Micro-Flying
Dave Robelen
Route 4, Box 369, Farmville, VA 23901 E-mail: [email protected]
Introduction
Hello, small-model fans! As I write this late in November, winter is creeping into Virginia and trimming down outside flying hours. For those of you fortunate enough to have access to an indoor facility, at least you can keep on putting up flights.
I have a situation I could use feedback on: my Lithium-Polymer (Li-Poly) cells seem to lose much of their capacity as the temperature drops. Have you had that experience?
The last time I put a column together I wrote about the National Indoor Remote-controlled Aircraft Council (NIRAC) Championships, to be held June 4–6, 2004, in Waterford, Michigan. Because of space constraints I left a couple of events to write about this month.
Indoor Electric Duration (Event 627)
Indoor Electric Duration is event 627 in the AMA Competition Regulations. The battery allowed in this event has been reduced to a four‑50 mAh Ni‑Cd cell pack to reduce flight times and give everyone more flying time. Since there are no airframe restrictions in this event, the modeler is free to design as desired.
There are only a few ways to extend the flight of a model with fixed, limited power:
- Reduce the wing loading by building a larger model (low wing loading approach).
- Reduce drag by cleaning up the airframe and using efficient airfoils.
Although an oversimplification, this is a valid starting point. Models that have posted high times to date have essentially been enlarged Indoor Free Flight–style airframes with single‑surface covering, relatively wide‑chord wings, and external rigging. This low‑wing‑loading approach has worked well for several prominent fliers.
I chose a different direction: reduce drag while keeping weight to a minimum. The resulting model resembles many Outdoor Free Flight rubber‑powered endurance models. Long, slender wings keep induced drag low, and a clean, double‑covered airfoil reduces drag further.
Test flying has been encouraging, with long‑flight potential evident. The battery is fixed by the rules, but other equipment can be optimized. The DC5‑2.4 motor has proven an excellent balance of weight and efficiency. Mating this motor to a smooth‑running gear set is important — the Didel gear trains and mounts available from Dynamic Web Enterprises (www.smallrc.com) are among the smoothest running around.
Dynamic Web Enterprises also carries a nice narrow‑band, lightweight receiver — the JMP — which allows multiple models in the air at the same time. I chose a light actuator for the rudder (no elevator control is necessary): a 200‑ohm Bird from Cloud 9 Micro R/C Models.
Why not break out the board and build something to compete?
Cargo Event
So far I’ve been a spectator for the Cargo event. The most successful models tend to have light construction with fairly large wing chords and external rigging for support.
GWS IPS drives are the power of choice, and two Kokam 340 mAh cells provide the electricity. It’s unnecessary to use equipment with more capacity than needed for trimming controls during flight; the lightest narrow‑band gear is desirable.
Large, free‑rolling wheels on a rigid landing gear can make the difference on maximum‑weight takeoff efforts. Last year’s models had single‑surface wings, but I believe they could be improved with good low‑speed airfoils and double covering. I also think external bracing remains the most practical choice. I bet there are some razor‑sharp designers who could lay out an efficient airframe.
All event rules can be found at www.nirac.org.
WACO SRE Project
I’ve included pictures of my latest micro fun: a WACO SRE. The wingspan is 14 inches and it weighs 1 ounce. Controls are my venerable RFFS‑100 with push‑pull actuators and hardware by Gary Hutchison. The drive is a KP‑00 motor with 6:1 gearing that turns a 5 x 4 propeller. Electricity comes from one 230 mAh Li‑Poly cell.
Significantly, this little project was built directly from Free Flight Peanut Scale plans — I simply substituted 1/32" balsa for the stick‑and‑tissue original. The little WACO is a delightful flier that handles almost like a trainer and can handle some breeze without being blown away. Watch for it at www.rcmicroflight.com.
Building from Free Flight Plans
The WACO project highlights the practical possibility of building these micros from old Free Flight plans using simple material substitutions. Model Builder magazine published many of these plans (one every month). Although the magazine is out of circulation, original publisher Bill Northrop has been offering packages of these plans for sale through advertisements in Flying Models.
With the ability to resize any plans at a copy shop, the subjects are almost limitless. Think in terms of 1/32" balsa‑sheet construction with single‑surface, curved‑wing airfoils and flat‑plate tails.
For finish, I’m pleased with the results of using automobile touch‑up spray paint. If possible, dilute it 50/50 with lacquer thinner and apply with a simple airbrush. The finish adds very little weight and really brightens a model.
Prebuilt Models and Power Systems
My old friend Jack Dobbins periodically sends another of his growing line of prebuilt models. The most recent is called the Sweetie and came completely finished except for joining the wing halves and mounting the tail. All linkage and control horns were premade and fit perfectly.
I mounted a GWS IPS A drive with a 9 x 7 propeller and two Kokam 340 Li‑Poly cells for power. Controls installed were the Pico system from GWS, along with the ICS‑50 Electronic Speed Controller. This aircraft is a real "Sweetie" in the air — smooth controls and no bad habits.
You can reach Jack at (309) 745‑8543 or write to him at 402 Lotus Ln., Washington, IL 61571. Jack told me he would ask $50 shipped for one of these gems. Buy American and enjoy!
Micro Hardware Sources
Several columns ago I mentioned a new source of micro hardware from Gary Hutchison in South Carolina. Besides misspelling Gary’s name (my apology), he sent a large variety of goodies after I sent the column out.
Along with keepers and push‑on buttons, Gary has added some neat control horns and actuator housing sets. There are also some of the tiniest hinges I’ve ever seen. You can purchase from Gary’s line through Dynamic Web Enterprises at www.smallrc.com. Tell ’em I sent you.
We seem to be on the threshold of a breakthrough in ultra‑light servo‑driven systems. The Cirrus line has been advertised for a while and will probably be available soon. Didel in France is producing a servo that weighs less than 2 grams and is available through www.smallrc.com. A 1.7‑gram gem called the Falcon is on the way from England, and CO2 expert Gasparin is preparing to introduce a light servo. Most of these feature magnetic Hall‑effect feedback and are beautifully built.
It may not be common knowledge, but a light receiver has been available for several years: the SHR PRO from Sky Hooks and Rigging at www.microcrc.com. Although it is not especially narrow band, the range is excellent and it is reliable. Mine has served me well for quite a while.
Closing
I’m going to wrap this up. Remember: I cannot show your projects if you do not send me material. The same goes for manufacturers. Many readers see this column, and I will be glad to give you some publicity if you send information and photos.
Transcribed from original scans by AI. Minor OCR errors may remain.
