Upscale Estes AGM-12D BULLPUP

In September I attended the Kansas Kloudbusters Airfest '97 launch at Argonia, Ks. I was purchasing a pile of motor reloads from Ross Dunton of Magnum fame when he mentioned that he was introducing the new 5-1/2" TCB Thunder rocket kits for the unheard of low price of $80 each. I could not pass up the opportunity to acquire a 5-1/2" diameter rocket that cheap and immediately bought one! (So did 6 or 7 others that day who knew a bargain when they saw one!) It was my original intention to build the kit stock... (Ha!)

I spent my spare time at Airfest like most other Rocketeer's--I walked around visiting with other people and admiring their rockets. One gentleman from Tulsa, Ok. (I cannot recall his name) had a PML Bulldog finished with the Estes AGM-12D paint scheme. I was very impressed with the visual impact this large "Bullpup" made. It did not take much thinking to realize that I had the makings of a large scale Bullpup with the TCB kit.

This gives an idea of the size of the rocket. It is scaled up 418% from the Estes kit. The airframe has been extended 3" in length to provide extra room for the recovery system and to compensate for the shorter relative length of the TCB nose cone compared to the Estes nose cone.

A closeup view of the boattail. The boattail is formed by epoxying two centering rings to the motor tube. The forward c-ring is the same diameter as the I.D. of the airframe. The aft c-ring is the desired final diameter of the boattail less .080" for fiberglass. In the case of the 'Pup, this was 3.90". The centering rings are spaced apart the length of the tailcone--4.68". Eight 1/16" plywood or fiberglass ribs are cut and epoxied longitudinally and equally spaced around the motor tube between the forward and aft c-rings.

A piece of lightweight poster board is wrapped around the assembly and epoxied in place. After curing, the poster board is trimmed flush with the c-rings. It is possible to lay out an exact size transition template for the poster board, but I find it easier to do this way. Next, two layers of fiberglass cloth & resin are applied over the poster board and trimmed after curing. The final step before painting is to sand the assembly smooth and fill in any low places with bondo.

This photograph shows the Bullpup in a mockup to check decal placement & fin placement. I did this to help visualize where the airframe could be separated without having to cut through a decal.

The decals for the Bullpup were relatively easy to create. First, I used a decal sheet from an Estes Bullpup kit. It was necessary to enlarge the decals by 418% in order to accurately measure the correct text size for the upscale 'Pup. I did this by making enlarged copies of the decal sheet on a standard copy machine. Once the correct size was determined, it was necessary to search through my True Type Font files to find a font closest to the one used in the Estes kit. I found Swiss 721 SWA Bold to be very close.

The more common Arial font would probably be acceptable if you do not have a large Font library.
I used Microsoft Word 7.0 to set the text for the small decals. It was necessary to make a few test prints at various font sizes and character spacings to get the size and appearance close to the original.
The large "U.S. AIR FORCE" stencil lettering was more of a challenge. I had no fonts remotely resembling the original. It was necessary to draw the lettering from scratch using my CAD program. It could also be done in a paint program such as Paint Shop Pro. After the letters were created, I imported the drawing into the Word document and saved it.

(Note: I have since found a font--Amarillo USAF--that is correct. unfortunately, it's maximum size is 72 points, so it would still need to be manipulated in a paint program to get the correct size.)

I saved the Word files to a floppy disk and--disk in hand--took a trip to my local Kinko's. There, I made laser prints of each file. I did this as my ink-jet printer did not produce the razor sharp prints a good laser printer is capable of. Once the laser prints were made, I handed them over to one of the Kinko's staff where they made photocopies on Sticky-back film. Sticky-back is a peel & stick self-adhesive clear (translucent) 8-1/2 x 11 sheet.
The red and silver stripes and small detail markings are cut from Monokote trim. After the decals and detail markings are applied, the entire rocket will receive a clear coat to seal and protect the decals. (have an extra couple of decal sheets printed so you can pre-test the compatibility of the clear coat with the copier toner and Sticky-back film.)

The fins have been epoxied to the fin cannister and clamped to my alignment jig in this photo. The fin cannister airframe is 12-1/2" long. Note that the boattail has not yet been epoxied in place. The fins are attached using through the wall construction technique. A 2.6" dia. tube runs the length of the fin cannister and 3/16"centering rings above and below the fins make for a strong mount. A third 3/16" centering ring is located at the top of the airframe. The 1/4" upper centering ring on the boattail will support the bottom of the airframe below the fins.

The boattail and 54mm motor tube will be epoxied into the 2.6" center tube later.
Note that the forward bulkhead on the coupler tube is sealed. The Bullpup will only fly with electronic recovery. It would be possible later to bore 1" vent holes through the bulkhead plate to allow the use of motor delay ejection, but I chose not to at this time.

The forward fins are made with an .080" deep notch for mounting through the airframe wall. The forward notch is 1" back from the tip. This provides an increased margin of strength by keeping the end of the fin slot away from the end of the airframe.

The four holes in the bulkhead plate are for ejection charge gases to pass through--visible in this photo taken of the inside of the parachute compartment. The U bolt is for attaching the shock cord. The aft bulkhead for the payload bay is visible through the vent holes. It is spaced 2" behind the first plate. The ejection charge will fire into this space where the hot gases and burning particles will be trapped by a stainless steel mesh before they can reach the parachute and shock cord.

Note: the view is from the fin cannister looking forward toward the nose.

This view is from the nose of the rocket looking toward the fin cannister. This is the aft end of the payload compartment. No wiring or altimeter vent holes have been installed yet, nor have the forward fins been installed. The threaded brass object mounted in the bulkhead plate is a modified 3/4" brass plumber's flare nut. In combination with a 3/4" brass flare plug that has been bored to a 5/8" I.D. and extended with 5/8" brass tube, this will comprise my own design for a reusable ejection charge system.

This pair of photos shows the ejection charge cup front and back views. The cup is made from a 3/4" brass plumber's flare plug. The flare plug has been bored to a 5/8" inside diameter and the flare flange has been ground off. A section of 5/8" O.D. brass tubing 1-1/8" long has been soldered into the end of the flare plug. A 1/8" hole has been drilled through the center of the flare plug to allow the wire from an electric match to pass through. The finished cup has a capacity of 5 grams of FFFFg black powder plus wadding.
The brass piece epoxied into the bulkhead plate is a 3/4" plumber's flare nut. The tapered part of the flare nut has been cut off just past the end of the threads. The hex head part of the flare nut has been ground down to a 1-1/16" round diameter except for a 1/8" thick section on the end. That part serves as a flange to keep the piece from pushing out of the bulkhead plate. This combination makes a permanent ejection charge cup and mount assembly that is simple and easy to use, prep, and clean.

The altimeter and wiring harness are ready to install. The 1/4" phone plugs are the power and safe arming switches. "REMOVE BEFORE FLIGHT" ribbons will be attached to these plugs to provide a visible indicator of power status. (see my AMRAMM photos)

• sand the spiral grooves with 120 grit sandpaper. I find a triangular pad style electric detail sander ideal for this job.
  
• fill the grooves with Elmers Carpenters Exterior Wood Filler.
  Use a putty knife , or single edge razor blade to push the putty down into the groove and smooth it out. Work just a few inches at a time so the putty will not dry out. I thin the wood filler slightly with a little water to make it spread easier & smoother.
  
• Wait at least 24 hours for the filler to dry completely.
  
• Sand the filler down flush with the face of the tube. Be careful not to sand too much away. Just sand until you feather the edges of the putty. The detail sander with a 220 grit pad works very well here.
  
• The photo on the right shows a spiral groove after sanding. The tube is ready for primer.

No matter how careful you are with the above steps, the first primer coat will still show some slight spiral grooves.

• Wipe the tube surface with Tacky Cloth and apply a coat of white primer.
  
• Allow the first primer coat to dry 24 hours before proceeding with the next step.
  
• Lightly sand the first primer coat with 220 grit garnet sandpaper. I prefer to do this by hand, not with the electric sander. This is the time for a light touch.
  
• The Second coat of primer described in the next step is optional.
  
• Dust with a Tacky Cloth as before and apply a second coat of primer.
  
• Repeat the second and third steps above.
  
• Wipe the tube clean with a cloth. Hold the tube at an angle to a strong light and carefully examine the surface. You will probably still see some traces of spiral grooves. They may look insignificant now, but will shine like a lighthouse beacon under the finish coat of paint!
  
• Fill these places with automotive glazing compound in the same manner as described with the wood filler.
  
• Allow to dry 24 hours again (I said this takes patience). Feather sand out the areas of the tube where you applied glazing compound and sand the entire tube smooth with 400 grit wet & dry sandpaper.
  
• The tube is now ready for a final coating of primer.
  
• Why wait 24 hours between steps?
  The wood filler, primer and glazing compounds directions say it can be sanded sooner, but you increase the risk of sanding before the stuff is 100% dry all the way through. If you get in too big a hurry, it will shrink after sanding, or even come out of the spiral grooves. If you want a super good finish--wait.

The decals made by the method described above--after a coat of clear finish to seal and protect them. I used Rustoleum brand white primer and paint. To avoid any potential compatibility problems, I also used Rustoleum clear finish spray. It is compatible with the sticky back film and copier toner.

The 150" X-form chute I made for the Bullpup. This chute is about 20% larger than actually needed, but I prefer to bring them down slow and easy.

The Bullpup's home between launches is now over the counter of Joplin R/C Hobbies in Joplin, Mo. That's Ron, the proprietor, wondering if the ceiling is going to collapse from the weight! The picture on the right is of the Bullpup being supported by my 10 year old son, Jeffrey.

R.I.P.

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