After you have a row of pins
along the front edge of the wing, lay the front spar (a piece of 1/16"
x 1/8" balsa wood) up against the pins. Then push a pin into the foam board
on the back side of the wood to hold in in place. make sure the wood is
standing on edge as shown on the plan. Also make sure not to stick the
pin into the wood itself of the wood will crack.
When you are done, the pins
will be holding the spar in place as shown.
It may be necessary to 'cross pin' the wood down if it will not lay flat on the plan. The photo below shows the 'cross pin' method.
Use a razor blade and cut
the leading edge spar to length, and then cut the wing tip spar at an angle
as shown below.
Once the leading edge spars
are cut to length, and the left and right wingtip spars are cut and positioned
it should all look like this.
The next step is to position
the wing ribs on the plan. This is done by using two pins to hold the rib
in position as seen in the two photos below. Do this for all of the ribs
except the very last rib on each end of the wing. Make sure to slide the
rib all the way forward until it touches the leading edge spar.
This is what it should look
like when the ribs are positioned properly.
Now the two tips ribs must
be cut to size and positioned in place. Use the razor and cut the front
of the tip rib to match the angle of the wingtip spar.
Then push the rib up to the
spar as shown below.
Once both tip ribs are cut
and in place, the trailing edge of the tip rib must then be cut to length.
After both tip ribs have
been trimmed at the trailing edge, then position the trailing edge spar
up against the back of the ribs in the same manner that the leading edge
spar was positioned against the pins when you first started to build the
wing.
Here is the wing all pinned
into position, and ready for gluing.
After the trailing edge is
pinned into position, check the tip rib cut length, if it is too long (as
in the photo below) the spar will bow. If it is too long, then use the
razor and cut it just a little off the end of the rib to keep the spar
from distorting.
