Custom Building Performance Rocketry’s 9.25” Honest John
by Dan Michael
all Photos by Andrew Michael
Of all the high power rockets I have ever built, the Honest John remains the one I always wanted to build and fly, as it has a reputation for being a very stable rocket, and it looks really cool!
My idea was to construct this rocket with a few “unique” features over the customary regular build. With almost every rocket, I scratch-build everything, but with this build, I decided to use Performance Rocketry’s 9.25” version of the Honest John, however, I still ended up making many parts due to the modifications. The quality of Performance Rocketry’s products are top notch. Over the years, I have built several of their rockets, and purchased scores of parts to construct various rockets, and have never been dissatisfied. Ok, on with the build…
First and foremost, when I build a rocket, I build it strong, really strong! I have a reputation for “over-building” my rockets. I would rather wipe the dirt off the paint, then repair and repaint the rocket! My analogy is, if the rocket gets too heavy, then use bigger motors! Notice the parts included with the kit.
Normally two short airframes come with the kit, however, since I decided to stretch mine, I purchased two 48” airframes. The photo only shows one. Notice I also have a 48” x 4” motor tube, which I am not using at this time, as I built mine with a cluster of three 75mm motor tubes, of which I also purchased separately. Before I started any construction, I sanded the exterior of all parts to allow superior paint and epoxy adhesion.
Fin Can/Booster Section Prep
Obviously this kit is constructed with a fin can. Fin cans are fine, as these are made of carbon fiber, and are therefore very strong, but, they can be brittle. I am not a fan of hollow fins, so I decided to fill all the fins in with epoxy. DO NOT use expanding foam, as the rapid expansion most likely will crack the fins from the pressure developed during expansion of the foam. Epoxy, on the other hand, will turn them into a rock-hard mass, and they will become incredibly strong. The fin can will also be considerably heavier due to the weight of the added epoxy. On the inside of the fin can, one can see the “dimpled” area. This area is where the carbon fiber cloth gravitated into the hollow area between the fin halves during construction of the fin can. Using a Dremel tool, I routed out all the carbon fiber so I could see into the fin cavity.
I then set up and leveled the fin can, as well as taping all the edges of the fins and putting a plastic bag over one of the fins and setting the fin in water. Why put tape and bags over the fins? Because sometimes there are small openings in the fin cavities and epoxy will gravitate out. The tape prevents epoxy from seeping out, and the plastic bag keeps the tape and fins dry. When pouring epoxy in the fin cavity, excessive heat will be generated from the curing epoxy, so keeping the fins cool is a must. Since this fin can is quite large, it took me several days and several pours of epoxy to completely fill all four fins.
I use West Systems epoxy throughout all my builds, due to its incredible strength and ability to never fail. I mixed #404 adhesive filler with the epoxy to make a syrup-like consistency so it is pourable. Adding fillers dramatically increases the strength of the epoxy and thickens it to whatever consistency is desired for the application. I decided to build this rocket with interchangeable motor mounts, so I centered a 7.5” x 48” G-10 tube inside the fin can and the aft airframe. Notice in the photo the 4 “thin” centering rings.
The thicker one on the right is the forward top centering ring to center the 7.5” tube inside the 9.25” aft airframe. The three on the left are the centering rings to center the 7.5” tube in the fin can, two rear, and one at the top of the fin can. The bottom bulkplates are the altimeter bay ends, which will be detailed later. The aluminum rings in the photo are as follows…
the upper center ring was made to sit on the outside of the fin can. Notice the four holes in this ring. These holes are tapped for ¼” #20 threads, to accept the other plates in the photo. The left ring is for a cluster of three 75mm motors, the right is for a 98mm motor, and the bottom center is for a 150mm motor.
The next photo shows me drilling the rear fin can plate with 3/32” holes.
I drilled 12 holes, three each evenly spaced between the ¼” holes. These holes are used as a template to perfectly position twelve 10/32 threaded inserts into the rear wooden centering ring on the 7.5” tube. In this manner, the rear aluminum ring can be removed if need be.
What I do anytime I need something to line up perfectly, is set the piece in place. In this case, it is the rear aluminum ring. I make an index mark on both the rear wooden centering ring and the aluminum ring so both pieces can be re-aligned perfectly. After the aluminum ring has been drilled, I then re-position it onto the fin can in the proper position, and run a drill through all the holes to mark the wooden rear centering ring. The rear wooden centering ring now has sixteen marks. Twelve of them are drilled to proper size to install twelve 10/32 threaded inserts. The other four are drilled large enough to allow a ¼” #20 screw to pass through, which are the tapped ¼” holes in the rear aluminum ring, which are the mount holes for the interchangeable motor mount assemblies. Notice the 7.5” tube is “proud” of the rear centering ring. This dimension is the exact thickness of the rear aluminum plate. The following photo shows the 75mm cluster plate mounted to the rear aluminum plate.
Before the 7.5” tube can be permanently installed in the fin can, allowance had to be made for fastening of the rail button stand-offs. I made the stand-offs out of hard maple.
I drew free hand, what I thought looked like a good angle onto 1-1/8” thick maple. The height of the maple stock was 4”, to allow for the bulging nose cone to adequately clear the launch rail. I then drilled holes in a position that dimensionally was half way between the top and bottom angle, right down through the maple stock. These holes were drilled with a brad point bit to prevent “walking” and provide a very cleanly drilled hole. I drilled these holes 5/16” to allow some play when fastening them to the airframe. In the center on top, I then drilled a 17/64” hole for the unistrut rail button bolt. Next, I flipped the maple stock over, and used a ¾” forstner bit to drill a “flat bottom” hole in the center of the 17/64” hole for the insertion of a ¼” tee nut to tightly fasten the rail button to the maple stand-off. After all holes were drilled, I then cut the stand-offs out of the maple stock on the table saw. Finally, I used another 5/8” forstner bit to drill flat bottom holes for the screws to fasten the stand-offs to the airframe. I then contour-sanded the bottom of these stand-offs to conform to the curvature of the airframe. After sanding the radius into the bottom of the stand-offs, I epoxied ¼” tee nuts into the bottoms of the stand-offs to fasten the rail buttons. Now that the stand-offs have been completed, the mounts can be constructed inside the fin can and the aft airframe. I marked one of the stand-offs to be aft and the other to be forward. I used the appropriate one to mark the fin can in the proper position, then drilled the 3/32” holes. I epoxied a small flat piece of oak over the 3/32” holes on the inside of the fin can. After the epoxy was dry, I drilled out the 3/32” holes with the proper size bit to install and epoxy ¼” tee nuts in place. After the aft airframe was epoxied to the fin can, I did the same thing for the forward stand-off on the aft airframe. The one thing to remember when doing this is an airframe that houses a recovery harness, is to make sure the entire mount has a low enough profile as not to snag any recovery components. I now mounted the rear aluminum ring to the rear wooden centering ring on the 7.5” tube and epoxied the tube in place. The rear aluminum ring will properly position the 7.5” tube. I stood the assembly up and poured epoxy onto the top centering ring at the top of the fin can. At this time, I also epoxied the centering ring near the top of the 7.5” airframe to center itself inside the 9.25” aft airframe.
Next step was to epoxy the aft airframe to the fin can. I decided to use a full 48” airframe on top of the fin can due to the length of the 7.5” motor tube and to allow enough room for the apogee recovery components. I roughed up the inside of the one end of the aft airframe to allow better adhesion with epoxy to mate with the fin can.
Sanding G-10 with a 60 grit sanding drum in a drill makes a real mess, and it is hazardous to breathe, so I insert the 2” shop vac hose from the other end to suck up all the dust while sanding. Just as a tip, there is no other more effective and efficient way to “rough up” G-10 airframes. I usually use an extension arm as can be seen in the photo, but also use a glove, as holding the spinning extension arm gets real hot real fast!
One last assembly was necessary for the booster section. Looking down the airframe from the front, there is only a very thin centering ring holding a 7.5” tube. There is no “U” bolts or anything to fasten the booster section to the altimeter bay. The centering ring made to center the 7.5” tube inside the 9.25” airframe did not have enough “body” left to make an efficient mount, and if so, it would be too close to the airframe wall. I made another centering ring to fit inside of the 9.25” airframe. I took two pieces of the ¾” Baltic birch, 10” square, and glued them together to make a piece 1-1/2” thick. I cut out a bulkplate on the bandsaw, sanded it to fit, and mounted two ½” thick “U” bolts to the plate. I also drilled a 2” hole in the center of the bulkplate. The 2” hole serves two purposes. One, if the motors should be too tight to remove, I can insert a wooden dowel through this hole to push out the motors, even though this entire motor mount assembly is removable. Two, as will be explained in the construction of the motor mount assembly, it serves to be an additional mount via a threaded rod for the motor assembly, and it will also prevent the bulkplate from being dislodged at apogee separation. On large and heavy rockets, I feel safer knowing there is a piece or pieces of threaded rod holding that bulkplate to more of the booster section. This was the only way to physically use a threaded rod on this project. Since the centering rings are too slim due to the 7.5” tube for the interchangeable motor mounts, none could be run through the rings, so one had to be used in the center. The only difference in the future is if I decide to make the 98mm and the 150mm motor mounts, the threaded rod will have to be threaded to the forward closure, which would work in the same manner. The bulkplate can be seen in the photo below.
75mm Cluster Motor Assembly
I began construction of the 75mm cluster motor assembly by initially making the centering rings. I made three rings out of ¾” Baltic birch. 1st thing is to make all three rings slide smoothly into the 7.5” tube. Very important… all three rings must be indexed, so they are always constant and in alignment with one another. Again, I marked them, aft, center, and forward. I used the aft ring to drill out the holes for the motor tubes, then sand them to the proper fit on an oscillating spindle sander. I then drilled a 1/2” hole, dead center in the aft ring. Once the aft ring was complete, I used it as a template for the center and forward rings. After all three centering rings were completed, I stacked them together, lining up the index mark and clamping them together. I now index marked one of the 75mm motor tube holes on all three plates. Reason for this is to facilitate a straight assembly of the cluster tubes. I now took one of the 75mm motor tubes and drew a line down the length of the tube. I used my table saw fence as a guide to set the line parallel to the tube as it lay on the table saw. Using the aluminum plate with the three 75mm Aeropack retainers, I inserted all three motor tubes into the plate and drew a line around them where they bottomed out. This line would indicate where the aft centering ring location would be. The next step was to take the 75mm motor tube with the vertical line and epoxy the aft, center and forward centering rings in place on the line. After the epoxy set, I epoxied the other two 75mm motor tubes in place, then followed up with epoxy fillets on all the tube/ring joints. Once again, I took the 75mm cluster aluminum plate, set in place over the three 75mm motor tubes, and against the aft wooden centering ring and drilled three holes through the plate and through the wooden centering ring. These three holes will be to mount the 75mm cluster tube assembly to the motor retainer plate. I drilled 9/32” holes in the aluminum plate and then beveled the aluminum plate for the flat head machine screws. Next was to install ¼” tee nuts in the aft plate to receive the aluminum plate.
I then cut a piece of ½” threaded rod and installed it down through the center. This completes the 75mm cluster motor assembly.
Altimeter Bay Assembly
In an earlier photo, both altimeter end plates are shown at the bottom of the photo. The following photos show the end plates in greater detail. Notice the “step” on both end plates. This is another ½” plate glued onto a ¾” plate. The step stops the ring against the coupler/altimeter bay. All the lines and markings on the plate are simply indicators as to where my all thread, BP charge cups, wire connectors and “U” bolts are located.
After marking all the locations, I drill 1/8” holes through one of the plates. I then align the plates opposite one another, clamp them, then drill a ¼” hole through the center of both plates. I insert a ¼” bolt through both plates and tighten them together with a hex nut, then remove the clamps. Now the plates are perfectly aligned and set-up together as they will be when assembling the altimeter bay. Again, make a vertical index mark so orientation remains constant during altimeter bay assembly. Now drill through all the previously drilled 1/8” holes with an 1/8” bit to mark the other endplate. The ¼” bolt can now be removed, and all the proper size holes can now be drilled in their respective locations.
I build all my altimeter bays with the aft end plate epoxied to the coupler, while the forward end plate removes to access the altimeter sled. Notice in the next photo how I “countersink” the threaded rod assembly holes on the inside of the forward plate. This guides the threaded rod through the holes when assembling the altimeter bay.
The photos below show the completed altimeter bay parts. 1st and 2nd photos shows the forward endplate. The “M1” and “M2” are main parachute indications from altimeter one and altimeter two. I stamp these impressions into the plates, outline them with a marker, then clear coat the plates with epoxy. The stainless steel screws and hex nuts are to fasten the e-matches. I drill an 1/8” hole in the side of the PVC charge cups at the bottom between the stainless steel screws for insertion of the e-match wires. I then wrap the e-match leads around the PVC cups a few times and fasten them to the screws. The inside view of the endplate shows the wires leading to a modular plug, which plugs into the wire harness on my altimeter sled. The last photo shows the inside of the coupler/altimeter bay assembly. Notice the wooden slats positioned vertically around the inside perimeter. These wooden slats, along with the stepped end plates will never allow the altimeter bay to be pulled apart once the threaded rod is through the plates and fastened.
I used a full length coupler to make the altimeter bay. All my altimeter bays have ¼” threaded rod positioned 4” apart on center to hold my altimeter sleds. In this manner, I can use any sled in any rocket. Attention to detail is very important in the construction of rockets to insure reliability and efficient operations. For my sampling holes, I drilled two ½” holes 180 degrees apart, so essentially, you can look straight through the altimeter bay.
The obvious unique feature of the Honest John is the shape of the nose cone.
The real Honest John has eight (8) small thrusters, in groups of two, set at four locations 90 degrees apart on the perimeter of the nose cone. When the missile leaves the rail, these eight thrusters fire, spinning the missile as it accelerates to provide better ballistic accuracy. So I decided to attempt to create some realism with this project. After epoxying and filleting the molded fiberglass “thrusters” in place at 90 degrees around the perimeter of the nose cone, I drilled holes in the face of the thrusters with a forstner bit to accommodate a 29mm motor tube. As I drilled through the face of the thruster piece, I carefully kept drilling right through the nose cone. Caution must be exercised not to excessively and aggressively drill the nose cone, as the nose cone could shatter, since the angle of attack with the forstner bit is at a sharp angle. Using a forstner bit for this angle of drilling provides the best results, as forstner bits are designed for this. Due to the rise of the thrusters, a 29mm motor tube was the maximum size I could use. Next step was to cut the 29mm G-10 motor tubes. The maximum length of the motor tube could only be 6-1/4”, as at this length, the motor tube would sit 3/8” proud of the thruster face, and the other end would contact the interior circumference of the nose cone. After all four tubes were cut, I then epoxied and filleted them into place. Small 5/32” holes were drilled next to each of the 29mm motor tubes for the e-match wires. Other than the rear bulkplate in the nose cone, I wanted to have another bulkplate just forward of the four motor tubes in the nose cone. The diameter of the interior of the nose cone shoulder is 8-3/4”, and I need to make a bulkplate 12” in diameter to sit where needed. Obviously installing a 12” bulkplate through an 8-3/4” opening is not going to happen. The ticket here is to make the bulkplate, cut it in half, and hinge it. This way, it can be folded, opened in place, and epoxied in place. I also drilled larger holes in this bulkplate and lined them up with the smaller holes in the rear bulkplate in the event I needed to add weight and/or expanding foam into the nose cone. After these steps were completed, I epoxied the rear bulkplate into place, with a ½” “U” bolt already installed. In order to light the 29mm thruster motors, I decided to use an Xavien XCIC-1 cluster igniter module. The Xavien XCIC-1 module is designed to initiate at 2.1 G’s, so in this manner, the four Aerotech G80 Blue Thunder motors will most likely light just as the rocket clears the rail. An assembly had to be constructed to house this module and a 9 volt battery. I made the housing out of a short piece of 1-1/2” PVC pipe, an end cap and a threaded end cap. Orientation of the module is important due to the on-board “G” switch, so I made small pieces of G-10 to hold the module and battery in place, then screw the cap in place to secure everything. E-match wires enter at the base of the module housing then attach to the module.
Arming of the module will be via an access hole through the airframe and shoulder of the nose cone. Fourteen #4/40 shear pins will secure the nose cone. Fourteen is more than necessary, but I do not want any influence from the nose cone thrusters to spin the nose cone in the airframe.
The rocket stands 14’ tall, will weigh 155 lbs. at the pad, and it will fly on three (3) Aerotech M1315 White Lightning motors, which will all be lit with thermite on the pad. Predicted altitude is 7100’. Maximum velocity will be approximately 227 meters per second or approximately 507 mph, with maximum acceleration at 5.73 G’s. A 7’ ballistic drogue chute will be deployed at apogee, and the 22’ main will be deployed at 1100’ with a back-up at 900’. Nose cone will descend on its own on a 10’ chute. Initial flight will be at MDRA’s Red Glare VII launch in the fall of 2009.