(Contributed - by Bob Harrington - 04/21/05)
Brief:
Conversion of Lansbergen Delta II to fly on 18mm motors. The particular Delta
II that I chose to model was Delta 7920-8 247, launcher of the solar
observation satellite ACE. The plans are available on the
Philippus Lansbergen web
site.
Modifications:
The model is a 10 page PDF file. I printed the 3 pages of instructions on
regular paper, the 3 sheets of boosters was printed on 65lb cardstock, and the
remaining pages were printed on 110lb cardstock. For the main tubes, I used
full width tabs so the body was double thickness. It turned out that BT-50 body
tube was perfect for the couplers. I made an 18mm engine mount with CR2050P
centering rings. The rings were spaced to exactly line up with the booster
mounting holes. The body sections were joined and the motor mount was glued in.
Holes were drilled through the booster mounting holes and almost through the
centering rings. 18 dowels made from round toothpicks were cut to 5/8"
each and glued into the booster mounting holes. The booster tubes were rolled
double thickness and the holes on the booster were opened up. I poked a pin
through the hole location and open them up with a round toothpick. The booster
tubes were glued onto the dowels with the dowel going all the way to the
opposite inside wall and glued there. The booster nose cones and exhaust
nozzles were rolled and attached. Boosters 4, 5, and 6 have a larger exhaust
nozzle so take care when attaching them. The main nose cone was rolled and a
nose cone shoulder was rolled from double thickness 110lb stock. I made the
shoulder 1" long so there would be plenty of room for nose weight. I used
a standard paper shock cord mount on each end of the 36" shock cord. I
used a 12" chute made from a plastic table cloth. I didn't know where the
CG should be so I took an educated guess and balanced it just forward of the
boosters. I then did a swing test and it turned out that it was stable at that
balance point. I put a C6-5 into the mount and added enough clay to the nose to
bring the balance point back to the previously determined location. It took
.7oz of clay to balance which brought the all up weight to 2.0 oz. A couple of
coats of clear were sprayed on and it was done.
Construction:
The following is a list of materials that I used in the construction.
- 110lb cardstock
- 65lb cardstock
- 24mm body tube
- 18mm body tube
- CR2050P centering rings
- 2.75" engine hook
- dowels (round toothpicks)
- shock cord
- clay ballast
- white glue
Finishing:
Everything was pre-printed and only a couple coats of clear were required.
Flight:
Based on the weight, I determined that an A8-3, B6-4, or C6-5 would be
appropriate. The day of the first launch was as ideal a day as one could ask
for: sunny blue skies, temperature in the 70's, and almost a complete lack of
wind with occasional gusts to 5mph or less. I chose a B6-4 for the first
flight. The motor mount has an engine hook so no tape was needed. I used
"dog barf" for wadding. I was a little apprehensive because of the
lack of fins but the flight was perfectly straight. The rocket was easy to
follow and ejection was just about at apogee.
Recovery:
The recovery on the 12" chute was slightly faster than I would have liked
considering all the boosters sticking out. It was flown in a corn field and it
happened to hit a corn stalk upon landing and knocked one of the boosters
loose. The damage was minor and was easily repaired. I didn't fix it until I
got home so I could inspect all the booster attachments. The rest were all
solid. I think I will switch to a 14" chute for the next flight.
Summary:
I am really happy with the end result. The rocket was not difficult to build
for anyone with a little cardstock modeling experience. The price was right
(read: free), and when completed, you have a good representation of a rocket
that is not often modeled.
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