- 8 -
you’re confident you’ll be happy sticking with the CG placement we recommend. It may be safer to
leave the ballast tube installation until after your first test flight so that you can first arrive at the
exact CG location that best matches your personal preferences. The downside of leaving the ballast
tube installation until last is that you’ll need to cut through the filament tape and covering you’ve
applied and then repair this with a sufficient patch of filament tape and covering. The choice is
yours. These instructions outline the method for installation at this stage in the construction. If you
will be installing the ballast tube later, don’t forget to ensure that the area is kept free of the radio
equipment and its wires.
The brass tubes provided jump two steps in size. We figured it’s better to put up with a little rattle
rather than have lead slugs that get jammed in the ballast tube and/or need to get filed or sanded
down to fit easily. If you’d prefer not to have a rattle, simply purchase a 12” length of K&S brass
tubing with a 17/32” diameter (#140) for use as the ballast tube instead of the 9/16” one provided.
If you can get your hands on a ready-made ballast kit of suitable size (9/16” max. diameter ballast
tube) we highly recommend doing so instead of trying to make this yourself. Lead is a hazardous
substance to work with (particularly the fumes during melting and fine dust during grinding) due to
its toxicity so appropriate precautions should be taken if you decide to proceed with the following
steps to make the ballast system yourself.
35.
Locate the 1/2” (13mm) diameter brass tube. This can be used as the housing for your lead-
filled “slugs” (cylindrical sections). Mark out the tube so that it is divided into 8 equal
lengths each measuring 1 1/2" (38mm).
36.
Use a hack-saw to cut the tube into 8 equal sections, seal of one end of each one with
masking tape and then push into some damp sand or soil to hold them securely upright.
37.
Melt some lead in a used tin can. Lead
fumes are extremely toxic so ensure this is
done outside well away from other people
and wear an appropriate respirator.
38.
Carefully pour the molten lead into the 8
tubes until they are all full and then leave
them to cool.
39.
Grind/sand the ends of these lead ballast
slugs so that they are all exactly the same
size and so that there are no sharp edges.
Lead dust is extremely toxic so ensure an
appropriate
respirator
is
worn
and
thoroughly clean away and dispose of the
lead dust afterwards.
40.
Locate the 1/2” (13mm) diameter pine dowel and cut into lengths exactly the same size as
the lead ballast slugs. You will only require 6 of these.
41.
Sand to size and smooth as per the ballast slugs.
42.
Locate the 9/16” (14mm) diameter brass tube. This is to be used as the ballast tube to
accommodate the lead slugs when ballast is required.
43.
Load up the ballast tube with all 8 lead slugs and measure/mark how much needs to be
trimmed off the ballast tube to bring it in line with where the lead slugs finish. Then cut the
ballast tube to the appropriate length with a hack-saw.
44.
Locate the foam “jacket” for the ballast tube, remove its foam “noodle” and trim it to the
same length as the ballast tube.
