Wednesday, January 12, 2011

Review: 'Scuse Me (While I Kiss the Sky)/Vlad the Impaler

The 'Scuse Me started life as a minimum-diameter, 38 mm, all fiberglass rocket. It was a very simple, basic design and was very rugged and high performance.

'Scuse me, while I kiss the sky'...-Jimi Hendrix 

I reworked the original review and added the rebuild, which I named Vlad the Impaler.

The following is a list of the components. The major items were all bought from Giant Leap Rocketry

1. ScotGlas conical nosecone, 8.5 inches long
2. Giant Leap filament wound airframe, 36"
3. Acme fin cannister
4. AeroPack motor retainer
5. ~10 ft 3/4" tubular nylon
6. Blacksky standard rail buttons (2)
7. Quick links (2)
8. Eyebolt
9. (1) bolt, 2" long (fits thru a Blacksky rail button)
10. Scrap section of 1" dowel
11. Giant Leap 29mm-38mm adapter (optional)

This is a *very* easy rocket to assemble:

Nose Cone Assembly - I drilled a hole in the scrap dowel to fit an eyebolt. The dowel and eyebolt were epoxied into the nosecone, which did not provide an attachment point.

Fin can - After roughing up the tube and inside of the fin can, it was epoxied to the airframe such that the aft end is ~ 1 1/4" from the end of the airframe. I initially had not decided on a motor retainer so I wanted to make sure there was room to install one.

AeroPack motor retainer - After roughing up the tube and inside of the fixed portion of the retainer, I glued it to the airframe with JB Weld epoxy (per AeroPack recommendation).

Rail buttons - I epoxied the aft button in the middle of the fin can. The second was attached via a 2" bolt approximately 11" from the aft end of the airframe. The bolt extends through the airframe and was cut flush with the airframe opposite the rail button, using a Dremel cutting disc. This limits the largest motor which can be used, but I decided I would never want to fly this rocket on anything over a small "I" (moving the rail button forward would fix this). A nut was used as a spacer between the rail button and the airframe since the rear button is on the body of the fin can.

Recovery harness - The harness is 3/4" tubular nylon with a quick link on each end. Loops were made at each end as described in the article "Attaching Shock Cords", Edward Shihadeh and Bob Moser, High Power Rocketry, Vol 14 #5, August 1999. This involves looping the cord, tieing it off with cloth fishing line (not nylon!), and gluing it with CA and epoxy. The rear quick link was lowered into the airframe as the bolt holding the front rail button was screwed in. This took a couple of tries to catch the quick-link. The harness is thus removable.

After its maiden naked flight, I painted the entire rocket (save the rail buttons and AeroPack retainer) using Krylon Chrome Paint. This looked really great, but showed every imperfection.  And fingerprints!

The components used for this rocket were fairly pricey for me at the time.  Coupled with the risk of losing a reload case, I started wimpy - the first five flights were on 'G' motors. I finally got the nerve to try an 'H', but a separation made it my final flight.  Here's a brief summary of the flights:

G80-10 - Fast, high flight, recovered fairly close to the pad with 18 inch chute.
G125-15 - Very fast flight with very late ejection and stripped 'chute.
G60-6 - This was a US Rockets motor. It took me 3 igniters to get the CATO! When I took the remnants back to Kenny, he told me that the manufacturer told him that the users had to drill the nozzle themselves. Huh? Anyway, he made it good by replacing it with another USR motor. Pre-drilled this time.
G80-10 - Great flight.
G120-8 - This was my replacement USR rockets motor. It was cast in a cute yellow fiberglass tube. Really fast flight.
H153-14 - It disappeared fast and the body was later found buried 3/4 of the way into the ground. Cone and 'chute went to the next county. Status: scavenged.

The Rebuild: Vlad the Impaler:

The 'Scuse Me suffered a MAJOR core sample (hence 'the Impaler') and, since it rose from the dead, I added the name Vlad (ala Count Dracula). I reused the lower 15 inches of  'Scuse Me, including the fin can and AeroPack.   I first cut the body flush and installed a 54mm LOC tube as the upper body.  The 54mm tube is centered on the original 38mm tube with 2 ply rings.  The new Kevlar shock cord is installed through both of these.  It is then epoxied to the lower ring.  Not the prettiest, but barely noticeable.

I also added a payload section so I could use an altimeter.  This was made from another piece of tube, a coupler, and a thick plywood bulk plate.  The new cone is a nice Giant Leap 'Pinnacle' cone.  This is a long, 5:1 (8.75") plastic cone that features a long shoulder with sandable ribs to ensure a great fit. The bulk plate holds a heavy eye bolt and two smaller bolts to attach the ejection charge.  The latter have knurled brass nuts on them.  The wiring is mounted through the bulk plate and is long enough to extend out of the payload section.  Where the wire breaches the  bulk, plate it is sealed with epoxy.  The wires are terminated in lugs, which also attach to the bolts mentioned above.

The final step was extending the rail buttons so the rail would clear the wider 54mm tube.  I merely got longer bolts and used a 2nd rail button as a standoff. I also added a 1/4" lug on the 54mm tube for added launch flexibility.

I never got around to refinishing the rocket nicely.  The lower body is the original silver and the upper body is painted red, but the payload and nose cone are still only finished with white primer.

The first couple of flights were on the venerable G80-10FWLs.  These were nice fast flights with good recovery.  Despite being electronics-capable, these used motor ejection.  Next up was a home made sugar motor which simmed to a 149G11-P.  The motor worked!  The following flight was a new 38mm G67-7.  The final flight to-date was on the neck-breaking G339-P, which uses the Warp9 propellant.  I tried the Xavien XSSET-1 that I won from EMRR.  It didn't fire but the rocket fell parallel into soft grass with no damage. The timer requires acceleration for 0.5 sec, but the motor burns for 0.3. D'OH!!!.