Author: Stan Alexander

Edition: Model Aviation - 2000/11
Page Numbers: 97, 98
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RADIO CONTROL SCALE

Stan Alexander, 3709 Valley Ridge Dr., Nashville TN 37211; E-mail: [email protected]

As I'm writing this in July, it's sunny and hot outside and it's time to go flying! However, when you receive the magazine in late September or October, many of us will start thinking about next year's project.

Say you have an idea of what you want to build this winter (that means you build faster than I do). But you want a Scale model that isn't your regular J-3 Cub, and you are really tired of building kits—many of which have to be modified to make really nice Scale models.

You start thinking about building from plans or scratch-building—there is a difference between the two.

Scratch-building vs. Building from plans

Scratch-building involves enlarging a set of three-view drawings to the size that best suits you and your equipment, then adding all of the model's structure.

When building from plans, you compare someone else's drawings and your documentation, and look for changes you need to make for your individual aircraft. This is assuming you have collected your documentation beforehand, and you know the dimensions of the aircraft.

I've built from plans, and I really like to build with sticks. I'm not a plan designer, and probably never will be. It's not that I think I couldn't design plans, but I don't have the time one must dedicate to this special set of skills.

Looking for a good set of plans from which to build a simple Scale model should be easy; there are several sets of plans out there for home-builts or production aircraft.

I've been looking at plans for a Corbin Baby Ace. A few of these airplanes were constructed at the factory, but most are home-built. The full-scale aircraft has its wing mounted above the fuselage, in the parasol position. The Ace uses many Cub parts, such as the cowl, and it can use Cub wheels.

Home-built aircraft can vary from airframe to airframe. Some have wheel pants and rounded flying surfaces, and other aircraft of the same type have their flying surfaces squared off, to look more modern.

Modifying the PT-19

Making changes to the PT-19 has taken more time than I originally thought it would.

Sometimes it just takes a while to figure out what will look correct (by going back to the photos and three-views) and what will work for a Radio Control (RC) model.

I checked several different sets of plans for the tailwheel setup. I moved the tailwheel into the right position (Scale)—

  • I used the cutoff wheel on my Dremel® to cut the wire axle so I could attach a steering arm from a nose gear.
  • I glued a wedge of plywood to the bottom rear of the fuselage, then I drilled a slot down the center for the tailwheel unit.
  • The plastic tailwheel unit will stick out of the fuselage after the model is completed, but it will be covered by the "feather" gear boot, as is used on the full-scale aircraft. Using the plastic unit and not adding a heavier part or more wood should help keep the tail lighter.

When I installed the horizontal stabilizer, I went back and checked the photos to see where the trailing edge of the stabilizer lined up. Was it with the rear of the fuselage? Nope! Just ahead of it.

After I mount the elevators, I'll add a removable cover spacer to complete the installation.

The aileron linkage has been a concern because of the way the full-scale aircraft's linkage was attached. All the aileron hinges are visible from the top of the wing, as is the torque rod for deflection of the control surface.

I used four Robert Hinge Points on each aileron, with the inside hinge point simulating the control rod of the full-scale aircraft. Using a fixture to correctly drill the 3/16-inch holes for the hinge points helps to center each one in alignment on the wing. This fixture, which is shown, was made from a piece of hardwood in my shop.

I moved the actual servo linkage out by one rib bay, to better center the load on the servo. By using the second rib bay, I can still conceal the servos and most of the linkage in the wing to each aileron.

I used JR 4721 servos for the ailerons. The ailerons will be permanently attached later, as the wing is finished.

More on the PT-19 in the next column.

Einstein XL Battery Management System

I recently decided to upgrade my battery chargers, and I still wanted to be able to cycle my batteries too.

It's not fun to go to a contest or to the local field, and watch someone lose a $1,000 model because of battery failure.

The unit I had been using was old, and it was failing to complete the charging cycle, so it quickly hit the trash can—much like old batteries do.

The Einstein XL Deluxe model from FMA Direct comes tightly packaged, with all the components boxed and bagged. After I read the instructions and identified the contents, I went back and read the instructions again.

With this system, it's easy to hook up two batteries of different radio types for charge or trickle charge, or to cycle your batteries.

Radio manufacturers have confused modelers with what they can and cannot do for cycling batteries.

With many newer computer radios, you have to take the battery out of the transmitter to bypass the diode—which will not allow the transmitter battery to be cycled. You need a second charged transmitter battery to replace the one you are cycling, or you could risk losing the data stored for individual models.

The lithium batteries included in JR, Airtronics, and other systems will hold your data, but not for an indefinite period of time. Therefore, it's necessary to use a second transmitter battery with this system for those transmitters equipped with the diode. It's a good idea to have a set of backup batteries anyway.

Does your transmitter have this diode? If it wasn't listed in the owner's manual, call the manufacturer to be sure. Batches of radios have been produced with and without the diode for the same model, sometimes by the same manufacturer.

On the plus side, the Einstein XL is small and easy to handle. You can charge almost any radio system, and the Einstein has generic jumpers and a Deans pin.

The charger/cycler is easy to use, and the LED readout lets you know what's going on while you have the batteries hooked up.

However, I don't like the "jumper pins" that have to be pushed into the unit to set the charge rate and the number of battery cells. The pins are 1/2 x 3/16, and they are easy to lose or misplace (at least in my shop). The charger/cycler comes with six pins, which gives you two spares. Dials or switches would be a much better choice for these controls—even if the unit costs a little more.

I've put my charger/cycler and its accessories in a box, and I put the extra jumper pins in a Ziploc® bag so they won't get lost.

Save the instructions; you did read them, didn't you? You will need to make your own connectors for the transmitter batteries, as you will do with most cycler/chargers. Wouldn't it be nice if radio manufacturers made their own maintenance equipment?

The Einstein XL is a very handy maintenance tool for the shop, and if used properly, it could save a model you spent many hours building.

Scale Pilot

A Scale airplane doesn't look right unless it has a good scale pilot in the cockpit.

Diane Chevalier has been making pilots for her husband's models for years, and she is his right hand and pit crew at each contest.

Note the attention to detail in the photo, with the shirts, Zap® logos, glasses, and everything else Diane added to the pilot and passenger in John’s Piper Tri-Pacer. They look great.

If you are interested in having one of Diane's pilots for your model, contact her at:

  • Pilots by Diane, Box 1865, Champlain NY 12919
  • Tel.: (450) 246-4543

Plans and resources

You may know by now that I like plans, and there are quite a few out there I want to collect. Although I'll never build models from all of them, I can learn by looking at sets from different designers, such as Jerry Bates.

I like naval subjects, and the Hellcat is one of the classics from World War II. Jerry has a plans set for an 80-inch model, designed for an ST-3000 or a G-45 engine. The Hellcat can be built as an F6F-3 or an F6F-5.

The neat thing about many plans today is that if you don't want to cut the kit out, there is a list of kit-cutters in the supplier's catalogs.

Jerry's plans are well-explained, and there are extra sheets for details. Documentation is easy to obtain for the Hellcat; after getting those retracts installed, the rest should be easy. Details include drawings and instructions to fit the segmented flaps.

Fiberglass fuselages and parts are available for many of the kits. Contact:

Close-Ups

A couple of this month's photos are from John Symborski of Silver Spring MD. He is in the process of finishing his RWD-8, a 1932 Polish trainer.

John is building from Steve Stratt Airdrome Plans and a partial kit from Arizona Modelers. Power is provided by an Aveox 1409 brushless electric motor.

Okay, John—we want to see the finished product!

Until next time, fair skies and tail winds. MA

Transcribed from original scans by AI. Minor OCR errors may remain.