Builders' Corner

Cutting a canopy to fit a fuselage can sometimes be a slow and tedious process. Some canopies can be cut by scoring the canopy with an E-Xacto knife and then flexed until it breaks. If you try this, be very careful because it is possible for the canopy break off the scored line. This usually means a wasted canopy. I prefer to use a pair of good scissors. Unlike scoring the plastic, you can cut thin shavings to get a better fit.

I will cut the canopy to a close fit, still leaving room for a final trimming. I then draw a line on the fuse exactly where I want the canopy to stop. I tape the canopy to the fuse with masking tape and then use narrow masking tape to mark where my line is on the fuselage. I can now cut the canopy to an exact fit. I finish up with a light sanding of the edge. I will also sand about 1/8 of an inch around the inside canopy for gluing.

More and more planes are using aluminum tubing for the main spar. When setting the wing incidence, there are several ways to support the wing. This method works well if you are alone and do not have any help.

I sheet the wing then shape and sand the leading and trailing edges. Next I apply the root cap. Then I slide both wings on the aluminum tube that is running through the fuselage. I let one wing rotate vertically and hang.

The other wing is ready to be set. I place the incidence meter on the fuselage (which is on it's gear) and prop up the tail with a foam block. The foam block I use has a slight angle cut on the top to follow the angle of the fuselage bottom and is about six inches square at the base. The foam block can be moved forward or rearward to set the incidence of the fuselage. Make sure the plane sits securely on it's gear. If the gear is too springy, then support the front of the plane with foam blocks also. I also check the incidence across the fuselage.

Next I prepare to set the incidence. I have two soft ¼x¼ balsa about 1 inch long and thick C/A glue ready. I place the incidence meter about 1/3 the distance from the root of the wing. I put a drop of thick C/A on one of the balsa sticks in one hand and I set the incidence with the other hand. Looking at the incidence meter, When I see the desired incidence, I simply glue the balsa block to the side of the fuselage under the rear of the wing root. The other balsa block I glue over the top of the wing root. Don't forget to hole the bottom block for a few moments until it sets. The wing is now ready for the anti-rotation dowels. Remember to keep the anti-rotation dowels parallel to the wing tube. The wing can now be removed without loosing the incidence and when ready, the balsa blocks will pop off easily and the glue sanded off.

When setting the incidence to the other wing keep the incidence meter facing the same side of the airplane. For example, if the meter faces left on the left wing, it should also face left on the right wing. This will insure an accurate set for both wings.

More and more builders are putting the servos under the tail of their aircraft these days. This can weaken the rear of the fuselage somewhat. Jim Garrahan, of Pitts Grove, NJ, builds a box of light ply and slips it through the rear of fuselage and under the tail gluing all around the box.

Each end of the box is ready to accept the servo rails. Jim recesses the servos slightly and also makes a cover so only the top of the servos stick out of the fuselage. The box also has a hole in the forward side for a place to run the servo leads. A cardboard tube can be used here to channel the wires to the rear servos. The servos are mounted perpendicular to the tail.

Jim Garrahan also sent in an idea for a tie-down. While I am not sold on the idea of using a tie-down in place of a spotter I feel it is necessary to address the issue because pilots will use this method of starting an airplane mainly because no one else is around to help. This is one of the better methods I have seen. The Jersey Skeeters club has installed these tie-downs and they seem to work well. They have cemented six-inch PVC pipe into the ground with a ¼ inch rod inside the tube (see drawing).

They use a nylon lanyard with clips at the ends to secure the tail of the airplane. I feel a two-inch pipe might be a bit safer with less chance of tripping over the hole.

Hobbytec, Inc. has come out with two new high tech products. One is the Voltage Proof which uses a digital 1.1" x .35" display. The Voltage proof displays the battery voltage to the nearest 10mV under the existing load. There is a Dip switch on the back of the unit to set the number of cells in the battery pack. A low voltage alarm will sound and an LED will flash when the voltage drops to less that 1.1V per cell. The alarm and LED can be disabled independently. The unit plugs into the receiver and mounts with four screws, usually inside the cockpit area or on the fuselage side for easy viewing. They can also be mounted under a hatch for scale airplanes. It weighs less than an ounce and uses less than 1 mA and works up to a 16-volt system. The cost is $39.95.

The other product is the Battery Fuel Proof. This unit is a programmable battery monitor and battery acquisition system. The display is similar to the Voltage Proof but displays the remaining battery capacity, voltage, current and temperature of your batteries. With over five feet of serial cable and Windows software (both included) on your PC you have a laboratory grade battery cycler and data acquisition system. This allows you to graph and keep track of your batteries through their lifespan. It also uses your existing battery charger with it's own built in trickle charge controller which allows you to plug in your plane and forget it. This unit has a low voltage alarm and works with NiCd, NiMH and Pb cell technologies from 3 to 16 volts. The weight is 1.25 ounces and uses 200uA of current in sleep. The cost is $149.95.

These units come with complete instructions and are warranted for one year from date of purchase.

InnoSol Inc. has a neat way of using 1/8-inch steel rod for 4-40 thread applications and 3/32 inch steel rod for 2-56 thread applications. They call this Rodchuck-Rod Threading System. With this system you can make your rods the length you want them. The greater diameter of the steel rod used adds greatly to the stiffness of pushrods. This is done by first cutting the threads oversized using a 5-40 die and then finishing up with a 4-40 die. You can use plastic, aluminum, brass, and steel rods. Steel welding rod is a perfect size to use for the 4-40 pushrods. The 2-56 tread is first cut with a 3-56 die. These dies are not commonly found locally. Introductory prices are #9601 Rodhchuck Die Stock - $16.95, #9602 Die Set for 2-56 thread - $19.95, and #9603 Die Set for 4-40 thread - $19.95.

Manufacturers mentioned in article: Hobbytec, Inc., 7416 W. 38th Street, Tulsa, OK 74107, (918) 446-6128, Fax (918) 446-0853. InnSol Inc., P.O. Box 251, Marcy, NY 13403-0251.