WING: Start the first panel by pinning the 6mm sq. lower spar over the plan onto your building board, positioning the ribs in their respective positions and (temporarily) placing a length of 6mm sq. balsa spanwise, underneath the rear of the ribs, to support them. As the two inboard ribs are designed to accept sheeting, they need an additional 1.6mm strip on top of the 6mm sq. for alignment don’t glue anything just yet!
Once the ribs are in place, position the upper spar. Check that ribs & spars are all aligned, then pin the leading & trailing edges to the ribs. Give the entire assembly a final alignment check, and when happy glue it all together (apart from the aforementioned alignment pieces) with your favourite type of adhesive – cyano is ideal.
I’ve not designed the wing with any shear webs as I don’t think the model needs them, but feel free to do so if you wish; I’ve add them only to the first 1/3 of the wing anything beyond here will simply add weight. One thing I do recommend, though, is to add the wingtip gussets as this area is prone to knocks and can be easily damaged, but not so easily repaired. Build the second wing panel in similar fashion, then bring the two together on your building board, one panel pinned flat and the other raised 0.8Ó (20mm) at the tip to give the desired dihedral. Take care to sand the spars, leading and trailing edges to a good fit at the root, as although some strength will be afforded by the addition of upper and lower centre section sheeting, its still best that all joints are as snug and precise as you can make them. Remember that smaller models are easier to build, but not necessarily easier to build true! A small building error can have very large effects on the finished model, whereas the same small error on a larger model might go unnoticed other than a little extra trimming. Glue the upper centre section sheeting in place and sand to a smooth finish. Remove the wing from your board and fit the filler blocks at the rear of the centre section, to both reinforce the wing and prevent the bolts from pulling through. Sheet the lower centre section, fit the wing tips, mounting bolt reinforcing plate and servo mounts. Fashion the ailerons, then sand the entire assembly prior to covering.
You may wish to fit the servos and run their leads through the wing at this point, prior to closing the wing with the final covering. Alternately you may prefer to run a cotton thread to allow for fitting the servos later on – the choice is yours.
The fuselage is, like the wing, a very conventional and simple construction. Note that the former’s are of lite ply rather than balsa; the additional weight isn’t significant, but these ply former’s are much stronger and less prone to crushing or deforming during the build process. Before commencing construction it’s a good idea to mark the former positions onto the inner faces of the fuselage sides. This assists quite a bit in keeping things square, as the former’s and fuselage sides aren’t keyed or notched, as in some larger models.
Pin one fuselage side to the building board, then glue former’s F6 & F8 into position, making sure that they’re aligned at 90¼ to the side. Note that the centre section of the fuselage (where the wings mount) has parallel fuselage sides, whilst the nose and tail sections taper. Once the glue’s set, fit the remaining former’s and u/c mounting plate, ensuring the firewall is mounted squarely (with no up, down or side thrust) and the fuselage is straight. Add light grade 6mm sheet to the upper and lower faces of the forward fuselage, and shape to profile. I’d recommend fitting your electric motor at this point while the nose section is easily accessible. When happy with its installation, assemble the cowl, using the nose ring as a reference for carving and shaping. It would be best to make the cowl removable, but this isnÕt essential. You must provide for ventilation and cooling, so cut a hole in the lower cowl at the very least. A hatch can easily be cut into the upper nose sheeting to allow for battery changes if you don’t want to remove the wing every time.
Construct the rear fuselage upper deck from 3mm sheet strips, shaped to suit your preferences, then add the lower 1.6mm fuselage sheeting. Add the deck for the tailplane, ensuring itÕs flat. Once the glue’s set, mount the tailplane and fin. Use light block, shaped to suit, as a fillet and to provide additional strength for the fin.
Give the fuselage a final sanding, then cover or paint the model using your preferred method. With this complete, fit the elevators, rudder, pilot and canopy.
Radio: Bambina is designed with 9g servos in mind, These, along with a micro Rx and ESC, won’t add too much weight but will provide all the control authority you need. Make sure the pushrods are as rigid as you can as with any model you want minimum slop in order to get the best possible control response.