Friday, January 28, 2011

Review: Three scratch saucer-like objects

This post documents three totally different saucer-like designs.  The Half-Spool Jack-o-Lantern is made from a used CD-ROM and a small jack-o-lantern, the Instructables Frisbee Saucer is a paper design made from, well, a DIY paper Frisbee, and the Quadrophenia is a quasi-scale lander inspired by Armadillo's Quad Lander.


Half-Spool Jack-o-Lantern

As the name suggests, this is a half-spool (top plate only) rocket merged with a plastic jack-o-lantern. I stumbled across these little plastic jack-o-lanterns that I had stashed in the plastic parts drawer. So, I made a quick Halloween-themed rocket to fly on the Quest D5-0/P.

Construction:
The parts list:

* One plastic jack-o-lantern
* Cardstock
* Clear spacer from a blank CD pack
* 24mm to BT-60 centering ring
* Masking tape
* Quick-dry Gorilla Glue and wood glue
* Black paint

I rolled the body from card stock using two D5 motors as a mandrel. The glue used here was wood glue. I also rolled a motor block from cardstock.

I cut the base out of the jack-o-lantern and reamed the CD blank to fit this tube. The tube is centered in the jack-o-lantern with a centering ring. Although the opening was too small for the BT-60 ring, it would fit if I flexed the jack-o-lantern. This was glued in place with Gorilla glue.

The tube was too small to fit in the ring, so I built up the middle with a few wraps of tape. I painted the tube black before inserting it from the top. This, too, was glued in place with the Gorilla Glue.

Finally, I attached the clear CD blank. I bored a hole next to the motor tube to act as a launch guide.

Flight and Recovery:
The jack-o flew fairly straight but arced a bit at the end of the long burn. It then tumbled softly to the ground.

Summary:
This build was quick and easy. If I were to do it over, I'd build it for 24mm motors. I have several of the jack-o-lanterns so maybe I'll build another version next year.

Instructables Frisbee Saucer

This is a simple cardstock saucer with a unique 7-sided design. I got the basic pattern and instructions from Instructables.com (with a hat tip to Kiteman)

Construction:
This project required 2 sheets of cardstock and a short 1 1/8" piece of BT-50. If you are a purist, you could roll your own motor mount with the leftover cardstock.

1. I downloaded the .pdf format patterns from the web site shown above.

2. I printed two copies on light card stock - the decorated version for the top of the saucer and a blank one for the bottom.

3. The top was cut and scored as instructed. It was easier to form than I expected. The results are shown in the right of the top photo.

4. The bottom is folded differently than the top and is shown on the left of the top photo. Although I scored all the dotted lines, I didn't need to score the inner circumferential path.

5. I then flipped the bottom over and glued it to the top. I used a light coat of white glue along the connecting surfaces and a bead along the valley fold on the top piece. The second photo shows the result. I let the glue fully dry before proceeding.


6. The saucer seems a little flimsier than an Art Applewhite 24mm card stock saucer due to the weight of the card stock I had on hand. I decided to go for 24mm anyway. I laid a section of tubing over the top and bottom peaks, marked the perimeter, and cut the holes with an Exacto knife.

7. I then glued the tube in and applied a heavy fillet on top and bottom. This photo shows the result next to an Art Applewhite 24mm Super Cinco.


Finishing:
No finishing is required. A clear coat will make the model more durable.

Flight:
I flew the saucer on a D12-0 with a masking tape thrust ring. Oh wait, there was a problem, where does the launch rod go? I hadn't cut the holes for the launch rod so I whipped out my Leatherman and cut two small triangles on the top and bottom next to the motor mount.

It weather cocked a little and had a distinct wobble. In my experience, a wobble is not uncommon for polygon-shaped saucer designs. I'd say this flies about the same as the Cinco.

Summary:
The main pro's for this design is that it is almost free and flies well. It would also fly well on 18mm motors. I don't think it is as durable as an Art Applewhite saucer, but if it breaks you can always make another.

Reader Comments:
10/09 - "In order to be able to download or print the "Cardboard Frisbee" template, one must first sign up for a paid "Pro" membership at Instructables.com. There is an option for a free membership to the site (buried way down at the bottom of the sign-up page), but it does not include permission to download PDFs. So the saucer template isn't actually "free" at all." (M.K.)

Quadrophenia

My latest saucer-like contraption is inspired by Armadillo Aerospace's Quad lander and is named after the groundbreaking The Who album from 1973. I took numerous liberties with Armadillo's concept--some to make it more robust (in my application), some because there is no reason to detail it until it has successfully flown, and some just because I "used what I got" for most components.

Construction:
The parts list:

* Four 4" Styrofoam balls
* Dowel
* Four 18mm motor tubes (approximate length used)
* 5" x 5" square of 1/16" plywood
* Three inch section of 24mm tube
* Scrap foamboard
* Launch lug
* ¼" square balsa rod
* Scrap foam rubber
* Four plastic drywall nuts

I joined the foam balls using pieces of dowel and 18mm tubes. The tubes were easily twisted into the balls and after the assembly was dry fit, I glued it together with Gorilla Glue. The alignment was all done by "eyeballing" it. To support the 24mm motor tube, I glued a 5" x 5" plywood plate on the top using 5-minute epoxy. This plate is not in the Armadillo "design", but it was an easy way to support the motor tube. I drilled the center hole on a drill press and notched a slot for the launch rod using a Dremel. A launch lug was added to the tube and I used scrap pieces of foamboard to brace the motor tube against the foam balls. Trim (to date) includes the balsa rod, squares of foam rubber, and the drywall nut shock absorbers. These approximate the look of the Armadillo lander. More trim components, such as "plumbing" tubes, may be added later.

Finishing:
I painted the top pieces and shock absorbers with silver acrylic paint and left the balls naked (I don't have a photo of the painted version.) I also smeared white glue on the balls in the areas that are likely to meet hot exhaust.

Flight and Recovery:
I friction fin a D12-P and let her rip. As I expected, it was stable on the way up and it came down a little harder than a typical "saucer" design of these dimensions. Even with the use of soft foam on the top, the balls separated from the plywood plate. No big deal, several dabs of epoxy fixed her up. Check out the video.


Summary:
I love saucer-like things and this is no exception. I got several favorable comments at the launch and one person even recognized it. It came out heavier than I expected and is likely to pop apart on each landing. I never thought I'd say this, but I need a material lighter than Styrofoam!

Reader Comments (including one by Armadillo!)
03/07 - "What a great model, I think you really did a great job! It is really similar in scale overall. How high does it go? Neil said in an email to me- "I wonder where they'll stack the 25-kg payload :-)" Bravisimo! -James Bauer Welder, Armadillo Aerospace" (J.B.)

04/07 - "Thanks for the nice comments. I'm not great at estimating altitude, but I bet it was lucky to hit 50 feet." (D.S.)

04/07 - "I had forgotten there is a video of the flight: http://www.mdra-archive.org/photos/ESL98/index.html#0000002099" (D.S.)