Safety Comes First
This column addresses items of concern regarding safety aspects of model aviation activities. The content of the column is the opinion of the author and does not necessarily represent the official position of the Academy of Model Aeromatics.
Topics in this issue:
- Are CyA glues dangerous to users?
- Information about PFM adhesive sealant.
- More on safe electric starters.
- Securing RC pushrod connectors.
Alleged CyA glue hazards
In my "Safety Comes First" column that appeared in the September 1988 issue of Model Aviation I stated that I disagreed with an allegation that CyA (cyanoacrylate—"instant" glue) when heated to 525° Fahrenheit can emit hydrogen cyanide in a quantity that "will be 10 times the threshold limit and be fatal."
In the December 1988 Safety column I included excerpts from a letter from an industrial chemist that, in my opinion, conclusively refuted that the emissions could be fatal when the glue is used for modeling purposes.
Two recent letters from Bill Rauch, a Hyattsville, MD modeler, each included articles containing a similar allegation together with three other alleged health hazards associated with the use of CyA glue.
The articles in Bill's letters were from the December 1990 issue of R/C Report and the Fall 1990 issue of High Flight. They were essentially identical and listed four alleged hazards associated with the use of CyA glues. Both publications attributed the listed hazards to "SAX," a publication containing about 3,000 pages about the toxic/dangerous properties of industrial chemicals. (Editor's note: The material from R/C Report was a letter from a reader to that magazine's editor.)
I have requested but not yet obtained a copy of this publication, but I very much doubt that it contains the alleged hazards in the form in which they were listed in the two articles. Each of the two articles appears to credit a different person for finding the SAX reference. However, I suspect that neither author actually obtained the information on the alleged hazards directly from the book. Why do I believe this? Because the language used to describe the alleged hazards in each article is identical to that contained in a report from SAM 35, a British chapter of the Society of Antique Modelers. That report appeared in the November 1989 issue of Sam Speaks, which is the official publication of that society.
I find it rather disturbing that articles alleging serious hazards do not accurately state their source. I believe the so-called SAX book is actually Dangerous Properties of Industrial Materials by N. Irving Sax, and the articles seem to have been modified to make it appear that the alleged hazards were direct quotes from Mr. Sax's book.
The first allegation concerning CyA was: "These compounds emit a fatal hydrogen cyanide gas if overheated. (Getting a hot soldering iron or covering iron close to them will do it.)" Unless Mr. Sax is a modeler, I doubt that he would know what a covering iron is!
To set the record straight on the alleged fatal emissions of hydrogen cyanide, the following is a verbatim reprint of my discussion of this topic as it appeared in the December 1988 Safety column:
"CyA glue: In the September 1988 issue I mentioned a warning notice that had appeared on a bulletin board in a major aircraft manufacturer's plant, which alleged that if you heat super glue to a temperature of 525° Fahrenheit, the resulting hydrogen cyanide gas will be both 10 times the threshold limit and be fatal. My column also stated that a chemist with whom I work did not believe this statement, and I asked if any readers could verify this."
After reading the September column, Dr. Jim Thomas, a chemist in the pharmaceutical research division of Parke-Davis, responded with some objective data on this issue. Jim's letter contained his calculations on how much CyA glue would have to be burned in order to reach the acceptable exposure limit (TLV—threshold limit value) of 100 ppm (parts per million) of hydrogen cyanide (HCN). His answer was that you would have to burn about 40 drops of glue to reach this limit if the burning occurred in an enclosure with a volume of one cubic meter, and breathe that atmosphere for 10 minutes. In other words, the warning notice was not based on facts. Dr. Thomas's conclusions are based on facts, and (as stated in his letter):
"It is possible that burning a usual amount of cured CyA could cause an instantaneous exposure to above the TLV, but not the 10 times the lethal dose noted in the article. The usual dissipation phenomena of diffusion and convection (since the burned CyA vapors would have to be hot) would reduce the local concentration of HCN very quickly, assuming a normally ventilated area. Also note that cyanosis is completely reversible, and (unless death occurs first) simply breathing uncontaminated air will reverse any symptoms of HCN poisoning.
"In case anyone is wondering if there is a potential risk of HCN poisoning in the event that a whole bottle of CyA glue is burned, say in a fire in the home, forget it. There are many other things in your home that present a much greater risk of producing toxic fumes in the event of a fire—your sofa, if it has polyurethane foam stuffing, being just one of them."
"I could respond with my own opinion on the validity of the other three alleged hazards associated with CyA glue. However, I'm a mechanical engineer, not a toxicologist or chemist. So to lend credibility to what I will say, I have to do a little more research. Look for more on this subject in a future Safety column. Meanwhile, I do recommend that you avoid prolonged use of CyA glue in a poorly ventilated workspace. The October 1985 Safety column reported that such a practice can result in respiratory problems similar to asthma."
Adhesive sealant
Another article in the December 1990 issue of R/C Report was the subject of a letter I received from Greg Namey, president of Innovative Model Products. Greg included with his letter an example of an adhesive sealant he produces that is sold by Hobby Lobby under the brand name PFM. He also included a sample of a competing product known as Goop.
A "Product Test Report" of PFM, written by Gordon Banks, appeared in the December 1990 issue of R/C Report, and Mr. Namey took issue with several statements in the test report, one of which involves safety. Excerpts from his letter follow:
"As you can see, Banks advises his readers to thin PFM with gasoline. PLEASE! Tell your readers NEVER to use gasoline as a thinner with our product or any other product. Gasoline is not only flammable, it's explosive.
"As if this were not serious enough, Mr. Banks adds a P.S. at the end of his article saying that PFM is Goop. NOT TRUE. Try this test for yourself on a piece of sheet metal: Put a blob of Goop and a blob of PFM on the sheet metal and take it outside. Put a lighted match to each blob. Goop will almost ignite before you get near it. PFM will not even burn. As a matter of fact, PFM will extinguish the burning Goop."
In accordance with the above instructions, I attempted to ignite a blob of PFM with no success. However, Goop lived up to the warning on its package: "DANGER: EXTREMELY FLAMMABLE. VAPORS MAY CAUSE FLASH FIRE." PFM is certainly not Goop in a different package! Furthermore, I would agree with Greg Namey: don't use gasoline as a thinner for anything.
Safe starters revisited
According to Jim Bockinfuss, two recent Safety columns gave some Free Flight power modelers quite a chuckle. Following is Jim's recent letter:
"Enjoy your column, even though it's RC oriented and I haven't been flying RC much in the last five years since I progressed to Free Flight. Anyway, just wanted to let you know that you gave all the Free Flight boys a good chuckle in your March and November issues when you talked about a new discovery that was recently designed and invented by such-and-such RC modeler, called a starter on a stand.
"It is obvious that you have never been to a Free Flight (Power) event in the last 20 years, because we all use this method of starting our engines. Remember, there is no throttle on a Free Flight model, and we use engines up to .60 size that are started at full power and some are hand started and others started on stands. The October 1989 Safety column told about electric starters used by some fliers; we have used these in Free Flight for years. Incidentally, what you call a magic wand is an electrified device that only heats the glow plug filament to aid starting. Enough said."
My thanks to Jim for his letter. I very much admire the Free Flight people who can fly their models for long durations — it's not as easy as it looks.
I realize that the average R/Cer thinks we use only .049s or rubber-powered planes, and it's a shame because the real knowledge and advancement is always within the ranks of the specialty groups (even within RC) and not usually seen in typical Sunday RC sport flying. Although some take offense at this statement, I know it to be true, as I've been on both sides of the fence for many years.
My purpose in publishing Jim's letter is twofold. First, to again emphasize how strongly I feel about the safety advantage offered by an engine-starting device that puts you behind the prop arc. Be it a "Safe Start Adapter" (1/91 column), "Kranking" (11/90 column), or Charlie Holden's version (3/90 column), if you don't have to reach over the prop to adjust the mixture, you are less likely to risk a finger or hand injury. For the record, during the past few months one of Bill Nelson's Krankings has been regularly set up and used at the Northern Virginia R/C Club flying field and has received very positive comments.
The second reason for publishing Jim's letter concerns his comment that "real knowledge and advancement is always within the ranks of the specialty groups." If you happen to fit into such a rank, and your group has developed any kind of new safety-related device, I'd like to share it with the readers of this column.
I apologize to non-RC modelers if they, like Jim, feel that this column is RC oriented. The reason for this is that most of the letters that sustain this column come from R/Cers. Yes, Jim, you are absolutely correct. I have not been to an FF Power event in the last 20 years. (Try the last 30 years!) I think the last such event I attended was on Chobham Common in England before I emigrated to the U.S. I believe that flying site is now one of that country's motorways!
Push-nut fasteners
I'm not sure I'm using the correct terminology, but what I call a "push-nut fastener" is similar to a star lock washer with internal teeth that bite into the shaft of an unthreaded bolt to retain it in place. The failure of such a fastener on a pushrod connector was the subject of the following letter from Lee Bernhardt, who refers to the device as a "star washer." Lee's letter included what looked like an E-Z connector, but I believe it was a brand-X variety.
"I had a crash resulting from the metal star washer falling off the pushrod connector, causing loss of elevator control. I am sure that the reason for this happening was my reusing the pushrod connector after a previous installation with a star washer. Installation of a star washer (and most definitely the removal of said washer) removes some metal from the pushrod connector. This results in a loose star washer installation when the connector is reused. While I inspected the reinstallation, the star washer did not want to come off, so I thought it was OK. However, the vibration experienced during use was sufficient to allow the washer to fall off.
"The enclosed connector and washer are the ones that failed. My Eagle 63, which crashed, had logged approximately 30 flights. The lesson learned here is to never reuse a pushrod connector that has been previously installed with a metal star washer. Also, while I feel that the connector installation with a star washer is safe, the washer should be installed to seat so that it is snug against the servo arm, and it should be inspected at regular intervals for signs of looseness. If looseness is observed, both the connector and washer should be replaced."
Reminder
As I write this it is still 1990. However, by the time you read it we will be well into 1991, and some or all of your radios could be unusable in AMA-sanctioned events unless they meet the new narrow-band receiver specifications. If you haven't already done so, have your equipment updated.
Be legal and safe in 1991!
Transcribed from original scans by AI. Minor OCR errors may remain.
