Jay Sessler wrote
>I am thinking of doing my lev 2 cirt on a LOC Bruiser EXP.
I have a Bruiser EXP which I flew at LDRS this year on a K700 and one of two
J350's air started (3615'). It has also flown at Orangeburg at the Freedom
Launch on a K1100 (1763'). I used one ALTS 25 at Orangeburg and two at LDRS,
since the K700 is not certified with delay.
I made the following modifications, FWIW, YMMV:
1. A 5/16" dia by 60' nylon bungee shock cord in place of the 20' piece of 2"
elastic. This shock cord connects from the main airframe to a U bolt on the
2. Two bulkheads, one near the top, and one at the bottom, of the payload
compartment coupler tube. The area between the bulkheads inside the coupler
tube is the electronics bay.
3. A piece of 3/4" thick oak for a brace across the diameter of the lower
bulkhead, inside the electronics bay.
4. A 2" dia U-bolt with metal backing plate for the shock cord attachment,
through the oak brace and the bulkhead.
5. Three rectangular holes cut in this bulkhead for altimeter bay access. If
I were doing it over I would put the shock cord mount off center, still braced,
and cut only a single larger hole. Altimeters were mounted on strongbacks.
Strongbacks were mounted to plates which covered and sealed the holes in the
bulkhead. (Very Important to seal the electronics bay. If the bay is not
sealed the altimeter WILL freak and you will not get deployment of the main
chutes. I learned this the hard way). Don't forget to drill the holes for the
static ports. They should be above the electronics so no direct crosswind
through the bay can affect the pressure sensors.
6. Three Radio Shack DPDT slide switches, with the slide cut flush, mounted
on the outside through the area where the coupler is glued into the payload
tube. (This will NOT work with SPST switches- they have an internal spring in
the slide and cannot be cut flush.) Each switch is wired so that one position
connects power to the altimeter or electronic stager and output to an ejection
charge flashbulb or electric match, and the other position turns off power and
shorts the electric match leads together. This way you do not arm the
electronics until the rocket is on the pad. I used cellophane tape to secure
the switches in position after arming. Crude but effective.
7. The kit's shock cord eye bolt went in the center of the upper bulkhead,
with the eye in what would be the payload compartment. I used about 30' of half
inch tubular webbing for this upper shock cord, between the eye bolt and the
8. An R4 Rocketman chute for the drogue, secured on the 60' bungee with duct
tape. Both of the chutes furnished with the kit were attached to the 30'
tubular nylon shock cord.
9. Two layers of 5 ounce fiberglass cloth over the entire airframe and the
10. One inch diameter launch lugs, secured with fiberglass cloth.
11. I used two ALTS 25 altimeters and 7 gram ejection charges for the K700
flight. I used an ES236 stager for the air start.
12. Pour a layer of epoxy finishing resin on the bottom motor centering ring
13. Run wire through the motor mount/fin assembly for the air starts before
inserting this assembly in the main airframe tube.
Total empty weight was about 19 pounds.
CAUTION: This configuration HAS INSUFFICIENT STABILITY MARGIN with a K700 and
two J350's. I added a pound and a half of nose weight (gatorade bottle with
water) to get a full caliber stability margin for that flight. Al Swayze the
Kloudbusters RSO at LDRS won my respect by catching this problem and ensuring I
had a successful flight. And the water was waiting on me when I got to the
rocket to retrieve it after the flight <G>.
This is a bit much for a cert 2 flight. If you are not interested in flying it
in L total impulse range, you should be able to make a cert 2 flight with a
J415 with no fiberglass. If you glass it you should be able to make the cert 2
flight on a J800 or K1100. Do not try the complex stuff- air starts- on your
cert flight. DO NOT FORGET TO PLUG THE SIDE MOTOR TUBES WHEN FLYING WITH ONLY
A SINGLE MOTOR. Best of luck to you. Any questions, email me.
Jack Kale, TRA 5798 L2, NAR70384 L2 Insured.
Jack W. Kale, Jr. NAR #70384 Insured, Tripoli #5798 Level 2 March 16, 1998
Timmy, you can't take it with you, so if you have a sandwich and your blue
jeans, chill. Your old man, Paul. (1st century, paraphrased)