Model Forum / General / Rockets / March 2006

I have a friend who does something like what you are suggesting, and it
has worked every time. My fear would be the shock cord getting tangled
up in the e-match, but he has yet to have a problem.

I have another friend who mounted a removable bulkhead inside his
rocket, high enough to support the largest motor he is gonna fly. On
the bulkhead he has mounts for banana plugs which are connected to the
ejection charge. He has also yet to have a problem with the leads
getting tangled up with the chute.

My vote is to just try it and see what happens. Being just a drogue,
you're not going to be too lost if you have any problems.

The wires on e-matches are long, yes, but that doesn't mean to extend them
down to the motor.  E-matches are used in the fireworks industries as well
and are made for lots of different applications.  For dual deployment, your
wire only needs to be long enough to fit into the canister you're using to
hold the black powder and connect to the terminals on the altimeter.
Placement of the charge is irrelevant as all you are doing is expanding gas
into a chamber.

You also should seal up any holes you run the wire through with either
plumbers putty or a touch of 5 min epoxy as I've seen many do.  The main
thing to keep in mind is you don't want the gases to get into your altimeter
chamber.  Some people also use terminal blocks to avoid having to seal the
holes every time.  I'm curious as to how many dual deploy flights you've
done and what motor your using to loft the 32lb rocket.

-Booms

. Do I use a 4

Many I know put the charge at the bottom facing up from the motor mount, so
it blows everything out.

Alway seems to wrok, and I've never seen a e-match wire cause an issue on
the recovery Harneses.

Now I have a friend who puts charge containers on his ebays firing down.

I've seen that actually push off the ebay and push the drouge chute back
down into the body tube and foul.

if it was drougeless, then it never seemed to cause an issue.

Myself, I like the fact the charge is "blowing" the stuff I want out if it's
mounted down at the bottom.

You are making a cannon, and your nomex pad is the cannon wadding and the
parachute is the ball.

I've been doing it that way for years and never had a problem.  What you
might want to think about is to use binding posts on the bulk head for
your rematch lead connection.  This way if the ematche wires do get
tangled with the recovery system then the rematch leads won't get ripped
out the altimeter.

Ted Novak
TRA#5512
IEAS#75

In all of my apogee-only rockets, I've tucked the electronics in the nose
cone and use the dangling wires method a bunch, and not had a problem. I try
to make the wires short enough they don't reach the parachute attachment
point. A connector is on the base of the N/C to attach the leads.

A "neat" installation is to use a piece of tubular kevlar and run wiring
internally, terminating in a connector attached to the recovery harness at a
point far enough along that you can tuck it into the airframe ahead of the
chute. When I do this, I sew a nomex blanket to the harness at the same
point. This allows you to use very short leads on the ematches themselves.

Be sure to seal any holes between the charge and the altimeters. Combustion
by-products and altimeters do not mix.

Kevin OClassen