Preparation for Spring
by Marty Zeller
Some of you have seen my new Extra 300 with the Kavan FK-50. I finished it at the end of the good weather season and have had numerous engine problems getting it to be consistent. It is a bit complicated as it has several adjustments that must be made in order for it to work well. The carburetor has a cam on the actuating arm, which varies the mixture from idle through top end. This allows you to set the mixture through the entire profile. It also has a conventional air bleed adjustment for idle. Also on the carburetor is a micro switch, which gives a retard and advance to the ignition timing. This switch also has to be set so the engine is easy to start and advances when the throttle is opened.

I just could not get the proper engine operation at the field so I was determined to make this system work. The first step was to put the engine back on my test stand where everything was accessible and easy to adjust. The carb was removed, cleaned and inspected. I found that accumulated castor oil had collected and stopped the rich/lean operation of the cam follower. I also found that the timing switch was very hard to adjust because it was driven by the actuator arm. In addition the wires attached to the switch were subject to continued engine vibration. The fix was to thoroughly clean the carb and remove the micro switch. I replaced the switch with a separate remote switch driven by a slave servo off the throttle channel. Now I have complete independent adjustment of the timing from my transmitter. Now the carb works freely and the engine again runs like a champ. I hope you will see it a lot this year at the field.

This brings me to the point of this article. If you haven't flown your ship for several months, now would be a good time to do some preventive maintenance so you will be able to fly once you get to the field.

If you use fuel with castor oil in it, any fuel left in the tank over the winter will evaporate, leaving the castor oil behind. This congealed mess will eventually dissolve when fuel meets it but it will take some time. If you have a fuel filter in line, castor oil may congeal on the screen and prevent fuel flow until it dissolves. Castor oil will also collect in the carb and possibly plug vents or tiny spots where fuel is supposed to flow. The simple fix for all of this is to remove your carburetor, disassemble and soak it in fuel for a few days. Clean it thoroughly and reassemble to the original settings. Also fill your tank and leave it sit as well to dissolve and congealed castor oil. You can also test your fuel line integrity at this time by plugging the vents and apply some pressure checking for leaks. Its very easy to get a small cut in the line which may not otherwise show up and your engine will want to run leas as it will suck in air from the tear. If it is possible on your next model, build it so you can remove the entire tank easily then you can assure yourself that there are no leaks, the clunk is still attached and all the lines are good.

If you use fuels with synthetic oils, the problem is not so great, but the preventive procedures described above are still worthwhile. Synthetic oils give the best after run protection. Castor oil can stand higher temperatures if you begin to run lean and will protect longer. Some fuels have a blend of castor and synthetic to give the most protection.

After run engine oil is a very good idea to preserve the life of your engine. You can make your own for very little cost. Use a 50/50 blend of Marvel Mystery Oil and Automatic Transmission fluid. On your last flight of the day, while your engine is still warm, place it on high throttle and pinch off the fuel. This will use up most of the residual fuel in the engine. This gets rid of the nitro and alcohol that will attract moisture. Disconnect the fuel line from the engine. Place several drops of after run in the carb and glow plug and turn the engine over several seconds to bathe the bearings with oil. This procedure will help you have less engine problems this year and you won't have to go through the frustration that I went through last year with the Kavan.

No dead sticks this year! See you at the field, Marty. (mailto:mzeller@nni.com)

For Further Information
http://www.mecoa.com/kavan/kavan.htm

The Weight in Your Plane-Where's It At?
By Clay Ramskill
Every kit we buy will show where the point of balance is supposed to be, and it's up to us to see that it gets there. The point of balance is the front to back measure- ment of where the center of gravity (CG) should be.
The CG placement is a very important part of how any plane is going to perform, essentially adjusting the plane's pitch stability. If the CG is too far to the rear, the plane will have marginal stability. That is, it will take very little elevator movement to effect a significant pitch (and angle of attack) change. A plane with an aft CG will be very quick to respond in pitch and will not be inclined to seek out a trim position.

With a forward CG, a plane may require some "up" ele- vator to fly, and will require a lot of elevator i-novement to make any pitch changes. However, if upset from a trim attitude, it will very quickly try to regain that atti- tude. In short, the farther forward the CG, the more sta- ble the plane, pitch-wise. A plane that is too stable will seem "sluggish" when maneuvering. A less stable plane with a more aft CG might be "sensitive," or even "skit- tish." In extreme cases, the term has been "unflyable!"

While on the subject of balance, let's not forget lateral balance. The plane should be balanced laterally, as well as longitudinally. Just an ounce of weight in a wingtip for lateral balance can make a big difference in whether your wings stay where you want them while maneuver- ing.

But there's more to weight placement than CG. Weight distribution also can affect a plane's perfor- mance. The further out in "the ends" (of fuselage and wings) weight is located, the slower a plane moves ini- tially to control inputs. Imagine, for instance, putting a half pound weight on each wingtip of a plane. That plane will eventually have the same rate of roll, but due to the inertia of the weights, it will take a while longer to achieve that rate.

The same goes for pitch. If we have a heavy engine, for- ward of the CG, we will have to compensate by moving servos and batteries (and maybe all lead) aft in the fuse- lage. Inertia from that weight distribution will cause a slower initial reaction to elevator control. The same rea- soning concerning weight in the ends ol'the plane also applies to directional control, slowing down reaction to rudder inputs.

Care and Feeding of Glow Plugs
Here's a list of glow-plug readings to help you find the perfect mixture.
Shiny element (like new): You have picked up a new plug by mistake, or your engine is set to a rich setting. You can lean down the engine and test it again.

Dull element: A dull element is one that has lost it's shine, but it is not frosted. If the element is still in it's original shape, not mangled or twisted, your engine is lean enough to work hard without being damaged. This is a good setting for prolonged running.

Frosted element: The frosted element has an "orange-peel" surface and is an indication that you are, in fact, running lean. Lean is mean, but don't expect your engine to hang in there during prolonged running. If the element is not mangled, you are simply running lean. Ritchen it up a bit.

(Frosted or missing) mangled element: When the element is frosted or completely destroyed, it can be an indication of a lean run. You must set the engine rich and run it again to determine the cause of damage. v Black element: A black element is not a good one. It can be an indication that a rotor is being eaten up or that aluminum filings are in the engine. A black residue at the tuned pipe or muffler exhaust is an indication that something aluminum is coming apart in the engine.

Small shiny flakes: Small shiny flakes on the low-plug can be an indication that new bearings are in order.

Missing plug: This scenario shows that you forgot to tighten the glow plug.

Dull and pulled out: When the element is dull and pulled out toward the piston, your needle setting and tuned pipe are on the money. The pulled element is an indication that pipe scavenging is working great.

Hobby Knife or Scalpel?
by Paul Neves
Used properly and carefully, the hobby knife is an excellent tool for cutting, carving and shaping balsa. Used improperly, it will cut or pierce anything that happens to be in it's way.

I speak from experience. While working on a model late one January night in 1994, I was attempting to chip excess epoxy from some nylon aileron hinges.

With the wing in one hand and the knife in the other, I applied alot of pressure on the work and guess what? The blade slipped ! Operator Error !

When the knife slipped, it transformed itself from a great tool to an unfriendly scapel. It was now moving at great speed towards my other hand. It picked a spot just below my left thumb and opened a one inch long very deep cut. Then I realized that my thumb was numb.

In the operating room, the doctor used a real scapel to open the wound even further in order to repair the severed nerves. Fortunately the tendon that controls my thumb was not severed.

Nerves take a long time to regenerate. As I write this in August of 1998, I still have a numb thumb, although it is slowly regaining some feeling. This episode also has lightened my wallet to the tune of about $5,000. It was not just a dumb mistake, but a costly one as well.

What did I learn that I would like to pass along to my fellow modelers? Always cut away from your body, let the knife do the work.

Don't use alot of pressure.

Care will keep your knife from becoming a scapel.

P.S. I could have bought alot of nice planes for $5,000.

Speaking of Safety
by Tim Sherwood
Tunnel vision. How many times have you been flying and had the bejeezes scared out of you when another plane flew through your field of view?
It is amazing how little we actually see when we are flying our model aircraft. The intense concentration that it takes to fly via remote control makes it difficult to maintain a good field of peripheral vision. This tunnel vision is one of the reasons that a spotter is so important to safe flight operations. The extra set of eyes will expand your vision even more and can be of tremendous help in an emergency, but there is something else you can try.

Pattern flyers work very hard at expanding their field f view as this improves their situational awareness allowing them to make full use of the acrobatic "box" and to place their aircraft precisely within it for each maneuver.

After reading a pattern flyer's article about expanding the field of view, I've tried it, and yes, a little work can be done. The first thing that you work on is to relax while flying. Work at relaxing? Isn't that an oxymoron? Once airborne and trimmed out, throttle back and get comfortable. Take a few deep breaths and loosen up. now look around, practice looking ahead, behind, above, and below your aircraft while keeping your plane in view using your peripheral vision.

This may sound complicated, but think of your field of view as a TV screen. Normally you see a picture that is "zoomed in" with the aircraft filling up most of the screen. To look ahead we are going to see the airplane slide over to one side of your "screen" and magically apear to shrink. The farther ahead we look, the smaller the plane will become. To look ahead and down, the plane slides to the upper comer on the "screen," and so on.

Sounds silly doesn't it? Try it and with a little bit of practice, you can begin to see more of what is actually out there. This makes it easier to keep track of where you are over the field and will give you a greater degree of precision in placing your aircraft exactly where you want it for maneuvering or landing. This can be a big help in an emergency such as an engine-out situation. If you know precisely where you are, you can execute a better dead stick approach to a safe landing. It may also help spare you the embarrassment of making a beautiful three point landing ON TOP of your flight box, or taking off directly into one of the infamous balsa-eating trees that ring our favorite flying fields.