Safety Comes First - 2006/05
Be careful of cyanoacrylate fumes in confined spaces
A note from Sandy Frank:
“Yesterday I was working on a balsa-framework built-up model. It needed some slight repairs, so I used cyanoacrylate glue and accelerator to fix it prior to patching the MonoKote covering. I used a flammable cyanoacrylate accelerator.
“About 20 minutes later I noted some frayed servo wires, so I soldered them back and was installing some heat-shrink tubing over the solder joint when to my surprise, kaboom! The covered structure popped loudly. It was a small boom with no visible fire, but it did melt the covering and destroy the balsa structure.
“Apparently I had trapped the accelerator vapor inside the structure with the covering, and the butane match (used to heat the shrink tubing) lit it off. No harm or permanent damage but lots of shock and a destroyed model.”
Who would have thought about flammable fumes confined in a fuselage? As rarely as we use an open flame in our hobby, igniting such fumes would not have occurred to me—I would have switched mental gears from chemicals (is the room ventilated well enough?) to electrical work (watch that hot soldering iron!). I never would have thought about possibly blowing up the fuselage. Thanks to Sandy for a unique story.
If you have a tale of disaster or narrow escape and don’t mind a little fame (or infamy), please send it to me.
Letters and contact
My address is Box 7081, Van Nuys CA 91409. And yes, I answer my mail. The computer has not claimed me completely—yet.
An actual paper letter arrived from Frank Ritota, president of Model Rectifier Corporation (MRC). He was understandably perturbed by a recent column photo that showed an MRC helicopter burned to a crisp. As a loyal MRC customer I want Frank busy churning out new products instead of writing letters to columnists, so here’s a clarification.
When modeling products are shown here it is either because they are extra good and deserve a plug or they have been horribly misused and the wreckage is photogenic and/or educational. In this case, a beautiful little RC helicopter was destroyed because a damaged charger overfilled the battery pack. Frank’s point was that modeling products are extremely safe when used properly. I agree with him.
The helicopter picture was an illustration of how not to treat a model, and I hope the funny yet tragic photo (along with the perpetrator’s amusing account) got the message across. I received several emails from readers who commiserated with the pilot, and the phrase “follow the instructions” kept cropping up. Why is it so hard for grown-up hobbyists to do that simple thing? If I had a nickel for every modeling item I’ve foolishly ruined, I’d have a nice pile of nickels to go with my collection of busted airplanes. The guy who sent the picture was so pleased with his MRC helicopter that twice he bought replacements for models that “bit the dust.” A man after my own heart.
Rotary-tool “Mary Poppins” brushes
I recently shared a note about the “Mary Poppins brush” type of rotary-tool accessory. A modeler had several come apart when in use—new right out of the package. I got many emails about the story, so more research was required.
This type of brush does not get much use in my workshop, but I found several in my rotary-tool rack, with metal and nonmetal bristles. Some were Dremel products and some were no-name items from unknown manufacturers. Several companies make similar items. Dremel is the standard by which such tools are measured, and a close inspection showed that that brand’s products are of much higher quality than some others.
I contacted Dremel and learned that its versions of this product (in several styles) are rated for 15,000 rpm. That seems like a high speed, and I wondered how the poorly made knockoffs would hold up. After taking extreme precautions, each brush in my collection was run for a little spin at top speed. No actual polishing or grinding was done.
By the way, we use eye protection whenever we use rotary tools, right? That way if a brush sheds its bristles, for any reason, we will be protected—every single time. Anyway, all of the brushes stayed together during the test, but I tossed a poorly made one afterward. The close look I took at the construction variations made me decide to stick with higher-quality tools.
Never fear; there was some blood drawn during this experiment. After steel-bristle brushes are used once or twice, individual bristles poke out at odd angles. My rotary-tool rack is a board with holes in it, and the bits slip neatly into the holes for storage. When I grabbed a steel brush, I got punctured. Your safety columnist in action—bandages and all.
Youth outreach and AMA Convention
Skilled modeler Dick Terry is recovering from heart surgery, so I’m using one of his photographs this month to cheer him up. He took the picture at AMA Convention 2006, in the make-and-take test-flight area. Each kid not only got to construct an airplane but received guidance from an instructor in building and flying it safely and successfully.
It is a fine thing when experienced modelers pass their knowledge on to beginners. Not only does it perpetuate our hobby, but it saves newcomers from learning safety lessons the hard way.
I also visited a local high school and noticed how these kids get an enthusiastic welcome during a visit to a local hobby shop. North Hollywood High School, in sunny California, boasts a crack team of Science Olympians who work together to produce meticulous indoor models. The safe and methodical way these kids work will serve them well later if they step down from indoor flying to RC. (Just kidding about stepping down—no irate emails, please!)
Li-Poly battery charging
Bob Lindoff asked a great question about Li-Poly batteries: why should we remove the pack for charging? Some models that are converted from other power systems do not lend themselves to this, and hatches add weight and complexity.
One great reason to remove Li-Polys from the model for charging (and to construct the airplane with this in mind) is that a visual inspection is needed during each cycle to ensure the pack isn’t “puffed up” and ready to have an episode.
We always stand by while a Li-Poly pack charges, unlike with Ni-Cds which can be left unattended. But if you can’t see the pack, not only will you miss the warning signs of problems, but when it pops you lose the model too.
Just as we modify a gas-powered model’s engine mount to accept electric power, we should add a hatch to provide access to the batteries. Safe practice is to remove the pack from the model and put it in a proper container for charging. Good options include:
- Ceramic flowerpots
- Sand buckets
- A Battery Bunker (a product made specifically for this purpose)
Target fixation at the RC field
David Narance sent an account of an incident at his RC field that illustrates target blindness—the tendency to become so focused on a task that you disregard your surroundings.
"During an air show, an RC pilot and his ground crewman fired up a large-scale Demoiselle. As in the original aircraft, ground steering during takeoff was a challenge in a crosswind and the model became caught in the taller grass on the downwind edge of the paved runway.
"The helper ran out onto the runway to free the aircraft. Just then, a 1/3-scale Fw 190D was on approach to land. The Fw pilot just caught sight of the man running onto the runway. He firewalled the engine and pulled the Fw up into a steep climb to avoid hitting the man.
"A young teenager and his dad were sitting next to me in the spectator area, and I saw that he had captured the moment on his digital camera. The boy remarked how close the Demoiselle air crewman came to a decapitation as he played back the event on the view screen.
"Although the two pilots had a very animated discussion, the angry talk gave way to apologies and we witnessed everyone shaking hands.
"The Demoiselle pilot and crew had target fixation. They had become focused on untangling their airplane from the grass and forgot that there were other airplanes in the air above the runway. The sight of that Fw just missing that man shows how quickly a tragic accident can happen."
Cell phone interference
A recurring topic on the Internet is whether cell phones can interfere with RC systems. This trace back to a study at the School of Mechanical and Aerospace Engineering at Oklahoma State University where students found that under certain circumstances certain radios were disturbed when they were close to certain types of cell phones at the moment they received a call.
I researched the matter and feel there is no call for panic. It seems like a rather bad idea to use your cell phone while flying (can you imagine how much worse my landings would get if I were chatting during the approach?). A simple test of your system and phone will determine if there is a potential problem. Most radios are invulnerable. I suggest leaving your phone in the car or turning it off, for the benefit of the flier next to you.
This story has become something of an urban legend, so I repeat: there is no need for panic. If panic is appropriate, I will lead the way as usual.
MA
Transcribed from original scans by AI. Minor OCR errors may remain.
