SAFETY COMES FIRST!
By John Preston
Working with foam plastic can have unexpected effects on your body!
Styrofoam and health
Would you believe that Styrofoam may be hazardous to your health? Before we describe why, perhaps we should define what we mean by Styrofoam. This is a registered trademark of the Dow Chemical Company and, to the best of our knowledge, is not the foam material used to manufacture coffee cups and ready-to-fly model aircraft. The material we are talking about is usually sold in large sheets of varying thickness and is very often used for home insulation, but may also be purchased by modelers to make foam wing cores. When sold in sheet form, it usually has a paper covering on each side with the Styrofoam name (together with the name of the manufacturer) printed on it.
A letter from Ben Brackett of Cincinnati, OH describes what can happen to the unwary. "I was helping a schoolteacher friend work up some boat hulls from Styrofoam for a class project and came down with the 'pre-flu' symptoms — drunk as a skunk, tired, achy, everything but the elevated temperature. Well, to make a long story short, after staying out of the workshop for two days, I felt okay. Then, 15 minutes of hot-wire cutting almost put me on my ear. My schoolteacher friend wrote to Dow, and they were kind enough to send the (enclosed) booklet."
Although in Ben's case the hazard resulted from cutting the Styrofoam using a hot wire, the same problem can occur during any sawing, shaping, or grinding operation. The explanation of Ben's misfortune is contained in the Dow booklet, extracts from which follow:
"Styrofoam brand plastic foam is made by pushing a chemical gas into melted plastic, making it into foam. When it cools it forms the solid, lightweight Styrofoam brand plastic foam you know. The plastic is harmless polystyrene. But, the gas is methyl chloride — a chemical gas which can represent a potential hazard if you breathe too much of it. Most methyl chloride gas escapes from the Styrofoam brand plastic foam before you work with it, but some stays locked in. When you cut or saw Styrofoam brand plastic foam, the foam walls are broken, letting out the gas. This can cause a problem if too much gas is released and if it stays in your work area.
"Some of the first signs of overexposure to methyl chloride gas are dizziness, staggering, and blurred vision. Sometimes these signs may show up a day or two later, and recovery may take several days, depending on the amount of exposure. Since the first results of overexposure are similar to being drunk, a person suffering such effects will have a hard time working safely. Such a person won't be able to control his actions and risks injury to himself and others.
"To avoid overexposure to methyl chloride gas, properly operate and maintain equipment and exhaust fans. Practice good housekeeping; keep finished pieces and waste storage at a minimum. Have plenty of fresh air around your operation; don't work with Styrofoam brand plastic foam in a small, poorly-ventilated area or room."
In short, the human body was designed to breathe fresh air. If it is asked to operate in an environment polluted by other gases it may not function well or — if the concentration of pollutants is high enough — it may completely cease to function. Our workshops need ventilation. Does yours have an exhaust fan?
Propeller incidents and safety
Recent conversations with a couple of modeler friends, together with a letter from Australia, indicate that it's time to return to an old topic — propellers.
Blade-shedding: David Hipperson (Victoria Park, W. Australia)
David Hipperson wrote to tell us of a blade-shedding incident with a wooden propeller. Dave's wife bought him his first "big" motor, a 22cc Tartan. Equipped with an 18 x 6 prop that had been checked for balance, we pick up Dave's story after the engine had been run only once on a robust test stand:
"(I) allowed it to cool while I gloated and told the wife she had done a good thing. Came back, checked all the bolts and prop nut, filled the tank, and started the motor. Moved to the rear, and as I did so there was a sharp 'pop,' and something light-coloured shot through the air. This was followed by two or three seconds of vibration, and before I could shut down the motor, there was a sharp crack; the propeller, prop nut, washer, and prop driver flew through the air. Believe it or not, the vibration smoothed completely, and I would say the motor would have run perfectly well on the shaft at 1/4 throttle, but I wasn't chancing that, and the motor was shut down, pronto."
On inspection, it was found that the blade tip had sheared off where some "pretty" dappled effects could be seen — likely a quarter-grain effect. No damage to the motor, and a cup of tea restored the tattered nerves. I have used this company's props before, and they were great — but I blame myself for not realizing a failure could occur in an area like that. The cure — straight grain in all my propellers from now on — and great care in making sure I'm well out of harm's way.
This is not the first incident we've heard of involving the spontaneous shedding of a blade from a wooden prop. However, the problem is more commonly associated with plastic props. What is surprising in this case is that it happened on an engine that we would guess couldn't have been turning at more than 3,000 or 4,000 rpm — maybe even less, since at full bore the Tartan with an 18 x 6 prop will only turn at about 7,000 rpm. One could argue that, since the Tartan is a converted industrial engine, it probably vibrates a lot, but this is just not so. Our friend Bill Winter has a Tartan in his 1/4-scale Aristocrat, and we find it to be one of the smoothest of the industrial engine conversions.
We think Dave was correct in his diagnosis that the grain in the wood had to be the culprit. Since an 18 x 6 doesn't come cheap, we suggest that modelers take a little extra time to examine props before purchase. This is a good example of a product that is better purchased at the local hobby store where you can see what you are getting rather than from the discount mail-order house.
Other propeller injuries
Dave's incident, thanks to his prudence in moving behind the engine after starting, did not result in an injury. A local modeler and friend was not so fortunate when he inadvertently grabbed a handful of blades on a prop being turned by a .90 engine. Our friend shall be nameless, since he was starting the motor unaided. This is a common practice, but when the engine size goes past a .60, we think it is time to have a helper.
In our friend's case, the engine had been started at low throttle with the radio transmitter lying on the ground within easy reach. Nobody is sure exactly what happened, but either a rag was blown by the wind across the transmitter throttle stick, or our friend accidentally dragged it across the stick. Anyway, the engine went to full bore, and to prevent being struck by the prop somewhere in the groin area, our friend put up his right hand and arrested the plane, prop, and motor with three fingers. The result was a trip to the hospital, loss of the use of the right hand for several weeks, and maybe a permanent loss in the use of one of the fingers. Miraculously, no fingers were lost nor any bones broken, but the loss of use of one's dominant hand for a few weeks is sufficient cause to be very careful in the future.
The last propeller incident happened at our own club's field and came to us second-hand via another club member. A Quadra-powered model was being started by hand propping and was showing no sign of even firing, let alone starting. Its owner was apparently becoming complacent and was flipping the prop with great rapidity. The engine caught without warning and was immediately stopped as the hand came back for another flip. The result — lacerated fingers that required medical attention.
Several years ago, the government agency for whom we work received a petition to issue a federal regulation that would require all model airplane engines to be sold with a self-contained, remotely-operated self-starter. This was at a time when the onboard self-starter had yet to reach the marketplace. Needless to say, the petition was rejected. Since it isn't economically practical to have self-starters on all model engines, we have to accept that some of us will end up feeding our fingers through the prop if we use hand-starting techniques. It even happens once in a while to full-scale pilots — with obviously dire consequences.
All this column can hope to do is periodically remind you to be careful when starting and adjusting your engines. If you can afford it, use an electric starter. As alternatives, use a glove or a "chicken stick." If you are an RC modeler, always start the engine at low throttle, and move behind the prop arc before advancing to full throttle to adjust the mixture. If you fly models that are equipped with engines without throttles, exercise an extra degree of caution. Try to minimize the time you must spend in the prop arc.
To reduce risk:
- Use an electric starter when possible.
- Have a helper when starting larger engines (.60 and up).
- Start with low throttle and move well behind the prop arc before advancing throttle.
- Use a glove or a chicken stick if hand-propping.
- Inspect wooden props for straight grain and any defects before purchase and use.
- Keep transmitters and loose items away from control sticks while starting.
Final notes
One final word to clarify the role of a contributing editor to Model Aviation magazine. None of us are employed full-time by the magazine, nor do any of us see what will appear in the magazine (other than our own columns) until it reaches our mailboxes at the same time as it reaches yours. Your safety column writer is not responsible for ensuring that the magazine only depicts safe activities. (That's the editor's job! — RMC-M.)
A letter we received this month chastised us for allowing the cartoon that appeared on page 126 of the November issue. This depicted an RC helicopter being flown around the head of a lady seated in a lawn chair. She promptly swatted it out of the sky with a fly swatter. Quite frankly, we don't see anything objectionable in this cartoon from a safety point of view. Had it been a photograph rather than a cartoon, we might think differently. However, our correspondent believes that "There are a few too many yoyo types out there who would fly close to people, especially because they saw it in your magazine." So, in addition to wishing you all a safe month, to the "yoyo types out there," keep thy RC choppers away from the folks, lest thou get chopped (by a fly swatter).
John Preston 7012 Elvira Court Falls Church, VA 22042
Transcribed from original scans by AI. Minor OCR errors may remain.
