Prevent uncontrolled energy releases
Dave Gee [email protected]
I was told this column would appear in the first newly revamped issue of MA — completely redesigned and everything. I am still allowed to type the column while wearing my lucky T-shirt with the stains, but I am now required to wear a necktie as well.
In all seriousness, I get a tremendous kick from this gig. When I was younger, I was inspired by model magazine columnists such as Bill Hannan, and now he occasionally sends kind words of encouragement and advises me to keep my day job. Cool!
Thanks to all of you loyal readers, and please keep those emails coming.
Energy Sources
One of the earliest challenges of aeromodeling was to find ways to safely carry sufficient energy in miniature flying machines. Flight requires plenty of power, and pioneer modelers tried running models on everything from acetylene gas to gunpowder. Exciting is not a strong enough word.
Rubber bands were found to be the best way to store power, at least until gasoline engines became small enough. Today, high-tech battery systems are big. What will be next?
Every method of storing and carrying power has its own advantages and risks. A novice modeler must learn how to safely refuel his or her model’s power system. Even glider pilots use stored energy to get their models off the ground. A miniature energy system can be troublesome if not given proper care.
“Uncontrolled release of stored energy” is a nice way of saying that something bad happened. Many of our hobby’s safety issues involve the unexpected release of energy. When it’s a surprise, it’s usually a bad surprise.
I had an email discussion about storing energy via rubber winders with Mike Pykelny, who runs Starlink-FliteTech International Model Products. He had some extra winders to give to the middle school airplane club with which I work. The geared winders he sent are for smaller models with up to two loops of 1/8-inch rubber.
Mike’s customers fly rubber-powered aircraft, but not like the little sport airplanes you might see in a schoolyard. These big models range from P-30s to F1Bs to Unlimited, and their rubber motors have enormous power packed into the twisted strands. Mike sells heavy-duty winding stooges to hold the models, and beefy, geared winders that can handle the load.
If you visit a field when these airplanes are being “fueled,” you’ll notice that people stay away from either end of the stretched rubber bands. Those motors sometimes have bobbins or metal hooks on the ends and can suddenly break, snapping someone into the next county.
Sometimes there is just a broken strand or two in a larger motor, so there is only a partial “uncontrolled release” of energy. I’ve heard that rubber has a higher power-to-weight ratio than gasoline, and pilots take this danger seriously. They may joke about protecting the model before their own fingers.
Those who fly smaller, rubber-powered models understand that even a tiny broken motor can cause an injury, especially to one’s eyes, so winding is done at the safest angle and direction.
When gas engines came into fashion, modelers had to learn to deal with highly explosive liquid fuel and fumes that could ignite from unexpected sources. There have been some hard lessons learned throughout the years, but pilots still take chances at the field by carelessly handling flammable fuel.
There is no excuse for having ignition sources near a fueling area, and we should all know better. I’ve heard more than one report about a fire that mentioned how the lawn mower gas was in a proper can, but the airplane fuel was stored unsafely—contributing to structural damage. In one case, it caused a fire.
The new leader in our hobby is electric power, and batteries have improved by leaps and bounds. The early LiPo cells were involved in numerous fires, but now either the packs are getting better or we are getting wiser and more cautious about handling, storing, and charging these high-tech batteries.
I am wary of even the little ones I use on my indoor RC airplanes. I can only imagine the damage that could result from one of them igniting, so I keep them in a storage box that (I hope) would contain an uncontrolled release of energy without burning my home down.
Pilots who use larger packs must worry after seeing Internet videos of bursting/flaming batteries. There are plenty of good storage products available now, and it is easier than ever to see that LiPo cells are properly contained during storage, travel, and charging.
We seem to be coming full circle, because now there is renewed interest in some old power systems. CO2 motors are generally small, but the refill tanks can be big. Using compressed, pressurized liquid at a hot airfield brings new problems.
The paintball industry has helped. Modern tanks have pressure/temperature relief valves, and are inexpensive compared to welding-type tanks. I use paintball tanks and refill services for my CO2 needs.
Compressed-air systems are gaining popularity. Mass-produced units are found in Air Hogs toys, which can be fun despite their limited power and duration. Some skilled modelers are working on refined compressed-air motors that have astounding power and long runs.
In the past, a brass tank was handmade and sometimes wrapped with wire for extra strength. Modern fliers found that certain metal beverage cans can be cut and joined into strong, lightweight cylinders that will reliably hold the “fuel” for an expansion motor. Deliberate abuse of the new tanks showed that even when they fail, there is no dangerous shrapnel because the lightweight material is so flexible.
Most pilots take great care when making and filling the tanks. I have one of the new prototype motors and it is truly a gas to run! If they become available for purchase, you will see a plug here.
We have a body of knowledge in our sport from many decades of experimentation, successes, and mistakes. Whether we are using the newest high-tech gadget or a replica of something 100 years old, let’s learn from the mistakes of others so we don’t have our own incidents.
Hobby Knife
Sharp-eyed Ken Achee sent me an email about a hobby knife he saw in one of my photographs a few months back. He noticed that it had a triangular rubber piece slipped over the round handle to keep it from rolling off the table and stabbing my foot. It’s been a while since the last mention of this simple, yet effective trick and Ken wanted to know where to find an anti-roll sleeve.
Commercial products such as this can be hard to find. Your local art store might have a bottle of them next to the cash register. I couldn't find any sellers on the Internet. Some modelers just add a "flag" of heavy tape to the handle. Others glue a piece of dowel crosswise onto the knife, or screw a small bolt into the side of it.
Propeller versus Wrist
A different Ken also wrote to me. Kenneth "Kep" Kepner told me about a past moment of inattention that still fills him with embarrassment. Despite that, he still wanted to share his tale with the world, hoping that someone else can avoid making the same mistake.
Kep said that sometimes the adrenaline and excitement of the first flight of your latest pride and joy can cause cerebral disconnect. He wrote:
"Fifteen years ago I was tinkering with my then-new Astro Hog in the pits. The O.S. .91 was purring at the first flip and a buddy was holding the tail. I reached right over that brand-new 14 x 6-inch maple prop to fine-tune it right there, and with God as my witness, I reached right over the whirring prop. I heard it hit and then felt my right wrist burn.
I was afraid to look down, but only saw the skin scratched enough just to leave a little red line of blood. It ended up leaving a 1½-inch lifelong white scar that I see every time I look at my arm. I consider it a very lucky and cheap reminder. That was over 15 years ago and I still fly the old Hog."
Kep did a generous thing by sharing his accident with us. Please take it to heart and keep in mind that this could happen to any of us if we drop our guard. If you have a close-call story, a suggestion, or a correction, please drop me an email. Your name can be withheld if you prefer to avoid the thrill of national embarrassment.
Aircraft Photo Quiz
I was overwhelmed by the response from the last aircraft-identification photo quiz. It showed the landing gear of an F-82 Twin Mustang, and hundreds of readers correctly guessed it and received a Marlow Shark model plan via email.
Want to try it once more? Look at the cropped photo and tell me what aircraft it shows. Hint: this airplane was seen at the Flying Leatherneck museum.
This time the prize is one of my own designs, so don't get too excited. As part of my continuing and transparent plot to encourage Rubber Sport models, everyone who emails me will receive plans for the OFFC Pursuit.
This profile low-winger will fly in small gymnasiums and easily launch from the floor. Outdoors, it is stable and looks racy in the air. You don't have to correctly guess to get the digital plans; just ask for it.
SOURCES:
- Starlink-FliteTech International Model Products
- (858) 231-4994
- www.starlink-flitetech.com/index.htm
Transcribed from original scans by AI. Minor OCR errors may remain.
