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The Goldberg Extra 300 is modeled after the full-size aerobatic aircraft. It is called a .60 size airplane but really requires something a little "hotter" such as a .90 2-stroke or 1.20 4-stroke. This was the second Goldberg kit built, and lessons taken from the Ultimate were applied to the Extra, which greatly eased the building process. Some modifications were made to the on-board gear installation, which will be detailed here. The kit arrives well packed in a large box. Die-cut stock is held together with rubberbands together and the hardware is in bags. Time should be taken to label all the parts. The manual shows all the die cut sheets for this reason. The plans are folded, which works fine but rolled plans are always preferred. It is now time to begin construction. Typical Goldberg construction is used for the tail feathers. The stab and fin are framed with 3/16" stick and then sheeted with 1/16" balsa. The rudder and elevators are left open frame and just use 5/16" sticks. It was the builders choice to extend the rudder about 5/16" and also make the cutouts in the elevators 1/4" bigger to allow more rudder swing. This is up to the modeler but it certainly does not hurt anything either way. Take time on the stabilizer as others have noted this to be a high stress surface. The Goldberg drill-type hinges were used and work very well. Take care to add a back-up piece of balsa where they are inserted through the balsa sticks. The hinge is shown to stick through and be left unsupported inside the rudder, elevator, fin and rudder. A short 1/2" piece of stick glued to the inside edge works great. The wing is built using die-cut ribs, spars, and preshaped leading edges. Take your time and there should be no problems. Be sure to opt for the dual aileron servo arrangement. Once both panels are built and sheeted, join the wings using the 4 lite-ply jigs and the plywood joiners. The joiners in this kit were too long to allow the wings to fit together properly, so be sure everything lines up tightly before adding the 30 minute epoxy. The one dowel setup works well with the fuselage design. It is handy to have the engine on hand to begin the fuselage construction. The firewall is laminated together using epoxy and the mounts are drilled. The Goldberg mounts work fairly well but another brand can be substituted. To accomplish the desired right thrust, the Goldberg mounts were space from the firewall with the supplied basswood spacers. The spacers can then be sanded on one side to bevel them and create the needed right thrust without stressing the mounts by using washers. The fuselage frames up without any problems using die cut sides, bottom, and formers. The builder must decide whether the supplied wire gear will be used or if an aluminum will be substituted. The wire was used and works okay. It is lighter than aluminum gear. If an aluminum landing gear is used, the landing gear mount will need to be sufficiently reinforced to support the new torsional load. The landing gear should be mounted with 4-nylon bolts instead of metal screws to avoid ripping out the mount during a less than perfect landing. The plywood turtledeck works out very nicely on this kit if they are soaked before bending. When the fuselage is completed, the wing is mounted and measured to make sure it is aligned before drilling for the mounting screws. Once again, nylon bolts should be used instead of the supplied 6-32 metal screws. Next, the model is sanded and prepared for finishing. Three (3) rolls of Ultracote were used to cover this model. The ABS cowl was made to work and is holding up reasonably well. It is an option to buying one of the fiberglass units on the market. To offset the YS 120NC used on this Extra, 2-elevator servos were mounted right under the leading edge of the stabilizer. With minor modification to the back of the fuselage, this setup works extremely well and helps balance the aircraft if a heavy engine is used. The throttle servo was mounted up under the front turtledeck, and the high torque rudder servo moved back one fuselage bay. This leaves the bay over the CG open and the fuel tank can be placed here if using a YS with a pressurized fuel supply. This aircraft uses a 20-ounce Dubro main tank along with a 16-ounce Dubro smoke tank side-by-side on the center of gravity. With this setup, the airplane balances perfectly with a 5-cell battery pack on the original fuel tank tray. The aircraft weighs 9 pounds 11 oz ready to fly. The initial flight was performed on a calm day at a temperature of about 70° F. The Extra can be a bit "tipsy" on the ground so full up elevator is used to help maintain control. Other than that, it handles very well on the ground. On takeoff, the Extra climbed out and required only minor trim changes. The specified CG range was right on for initial flying. Flight performance with the YS 120NC was in a word, "smooth". It makes a great beginner to intermediate pattern plane. It will also easily do all the aerobatics that the pilot is capable of doing and can be coaxed to tumble. Takeoff to a knife-edge climbout, pull vertical and roll once going straight up, reduce power and come back down in a flat spin. The Extra can do it all. Slow rolls, point rolls, cuban eights, knife-edge spins and lomcevaks are what this plane was designed for. Bring it in close and pull to a hover. With a YS 120 and a 15x10 APC it will hang on the prop at 65% power. When it is time to bring it in, the Extra glides almost too well. As an option on computer radios, a small percentage of airbrakes can be programmed in to help bring the aircraft in. The Goldberg Extra 300 will make a great fourth and up model. This plane certainly has the extra performance that a lot of pilots have been looking for. |
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