Airwaves

ENGINE SIDE THRUST

First, thank you for giving such honest and excellent reports and articles. Great job! I try to read every issue of most modeler magazines, and you're the best. Keep it up! I would love to see an article relating to engine-- thrust angles. It. seems that most models have about 3 degrees of offset built into their firewalls, but what exactly is the reason for this? Is there a factor for better performance with 2 degrees versus 5 degrees? Why is it to the right? What about pushers and twin-engine aircraft? Some local modelers even say not to use any thrust offset at all. Maybe you could address these questions for me.

MICHAEL REIMAN

Palm Beach, FL

Michael, the topic of engine side thrust relates to correcting (or at least minimizing) engine torque. As the engine spins the propeller (counterclockwise, as seen from in front of the model), torque tries to veer the model to its left. Adding right thrust helps offset this torque-induced left turn and helps the model stay on a straight course. For most .40- to .60-size airplanes turning a 10- or 11-inch prop, 2 to 3 degrees of right thrust offset seems to be the norm. The more torque an engine produces, the more offset it needs. For pushers, 'the offset is also in the opposite directon of the torque force. For twin-engine aircraft, engine offset helps during takeoffs and during, potential engine-out situations. Although there are many opinions about which setup is best, most designs have 0-- degree of offset on the left engine and 2- to 3-- degrees right thrust on the right engine. But, as with most airplane setups, the exact amount of offset is determined by the model's own characteristics. Trial and error is needed to dial in any plane.

MORE TISSUE COVERING TIPS

I enjoyed Dave Robelen's excellent article on covering with tissue (February 2000 issue), and I am about to put it into practice on a Speed 400 electric Super Cub. Is Elmer's school gel significantly different from Elmer's white glue? Should they be diluted to save weight? Regarding tissue-- grain versus shrink: as I read your instructions, the grain should go on the wing cord, not the span. Is this correct? Is Krylon Crystal Clear lacquer recommended even on an electric motor (no fuel or oil)? Can you explain why you shouldn't wrap tissue around the corners on the fuselage? Is lacquer recommended on small, light parts? Thanks for an excellent (and timely, for me) article and your answers to my questions. [email]

DICK ERRATT

You're welcome; glad you liked the article. To answer your questions: the school gel dries faster and is simpler to dispense. The white glue also works fine if the other is difficult to find. I don't dilute either one, but I do spread them thin. The tissue grain should cross the chord. This gives less sag between ribs. Lacquer weighs very little and, except for indoor flying, it stabilizes the tissue and makes it moisture-proof. Since tissue is a paper product, it will bend only one way at a time. Wrapping it around the frame would promote wrinkling. Also, if you use colored tissue, overlaps should be avoided because of the color-density difference.

DAVE ROBELEN

POKEY PLAN, PLEASE

Is there a plan available for Pokey, the model that Dave Robelen used in his tissue-covering article? I really liked the design's appearance and simplicity. I've been looking for a rubber-to-RC conversion project, and Pokey looks like a good place to start. With a little guesswork and a ruler, I think I could draw up a copy of the airframe from the article, but I'd still be in the dark as to the RC gear.

Which motor, prop, gearbox, servos, ESC, receiver and battery pack did you use? Experimenting with micro gear is an expensive proposition, so knowing what works in Pokey would give me a good start. [email]

GEORGE KUEHN

You're in luck, George; due to popular demand, my Pokey model will be featured in an upcoming Model Airplane News construction article. It's equipped with 3-channel control for flying in really tight quarters. I am using a WES-Technik DCS-2.4 motor and gear set (and am quite fond of it). There are other power options among electric motors. In fact, by the time you read this, there will probably be still more possibilities. This is also true of the RC equipment; new and lighter hardware appears almost weekly. For my installation, I chose Hitec HS-50 servos and then trimmed away the excess from the plastic case. I used the Hitec Feather receiver and 7-cell, SOm.Ah Ni-Cd battery pack. I also used an ESC from Sky Hooks and Rigging and an ARC-1 prop from Anything RC. For more information, check out the RC MicroFlight newsletter at www.rcmicroflight.com (or call [800] 2436685 to subscribe).

DAVE ROBELEN

MICRO-FLIGHT FANS

I am an RC flyer, given to flying large glow- and gasoline-powered models. Recently, my closest flying buddy and I decided to look at the world of micro flight and come out of the cold, perhaps! We have both built the little Pico Indoor J 3-S models. I have flight-tested mine, and we are waiting for our next opportunity to fly indoors.