amount of gel-type Super Glue™in a
thin layer on the underside of the light
blade at the tip (Figure 15). Using an
accelerator spray to instantly cure the
glue is advisable. An even quicker
solution is to place a small bit of
cellophane tape on the underside of
the propeller (Figure 16). The tape can
be trimmed and easily removed,
making it a good choice for beginners.
If you’d like to remove weight from
one side of the propeller, you can use a
fine grit sandpaper; 220 works well.
Sand off a small amount of material
from the heavy blade (usually from
the underside). Try to evenly remove
material so that the propeller does
not become imbalanced from the tip
to the tail of the blade (Figure 17). If
you use this technique, be sure to recheck the balance often because if
you remove too much, you will either
need to sand the opposite blade —
After adjusting the mass of the
blade, put the propeller back on the
stand and see how you did. Maybe
you’ll need to remove more mass, add
more tape, or otherwise play with the
balance. After a few tries, the propeller
should be getting close to balanced.
When balanced, it will sit in any
position at which you place it, without
any blade always falling to the bottom
(Figure 18). With practice, you’ll be
able to balance a propeller in a few
minutes. I can balance a set for my
quad in less than half an hour, and that
is time very well spent.
Closing Thoughts
We didn’t have time to get into
how to choose the proper motor
/propeller combination, but I suspect
that will be coming soon as I look at
upgrades to our homemade quad and
the possibility of building larger and
smaller vehicles. Don’t be afraid to pick
up several sets of different propellers
next time you are at the hobby store or
ordering something from Amazon.
Experimenting with them could
lead to performance gains on your
multi-rotor for your particular
application. SV
SERVO 12.2016 51
Figure 14: Most
propellers will very
quickly settle with
one blade hanging
down. This is the
heavy blade. We can
add weight to the
light blade, or
carefully sand
weight off the heavy
blade to balance the
propeller.
Figure 16: Adding bits of cellophane
tape is another way to add weight to
the light blade. This is the quickest
way to balance propellers, but is not
as permanent of a solution.
Figure 18: A well-balanced propeller
will maintain any
orientation it is left
in. You will notice a
marked difference
in the amount of
vibration and noise
your quad makes
during flight after
balancing.
Figure 15: Weight can be added to
the propeller by applying a thin
layer of gel-type Super Glue, and
either waiting for it to dry or by
using an accelerator to instantly
cure the glue.
Figure 17: Some 220 grit
sandpaper can make quick
work of removing mass from
the heavy blade. Be sure to
sand evenly at the end of the
propeller and check the
balance often.
