Safety Comes First

Safety Comes First

John Preston

Big models / little models: they all have kinetic energy in flight, and most can pose danger to people and property. Summary of hobby health hazards.

Summary

This column addresses safety aspects of model aviation activities. The content is the opinion of the author and does not necessarily represent the official position of the Academy of Model Aeronautics.

Big Models

In the April 1987 issue of Model Aviation, I outlined two plans submitted to an AMA vice president suggesting how models weighing more than the current maximum of 55 lb (see "Official AMA Safety Code," General, paragraph 5) might be safely flown. In a nutshell, the plans were:

1. Remove the 55-lb weight limit entirely and allow models of any weight to be flown, provided they meet certain safety criteria.
2. Keep the current 55-lb weight limit but establish a special Experimental category which would not have the weight limit and would require that models in this category meet certain safety criteria.

I asked readers to comment on the merits of the two plans. Response was not overwhelming, but I received enough letters to convince me that Plan No. 1 (remove the 55-lb weight limit entirely) was not favored. Respondents cited a number of reasons, generally feeling that without a weight limit heavy models would be built and flown that would not conform to the safety criteria.

Many who favored Plan No. 2 stated that modelers desiring to build a heavy model in the Experimental category should have to bear any extra insurance cost themselves and not impose such a burden on the majority of the AMA membership who have no desire to build such large models. That seems fair to me, but may not be possible now that we are essentially a self-insured organization. As AMA President Don Lowe pointed out in a segment on Big Models in his column (AMA News, May 1987): "The bottom line? We must all fly safely whether we fly big ones or little ones. With our current self-insurance program, the total assets of the AMA are on the line."

Before leaving the subject of model weight limits, I want to pass on some comments from Bill Kincheloe of Magalia, CA. Bill favored Plan No. 2 and enclosed a graphical plot of kinetic energy for models weighing 1.5, 10, and 50 lb with respect to velocity. In previous discussions I've talked about kinetic energy and how this should perhaps be of more concern than just model weight. Bill included additional information on his plot that may interest readers — specifically a term he called the "Lethal Threshold."

"I have one new piece of information from my experience which may not be available to those who want to argue the safety point: the 'Lethal Threshold = 57 ft.-lb.' line. Now no longer used by the military, this was once the criterion by which a weapon was judged. It was calculated from the results of thousands of wounds recorded during the Civil War, World War I, World War II, and Korea as being the energy which, when dissipated into the vulnerable area of a human being, has a 70% chance of killing the person. If you enjoy statistics and probabilities, this probability is then modified by multiplying it by the probability that the missile in question hits the vulnerable area. So you can say that the probability of a lethal accident is low because the probability of being hit is low. I'm not prepared to estimate how low is 'acceptable,' and I'm sure the underwriters won't accept a very large number like even 10%.

"But what do we see on the chart? For equal potential for harm, there is a seven-to-one velocity increment for a 50-to-one weight change. (This is surprising, since seven squared is 49, and the calculations which led to seven were rounded.) What is important is that whatever the lethal threshold you accept, the heavier model has significantly greater potential for harm than a smaller one."

I agree with Bill that the heavier the model, the greater its potential for harm. However, as others have pointed out, larger models tend to fly slower than small ones and therefore give bystanders more time to get out of the way in the event of loss of control. In other words, the probability of being struck by a large model (despite its extra frontal area) may be less than that of being struck by a small, fast model. The key point is that all models are likely to exceed a Lethal Threshold of 57 ft.-lb under some conditions, so we must all fly safely.

Cyanoacrylate (CYA) Glue

Two recent letters mentioned unpleasant experiences while using cyanoacrylate (CYA) glue. Neither resulted in serious injury, but the incidents are worth noting to help others avoid trouble.

• Dave Powers, Gastonia, NC: He wears hard contact lenses and found that CYA residue on his fingernails sometimes scratched his contacts when he cleaned them with his fingers. Debonders did not remove every bit of residue. He plans to use latex fingertip protectors available at drug stores. Contact-lens wearers should be careful — the consequences can be expensive.

• Hank Nystrom, Johnson City, TN: Hank wears glasses and credits them with preventing an eye injury when he had an incident with CYA glue. He wrote to the glue manufacturer describing his experience. (His letter credited protective eyewear with preventing more serious harm.)

If you wear contacts or glasses, take care when handling adhesives and solvents.

DuPont: "Your Hobbies Can Hurt You" (Managing Safety)

I received a copy of a DuPont publication titled Managing Safety from Anthony Cantarella, Western Region manager of Safety Services for DuPont and an RC modeler. An article in that publication, "Your Hobbies Can Hurt You," contains tips worth passing on.

People who enjoy arts and crafts at home may not realize that materials they use can cause health problems. For example:

• Lead used in glazes can be inhaled, build up in the body, and cause nausea, constipation, and various aches and pains.
• Solvents used in spray paint, permanent markers, rubber cement, and epoxy glues can cause headaches, dizziness, eye irritation, and dermatitis.
• Exposure to some substances may take years before ill effects appear.

Industrial workers may be supplied with protective equipment and work in more controlled environments; that may not be true in homes. To minimize risks, take these precautions:

• Make sure your work space has adequate ventilation. You need some kind of system to remove contaminated air and supply fresh air — more than simply opening a window.
• Don't eat, drink, or smoke in your work area.
• Wash your hands carefully each time you leave your project to reduce the chance of accidentally ingesting hazardous materials.
• Wear proper protective equipment. Depending on materials or processes, wear gloves, dust masks, safety goggles, special clothing, or respirators.
• Learn about the chemicals in your materials and what precautions to take. Study warning labels, and if you have questions, contact the manufacturer and ask for safety data sheets. Replace hazardous materials with safer ones when possible.
• Store all materials in their original containers and keep them covered.
• Keep the work area clean. Wipe up flammable liquid spills immediately, and put soaked rags in a tightly covered trash container. Dispose of chemicals properly; if you have questions about disposal, contact your local health or fire department.
• Don't work with flammable materials near ignition sources such as open-flame heaters, water heaters, or cigarettes.
• If you suffer from asthma, emphysema, allergies, or a heart condition, check with your doctor about the materials and processes you work with.
• If you are pregnant, ask your doctor about continuing your hobby (this also applies to wives of male hobbyists).
• Space out your sessions with your hobby to give your body time to recover between possible exposures.

I have previously mentioned many of these DuPont safety tips, but it's worth repeating them because newcomers may not be aware of the hazards associated with common hobby products.

Chemical Hazards: MEK vs MEKP

Two chemicals with similar names have very different properties and hazards:

• Methyl ethyl ketone (MEK) is a solvent commonly used to join styrene plastic modeling parts. It is chemically related to acetone (a common nail polish remover). MEK can irritate the eyes but, if flushed immediately with water after contact, usually does not cause lasting damage. I am not aware that MEK presents a serious hazard from skin contact in normal hobby use.

• Methyl ethyl ketone peroxide (MEKP) is the hardening agent used with polyester resins. It is a strong oxidizer and requires extreme care. MEKP can cause severe burns, necrosis, and permanent eye damage or blindness if it contacts skin or eyes. It must be handled with appropriate protective equipment.

Some people have confused CYA glue with MEKP, fearing a drop in the eye will cause instant blindness. A drop of CYA in the eye will likely glue the eyelids together and be very uncomfortable, but it is not likely to cause permanent blindness. Nevertheless, take precautions to avoid getting adhesive in your eyes.

One day I hope to list all common hobby chemicals along with hazards and handling precautions. Meanwhile, please take care.

John Preston 2812 Northampton St., N.W. Washington, DC 20015

Transcribed from original scans by AI. Minor OCR errors may remain.