Sunday, December 19, 2010

Review: Too Rolling (Red)Stoned






The Too Rolling (Red)Stoned is is a semi-scale version of a Mercury Redstone. It is a large, light rocket that is built using card stock and foam board and is basically a 4” rocket in an 8” rocket’s skin. This review will emphasize the general build techniques rather than providing a detailed set of steps, exact dimensions, etc. I doubt if anyone would try to copy the details of this build, but the general approach might prove interesting if you are going to build something similar. Nor not, but I wrote it down anyway. Several people have stated that 29mm power is way to small for this sized rocket, and that is the point of the build. This build is too big to fly on a G80, but it should be safe (albeit low and slow) on an H165.  The name was inspired by the classic Robin Trower album, "Bridge of Sighs"






Parts
These are the major components used. I’m sure I missed something. I provided this breakdown not as shopping list but to show the depth and diversity of materials that went into the build.

Bottom Section
3 sheets of white card stock for the body wraps;
1 sheet of black card stock to form a faux roll pattern on the fin area;
1 sheet of 1/2” foam board for the rings that support the outer skins;
1 sheet of 1/4” black foam board for fins;
1 sheet of 1/4” white/black foam board for fins;
3 thick paint stirrers and 3 thin ones for the fin guides;
2 blocks of wood for rail button mounts;
2 rail buttons;
1/16” ply for the bottom thrust plate and 29mm-4” centering rings;
2 small bolts with nuts for positive motor retention;
One 4” mailing tube;
One LOC 29mm motor tube;
~5’ of 1/4” tubular Kevlar for the lower shock tether;
60” ‘chute.

Top Section
1 sheet of white card stock for the body and capsule wrap;
2 foam board rings (1/2”, cut from the same sheet listed above);
1 foam board ring (1/4”, cut from the same sheet listed above);
1 plastic dish, 8 1/2” dia x 2” high, for the lower part of a capsule (alternately could use another foam board ring and card stack wrap);
One spent 24mm motor and one spent 18mm motor;
~3” of a foam pool noodle;
1/16” ply for the bulkplate on the top of the capsule and the base of the upper section’s shoulder;
One 4” full length coupler (from the mailing tube) for the inner core;
One yard of 3/4” elastic for the upper body shock tether;
42” chute for the upper (recovering separately from the lower section).

Removable Tower
3 foam board rings (1/4”, cut from the same sheet listed above);
1 cap end of the mailing tube for the escape motor;
1 - 1/2” dowel
2 - 3/8” dowels;
2 - 1/4” dowels;
3 small foam cones for escape motor nozzles;
Scrap white card stock;

See, nobody would EVER try to use this as a shopping list!

Construction
This build, like my Grand Whazoo, features an inner core made up of a full length LOC 29mm tube and 4” mailing tube. The long motor tube both acts as a stuffer tube and saves weight. The 4” mailing tube is cheap and allows plenty of room for the laundry. One-half inch foam board centering rings are used to support the outer poster board skin. There are four foam rings on the bottom section and two on the upper. The majority of the rocket was assembled with wood glue, with a little 5-minute epoxy here and there. This results in a 9 foot rocket that is 5x lighter than many comparable 8” diameter birds. The weight at launch time, with motor, was 81 oz.

I used a spreadsheet to scale the measurements provided in Rockets of the World to the 8” body diameter. When using commercial tubes, the available diameters often determine the scale of the whole build. With this build technique, however, you could just as easily pick most any diameter. I picked 8” merely because I was happy with the size of the Grand Whazoo. Although I used these measurements for rough dimensions, this build is not very exacting and I did take many liberties. I wanted the rocket to be recognizable, but didn’t really want to win any scale points.

The photo to the right shows the fin section. I decided on a full diameter plywood plate to give a firm base for the motor tube and the fins. I cut the outer diameter with a RotoZip and the inner hole with a hole saw in a drill press. Two bolts are mounted from the inside and affixed with epoxy. I decided to use 1/2 foam board for the rings that support the skins. I thought the wider rings would help when installing the skins. I also used multiple small pieces of the thick foam board along the inside rim of the rear plywood plate to provide additional support for the inter-fin skins.





The foam board fins include through the wall construction and are sandwiched between the rings. I wanted them to be easily replaceable since unenforced foam board fins will bend on landing. On the Grand Whazoo, I merely bent them back in place and applied, in true trash-rocket style, duct tape across and long the bends. They continued to be functional but looked pretty ugly. On this build, I added wooden guides to the upper and lower rings. I used thick ~1/8” paint stirrers on the base end and thinner standard stirrers for the top. The fins were not that secure, so I added small screws through the top set of guides to pin the top of the fins in place. So, they will be replaceable, but I’ll also have to remove/replace one or two of the inter-fin card stock skins. Simple enough. You can also see the blocks that hold the rail buttons (scavenged from the Grand Whazoo).


The next photo shows the guts of the lower section before the skins were applied. The skins were applied such that a single 22” tall piece of card stock would cover the top, a second would be used in the middle, and then a third would be used to fill the remaining area above the fins and for the inter-fin panels. The card stock skins were applied from the bottom up starting with the inter-fin sections. I first glued one edge of the skin, let it set, and then glued the rest down. I used a combination of white and black card stock between the fins to finish out my roll pattern. I found the black was a lot harder to work with than the standard white. In fact, I only ended up with one black panel. And it warped when I coated it with Future Shine (which I only tested on the black foam board). The good news is that I’ll probably get to replace it with white when I replace the bent fins. It actually became less warped after several days of drying and is acceptable.



Although I overlapped the skins such that they wouldn’t catch air during boost, I covered all the seams with duct tape. White for most of the wraps and black for the center stripe and on the upper roll pattern. The sturdy 1/2” foam board worked well just above the fins and on the very top of this section. However, the width itself did not seem to help much with the mounting of the skins. A greater number of thinner 1/4” rings along the length of the body would be better.


The core of the upper section is a piece of the telescoping inside tube from the mailing tube. I added a short piece of the outer tube to form the shoulder and added plywood bulk plates inside each end. The lower one has an eyebolt installed and the upper one has a 24mm hole in it. In that hole, I mounted a spent 24mm casing that forms the attachment point for the removable tower.





The build-up of the capsule is, from bottom to top:

* The upper 1/2” foam ring.
* A plastic serving plate.
* A cardstock transition, which interlocks in the lip of the plate. The rim was sealed with Perfectglue (like Liquid Nails).
* An exposed section of the core tube.
* A spent 24mm motor mounted in the end of the tube with in a single foam ring inside and the ply ring on top.
* An 18mm spent motor friction fit in the 24mm motor case. This holds the top of the capsule in place and is a receptacle for the central dowel in the removable tower.
* The top of the capsule is ~3” of a foam pool noodle friction fit over the 18mm case. The diameter was close enough for this build and it should help with recovery. The down side is its surface is rough. In scrap-rocketry, you can’t have everything.

One additional card stock body wrap completed this section.


For the tower, I started with the cap section from the 4” mailing tube. Mounted in its center is a 1/2” dowel that slips into the 18mm case on the top of the capsule. This structure doesn’t exist in the real thing, but makes mounting easy. There is also a 1/4” foam ring on the outer base of this tube.

Next, I cut a piece of scrap tube that slips over the top foam section of the capsule. So, with the tower on, the rough noodle foam will not be very visible. I added a pair of concentric 1/4” foam rings as the tower’s base. These support the Y-shaped structure which was made with 3/16” dowel. More of this sized dowel was used as the three main tower struts. Then, the intervening structure was made using 1/4” dowel. All the dowel cuts were made with tough in-situ measurements, sanding, and my eyeballs. The finishing touch was the aerodynamic tower, which is made with another piece of 3/16” dowel and a small balsa cone that I found in my junk box.

Finishing

Most of the finishing came free with the natural color of the card stock and foam board. As I mentioned, I used white and black duct tape for the seams. I marked a somewhat-scale-like roll pattern on the top section’s wrap and filled it in with a jumbo-sized Sharpie. This section got a couple of shots of clearcoat.

I painted the capsule section before the top wrap was added and used Krylon H2O. I hand painted the tower red, except for the ‘extra’ center dowel that I painted white. It turns out that white stands out a lot. Maybe a gray would have been better. Of course, an acrylic tube would have been better still.

I’m still contemplating how to apply ‘UNITED STATES’ vertically on the side.

Flight/Recovery



I used a 60” parachute for the bottom section and a 42” one for the top. The latter was inserted first to help get the other out. Prep went well and I only endured a minor amount of harassment at the RSO table. I hit one problem - both rail buttons pulled out of their mounts after it was erected on the rail! I obviously didn't account for the forces created by such a large, albeit light, rocket. I always have a whole bag of spare hardware so I managed to re-install them.

The flight was great with a red-flamed boost to about 400ft. Ejection was with the nose cone still up. Both 'chutes came out on cue and provided a gentile landing. However, while a big 'chute provides a soft landing, it can also drag your rocket. Let me just say that foam fins don't like being drug through a plowed field! I have some rework to do before flight #2. Peter ‘Shaken Not Stirred’ Abresch caught a great video, which is in MDRA’s photo gallery.


Tip: When using cardstock, ALWAYS use a clear coat. The upper section, which was treated, cleaned up well. I forgot to treat the main body and it has permanently ground in dirt. It’s a job for Tide(TM), but it won’t fit in our washer.