SB-7 Early (oz12108)

About this Plan

Hegi SB-7 Early. Radio control scale model glider. Wingspan 2300 mm.

Note this early version of the kit used a ready-moulded styrofoam fuselage (in 2 parts, see pic 004) which as part of the build was planked with balsa. For the later version which included a full GRP fuselage, see see SB-7 Late (oz12109).

Direct submission to Outerzone.

Update 20/04/2020: Added instructions (in 4 languages), thank to tiptipflyer.

Quote: "Hi Steve and Mary, here are the instructions in German, English French and Spanish for the Hegi SB-7 early (oz12108). I was flying the early version for over 30 years on high-start, on the slope and with power-pod. Great glider. I still have it but it needs an overhaul. Best regards,"

Quote: "Building Instructions for HEGI 153 SB-7 Scale Sailplane.

General information: This high-performance scale SB-7 is based on the original drawings for the fullsize sailplane designed and built by Brunswick Technical College Flying Club, Germany.

Despite the model's accuracy to scale, its performance is outstanding due to a long series of test models. Flown either as a towliner or power-assisted sailplane, your SB-7 will be admired for Its distinctive sleek lines and soaring glide. While construction is not difficult, we do not recommend the SB-7 as a first model.

Study the plan and Instructions carefully before beginning construction. Wing, fin and tailplane (stabilizer) are built on the plan; in these cases, first lay a piece of greaseproof or wax paper, or thin polythene from a plastic bag, over the plan to protect it from excess cement.

Warning: Use only the special styropor adhesive included in the kit directly on the foamed plastic parts. Other glues and cements (except UHU-coll PVA-type white glue) will damage styropor.

Fuselage: Cut out all printed plywood parts with a fretsaw and sand them smooth. Fit and glue formers 1+2 and tongues 3 together (UHU-coll). Fit and join keel 5 and stringer 6 to one of the fuselage half-shells 4 with styropor adhesive; the exact length of stringer 6 is shown on the plan. Bore holes in the fuselage half-shells for the pushrods (see slot for part 30 on plan). When the sub-unit made up of parts 1-3 has thoroughly set, fit it into the half-shells.

Join the half-shells together (styropor adhesive). Fit and add former 7 (UHU-call). Cut stringers 8 to length and glue in place (UHU-coll). Fit and glue sub-former 9 in place (UHU-coll). Fit the wheel well 10+11 and glue in place (UHU-coll). Cut the fin leading edge 12 and fin trailing edge 15 to length. Fit the fin ribs 14-18 into their slots, true up the whole unit according to the plan, and cement (UHU-hart). Carve fin tip 19 to rough shape and add to rib 18 with contact cement. Cement the two bellrank mounts 20 in place where shown (UHU-hart). Add the completed fin unit to the fuselage with styropor adhesive; work carefully, as only an accurate fit will result in the correct tailplane incidence angle (0°).

Glue the taliskid 21 to parts 6 & 13 (UHU-coll). Add the tail blocks 22+23 on each side of the tail where shown and sand them to conform with the fuselage. Use styropor adhesive to add planking 24, making sure that the wood sticks firmly to the styropor; your can put the planking on either in large sections or in strips.

Saw out the noseblocks 25 as shown on the plan, carve them roughly to shape and glue in place (UHU-toll). Fit and cement fillet 25a to the fin (UHU-hart). Cement compartment lid 26, nose filler 27 and sub-former 28 in place where shown (UHU-hart and styropor adhesive). Install the two belicranks 29 (if you intend using elevator control) and pushrods 30 so that they operate smoothly and without play. Next add fin sheeting 31 and tail platform 32 (UHU-hart).

Sand the entire fuselage smooth with fine sandpaper. Sand the rudder 33 and fin to the section shown on the plan, before hinging them together with the perlon fabric strips included in the kit (UHU-hart). Finally fit the canopy 36. Bore holes for the dowels 34+35 where shown, and glue the dowels in place (UHU-coil).

Tailplane (stabilizer): Build the tailplane on the plan, which should be protected as described in 'General information. Tailplane construction is straightforward and should present no difficulties. Assemble the tailplane from parts 59-46, adding each part in numerical order with UHU-hart. Pin the parts down until thoroughly set (overnight if possible). If you do not intend using elevator control, you can cement part 46 permanently to the tailplane, otherwise hinge the elevator to the tailplane with the perlon fabric strips included in the kit, Just as you did with the rudder. Sand the elevator and tailplane to the section shown on the fuselage side view before hinging them together. Sand the entire tailplane smooth with fine sandpaper.

Wing roots: While the tailplane is setting you can build the wing roots 37. Cement the balsa sheets together with contact cement as shown on the plan; note that the grain of each sheet runs at right angles to the grain of those above and below it (as in plywood). Next cut this unit in two; this gives you two rough wing roots.

Sand these to shape, using root rib 38 as a guide, slide them on the tongues 3 and fit them to the fuselage. This stage should be done with great care, so that a neat joint results. When satisfied with the fit, cut parts 37 to exact length and cement them to the tongue (UHU-hart). Push root ribs 38 on the tongues and cement them to parts 37 (UHU-hart). Finally sand the wing roots smooth with fine sandpaper.

Wing: Build the wing on the plan, which should be protected as described in 'General information'. Begin with one wing-half; while it is drying you can build the other. Begin with the constant-chord (inboard) panel first. Be careful you do not mix up the spars; the outboard spars are thinner. Prop up the bottom mainspar 47 with pieces of scrap 3/16 balsa from the kit before pinning it down on the plan. Prop up the wing leading edge 48 with scrap 3/16 balsa, also from the kit, when pinning down. Prop up the subspars 41, 1/16 for the forward one and 1/8 for the rear. Fit the wing ribs 50-55 in place, check that they are properly lined up and cement in place (UHU-hart). When dry fit and cement the top main-spar 54 (UHU-hart). Allow the completed framework plenty of time to set thoroughly (over-night if possible) before removing from the plan and cementing the wing trailing edge 57 in place (UHU-hart). This completes the constant-chord panel; build the tapered (outboard) panel in the same way, using the thinner mainspars.

Next join the two panels together after trimming the spars and edges to correct length. Cement the braces 76 to the spars, one on each side, as shown in section A-A (UHU-hart). Butt-joint the leading and trailing edges together (UHU-hart). Cement wing half-ribs 77 and gussets 78 where shown on the plan. When thoroughly set, sand the wing-hall smooth with fine sandpaper before sheeting. Leading edge sheeting 79-82 is most easily added with contact cement. Fit centre-section sheeting 83+84 carefully between the ribs and cement in place with UHU-hart. Cut out wing tips 85 with a fretsaw, carve to rough shape (see section B-B) and cement in place (UHU-hart). Finally sand the completed wing-half to final shape with fine sandpaper. When both wing-halves are finished, fit them on the tongues; they should be a snug push-fit. If too tight, sand the tongues slightly; if too loose, give the tongues several coats of dope.

Covering: You can cover the entire model, including the fuselage planking, with the tissue included in the kit, or you can use silk or nylon for extra strength.

Clear-doge the covering until all pores are sealed and the surface is smooth. After the first 2-3 coats you can sand the covering carefully with very fine sandpaper between coats, but make sure each coat has plenty of lime to dry out (overnight at least) and do not bear down heavily on the covering, or else you may sand right through. Atter each coat, pin the wing and tailplane down on your building board, packing up the trailing edge with a wedge of balsa beginning at rib 67 and rising to 1/4 - 5/16 at rib 73. This gives the wing washout (ie less incidence at the tip), which is important for towline flying.

If you wish you can colour-dope the model, using the box lid illustration as a guide. Next put on the waterslide transfers (decats); press down with a soft cloth until all water and air bubbles are out. Finally install the wheel in its well, securing the axle with a drop cement.

Radio Installation: First mount the servo(s) on a small plywood board (3/32 - 1/8 thick), and fit this into the fuselage where shown. Install the receiver and battery in the positions shown on the fuselage side view.

Link up the pushrod(s) with as little play as possible. The prototype model was fitted with the Metz 3/5-channel unit.

Test-flying: Test-flying follows the normal pattern. The centre of gravity is shown on the plan. Hand-launch the model until you achieve a straight, flat glide before beginning radio-controlled flying. If you are using elevator, you will have to get accustomed to the effects of the control; always use plenty of height at first, with the minimum control movement and short 'up' signals to prevent stalling. While the SB-7 was not designed for full stunting, it can do loops and wing-overs with ease.

Power pod; The SB-7 can also bo flown as a power-assisted sailplane. The plan shows where the power pod (materials nol included in kit) is mounted. Saw part A from 1/8 plywood, and glue in tank B (Hegi No. 229/20) with UHU-plus or similar metal adhesive. Cut aluminium rod C to to length; tap the bottom to take a 3/16 x 5/8 bolt and cut a slot in the top. Glue part A to part C with UHU-plus. Fit balsa block D and cement it in place (UHU-hart) Glue an aluminium tube into the fuselage where shown with UHU-plus; rod C must be a good sliding fit in the tube. Sand the entire pod smooth to streamline shape, and dope as for the rest of the model. The Webra Piccolo .8 cc (.049 cu in) is ideal for the SB-7, giving a steady gentler climb on a 6 x 4 propeller. Power-assisted flying allows the model to gain more height with less effort than towline launching.

We hope you will enjoy building and flying your SB-7, and wish you good gliding and many happy landings."

Supplementary file notes

Instructions.

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