RC Scale
Stan Alexander [[email protected]]
Scale building: Change with the times or die on the vine?
When you build a Scale model, you have to think about how far you want to go with it. There are several levels you can work toward, which include the following.
- To obtain a model with which you are pleased.
- To obtain a model that is accurate to some degree.
- To create a model that could be competitive if you decided to enter competition.
- To construct a model that is exact scale.
Most aircraft fall somewhere within those categories. Some scale kits have so many problems with the outlines that scale modelers who know about or have judged competitions sometimes call them "cartoon scale." It seems that scale modeling is rapidly changing; we see it all the time.
In the United States, you see more airplanes, jets, and other types of ARFs for which most or all of the parts are preformed. Looking at past coverage in MA of Top Gun and other scale events, most of the models have all the parts pre-shaped. Are these ARFs? Some would say they are. Others would say that this is the current state of prefabrication that has been attained in the U.S. and around the world. The only craftsmanship needed to assemble those models is to install the electronics, join the major parts, and finish the airplane. Most of the graphics are stickers—not painted-on markings. But many of the newer full-scale jets have stickers too. So that would make the model correct, right? In many cases, panel lines and rivets are also premolded into the wings, fuselages, and other surfaces.
So which way do you go? Which way is scale modeling going? It's obvious that the old standards for AMA Sport Scale are outdated when you view the current crop of aircraft and their means of construction. Should we allow ARFs in Sport Scale, with no deductions for preformed parts? The AMA Scale Contest Board has many questions to answer for the next rules cycle. Many modelers consider scratch building to be constructing from plans, which is not the case. When you build from scratch, you have scale drawings or three-views and you measure a full-scale airplane with a cloth tape measure. Sometimes you must change the drawings so they match the full-scale version. Then you draw plans for the model, cut the parts, and build the airplane. There is a contest class for this type of construction; it's called Designer Scale, or F4C class in international competition. Building from plans or building from a kit is generally done in Expert class, which is for those who are experienced, and Sportsman class, which is for those who are not.
But what is a kit now? With all the available hardware, retracts, and prefinished items that are included in some kits or are available as extras, where does the craftsmanship go? I would love to hear your thoughts about this. Your Scale Contest Board member also needs to hear suggestions and comments from the Scale fraternity. Change with the times or die on the vine; this appears to be what's happening with all scale modeling.
Piper PA-11 build progress
The Piper PA-11 I'm building from the Goldberg J-3 Cub is coming along. The basic fuselage structure is finished. I've been working on the wing, which is ready for details and any internal parts that are needed to complete it.
After I looked at the three-view drawings and photos, I decided not to change where the ribs were located. However, I did modify the length of the full-wing ailerons to a more scale-like 16.5 inches, which is approximately 4 inches shorter than the kit specifications. That also changes the other areas on the wing trailing edge (TE), including the center section.
How do I mount the aileron servos? There are several ways. You can add the one aileron servo as in the instructions. But after subtracting the additional length of the nonscale ailerons, it might be a good idea to have two servos for the ailerons. Long torque rods can be weak. After completing the model, you can adjust the servos independently during flight tests to make whatever deflection changes are necessary.
I made holes in the wing ribs in front of the main spars using a power drill with a 1/2-inch Forstner bit. You could probably use any 1/2-inch bit. Why this size? Because it's easier to run the servo extensions through the ribs with this size hole. If it is much smaller, the extensions can stick or, worse, come apart after the wing has been covered.
Group the number-5 ribs in two stacks, and then join the stacks with T-pins. That will allow you to handle the ribs without their coming apart. It's also a good time to sand the stack of ribs, both the top and bottom edges, with a sanding block and clean off the die-cut edges. It's better to do it now than wait until they are installed.
My sanding block is a sophisticated tool; it's a 2 x 4-inch piece of wood with push pins stuck into the sandpaper and through the wood. It works well, and I've used it for years. I have several other sanding blocks, some of which I've purchased and others I've made for a particular shape as needed.
For all the parts, balsa sheets, sticks, and hardwood I've cut while constructing this kit, I've used my Tamiya Modeling Razor Saw. It is as sharp as it is functional.
When picking out a razor saw, look at the number of teeth on the saw blade. The more teeth, and the finer they are, the more accurate and quick the cut will be. But if you get a finger in the way, you'll cut yourself before you know it. Be careful!
After finishing the basic wing structure on my 47-inch computer-desk workbench, I realized that I would need something to prop up the other half of the wing when I joined the halves. I forced a camera tripod into the shop and adjusted it to the proper height to complete the wing. It worked great.
It's almost time to add the aileron servos. Pilots have their own preference of radio systems; it doesn't make much difference to me. I've flown JR for many years, I enjoy flying with my PCM10, and I still work with the JR 7202. I have roughly six models in that radio system.
Looking at the servos that were available and what I needed to make this work for the wing, I realized that I needed something other than a standard servo. The standard variety has 47 inch-ounce of torque and costs a reasonable price locally.
However, the standard servo weighs an average of 1.55 ounces. Adding this much weight to the outer regions of the wing is undesirable.
I browsed the Horizon Hobby offerings and found the Ultra-Torque Micro DS368 Premium Digital servo. It is roughly half the size of the standard unit in both height and width. The DS368 weighs only 0.80 ounce and supplies 53 inch-ounce of torque. Great control at half the weight.
I installed the servos with the control rod that will exit the top of the wing at the TE. (Yes, the top. I will describe this linkage method in another issue.) The servos are so small that you can mount them at the rear of the ribs.
Use a 1/16-inch sheet of plywood that is the width between two wing ribs. Cut these out using the razor saw, make four or so swipes with that blade, and it's done. Because you'll want to make this a tight fit, it's better to cut it a bit large and sand it down than have to cut the part again.
Hardwood sticks cut to length are attached to the ribs with ZAP adhesive and allowed to dry thoroughly. Use the plywood servo mount you cut and make sure there is a flush fit for the top of the wing ribs on the underside of the wing.
Drill four holes to hold the servo mounts on the hardwood blocks. Screw the servos to the hardwood blocks. Attach the servos to the underside of the mount at the back edge of the wing with thick ZAP.
Now the TE wing center section will be cut from the longest piece of balsa that is left for the entire wing TE. You need halves for this section that are 15.75 inches each. Use thick ZAP to glue these to the rear spar, which also has its sheeting applied.
The wing center section features only one dowel with which to hold the front of the wing to the fuselage, and the wing weighs more than the fuselage with no engine at this point. I elected to change this by adding a dowel and equally spread them 3 inches apart across the center.
I'll have more about the PA-11 next month.
Transcribed from original scans by AI. Minor OCR errors may remain.
