Build your first flying scale Jet - Chapter 4 - Wings
You may remember that in the Comper Swift article I stripped all my wood using a steel rule and a scalpel.
Since I wrote that, Pete Money very kindly sent me a “Master Airscrew” balsa stripper to try out, and I have
to say it is very easy to use and produces more consistent results than I can achieve with a ruler and Mk.1 eyeball.
The width of the strip is adjusted by rotating the knob, which moves the position of the scalpel blade relative to the
side of the stripper that runs along the edge of the sheet.
For the wings I stripped the 1/16” square spars from a sheet of hard 1/16” sheet, as shown here. The 1/16” x 3/16” trailing edge was stripped from a medium sheet of 1/16” balsa.
The leading edges, which have to be tapered in front view, were cut from a sheet of medium 1/8” balsa using the steel rule.
Both wing plan sheets were pinned to the building board, and covered with cling film.
First stage was to cut out the notches in the trailing edges. Mark the positions over the plan, but make the final
cuts on a cutting board. The trailing edges and leading edges were pinned to the plan sheets, placing the pins either
side of the wood, and not through it.
Wing construction is fairly conventional, but because they are swept, you have to take special care to angle the front and
rear of the ribs correctly, plus all the spar slots. An emery board is a useful tool for angling the slots.
I let the bottom spar float on the plan while I glued in the first rib, R2. No point in pinning it down then finding
that the slot did not match. You may have to adjust the length of the rib at the back to get a snug fit in the trailing edge slot.
The tip rib R6 was glued in next, effectively fixing the position of the bottom spar. When adding the ribs
between these two, you should find the lower spar matches the slots in the ribs very well.
The root rob R1 is from 1/8” sheet, and should be angled over very slightly using the dihedral jig on the plan as a guide.
I glued mine to a balsa offcut before cutting it out.
This vertical view shows how the bottom spar, although straight, does not exactly match the position shown on the plan,
which throws out some of the diagonals as well. I can assure you this will make absolutely no difference to how the model
will look, or fly!
Next the two upper spars can be added, and I found that the slots lined up pretty well. If you do notice a kink anywhere,
use an emery board to enlarge the slot in the appropriate direction.
Final job before the panels are removed from the board is to add the diagonal braces, which can be from medium 1/16” square balsa.
The purpose of these is to prevent the swept wing distorting (trying to straighten) when the tissue is shrunk, resulting in unsightly wrinkles.
Here you can see that some shaping has been done on the leading edge, the aim being to get a streamlined blend to the front of the ribs.
And here is the trailing edge, which has been sanded to a wedge shape.
The tip blocks are roughed out from soft balsa, and glued to the tip ribs. The pins were just to hold the block in place unti the glue dried.
To strengthen the wing, 1/32" sheet is glued to the front of the two wing spars, between each pair of ribs.
Here the first two bays have been done. Note the grain is vertical, and the sheeting in just sub flush of the wing surface,
to avoid it showing through the tissue.
Here the sheeting has been added to the whole wing.
This wedge shaped piece of balsa is added to match the wing root shape to the fuselage contours. The trailing edge notch was extended to
Here are both wings with all the gussets added and final shaping completed.
Here is a close up of the shaped tip blocks, which also shows the trailing edge gusset (basically there as a wrinkle stopper).
This shows the gusset at the leading edge root, which is flush with the upper surface. You should be able to make a neater job of those spar slots than
At the trailing edge the gussets are flush with the bottom surface, either side of the diagonal.
Test fitting the wings to the fuselage revealed that a fair amount of butchery was needed to the location holes to get the root ribs to fit snugly, as you can see here.
The trick is to get both wings at exactly the same incidence when viewed from the front
(leading and trailing edges at the same height both sides) and also exactly opposite each other when viewed from above. Just dry fit at this stage, the wings
will only be glued on after covering.
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