R/C Flying: rec.models.rc FAQ

Contents:


Chapter 6) Pre-flight Checklist

When your model is ready to fly, make sure it is thoroly checked over by someone who has done a lot of building and flying. When I say thoroughly, I don't mean just picking it up and checking the balance and thumping the tires a few times. Every detail of setup and connection should be gone over in detail. If your instructor doesn't want to spend this much time checking your plane, find a new instructor.

The importance of this pre-flight check cannot be overemphasized! Many planes are lost due to a simple oversight that could have been caught by a pre-flight!

Here's a checklist:

Before the first flight

  1. Weight

  2. Balance

  3. Alignment
  4. Control surfaces
  5. Control linkage
  6. Engine and fuel (if applicable)
  7. Radio

After_repair

The checklist should be gone through again, with particular attention to the areas that were worked on or repaired.

Before EVERY flight

  1. Start the engine (if applicable) and test the entire throttle range. Run it at full throttle with its nose in the air for 15 seconds or so.

  2. Check the receiver flight pack with a voltmeter to ensure enough charge.

  3. Check the control throw direction for all surfaces. It's very easy to do a repair or radio adjustment and forget to switch these.
If you can't find an expert that is willing to teach you, it is best to start with a 2-3 channel model with a long wingspan and alot of dihedral. The ideal thing to start with here would be a 2 channel glider. If you MUST start with a powered plane, a 6' foot powered glider, like the Piece O' Cake from Dynaflite is a good way to go.


Chapter 7) Gliders (Launching, Staying Up, Recommendations and Costs)

(From Shamim Mohamed)

A 2-channel (rudder+elevator) polyhedral [see below] glider is just about the easiest way to learn to fly, and is highly recommended. Once you can handle that you can move up to rudder-elev.-spoiler-flap competition ships or (on the slope) rudder-elevator-aileron-spoiler aerobatics ships.

Sailplane plug (aka religious sermon): ... don't think glider flying is just "launch, glide back"---It's very easy to get 30+ minute flights and about 1000' altitude. Remember, power flying is limited by the size of the fuel tank (about 10 minutes) and gliders are limited by the receiver batteries (about 2 hrs). And glider flying is *much* more challenging (my opinion, of course), while at the same time being easier to learn. And no fuel costs, no starting hassles, no cleanup afterwards... Also, many cities have ordinances prohibiting model engines, which means the flying fields are outside city limits. BUT, since sailplanes don't have those nasty, messy smelly things, we can fly in any large enough area!


  7.1) Are most gliders hand launched, or do they have a small engine to get them up?

Gliders are usually launched by a "hi-start"---a section of rubber with about 500' of line. It is hooked to the plane and pulled back---the rubber then pulls it up kite-like. (It is NOT like a catapult launch!). Launches of heights up to 500' can be obtained on a good day. The launching procedure is simple---keep the elevator neutral (for now) and keep it flying straight. At the top the glider will just fly off the line. A small engine can also be used but it creates a lot of drag which is very detrimental to gliding performance. Hi-starts range from around $20 for light-weight models to $100 for heavy-duty ones.

Winches are also used---it's very similar to a high-start except that you (the pilot) always have control over the line tension so you can usually get better launches. It does take more skill, though; as a beginner you don't need to worry about winches just yet.

Flying at the slope you just chuck the plane into the wind---that's it!


  7.2) How do sailplanes stay up?

Since a sailplane has no engine, it follows that it must always sink through the surrounding air. The trick then is to find some air that's going up faster than you'll sink through it... and for our purposes, there are two kinds of such air:


    7.2.1) Recommendations - Sailplanes

6' or 2m class: (recommended)

Carl Goldberg Gentle Lady, Dynaflite/Craft-Air Drifter II, Airtronics Olympic 650, SIG Riser, Great Planes Spirit, etc.

These are all polyhedral ships with rudder and elevator controls. All are highly recommended.

Carl Goldberg Sophisticated Lady: basically a souped up Gentle Lady, it is in general not recommended---it's heavier and the T-tail structure is very easy to break, even on a slightly rough landing.

100" or standard class:

Dynaflite/Craft-Air Butterfly, Airtronics Olympic II, SIG Riser 100 etc.

These models fly better but are more cumbersome to launch and transport, and are also slightly more expensive. These are basically scaled up versions of the 2m ships above.


Chapter 8) Costs

Q: What kind of cost am I looking at for a solid training glider or powered plane, with all gear?

$200 is in the ballpark. $120 for a 4-ch radio, $60 for a 2m glider, covering and other supplies. ARF Gliders---$100 + radio + supplies.

Powered planes: about $350-400---$120 radio, $70 plane, $120 engine + supplies.

(By "supplies," I mean things like rulers, knives etc.)


  8.1) Where can I mail-order stuff from?

Try Tower Hobbies (1 800 637 4989) and Sheldon's (1 800 228 3237) [Inside CA, 1 800 822 1688]. Also look in modeling magazines for ads. Try Radio Control Modeller, Model Airplane News, Flying Models, Model Aviation.

Tower Hobbies also has a WWW home page; the URL is http://www.towerhobbies.com/

(From Filipg)

Another Hobby store that has an on-line WWW home page is Skycraft Hobbies Inc at URL http://wchat.on.ca/sky/sky.htm

There are links to more Hobby stores, personal pages, clubs, and other sites from my page RC-related Links at URL http://www.repairfaq.org/filipg/RC/F_Links.html


Chapter 9) Powered (gas)

(From Gary Hethcoat and Ken Summers)

Even though "wet" power is called "gas", it's not the same as car gasoline. Model fuel is usually a mixture of a lubricant (synthetic or castor oil), methanol and nitromethane. The power plants are usually called engines, as opposed to electrics, which use motors (see below). Engines are available in 2-stroke (louder, cheaper, and more powerful for the same displacement) and 4-stroke (a more scale sound, less vibration, but more expensive). Engine displacements are usually measured in cu. in. the US (A 60 engine = 10cc [actually 0.61 cu. in.]).

Compared to beginner's gliders, powered trainers are more difficult to master. This means that everything about instructors and equipment checks goes DOUBLE for powered planes. There are many, many ways a beginner can make mistakes and destroy a model that he/she has spent a lot of time and money on. With the typical powered trainer, going it alone is foolhardy and will likely end with a destroyed model and a very disappointed modeller.

If you can't find an expert that is willing to teach you, it is best to start with a 2-3 channel model with a long wingspan and a lot of dihedral. The ideal thing to start with here would be a 2 channel glider. If you must start with a powered plane, a Sig Kadet is one of the more docile trainers.

If you have an instructor, but have not flown R/C before, you can start with something a bit more advanced. In general, the larger the plane, the easier it is to see and to fly; but at the same time, the more expensive it is. The most popular size is the so-called "40-size" plane, with about a 50" wingspan and .40 cu. in. engine. The Great Planes PT-20/40/60 series are good. You can build these with ailerons, but due to their large dihedral, they can also be flown without ailerons. It won't hurt to have them built-in. Even though they will not be very effective, they will get you used to using them. Other recommended planes are the Midwest Aerostar and the Goldberg Eagle. Something with a "tricycle" undercarriage, that is one with a nosewheel and two main wheels, is the easiest to learn on.

If you have an instructor, and have flown R/C gliders, you might want to start with something still more advanced, say a Great Planes Trainer 20/40/60 or the like. These have a fully symmetrical airfoil and less dihedral. They are capable of more in the way of aerobatics, but are trickier to fly due to higher speed and less stability.


Chapter 10) Electric Flight (Advantages, Equipment, Motor Specs., Recommendations)

(From Wayne Angevine)


  10.1) I didn't know that you could put an electric motor and batteries in an airplane.

Isn't that kind of heavy?

Modern NiCd batteries are pretty amazing. You can charge them in 15 minutes, take power out of them at up to 50 amps or so, and do it all day. That capability is what makes electric flight possible. Electric power can be used for any kind of flying---gliders, aerobatics, even racing. It's an excellent choice for sport flying.


  10.2) What are the advantages and disadvantages of electric flight compared to wet power?

Electric power systems are heavier for a given power output. This means that planes must be built lighter, which may be more challenging (especially for the beginner). That's really the only significant disadvantage. The big advantages are that electrics are quiet and clean.

To me, the biggest advantage of all is that electric flight is unusual and interesting.


  10.3) What is the best way to get started in electric flight?

That depends on what you want to do and where you're starting from.

If you've never flown RC before, and you want to start with an electric plane rather than a pure glider, I recommend an electric glider like the Airtronics Eclipse. This will give you the best chance to stay ahead of the plane. In the sport/trainer category, I hear a lot of good things about the Leisure Amptique.

If you know how to fly RC, you have a lot of choices. The simplest and most available electric power systems use six or seven cells. These are called "05" systems, and are very similar to the power system of an RC car. You can find all sorts of planes in kit or plan form which will work well with these systems. Outstanding examples are the aforementioned Eclipse and Amptique, old timers such as the Leisure Playboy and Astro Viking, a variety of semi-scale kits from Davey Systems, all sorts of gliders, and the aerobatic ElectroStreak from Great Planes. Any two-meter glider kit can be easily adapted to six or seven cell electric by a moderately competent builder. Just stick a motor in the nose, battery under the wing, and go.

If you want more performance, good ground handling, or just like larger planes, there are larger power systems available, all the way up to systems which will handle a 60-sized power plane. The cost and complexity, of course, go up with size. Any reasonably well-designed power plane kit or plan can be adapted to an appropriately chosen electric power system. The first step is to leave out half the wood---all power planes are grossly overdesigned. Electric motors generate very little vibration, which helps you get away with lighter structures.


  10.4) What are the elements of an electric power system?

The power system includes a battery, a motor, a control, and wiring. The battery is almost always made up of Sanyo NiCd cells in the appropriate number. Motors vary from the simple, cheap "can" type (otherwise known as "540" or "550" style), through more sophisticated styles adapted from RC car motors, up to the cobalt powerhouses.

Controls can be a simple on-off switch controlled by a servo, a directly controlled on-off switch, or a proportional electronic control.

If you are going to fly a glider or old-timer type plane with less than a 500-watt motor, think seriously about getting battery packs made of Sanyo 900 SCR cells. They are significantly lighter than the more usual 1200 mAH (sub-C) cells and give excellent performance.


  10.5) What do the various letters used to refer to NiCd cells mean?

"SC" is the basic cell. SC cells will take fast charging and have reasonably low internal resistance. SCR cells have lower internal resistance and a somewhat flatter discharge curve, that is, they put out nearly the same voltage from beginning to end of the discharge. SCRs are best for high current drain applications. SCE cells have somewhat more capacity for the same physical size, but also have higher internal resistance. They are best for low current drain use (less than about 10 Amps.) The higher capacity of SCE cells will not be realized at high current drains, and they will heat up more than SCR cells.

Many kits nowadays come with a power system. In most cases, these systems are adequate for the application. It won't hurt to try what's there to start with, you can always experiment later. If the kit you choose doesn't come with a motor, of course, you'll have to choose one. If you are a beginner, go with the recommendations of the kit manufacturer. If you are an experienced RCer, you probably don't need my help.

For a six- or seven-cell glider or old-timer with a cheap motor, an on-off switch is sufficient control. For anything else, you will have much greater enjoyment with a proportional throttle. Get a high-rate control, they are much more efficient at part throttle. There are several good brands out there, but I like Jomar for good controls at good prices.


  10.6) What support equipment do I need?

You need a charger of some sort. If you are using six or seven cells, any RC car charger will do the job. You don't need peak detecting or any of that fancy stuff to start with. For larger packs, there are good high-voltage chargers around. Check out Astro Flight and TRC, among others. Remember, the biggest enemy of NiCads is heat, so try and keep those batteries cool when charging. Expect to pay about $40.


  10.7) How are motor sizes specified?

Motors are traditionally specified by a system which attempts to equate them to wet engines. There are significant problems with this, but they probably aren't of concern to beginners. An "05" motor takes a six or seven cell battery and puts out 75 to 120 watts, and so on up to a "60" which takes 28 cells and puts out 1200 watts. Incidentally, there are about 750 watts in a horsepower.

The actual power output for a given voltage (number of cells) depends on the load. Unlike wet engines, electric motors put out more power with more load. If you don't like the performance you get from your plane, you can try a bigger propeller---up to a point. More power, of course, means less run time.

In the ideal world, motors would be specified by the total power they are capable of supporting and by the number of cells (or voltage) with which that power is produced.


  10.8) What's a cobalt motor and why would I want one?

Rare-earth magnets, of which the most common type is samarium cobalt, are stronger for a given weight and volume than ferrite magnets. Perhaps an even more important reason for getting a cobalt motor is that they also have better brushes, bigger shafts, better bearings, are built more carefully, and so on. For the serious electric flier, they are worth the extra expense.


  10.9) Where can I get this stuff?

Electric equipment is somewhat specialized, and most hobby shops aren't yet sufficiently enlightened to carry very much. You can use RC car equipment for a lot of things (after all, they developed this stuff in the first place) and your local hobby shop will have lots of that. If you want to get more sophisticated, get the catalogues from Hobby Lobby and Hobby Horn (both have ads in all the usual magazines.) Both catalogs contain a lot of detailed information that I can't fit in here. Hobby Horn has good prices on mainstream stuff. Hobby Lobby sells the lines of several European manufacturers, and tends to have higher prices for fancier (or at least more unusual) stuff. I haven't dealt with CS Flight Systems on the East Coast, but I read good things about them.


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