Radio Control: Sport and Aerobatics
Ron Van Putte 111 Sleepy Oaks Rd. Ft. Walton Beach, FL 32548
Correction: Canard Center-of-Gravity Equation
First I want to rectify an error. In my August 1988 column I discussed how to determine the center-of-gravity of a canard (tail-first) airplane. I noted that the sign of the term involving the tail length had to be changed, and it should be multiplied by two when converting the equation from a tail-last equation to a canard equation. Unfortunately, when the canard equation appeared in the August column, the "2" multiplier was missing. It's necessary to get that canard center-of-gravity equation printed correctly. It appears below as Equation 4a.
Equation 4a (corrected): CG = - 2L × (Stab. Area) / [3 × (Wing Area)] - (R^2 + R T + T^2) / [15 - (R + T) × wing]
(Note: the important correction is the factor of 2 multiplying the tail-length term when converting the tail-last equation to the canard equation.)
Vintage RC Plans Sources
Several months back I got a letter from Bill Hintz (Glendora, CA), who was looking for plans for old RC designs. Since I published Bill's request in the August column, I received two letters containing sources.
- Doc Mathews (Model Aviation's "RC Old-Timers" columnist) suggested readers send $1 for the RC plans list from:
- John Pond Plan Service, Box 90310, San Jose, CA 95109
- Tom Dixon (Suite 401, 1938 Peachtree Rd., Atlanta, GA 30309) has a plans service and a vintage RC catalog. In addition to a long list of airplanes in his catalog, he has plans for several designs not listed in the catalog, including:
- deBolt Livewire, Cruiser, Jenny
- Berkeley's Royal, Rudder Bug, Bootstraps RC
- Spreng's Stormer, Roots Ascender, Guillows' XA Vanguard
- Send $2 to Tom for the vintage RC plans catalog.
Servo Torque Requirements and Back Issues
If you remember, in my September column I said I was going to write about servo torque requirements. MA's associate editor reminded me that George M. Myers (Model Aviation's "Radio Technique" columnist) covered this topic extensively back in 1981, so there's no need to reinvent the wheel. To learn more, consult Model Aviation issues from March, April, and May 1981 and read "Radio Technique." The first two cover servo torque requirements; the third is about picking a battery. If you don't have access to back issues, mail me and I'll copy the articles and mail them to people who send a SASE with 50¢ postage.
Send letters to: Ron Van Putte, 111 Sleepy Oaks Rd., Ft. Walton Beach, FL 32548.
How to Put Glass Cloth on a Balsa-Covered Foam Wing
A clubmate, Fred Carnes, asked me how to put glass cloth on a balsa-covered foam wing. I prefer to apply the glass cloth to the balsa wing skin before the skin is glued onto the foam — it's easier and the glass protects the balsa when bending around the wing contour (especially if the skin wraps around the leading edge). Regardless of when you apply the cloth, the technique is the same.
Preparation
- Fill any imperfections in the balsa with a light filler. Glass cloth fills over the wood grain well but won't perform miracles.
- Use lightweight cloth: Sig's lightest glass cloth is fine, but any 2–4 oz/yd² cloth will work.
- Cut the cloth slightly oversize — about 1 inch extra is plenty.
- Lay the cloth on the balsa and smooth out wrinkles as much as possible; remaining wrinkles will be removed when you epoxy the cloth.
Epoxy application and bonding
- I use Dave Brown's Mix A-Matic (30-minute) epoxy thinned with rubbing alcohol to a watery consistency to stick the cloth.
- Start at the center of one end of the cloth and work toward the outsides and toward the opposite end.
- When the cloth is completely stuck down, blot up excess epoxy or the surface will be uneven and heavy.
- Use a roll of toilet paper as a makeshift roller: insert a short section of broom-handle into the paper tube so it acts as an axle and roll across the cloth. Remove and discard saturated sheets as needed.
- Continue rolling until the cloth is securely stuck and the roll picks up no more epoxy. You'll know when to stop — rolling becomes effortless and the paper stops sticking.
Finishing
- After epoxy cures, trim excess cloth at wing tips and trailing edges with a sanding block and #240 grit sandpaper.
- Then use #400 grit wet-or-dry sandpaper with rubbing alcohol applied via a squirt bottle to sand the whole wing. This leaves a smooth surface ready for painting.
- I also place a 6–8 in. wide piece of 1½ oz/yd² glass cloth over the wing center section and overlap it with the lightweight cloth. I usually glass one side at a time (e.g., top, then bottom), so the center section ends up reinforced with three layers of cloth for extra strength.
Receiver Switches and Kwik Switch Mount
Words to the wise: check the operation of your receiver switch. Sometimes switches are not positive enough in their action, and engine vibration can cause the switch to turn off.
- Du-Bro's Kwik Switch Mount is usually reliable and requires only one hole in the fuselage. However, Bruce Underwood (Lake Guntersville, AL) reported a problem where engine vibration caused the On-Off shaft to "creep" in a too-tight switch fitting, thereby shutting off the receiver.
- Recommended action: check the switch housing and make sure the shaft fits smoothly (not too tight). Drill out the housing if necessary so the shaft moves freely. Several readers have reported similar issues and similar fixes.
- Don’t stop using the Kwik Switch Mount — just check the fit and correct it if needed.
Radio South Hinges and JR Radio Repair
When I talked to Radio South's Tony Stillman (43 West Nine Mile Road, Pensacola, FL 32514), he asked when I'd give Radio South hinges a plug. They deserve it. Installation is extremely simple:
- Mark hinge locations.
- Cut slots with an X-Acto #11 blade.
- Slide in the hinge and put a drop of CyA (Jet, Hot Stuff, Zap, etc.) on each side of the hinge.
They’re hard to install incorrectly and are very durable. If you aren't already familiar with them, ask your dealer about Radio South hinges.
Tony also told me Radio South is again performing repair/service on JR radios. That’s good news for JR owners who previously relied solely on Circus Hobbies, whose repair department was periodically overwhelmed. Tony says he now has less than a week’s backlog of work, now that the frequency-change crush seems to be abating.
Transcribed from original scans by AI. Minor OCR errors may remain.
