Marvin Martian Jr. Build

Discussion in 'High Power Rocketry (HPR)' started by jmmome, Dec 21, 2019.

Help Support The Rocketry Forum by donating:

  1. Dec 21, 2019 #1

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Creeping along with my half-scale build (approx.) of The St. Louis Kaboom Krewe's 10 feet tall "Space Oddity", which was launched at LDRS 38. My version will be 5 1/2 feet tall, 24 inches at the fattest body diameter, and a 48 inch fin wingspan. It should weight south of 50 pounds.

    First thing I wanted to figure out was the round ball at the top of the rocket. Because I'll be using a launch rail tube for a 1515 launch rail (the 48" long tube will be epoxied to the full 48" length of the 4" dia. Blue Tube internal motor/parachute tube), the ball on top could be no larger that 4" in. diameter.

    I found hollow 4" stainless steel hemispheres on the web- each with a 1/8" dia. weep hole in them. I drilled the weep hole with a 1/2" metal-cutting drill bit to accept a 1/2" dia. all-thread rod. I'll fill each half with BB's and epoxy for added weight and J-B Weld/ bolt the halves together on the all-thread rod.

    I'll mate this assembly to a 2.56" dia. Blue tube (probably 13" long) also filled with BB's and epoxy. Once i cut and weigh the three 1/4" thick Baltic Birch plywood fins, I'll have a better idea of the total nose weight necessary.

    I'm going to drag out this project build throughout 2020, and I'll post updates periodically. Plan is to fly it at the 2021 Midwest Blast at Three Oaks, MI.
    78258198_1000978586918371_2052598693625856000_n.jpg IMG_4750.JPG 69645405_1395081477299920_6309345183032934400_o.jpg
     
    dshmel likes this.
  2. Mar 8, 2020 #2

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Made some progress with the build. Had to make sure I could get it out of the basement, so I'm constructing it as a fin/motor section, an upper body/parachutes section, and a elongated nosecone section. The two bottom sections will be bolted together at the launch site.

    The first pic will give a general idea of what the finished product will look like, minus the finlets. The rocket will stand six feet tall, the body will be 24" at the widest point, and the three fins each extend another 12" past the widest body diameter. The center 24" diameter plywood circle is of 1/2" Baltic birch 9 ply plywood, as are the fins. Fiberglassing of the fin/4" dia. Blue Tube body tube joints is to come, as well as the fin/fore & aft plywood circle joints. Corner braces will also be used to support the fin/plywood circle joints. The bottom of each fin leg will be a triple ply of the 1/2" plywood, and will extend several inches north of the smallest fin width.

    The smaller 2.56" dia. Blue Tube will slide over a 1515 launch rod. The 4" dia. steel hemispheres filled with epoxy and BB's will top the 14" long nosecone section. So far, that component weighs in excess of 7 pounds, with the expectation of filling the 2.56" central nose cone tube with more epoxy & BB's to achieve the proper rocket CG.

    1" thick foam board circles will be cut and sanded to achieve the overall shape. A fiberglass skin will be applied over the foam. One altimeter and one timer will be placed in a cavity forward of the 24" dia. central point (most likely a section of sealed body tube with sampling port holes leading through the exterior skin). Separate parachutes will bring down the nose cone section, which could weigh 20 pounds, and the rocket body section. The fin/motor section currently weighs 21 pounds. An L1520 Blue Thunder reload should push it off the launch pad nicely.

    All comments/suggestions are welcome!!
     

    Attached Files:

  3. Mar 15, 2020 #3

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Fiberglassed the fin connections to the 3.9" dia. Blue Tube, as well as to the 24" and 12" upper and lower centering rings on the fin/motor tube section (I guess I can call the rings that). I ended up using Bob Smith 20 Minute Finishing Epoxy for this fiberglassing step. I will use West Systems epoxy for fiberglassing the "sort-of-football-shaped" body. Installed steel corner braces between the fins and the upper & lower centering rings.

    Now it's time to cut the 24" centering ring which will serve as the base for the 28" long parachute Blue Tube and the attached 1515 rail tube. The two 24" centering rings (and thus the lower and upper body sections) will be secured together using six 1/4" pronged T-nuts installed and spaced equally around the top 24" centering ring, as well as 1/4" bolts, washers, locking washers and nuts through to the bottom 24" centering ring. This assembly will take place in the field so that I can get this rocket out of the basement.....lol.

    So far, so good. The cutting of the 1" foam insulation concentric circles which will make up the basic body shape will be a new experience for me. I will try an electric wire cutter, with the jig saw as the back up plan in case that doesn't work efficiently. Thinking of maybe mounting the concentric foam circles together on a spindle turned by my hammer drill so that I can sand them down to the football shape. That will be an outdoor activity when it gets warmer!
     

    Attached Files:

    grouch likes this.
  4. Mar 17, 2020 #4

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Assembled the middle section of the rocket, which is the 28" long parachutes/1515 guide rail tubes, epoxied to another 24" diameter "centering ring". Ive shown it sitting off-center on the bottom fin section of the rocket. I'll fiberglass the tubes to the centering ring for added strength.

    The two 24" dia. centering rings (and thus the lower and upper body sections) will be secured together using six 1/4" pronged T-nuts installed and spaced equally around the top 24" centering ring, as well as 1/4" bolts, washers, locking washers and nuts through to the bottom 24" centering ring.

    My historical rocket collection can be seen in the background- 7 feet tall Gemini-Titan, Apollo-Saturn V & ""stretched" V-2 custom builds, as well as the pyramid-shaped McDonnell Douglas "Delta Clipper".

    The nose cone section, with it's 4" dia. steel hemisphere topper, will be built after I weight the finished rocket product and know how much nose weight to add to the rest of the nosecone section, which will be about 18" long total.

    IMG_4766.jpg
     
  5. Mar 21, 2020 #5

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Built and installed the two charge wells, along with a 3/8" eye bolt and the igniter connectors at the top of the fin/motor section. Had to drill through the motor tube to fish through the igniter connector wires, so they can be channeled up to the middle section, which will contain an accelerometer altimeter and a baro altimeter. Still have to figure out how to create a removable door which will fit the curvature of the rocket for the avionics bay, but I have an idea or two.

    Next step is to start cutting the 1" foam board circles which will be eventually sanded down and covered with fiberglass cloth to create the "skinny football" rocket body shape. Already calculated the differing diameter for each foam piece to achieve that end.

    "Delta Heavy Lander" is in the background of the second pic. This 6 foot tall rocket will have four deployable landing legs during descent, as well as two side pod "retro rockets' which will fire an 8 second reload with black exhaust and almost no thrust, but hopefully will be eye-catching during final descent. Drogue chutes deploy from the top of the side pods. LOTS of failure possibilities with this rocket, but I think (hope) I can make it work.

    IMG_4768.jpg IMG_4767.jpg
     
  6. Mar 23, 2020 #6

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Made some progress with the 1" thick foam board internal shaping pieces. Started cutting the 24" x 24" pieces by hand, but eventually figured out that using a jig saw, with a tongue depressor taped to one side of the guide, would give me the bevel I need from piece to piece. 5 layers done on the bottom section of the rocket; 15 to go until the layers will meet with the motor "bell".

    I'm using the simplest of tools to make the ever-reducing circles- half of a yardstick with a screw as the pivot, and a thinner #2 screw as the scribe. Based on my calculations for the arc of the body curve, I keep drilling holes for the scribe screw closer to the pivot screw.

    For these bottom section pieces, I cut a 4" hole in the center of the foam board, and cut the foam circle into three pieces to fit between the fins. 1/2" is removed from each foam piece to account for the fin thickness. The two openings in the foam board between each fin pair will allow me to connect the bottom fin/motor section with the middle parachutes section by means of six washered wingnuts. The rocket is too wide to get out of the basement in one piece.

    IMG_4769.jpg IMG_4771.jpg
     
    Speaknoevil likes this.
  7. Mar 25, 2020 at 2:50 AM #7

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Made some more progress cutting the concentric foam pieces which create the shape of the fin/motor section. Four more foam pieces to go, then I can create and mount the "engine bell nozzle". Laying the fiberglass cloth over the foam will then follow.

    I have found that using deck screws to attach one foam piece to the next works well, as I can easily realign a piece if necessary, as opposed to epoxying them together.

    The particles from cutting the foam board have been a real nuisance. And I'll have even more concentric pieces to cut for the parachutes section, but that will have to wait until after the Ohio "shelter in place" order is called off, as I have only enough board for the remaining four bottom pieces.

    IMG_4772.jpg
     
  8. Mar 27, 2020 at 2:44 AM #8

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    The 1" foam circles are finished for the lower part of the rocket. I made an "engine bell" from an old brown plastic flower pot and fiberglassed it inside for reinforcement. Tomorrow I'll epoxy a 6" to 3.9" centering ring inside it, epoxy a like-sized centering ring to the motor tube at the base of the lowest foam ring, and screw the two centering rings together to secure the "engine bell" in place. The bell will be painted with heat-resistant paint inside and out, although the actual motor nozzle will be flush with the opening of the bell, and the bell is 12" in diameter, compared to the motor's 3" diameter.

    I'm going to try a shortcut for the skin of the rocket. I'll Five Minute Epoxy a precut triangular (more or less) piece of fiberglass cloth to the 1/2" thick edge of the top plywood circle. The piece will stretch between two of the fins. Once dry, I'll see if I can stretch the fiberglass piece to take on the curvature of the foam pieces, and epoxy the bottom of the fiberglass piece to the 6" to 3.9" centering ring at the bottom. If it all seems to fit well, I'll then simply "paint" laminating epoxy on the outside of the fiberglass sheet. I'll probably use an additional 2" wide strip of wetted fiberglass to create a seam between each fin and the rocket body's fiberglass skin.

    IMG_4773.jpg
     
    Greg Furtman likes this.
  9. Mar 28, 2020 at 2:57 AM #9

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    Had enough fiberglass cloth left to cover 1/3 of the bottom part of the rocket- more on order through Ebay. I "5 Minute" epoxied the cloth to the 1/2" thick plywood circle forming the top of the section. When dry, I painted some epoxy half way down the fins where the foam pieces meet them, and held the fiberglass in place until dry. I repeated the process for the second half of the fins, as well as the lower foam pieces down to the central motor tube. I tried to keep the fiberglass cloth taut during each step.

    I still have to strip off some excess cloth at top of the plywood piece, but so far, this method seems to work. Tomorrow I'll try to "paint" on a coat of laminating epoxy onto the cloth to stiffen it up. Hopefully, the tautness will hold and keep the conical shape it currently has.

    Before I do that, I'll slit the fiberglass cloth covering the two openings (just below the plywood circle) where the middle rocket portion will attach to the bottom portion with washered wingnuts, and epoxy the cloth inside the openings. On fight day, I'll probably simply cover the openings with silver duct tape, unless I come up with covers which contain flashing lights or some other silliness.

    IMG_4775.jpg
     
  10. Mar 28, 2020 at 3:07 AM #10

    Speaknoevil

    Speaknoevil

    Speaknoevil

    Well-Known Member

    Joined:
    Mar 18, 2018
    Messages:
    794
    Likes Received:
    314
    I am surprised at how smooth that came out. I am used to stacking foam and cutting with a hotwire to get a smooth transition between pieces. Yet in your case each piece was cut separately and you are spanning the gaps with the cloth. What is that surface like? Is it soft/spongy in the gap areas? BTW, not a bad thing in particular, as no force/pressure will be on that area.
     
  11. Mar 28, 2020 at 12:14 PM #11

    jmmome

    jmmome

    jmmome

    Forum Supporter TRF Supporter

    Joined:
    Jan 11, 2013
    Messages:
    311
    Likes Received:
    52
    Gender:
    Male
    Location:
    Maumee (Toledo) OH
    It's quite taut in the gap areas, because I pulled it tight as the 5 minute epoxy at the fin/foam joints dried. i only epoxied 5 to 6 inches at a time down the fins, so I could keep it all tight.

    When applying the laminating epoxy, I'm going to use a "light touch" with the brush. Probably do a couple of coats.
     
  12. Mar 28, 2020 at 2:13 PM #12

    Speaknoevil

    Speaknoevil

    Speaknoevil

    Well-Known Member

    Joined:
    Mar 18, 2018
    Messages:
    794
    Likes Received:
    314
    Cool.
     

Share This Page

Group Builder