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Topaz

We recently had the opportunity to test Hobby Club's brand new 3 meter molded RES sailplane - the Topaz. The following photos show details of this model. Our particular model used 3-JR DS368 servos, an Airtronics 97555 blue cube receiver, and an 1800 ma NiMH AA receiver pack in square configuration. The finished model weighs 37.5 oz's and is an excellent flying model.

The Topaz shows obvious Dr. Drela design layout. It has good handling characteristics, rides the lightest lift and still has reasonable penetration considering the low weight. The model launches well and is a dream to land.

Chris Jolly with the newly finished Topaz 1-25-04

4:30 Sunday afternoon - Typical winter flying attire in So Cal.

RUDDER AND ELEVATOR SERVO INSTALLATION

The elevator linkage comes cut to length with adjustment only at the servo end. To get the proper elevator placement you must put the clevis on to the threaded coupler so that you leave a little room for adjustment. Place your servos in the plywood servo plate as shown so that you can get maximum elevator and rudder throw. Put the servos in place, install the elevator clevis to the servo horn and adjust the tray so that the all flying stabilator is parallel to the tail boom. Once the proper position is found, tack the plate in place with cyano, carefully remove the servos and bond the plate to the fuselage with epoxy and fiberglass. The elevator servo has the black clevis.

TOW HOOK INSTALLATION

Plenty of room for ballast, I will work that out next. It's always a good idea to support the push rod snakes in several places along the fuselage sides. Tack the snake in place with cyano and go back and secure it with a Goop type adhesive.

EMPENNAGE SHOTS

The tail section is completed at the factory, the only thing for the modeler to install is to epoxy the rudder horn in place. After the test flights, I moved the push rod to the inside hole of the horn for more throw. BTW, both rudder and stab are screwed in place.

SPOILER SERVO/LINKAGE INSTALLATION

There is not much room for the spoiler servo. I'm not sure that you would want to use a servo larger than the JR DS368. The spoiler uses a RTV hinge. The spoiler horn is factory installed and the linkage supplied is a ball link with a 90 degree bend in the wire for the other end. I found the linkage worked well if you placed the 90 degree bend through the horn and then used a small length of 1/16th heat shrink as a retainer to keep the wire from backing out. Use low tack masking tape on the bottom of the wing so that you can locate the servo in the best place to ensure it fits in the recess in the fuselage. When you have determined the best place for the servo, remove the covering under the servo and 5 minute epoxy the servo in place.

FLIGHT TEST

The model was adjusted so that the CG was 3.5" from the leading edge. The tow hook was placed at 3.4" from the leading edge. As described, the model weighed 37.5 oz with no nose weight added. Test flights were late in the day in about 8 Kt winds. The model rotated well on tow and demonstrated a wide speed range in glide. The Topaz indicates any lift and has a great climb rate. The handling characteristics are benign and the ship is a delight to fly. I am looking forward to expanding the flight envelope in anticipation of competing with the Topaz in future RES contests. The linkage will allow you 90 degree spoiler throw, but this is way too much. The above picture shows full throw in my set-up. You will need minimum elevator compensation.