Frequently Asked Questions - 2012/10
Q557 — Tightening propeller nuts
Q: I have trouble when it comes to tightening the propeller nut on my electric motors. As I go to tighten the nut, the motor shaft begins to rotate. When that happens I can't get the propeller tight up against the drive washer. I'd hate to damage that washer if I used pliers to get a grip. Is there a better way?
A: Reader and AMA member Larry Bresson of Nampa, Idaho, provided a good solution. Larry made a spinner wrench that holds the motor shaft in place while tightening the propeller nut. The wrench is constructed from 1/16- or 1/8-inch-thick aluminum (available at stores such as Lowe's or Home Depot). About $3 of material will make up to six wrenches. The tools can be made with a hacksaw and a file. Larry has a CAD drawing of his wrench and will email it to anyone who requests it. Contact details are in the Sources section.
Q558 — Accessing Du-Bro EZ Connector screw from the top
Q: I like using the Du-Bro EZ Connectors to attach my throttle control rod to the throttle arm on my engine's carburetor. The problem is being able to easily access the screw on that connector to make adjustments to the linkage. As it is, you must come in from the side which often requires drilling a hole in a cowl or fuselage side. Are there any alternate schemes available that let you come in from the top?
A: Reader Ron Ogren of Orchard Park, New York, sent a simple modification. Ron drills and taps the side of the Du-Bro EZ Connector for a 4-40 screw, then fits a hex-head 4-40 screw cut to about 3/16 to 1/4 inch. He suggests using a 3/32-inch ball-end hex screwdriver. With this modification, the hex screw can be accessed from the top, allowing easy adjustments without side access. It's a straightforward field-friendly solution. Thanks to Ron for the tip.
Q559 — Cleaning glow engines (Dawn product)
Q: Several years ago, I read an article about cleaning the exterior of glow engines with a product made by Dawn detergent. I used it and it did a great job. Unfortunately, I cannot find it in my shop anywhere so I must have thrown it out. Would you happen to know the name of the product? I think it was stronger than regular Dawn detergent that is made for cleaning pots and pans.
A: Reader Bob Lee identified the product as Dawn Power Dissolver. Although it was rumored to be discontinued, it remains available. It can be purchased at Walmart or through Amazon. A 12.8-ounce spray bottle was found at Walmart for $2.83. Bob recommends plugging the engine's carburetor and exhaust port with paper towel before spraying, and not leaving the spray on for more than 20 minutes to avoid possible aluminum discoloration. It works very well for exterior engine cleaning.
Q560 — Calculating wing area
Q: On kit boxes and in product reviews, wing area is often listed (which lets you calculate wing loading). Is the wing area on a non-tapered wing always wingspan multiplied by chord, or do you subtract the part of the wing that goes through the fuselage? What about a parasol wing airplane where the wing doesn't pass through the fuselage, or a typical biplane where the bottom wing goes through the fuselage and the top wing is essentially a parasol wing?
A: The wing area used as a reference number is always the entire wing, including the portion blocked by the fuselage or other structure. This guidance comes from AMA Hall of Famer Tom Hunt.
Q561 — Altitude-limiting device (Sky Limit)
Q: What can you tell me about that new altitude-limiting device for model aircraft?
A: The device is called the Sky Limit, manufactured by Winged Shadow Systems. It consists of two units: a small 3.6-gram sensor that rides inside the aircraft and a separate plug-in programmer used to choose altitude and time limits. The combination retails for $54.90.
The Sky Limit can help limit aircraft altitude for sailplane contests or to meet field rules and regulations. In operation, it cuts the motor/engine throttle at the chosen altitude or time limit and works with electric, gas, or glow airplanes. Altitude limits range from 50 to 9,999 feet and time limits from 5 to 9,999 seconds. The company's website has detailed information.
Q-and-A Follow-up
I have several follow-up Q-and-As and encourage comments. I try to cover as many reader points as possible.
Follow-up to 0546 (Doculam or Clearfilm, April 2012 MA, page 82)
Reader Bob Whipple wrote: "I have been using Doculam since 1979 with great success. It is light and durable.
"There is one thing that was not mentioned and that was using this covering on fueled planes. I found that the glue on the Doculam is loosened by the engine exhaust and fuel. However, it works great on electric-powered aircraft, sailplanes, and rubber-powered planes."
Response: I apologize for not emphasizing this earlier. While Doculam is excellent for electric and non-fueled applications, the adhesive can be affected by fuel and exhaust. In some cases, fuel-proof paint can be applied over Doculam, but always test on a scrap piece first and spray glow fuel on the test strip to confirm compatibility before treating an entire aircraft.
Follow-up to 0554 (electric motors, quick repairs, August 2012 MA, page 78)
In the original FAQ I showed how easy it is to remove the outer barrel (stator) of a brushless outrunner motor—the magnetism is what holds it in place. With a firm pull the barrel and shaft can come off; keeping a spare barrel in your field kit can allow instant repair of a bent shaft.
Clarification: That technique does not work on every outrunner. Canadian modeler Chris Moes noted it works on E-flite Park 180- and 250-size motors, but the Park 300 motor has a snap ring that must be removed first. Not every motor can be fixed the way I originally described. I hope manufacturers will consider offering the barrel and shaft as replacement items.
Follow-up to 0550 (simulated windows and windshields, June 2012 MA, page 72)
I mentioned black contact shelf paper from Ace Hardware as a good source for simulated windows and windshields. Reader Brendan Schulman suggested an alternate source: flat black chalkboard contact paper available through Amazon in 18-inch by 6-foot rolls for about $8.52. This may be the same manufacturer as the Ace product, but it provides another option.
SOURCES
- Larry Bresson
- Ron Ogren
- Dawn Power Dissolver
www.dawn-dish.com/us/dawn/product/037000006329
- Winged Shadow Systems
(630) 837-6553 www.wingedshadow.com/skylimit.html
- Amazon (chalkboard contact paper)
www.amazon.com/Jittrich-Corporation-Chalkboard-Contact-Paper/dp/B000KKM090
Transcribed from original scans by AI. Minor OCR errors may remain.
