China PT-19 tips

The last version of the PT-19 was available at my local hobby shop up to about 2000.  They came with a $5 rebate certificate. We bought over half a dozen and cashed in the rebate certificates and used the money to buy another PT-19.

Although the last version had some really nice improvements like the wing tip weight and  super durable plastic, it also had some problems that needed to be fixed before it would fly, or run for that matter. Here is what we found and corrected:

1. The first thing I noticed was the elevator was hanging up and would not flop up and down freely.  Turns out to be the wire pushrod was not above the bellcrank but under it and binding. Removed the bellcrank screw and pushrod, re-connected it through the top of the bellcrank and put the screw back in place.

2. With the pushrod removed, the elevator was binding.  There was molded plastic flash on the upper clam shell half of the elevator hinge, which is part of the rudder. A few passes with an Exacto knife and final sanding with an emery board fixed that. Moved pushrod to hole closest to elevator for more throw

3. The fuel tank was oriented with the pick-up forward, and towards the inside of the circle (to the left). It was not possible to rotate the tank to orient the pickup  to the right and slightly aft due to the fuel line being too short. A 3/4"longer fuel line was cut and fitted so the tank could be rotated.

4. The right wheel was binding up due to the way the end of the axle was swagged; it was acting like a drill bit and boring into the wheel. We bent the tip of the axles up 90 degrees to resolve that issue.

5. Engine required repeated prime to start and was not drawing fuel consistently, erratic running and not holding a needle valve setting. Removed glow head and found  engine had very poor crankcase compression and reed was not making a snapping noise( not sealing). Removed the engine back plate and lapped the crankcase gasket surface  flat on a piece of glass using 400 grit to remove burs around the 4 screw holes. Discarded the plastic crankcase gasket as it was not compliant enough to seal against the back plate which had an uneven surface. Replace the plastic gasket with two original Cox paper crankcase gaskets which sealed the crankcase, restored case compression and reed began to work properly. Added an extra glow head washer to make engine needle adjustment  less sensitive as I had 15% fuel.

6. Cut new lines using Spectra/Spider wire, lines were extended to 42 feet.

7. Brush on a coat of clear polyurethane paint on the pilots to protect the paint from the fuel, and seal edges of the stickers with it too to make them last.

8. Optional: Remove the Snap Starter and spring, and use a 6x2 left hand prop. This gets the torque working for you and helps maintain line tension as well as allowing the engine to rev up a little more and reducing the load on it.

These changes made a dramatic effect.  First off, I was able to start the engine by choking it, no prime required. The line sag is almost non-existent with the Spider wire Spectra braid, it is super low drag and light weight. This also makes  for a more positive feel due to no line stretch; control is more effective. Engine runs are on the order of 3 minutes or more with tank pickup re-oriented to about 4 o clock as seen when looking down on the plane from above. Loops are also now possible with more elevator throw, and longer lines.  You can also try taping a nickle inside the rear of the fuselage to move the CG aft for stunts.   If you want to fly in windy conditions, shorten the lines to 35 feet or less. The longer lines make flying much more fun. Re-tighten the glow head after a few flights, wait for the engine to cool off and check it with the wrench.

After flying, remove engine, take the plane apart and after wiping off excess castor oil and fuel, rinse the fuselage in hot soapy water, rinse and dry. Nitro residues are what dries out and embrittles plastic, so a little cleaning goes a long way.