Sig Mfg. Somethin' extra

Model Airplane News, Nov 1999 by Abbe, Peter

WALTER EXTRA COULD NOT possibly have imagined how many variations

This full-scale aircraft would inspire. From exact scale to profile versions, Extras remain among the most popular aerobatic models on the market today. The new Sig Mfg.* Somethin' Extra represents a unique interpretation of this design. Blending modern fun-fly performance with a traditional built-up fuselage, Sig has created a model that is aesthetically pleasing and a blast to fly.

OVERVIEW

I was immediately impressed with the neatly packed and organized kit contents. The laser cutting is immaculate, and the quality of all the wood is first rate. The supplied wheel pants, canopy, aluminum landing gear, rolled CAD plans and decal sheet are typical of Sig's high quality. Nearly all the necessary hardware is included: the builder needs only to buy an engine, radio, fuel tank and wheels. The 26-page instruction manual has more than 60 photos and diagrams. With helpful tips throughout, no guesswork is required.

WINGS

The wings are built directly over the plans using typical "pin-to-the-board" construction. Jig tabs on the ribs help to ensure a straight, true wing. The spars are made of 1/4-inch balsa sticks and slide into their respective wing slots with no sanding required. The three inboard ribs have laser-cut holes designed to receive the outer phenolic wing tube. It is a good idea to trial-fit this tube in the ribs before gluing the assembly together. I had to sand the inside of these rib cutouts very lightly to obtain a proper fit. Don't overdo it; if you remove too much wood, the wings may not be aligned properly when you attach them to the fuselage later. l he fit should be snug but shouldn't bind during installation. The leading edge is preshaped and requires little sanding. The 1/4-inch-square balsa trailing edge must be planed and sanded to shape. Take care when installing these edges, as it is very easy to pull the ribs out of alignment. The inboard ribs must be exactly square; otherwise, the wing panels will not be seated properly against the fuselage.

EMPENNAGE AND AILERONS

The tail feathers and ailerons are built up out of all laser-cut pieces. Simply apply a bead of thick CA to the mating edges and assemble them. The laser-cut notches make lining up these pieces almost foolproof. I didn't have to pin these parts to the plans; I simply used the plans as a reference and held the parts flat to the building board, applying accelerator to set everything up. Re sure to sand the hinge lines of the control surfaces to the recommended 45-degree angle; otherwise, control throws will be limited. Use fiberglass to reinforce the precut control-- horn holes, elevator joiner and tailwheel assembly, then set them aside.

FUSELAGE AND HATCH

The fuselage is a unique part of the construction. 'Take your time to carefully line up the balsa fuselage sides and doublers; when this has been done, everything else falls into place. The firewall, formers, servo tray, tank floor and landing-gear plate fall precisely into their respective laser-cut slots. The upper and lower decks are notched to mate with the fuselage sides, and this makes it nearly impossible to build things out of alignment: The turtle-deck formers fit into precut slots, and the stringers line up straight and true.

The hatch is constructed of a lite-ply base and sheeted balsa formers. It is attached to the fuselage with a dowel and a nylon bolt and provides the necessary access to all radio gear, fuel tank and wing-- attachment bolts. At this time, trim and test-fit the canopy in place. I tinted my canopy with dark blue Rit dye by submerging it in 2 gallons of hot water and a single package of Rit. The longer you leave the canopy in the dye, the darker the tint will become.

FINAL ASSEMBLY

Trial-fit and sand all the subassemblies. The wing slides onto an aluminum tube and is keyed up by a single dowel near the trailing edge. It is then held in place with a single no. 64 rubber band wrapped around a pair of J-hooks screwed into the inboard ribs. Make sure the J-hooks do not have any nicks or burrs that might damage the rubber band; a lot is riding on the integrity of this single rubber band, so I backed it tip by adding another one. Although I have had no trouble with this method of attachment, I would have preferred a more secure design.

I glued the two-piece wheel pants together and painted them with 21st Century* paint. I covered and trimmed my Extra using Carl Goldberg Models* Ultracote. To achieve the best results, be sure to use the wet application method when you apply decals. Although the manual suggests installing the fin and stab before covering, I found it much easier to simply cover the parts individually, remove the covering where wood meets wood and then glue these parts into pLace. I opted to omit reinforcing the tail surfaces with pushrod wire as recommended; this merely adds unnecessary weight to the tail of the model. If, however, you feel more comfortable with this added rigging, all the hardware needed to do the job is provided.