand is made from wood and has a single pivot point. The motor is mounted on top, and when it operates it moves the pivoting stick forward. The other end of this stick rests on a digital scale. Operating the motor, in turn, pushes down on the scale, resulting in a measured amount of thrust. The entire test stand sells for only $20, which is inexpensive.
You will also need a reasonably accurate digital scale. If you don't have one, BP Hobbies sells a test stand/digital scale combo for $36.
I've never been a big fan of measuring and/or using motor-thrust data, but some modelers feel comfortable using that kind of information. This thrust test stand will let you explore the possibility without making a big investment. For more information call BP Hobbies at (732) 287-3933 or go to www.bphobbies.com.
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Q282: "The Horizon DX6 2.4 GHz spread spectrum RC system has been on the market for over a year. I have one and it works great, but when will I see a system that isn't limited to the close-in flying of small models, like the parking lot variety?"
A282: In September 2006 Horizon Hobby announced the release of a new 2.4 GHz spread spectrum radio system that is claimed to be full range. To quote the literature, "you'll be able to fly anything from micro electric helicopters, to big gas-powered IMAC planes without regard to frequencies and free from the fear of interference."
The new system is designated the DX7. It is a seven-channel-function DSM2 unit with an AR7000 receiver and four DS821 digital servos. This full-blown computer radio system has 20 memory positions and all kinds of bells and whistles. DX7 units were expected to begin delivery in December 2006.
I won't go into any more detail at this time because AMA Technical Director Steve Kaluf began field-testing a new DX7 unit in August. His report on the technology used in the system was published in the December MA and his product review is elsewhere in this issue.
Please make it a point to read those informative articles. And for further reference Horizon Hobby has posted a story about the new DX7 system at: www.horizonhobby.com/Articles/Article.aspx?ArticleID=1626&Page=11
While attending the big JR Indoor Electric Festival in Columbus, Ohio, in November I had an opportunity to talk with Horizon Hobby technical staff about the DX7 system. At that time I also learned that there will soon be a micro 2.4 GHz spread spectrum receiver weighing only 3.5 grams.
That size and weight of receiver will be perfect for the micro and indoor enthusiasts. The new receiver will be compatible only with the new DX7 system.
At the 2006 NEAT Fair approximately one-third of the fliers used the Horizon Hobby DX6 2.4 GHz spread spectrum RC systems. The pilots who used those units did not have to use the transmitter impound area. They held onto their transmitters and simply went to an available flight station every time they wanted to fly.
Despite the fact that these spread spectrum transmitters were not impounded, not a single incident of interference resulted during the three days of flying. I heard many fliers say they were going to spread spectrum for this year!
It would seem that we have taken a gigantic leap in technical progress in the RC industry in the past year, but please keep in mind that none of the other existing RC bands are going to be taken away from us. If you are happy operating on 72 MHz, keep right at it!
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Q283: "I enjoyed reading your book titled Getting Started in Backyard Flying, but quite frankly, based on current technology, it is now somewhat dated. I like the format and organization, but is there any chance that you might come out with an updated or revised edition?"
A283: I realize this answer is going to be self-serving. I invested a lot of time in writing my book in the first place. I hope it has helped modelers get involved with parking lot and backyard flying. However, you are correct; the rapid progress in parking lot flying has made it necessary to revise my book.
The easiest way to do this was to delete the last four chapters, which created the opportunity to add approximately 20 new pages. These new pages will contain information about and photos of new brushless motors (especially the smaller ones), equally small brushless ESCs, Li-Poly batteries (I only covered Ni-Cd and NiMH in the original edition), and the new 2.4 GHz spread spectrum RC systems. The cover will be the same, but with a bold banner across the top reflecting the revisions.
The new version of the book should be in print by the time you read this. Copies will be sold through AMA’s museum store or you can order them directly from Air Age at: www.rcstore.com/RS/general/detail.asp?catnum=2028&catego=BO
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Q284: "I’m having trouble locating small-diameter plastic tubing for use with control-surface wire pushrods. Got any suggestions?"
A284: For parking lot models weighing approximately 8 ounces or more, the Du-Bro 20-inch Micro Push Rod System (item 847) with .032-inch-diameter wire works fine. But when you get down to the truly micro-size aircraft weighing 6 ounces and less, it is more practical to use a smaller-diameter wire, such as .020 inch.
My friend Steve Polles recently introduced me to a Stevens Aero Model product that fits the bill: pushrod tubing for 1/32-inch-diameter wire (item 16639). You can find it at: http://stevensaero.com/shop/product.php?productid=16639
This yellow tubing is manufactured by Sullivan Products and repackaged by Stevens. It has an outside diameter of .072 inch, an inside diameter of .040 inch, and comes in 36-inch lengths for just 50¢ (per length). The smaller-diameter .020 wire works perfectly inside this tubing.
Thanks, Steve! MA
Transcribed from original scans by AI. Minor OCR errors may remain.
