It's nice to use 2in for the first few feet of harness where it attaches in
the airframe so you have a two inch strap pressing against the airframe
opening, then transition to something smaller.
This helps to avoid zippers.
I also like to z-fold the cord and tape it together.
If you make the cord too long the sections can accelerate to higher than the
deployment forces before being stopped by the chute, so be carefull.
Sometimes I like to make a harness a few feet long out of Kevlar that
attaches to the bulk plate and the harness attaches to this, this can handle
higher heat. But if you use 2in TN it will be fine.
Just sew loops in the end and wrap with duct tape to protect the thread.
you can see the "Fireball", a patent pending commercialized version at
Giant Leap Rocketry
high power -> (top frame) products -> (left frame) recovery
Duane Phillips wrote:
I guess we'd have to see the patent claim, but this seems to be "prior art"
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD"
>>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf
www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
Save Model Rocketry from the HSA! http://www.space-rockets.com/congress.html
the problem is that in dynamically generated websites that use frames,
the frame URL does not reproduce the actual context
but here's your link to the frame
Jerry Irvine wrote:
You should think about rocket mass more than airframe diameter for shock
cord sizing. The shock cord has to dissipate the force of the two rocket
parts separating from each other by way of ejection charge. Therefore, the
mass of the rocket pieces on each end of the cord and the force (size) of
the ejection charge will determine the force (momentum) that must be
absorbed / dissipated by the shock cord under normal deployment. Using
longer shock cords will allow the pieces to slow down due to friction with
the air before the cord goes taught. rubber bands or tape as others have
mentioned also help.
"blow it out or blow it up" may help gaurantee 'chute ejection, but it
increases the force on your shock cord, so be carefull.
There are also other ways to deploy chutes to minimize the forces on your
I have a 7.5" X 8.5 ft rocket that weighs about 30lbs on the pad. It has all
9/16" tubular nylon shock cords. BUT... This rocket deploys at apogee in the
following manner. The charge blows the nosecone off which pulls a 36"
Skyangle chute into the airstream. As that chute fills, it pulls a
deployment bag housing the main (Skyangle Cert3 Large) out of the rocket. As
the nosecone and rocket body separate, the main shock cord is pulled taught
and then the shroud lines for the main are pulled out of the loops sewn on
the outside of the deployment bag. All of this dissipates energy from the
ejection charge. Finally, the bag is pulled off of the main. The main then
fills and brings the rocket down. The nosecone descends independently on the
36" chute. That looks like a lot when written out in words, but it is really
very simple and I have absolutely no fear of overstressing the 9/16" tubular
TRA # 8975 L2
NAR # 79398
OK , here is what I want to do. the 7.5 : rocket is like a bruiser exp with
a 4" motor mount. it will travel to about 7-9k so dual deploy is needed.
All the laundry will be in the payload bay.
The primary apogee charge cannon will blow the nose cone off and the nose
will pull a sky angle drogue chute out held to the payload bay with a ring
link held to an ARRD, say 25 feet of 3/4" cord. The secondary apogee charge
cannon will seperate the booster from the payload bay. say 35 feet of 1"
If the primary charges fails to fire, the seconday charge will end up
seperating the nose from the payload (no shear pins) in the standard inertia
mode that causes so many main deploy at the top situations. If the seconday
charge fails, then the seperation of the booster and payload will take place
with the drogue becomes taught.
at 800 feet, then the main match fires the arrd, and at 700 feet the
secondary match fires the arrd weather it needed to or not.
That realeases the ring on the arrd, and lets the droge pull the main and
it's deployment bag out and do all that stuff.
I've got to be missing something, so let me know if I did.
ohh, the harnesses have the "car polishing towel" wrapped in ducktape
anti-zipper ball on them.
anyway, my 5.5 rockets just do the drougeless two step and so far have been
fine, crossing streams, no that's fingers.
I would like to use another as a backup instead of just
a backup match in one ARRD.
the ARRD works in reverse, so if two are used, and only one fires, you
have deployment ?
I can't see how two of them does anything good ?
Why not two in series. That way if one does not fire or separate
hopefully the other one will.
Drogue less dual deploy is my most common high power rocket recovery
Works great and usually brings everything close to the pad.
Still lost here.
The ARRD holds a deploymen bad to the bulkhead by holding the hook.
two in series or paralle still do the same thing.
Unless they both fire, your deployment bag is still held to the bulkhead ?
I will gladly pay you tuesday for a motor on the flying field today.
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