20
perpendicular 90
O
angles. The dowels need to be the same length
and tall enough to accommodate the height of the assembled
airplane, as well as the width of the fuselage, plus about 1/2"
additional width. The tops of the dowels need to be padded to
avoid damage to the wing. We used 1/8" thick rubber sheet, cut to
1/4" diameter, glued in place, for the padding.
There are
commercial units available for balancing but be sure they are large
enough to support the weight and size of the EXTRA.
Set the model UPSIDE DOWN on the balancing fixture and shift it
back or forward until you find the exact spot where the model will
sit perfectly level. Carefully measure the distance of that spot from
the leading edge of the wing.
IMPORTANT NOTE:
Balanced means the airplane sets level
when supported at the desired balance point. Believe it or not,
we've had questions like; "When my model is balanced it should
sit slightly nose down right?". NO, balanced means level - not nose
down or nose up - flat level!
BALANCE REFERENCE POINTS FOR THE EXTRA 300XS
*
Percentage of Mean Aerodynamic Chord
**
Distance aft of wing leading edge measured right along side
of fuselage
*** Distance aft of wing leading edge measured at the wing tips
% MAC*
@ fuse side**
@ wing tip***
25%
4.0"
2.434"
26%
4.172"
2.568"
27%
4.343"
2.702"
28%
4.477"
2.836"
29%
4.611"
2.971"
30%
4.746"
3.105"
31%
4.880"
3.239"
32%
5.014"
3.373"
33%
5.148"
3.507"
Putting sticky-back decals on a model can be tricky! Especially
medium to large size ones like those in this kit. If you don't do it
right you will end up with unsightly air bubbles trapped underneath
the decal. Here's a method that eliminates that problem entirely
and makes the job easy and fun.
You will need a "soapy water" mixture (water mixed with a very
small amount of dish soap, or SIG Pure Magic Model Airplane
Cleaner, or Fantastic
®
, Windex
®
, or 409
®
type cleaners all work
good). You will also need a supple squeegee (the SIG 4" Epoxy
Spreader #SIGSH678 is perfect for this job), a couple clean soft
cloths (old tee shirts are great), a good straight edge, a ruler, and
a hobby knife with sharp #11 blades. We also suggest that you
have some trim tape handy for making temporary guidelines (1/8"
width or so is perfect) for help in aligning the decals.
First spray the surface of the model where the decal is to be placed
with a soapy water mixture.
Then peel the backing sheet
completely off the decal, being careful not to let the sticky side
double over and adhere to itself. Place the decal onto the wet
surface of the model. Do not push down! The soapy water solution
will keep the decal from actually sticking to the model until you
have had time to shift it around into exact position. Once you have
it in position, squeegee the excess soapy water out from under the
decal. Mop up the water with a dry cloth. Squeegee repeatedly to
get as much of the water out from under the decal as possible.
After setting overnight, the decal will be solidly adhered to the
surface.
BALANCE YOUR EXTRA
In terms of the flight characteristics you will realize, this is
probably the single most important step in preparing your EXTRA
for flight. The final placement of the longitudinal Center of Gravity,
or Balance Point, is extremely important and should be
approached with patience and care.
Completely assemble the model, including propeller, spinner, etc.
Do not leave anything off the airplane that will be on it in flight. DO
NOT fill the fuel tank for balancing purposes. Some people prefer
to balance their airplanes by lifting the model up by one finger at
each wingtip to find the spot where the model will sit perfectly level.
This has been done for years and is an acceptable way to balance
a model (we have included balance measurements for this
method). However with an airplane as large as the EXTRA 300XS,
it is virtually impossible to balance it by the wingtips by yourself.
We prefer to use a "balancing fixture" which checks
the model's balance point right along each side of the
fuselage (these balance measurements are also given). It can be
done alone and is actually more precise than a fingertip balance.
You can make your own simple "balancing fixture" with a couple of
1/4" dia. dowels glued into a fairly substantial wood base, at