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A cousin of the Carl Goldberg Super Chipmunk, the Goldberg Tiger 60, was this builder's first kit. That was by far the most pleasant of experiences in building an aircraft, including the packaging of the kit's contents, quality of the components, fit of individual pieces, ease of assembly and clarity of instructions. This will spoil modelers by how kits should be supplied. Unfortunately, the same could not be said of Goldberg's Chipmunk kit. Goldberg has the knowledge and the expertise to produce the very best. The Tiger kit had recently been re-worked with all laser cut parts to accommodate the increased consumer popularity of retracts, the Tiger 60 Deluxe. In contrast, the Chipmunk kit is an older design for this manufacturer and the effort put into the Tiger has not been replicated in the Chipmunk. The kit arrived via UPS directly from Carl Goldberg Models. The box is covered with an attractive sky blue background with a tantalizing view of the finished aircraft flying inverted trailing dense white smoke. Some initial excitement was dashed upon opening the box. The kit's contents were not well packaged. Parts were not well secured within the box. Balsa and plywood parts of like sizes were rubber banded together, but were found loose within the box unsecured without any padding or newspaper stuffing. The ends of several pieces were chipped or split due to the jostling occurring during the shipping and handling processes. As with any building project, the initial steps are to inspect the contents and assure that all pieces are accounted for. The plans are three folded sheets. The plywood pieces are die cut and of disappointing quality. The stamp cuts were dull, resulting in some misshapen crushed pieces, and there was great difficulty separating them from the background. Many of the pieces were stamped with Italy as the country of origin. Sheet #5214 containing the wing dowel block mount and fuselage bottom was not marked. This sheet also was severely warped, with a lateral displacement of 4 inches over its length. In addition, one (1) of the 24" aileron stocks, two (2) of the 3/16" square basswood leading edge sheeting supports, and one (1) of the 3/8" square basswood main spars were missing. A call to Goldberg for replacement was simple and the parts were received via first class mail in seven (7) days. However, only a long distance toll number was included in the kit's information. The toll free number was obtained from the Goldberg web site. The included hardware package is quite complete and of first quality typical of Goldberg. Their CG Center-Line marker is even included. This will be used over and over again. The next step is to assemble the sanding tools. Goldberg includes jigs for v-sanding the rudder/flaps and the ailerons/elevator, as well as for contour sanding the leading edges of the wings and tail feathers. These are really handy and have been used for many other kits. The building process is conventional, beginning with the horizontal/vertical stabilizers and the rudder. The stabilizers are interior framed with 3/16" balsa trusses then fully sheeted with 1/16" balsa. The rudder is standard open-truss framed. The wing assembly is basic D-tube arrangement and the halves are assembled upside down over the plans. Since the wing is built in halves, two (2) check boxes are included at each step in the instructions to assist the builder and to minimize mental lapses. Although the wing's airfoil is symmetrical, the ribs have tabs that aid in building flat on the building board. The process is straightforward and clearly described in the instruction booklet. Of note, rib #12 is incorrectly cut short by 1/4" and another had to be cut from scrap balsa. When it is time to join the wing halves, the task is made nearly foolproof by the inclusion of plywood jigs that correctly support the angle of the leading and trailing edges and set the dihedral. There was one significant deviation from the kit during the construction of the wing. The kit calls for one aileron servo, located at the wing center, and the use of bellcranks in each wing half that are connected to the aileron pushrods. According to the plans, the bellcranks are no longer accessible once the covering is in place. This was not thought to be an optimal arrangement. Considering that this is a highly aerobatic aircraft, a decision was made to control each aileron individually with a servo mounted in each wing half between the 9th and 10th ribs. This permitted ample room for a side mounted servo and hatch cover access. The flaps option was used in the construction of this model. Ample aileron stock is included for cutting ailerons only or the aileron plus flap segments. Additional items required but not included are the 3/32" flap torque rods and the flap control horns. The instructions are quite clear regarding the "aileron only wing" or "flap wing" steps and this helps to prevent any misunderstanding during construction. The fuselage assembly begins with assembling the firewall. The instructions call for gluing the two (2) 1/8" plywood halves with CA. However, epoxy was substituted at this crucial step. Four lite-ply wedge style clamps are conveniently included for securing the halves together during the drying. Construction of the fuselage continues in a straightforward manner utilizing the familiar interlocking parts. It is assembled and aligned with rubber bands. The instructions are very clear regarding the sequence of alignment and gluing. The only significant problem encountered with this portion of construction was that the two upper front tabs of the fuse sides were cut short by 1/8" where they mated with the firewall. A piece of basswood bracing was epoxied in for reinforcement. The joining of the firewall to the fuse establishes a downward angle to the fuselage resulting in 3° of down thrust. Three formers are used to support the stringers of the turtle deck. Former TA called for in the instructions is stamped "T", former TC is stamped "C", and former TD is not stamped at all. The fuselage of the full scale aircraft is elliptical in shape. The kit sacrifices this exotic profile for ease of building by squaring off the bottom and sides of the fuse while retaining the upper portion of the ellipse across the top half of the fuse. Thus, the upper half of the fuse forward of the cockpit and the turtle deck are curved surfaces and are sheeted with 1/8" balsa wedges. This thickness of balsa makes for a tough job in shaping them to the curved forms. In fact, it took several evenings of soaking the balsa wedges in ammonia water and strapping to the formers to gingerly coax them around the formers without splitting. Even so, one wedge split on the third night of soaking which necessitated a trip to the hobby shop for a replacement balsa sheet. The task would have been much more easily accomplished by sheeting these area in two layers of 1/16" balsa. The two (2) most difficult areas of construction involve the tail assembly. The fuselage-to-stabilizer fairings are carved from 7/8" square x 8" balsa blocks. A quality job will take several hours of carving, sanding, and fitting on each side to blend the multiple curves. The installation of the rudder pushrod involves placing a pushrod guide tube through this newly carved fairing, the fuselage plywood top and two (2) formers at the rear of the aircraft. The angle of the tube is well drawn on the plan, but the task is awkward at best requiring an 8" long drill bit to accomplish. These tasks will clearly challenge the builder. Patience will win out knowing this ahead of time. The wing fairings that blend the wing bottom to the fuselage bottom are made of vacuum-formed plastic sheets. These are considered to be the lowest quality components included in this kit. These hollow pieces would be easily damaged with normal handling of the wing during field assembly. In addition, the plastic pieces would be hard to cover with with film or cloth during the wing covering step. A decision was made to recut these from 3/16" lite-ply. After sanding, they were easily feathered into the wing with Model Magic filler compound. The included wheel pants and cowling are of high quality fiberglass construction. Even though the instructions describe the process of joining the halves of the wheel pants, this had already been done by the manufacturer. However, the width of the finished pants varied by 3/8". This subsequently required a bit of fitting to make one of the wheels fit inside properly. Early in the construction of the fuselage, a decision must be made on how the engine will be mounted, either side mount or inverted. For aesthetic reasons, the decision was made to mount the OS .91 Surpass inverted so that the engine would be completely contained within the cowling. A side mount would have essentially obliterated one of the cheeks on the cowling since the firewall is taller than it is wide due to the semi-elliptical shape. This design decision proved difficult when it came time to attach a smoke muffler. With the engine inverted, a stock smoke muffler could not be installed due to lack of access to firewall support and the shape of the cowling. A homemade smoke oil pre-heater had to be fabricated of soft copper coils wound about the muffler body. Final assembly consisted of attaching the canopy and installing the radio equipment, 16 ounce fuel tank, 6 ounce smoke oil tank, smoke pump and smoke pump battery. There is ample room inside the fuselage for all of these accoutrements. The room was even sufficient to place the smoke oil tank and smoke battery right over the CG. No additional weight was needed to balance the plane. The instruction manual includes paper gauges for setting the recommended low rate control throws. Ball bearing servos were used along with ball links at the control horns instead of the supplied nylon clevises. The landing gear wires must be bent forward so that they align with the leading edge of the aircraft, as shown on the plans. However, there is no mention of this in the instruction booklet. If they are not bent forward, they rest directly under the center of gravity and the plane will have a nasty habit of continuously nosing over during taxi. As noted, an OS .91 Surpass was used to power the aircraft, along with a Graupner 14x7 prop. In addition to the 3° of downthrust built into the firewall, 2° of right thrust was added, though there is no mention of this either on the plans or in the instructions. The wheel pants and cowling were omitted for the maiden flight from a grass runway. It was a clear day with 10 knot winds from the west, right down the runway. Ground handling was smooth during throttle up. No rudder correction was needed when the tail rose from the ground or during initial climb out. No trim changes at all were needed during the initial flight. After becoming comfortable with basic flight characteristics an aileron roll was attempted. With full aileron throw on the suggested low rates, the plane completed two revolutions in the blink of an eye. Surprise quickly turned to elation with the flight characteristics. There was no tendency to tip stall. As speed approached the stall, the plane simply mushed ahead, recovering quickly with a little throttle. The landing approach was also pleasantly surprising. Initial estimates were that this aerobatic airplane would need to be flown to the ground. However, the aircraft glides extremely well. So well in fact that the first landing attempt brought the plane no closer than 6' to the runway due to the lift in the wing. On the second attempt, landing was completed at a fast walking pace. The remainder of the day was spent "wringing" it out. If you have the skill to do it, the plane will respond. Knife-edge requires a lot of rudder throw with only a slight tendency to pitch towards the canopy. Due to the high location of the rudder, completely above the level of the elevator, a full 170° of rudder throw are attainable, if so desired. Use of the flaps requires a substantial amount of down elevator mixing. With flaps deployed at 30°, the plane will hover into a 5-10 knot wind. Landings are at a slow walking speed. Subsequent addition of the cowling and wheel pants did not alter the takeoff or flight characteristics at all. Flying the next day proved fateful. On a normal landing without any bounce or side load, the right landing gear failed which permitted the landing gear and wheel pant to rotate backwards and through the bottom and top sides of the wing covering. During initial construction, the landing block is epoxied in place, then one half of the lite-ply torque block is installed. A groove in this half serves as the drilling guide for the landing gear wire to be inserted through the landing block into the torque block. After the guide hole is drilled through the landing block, the second half of the torque block is epoxied into place, then supported with balsa triangular stock. Inspection of the damage revealed a failure of the torque block through the last two (2) laminations of the plywood. It was a clean sheer without any splintering. There was no plywood glue found in the area of the sheer. It was deduced that there must have been a bubble in the ply glue as the laminations were pressed together during manufacturing. This failure permitted "an opportunity" to rework the landing gear supports on both wing halves. The two piece lite-ply torque blocks were removed and solid hardwood was substituted. In addition, a plywood I-beam was added along the length of the landing block to distribute load and sheer stresses. The entire wing was recovered and trim scheme reapplied. After all, it was a brand new airplane. The overall performance of the Goldberg Chipmunk is exhilarating! It has no bad flight tendencies and is suitable for any pilot with moderate tail dragger experience. Anything that the pilot can do with the sticks, this plane will likely respond. On the other end of the spectrum, it is also a relaxing Sunday fun flying aircraft.
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