Grumman F7 F-3 Tigercat
Building instructions - Grumman F7 F-3 Tigercat
5
permanently!). Hold the half-former (52) against the fuselage as shown on the plan and mark on it the
position of the latch pin (20). Drill a hole at the marked point using a 2.5 mm Ø bit, and gradually open it
up to 3 mm Ø until the half-former (52) fits snugly on the latch pin. Note that the pin must not project
beyond part (52) - see plan. Place the canopy on the model and check that the half-former (52) fits
correctly. When you are satisfied, glue part (52) in place using Stabilit-Express.
The remaining work on the fuselage is largely self-explanatory. Note the following points: areas of the
fuselage where formers are to be glued should be roughened using abrasive paper. Drill 2 mm and 3 mm
Ø holes in the formers for the snake outers as shown. When installing formers in the fuselage, position the
part first, tack with a few drops of cyano, then apply a fillet of resin (thickened as required). Mark the
position of the snake openings on the fuselage as shown on the plan, drill them using a 2 mm Ø bit and
file them out to final size. Don’t install the snakes at this stage.
The line of the rudder is marked on the fuselage, but a second line must also be marked, located 4 mm aft
of the first (see section H-H - this is where the GRP shell of the rudder should end. The best tool for
separating the rudder from the fin is a diamond disc cutter, held in a firm hand! Clean up the edges of the
shell neatly.
The position of the GRP hinge lugs (62) is shown on the plan; mark them on the tail post, which is already
installed, and cut an additional oval opening about 6-7 mm wide as per plan. Cut pieces of the aluminium
tube (22) about 5 mm long and press one into each hinge lug. Check they are “square” and glue them in
place with thin cyano. Sand off the excess tube length. Drill a hole 5-6 mm Ø in the underside of the
fuselage in the position shown.
Sand back the leading edge of the rudder to the new marked line, and glue the false leading edge (56) in
place. Cut a piece of balsa strip (60) to fit in the bottom of the rudder, and glue it in place. Seal the rudder
with scraps of plywood. Mark the position of the hinge lugs (62) on the false leading edge (56) and cut the
slots for them - see fuselage side elevation and section H-H.
We recommend the following method of attaching the rudder: cut four pieces from the aluminium tube (22)
as shown on the plan. Apply slightly thickened resin to the slots in the tail post and the hinge lugs, push
the lugs into the tail post, and fit the aluminium tube (23) (or a length of 3 mm Ø steel rod) through the
hole in the underside of the fuselage. Now follow this procedure carefully: slip the bottom end of the tube
(22) onto the shaft, and fit this through the bottom hinge lug (62); continue with the next section of part
(22) etc. Press the rudder against the sections of tube (22), and tape the rudder to the fin. Align the hinge
lugs (62) carefully (they must be central and at right-angles to the tail post), and press the sections of tube
(22) onto the hinge lugs from above. This locates the hinge system accurately, and the sections of part
(22) can be tacked to the false leading edge (56) using single drops of cyano. Leave the fuselage
standing vertically on its nose while the glue sets hard, then remove the hinge shaft and apply more glue
to the hinge lugs in the tail post as required.
The rudder leading edge assembly is shown in section J-J. The best way of fitting parts (59) and (64) is to
cut them into sections corresponding to the distance between the hinge lugs (62). Check the leading edge
radius carefully, fit the rudder in the fin recess and check the freedom of movement. Once everything fits
and works correctly, seal the wooden surfaces by covering them with tissue.
All you need to do now is seal the top and bottom of the fin with plywood - note that the bottom piece must
have a 4 mm Ø hole. The rudder should not be installed permanently until the model has been painted
overall. Cut the tubular rudder shaft (23) to the correct length: it should extend right to the bottom of the
fuselage. Seal the opening in the bottom of the fuselage with tape to prevent the shaft falling out; just
remove the tape if you ever need to remove the rudder.
The tailplane is aligned on the fuselage using pieces of beech dowel (29), which also increase the
strength of the joint. Cut two pieces 80 mm long from the dowel (29) and fit them through the holes in the
fuselage. Fix the wing to the fuselage and check the incidence of the dowels relative to the wing. Check
also that they are square to the fuselage centreline. The dowels should be glued from the inside, so first
withdraw the rear dowel to give access to the front one. Using a piece of strip wood, apply slightly
thickened resin through the opening in the tail post and rotate the dowel to distribute the resin thoroughly.
Repeat the procedure with the rear dowel.
Sand the tailplane to the final profile (especially the leading edge) as shown on the plan, and sand all the
parts smooth, including the elevators. Fit one panel on the dowels and drawn a line on the root surface
corresponding to the outline of the fuselage. Trim the root area back using a sanding block until it rests
snugly against the fuselage. Repeat with the second panel. It is better not to glue the tailplane to the
fuselage until the panels have been tissue-covered. Drill 3 mm Ø holes in the elevators at the angle
shown on the plan, apply thin cyano to the holes, then run the drill through again.
At this stage all the wooden parts should be covered; we recommend using tissue.
The ideal material is our 23 g/m² Ply-Span, Order No. 7610/29. The wings are supplied with 3 mm of
geometrical washout as standard; be sure to maintain this during the covering process, and correct it if
there is any change. Apply several coats of clear dope to seal the covering. We recommend a final coat of
