(Contributed - by Dick Stafford - 06/20/02) Brief:
This is review of a pre-production version the 24mm Cognis Lunar Lander, the
LLV 201. Its unique design is based on a 6" Styrofoam ball, legs made from
wooden struts, and circular fins. The Cognis Lander is manufactured and
distributed in the U.S. by LawnDart Rocketry. I won the kit as a prize for the
Boink rocket contest. When EMRR heard my kit was tied up with production
problems (LawnDart had suspended operations but now appear to be back), he
offered this pre-production version. A real class act - thanks Nick!
Construction:
Components:
- One 6" Styrofoam ball, pre-drilled for the 24mm tube
- One long 24mm body tube
- Six short 24mm tubes
- Six spruce stringers
- 15 balsa stringers
- One sheet of balsa fin stock
- One nosecone (resembles a 24mm - 13mm transition)
- One eyehook
- One 24mm motor block
- Two launch lugs
- A long piece of Kevlar®
twine
- A section of elastic shock cord
- A 12" Mylar chute kit from Aerospace Specialty Products
Since this was a pre-production kit, the instructions consisted of only a
drawing of the kit, shown in two views. The changes from 18mm to 24mm was
indicated with hand written annotations. I had to figure the details out on my
own. The good part was the drawing provided full-scale templates for the struts
and circular fins.
Construction details:
- I used white glue throughout. (I built it in the kitchen not my rocket
workshop, was too lazy to get wood glue from basement)
- Tie the Kevlar®
twine to the 24mm motor block and install it. I also added a metal engine hook
(not provided).
- Glue the side tubes together in pairs, and then to the bottom of the main
tube, just like a tube fin rocket.
- Cut spars for leg structure per templates. Mark root and tip edges. Each
leg consists of two pieces of spruce and two balsa supports. Note that all the
stringers are the same length and are cut to fit.
- On a flat surface covered with wax paper, glue the main leg structures
together.
- Cut small triangular pieces from the scrap basswood to fit the joint
between the basswood leg sections. I used the legs as a template. Add this to
the leg assembly.
- The original 18mm version included a piece of balsa along the root edge of
the leg assembly, which fit between the 24mm side tubes. Since the side tubes
on the 24mm version touch at all points, this component was not provided.
However, I decided to add pieces of balsa along the root edge of the leg
anyway. I used one spare balsa spar, and made the remaining two from balsa
stock I had lying around.
- Install the leg assemblies one at a time. Find stuff to support them while
the glue is setting.
- Cut all cross members per the templates. For a better fit, I also sanded
the inner faces where they touch the main leg sections.
- Install the cross members. I didn't mark the position of the cross members
on the main leg sections before they were glued onto the body. This was a
mistake. Do this in step 4!
- Cut out, seal, and install the circular fins. I placed mine such that the
grain is perpendicular to the leg. This should keep the edges from breaking off
on landing.
- Add liberal fillets everywhere.
- Install the Styrofoam ball. I wrapped masking tape around the body tube
near the top to make the fit snugly and glued it to the body tube with white
glue. To allow the ball to sit on the outer rim of the side tubes, I also cut a
small conical section from the lower end of the ball.
- To install the launch lugs, I ran a 3/16" launch rod along the joint
of two of the side tubes and up through the ball. I glued one lug in the top of
the Styrofoam ball and the other at the bottom of the side tubes.
I hesitate to rate the kit because it is a prototype. However, assuming the
instructions are detailed and clear, I would give it a 4.
Finishing:
Haven't decided on how to finish the kit, so for now I will fly it nekkid. One
thing I should have done is seal the balsa spars before installing them. At
least I had the forethought to seal the fins prior to installation.
Construction Rating:
4
out of 5
Flight:
I chose a D12-3 for the first flight. On this motor, the rocket weather cocked
into the 5+ mph wind and there was
some wobble. The boost was nice and slow - everyone at the launch took notice.
Recovery:
I used my home made 12" nylon chute and a combination of Estes and
dog-barf wadding. A 12" chute isn't enough for this kit and one of the
legs broke on landing. The repairs were easy and are complete.
I'll rate the boost phase a 5 and the recovery a 2, for an average of 3.5.
Flight Rating:
3
out of 5
Summary:
This is a unique looking rocket. It took a bit more work than the average LPR
kit, which is a good thing. It was just challenging enough to be fun. The
flight characteristics are good, but a larger chute is needed. Since I built
the Lander and began writing this article, LawnDart came out of hiding and
delivered my kit. Hopefully, EMRR will build the production version and publish
a review.
(Note that my rating is provisional on the quality of the instructions in
the production kit.)
Overall Rating:
3
out of 5