rail guides were selected for Coldfire. These are available from
A custom aluminum backer
plate with threaded holes is used to hold them in place on the airframe.
Rail guide backer plate
epoxied in place at the forward end of the booster body tubing. Kapton
tape was used to seal over the threaded holes to prevent epoxy getting
into the threads.
Kapton tape is a polyimide
film, it is very thin but will not allow epoxy to soak though. Kapton tape
is used in the electronics industry and is available at places like
The same thing was done for
the aft rail guide backer plate at the tail end of the booster tube.
This one sits between two fin slots.
System epoxy with #406 Colloidal filler was used. The inside of the
body tube was sanded to allow the epoxy to bond better.
The photo below shows how
the booster coupler had to be slotted in order to slide into the top of
the booster body tube and pass by the rail guide backer plate in that
area. The size of the slot was
not very critical so it was simply cut with a coping saw. The
drawing below shows the locations for each rail guide.
After painting and decals
were finished, the last step with Coldfire construction was to add the
Rail guides were mounted
using two #6-32 x 1/2" flat head machine screws with
Loctite 242 thread locker adhesive
on them. This adhesive helps keep the screws tight but they can still be
removed when necessary to replace a damaged guide.