1/4 Scale Viking 7 sounding rocket

Discussion in 'Scale' started by GalantVR41062, Jan 6, 2020.

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  1. Jan 6, 2020 #1

    GalantVR41062

    GalantVR41062

    GalantVR41062

    Celebrate Recovery TRF Supporter

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    I have decided that I have rockets in the build pile that will go super sonic, and run up close to the 20,000' waiver at the local Tripoli high power rocket launch site in North Branch Minnesota. I also have a 1/2 scale SLS ARCAS that I built and fly, the only thing out of place are the launch lugs, vent holes, screw on retainer, and no air foiled fins.

    I also could do some larger motors in MD projects and push the limits with L's and go to Kloudbusters.
    I also watched a few youtube videos of large projects flown here in MN: Old Yeller, scale Nike, Good Enough. I am inspired by maximum performance multi stage projects but my rocketry budget can not support those ambitions so I am going to go down this path and see where it takes me.

    I feel I have a lot of room to grow into the L2 motor line up and I need to learn a lot more to justify the L3 dedication, I am on the path to get it at some point.

    For my current OR files I have focused on making the air frame as accurate as possible out side dimension wise to get a more accurate CP location, then I can deal with the CG and total weight out side the simulation. I just started my HP rocket flying in 2017, I flew rockets with my Dad years ago, nothing larger then a C though.

    I like the accurate recording or flight data, pictures, video from the ground, at the pad looking up, onboard video, a straight column of smoke rising into the blue sky, going by a few clouds on the way just like the final flight from October Sky as viewed from the hospital room.

    I promise there will be a build thread in here somewhere.

    Then walking through Home Depot racing, I come from a automotive background and making them go fast, and see concrete form tubes and like any other BAR I started thinking of how I could turn all things into something rocket related. The 8" form tubes were calling me as to itch the how big could I make it part. I was able to hold off on buying parts for a while but gave in this summer.

    I will start with a over view of the project, what I think it should be and my plan to get there. I could use help in processes, technique, scale details, fin flutter, a more complete model and simulation with Open Rocket, mainly rail guide length, wind, simulation of chutes to be used and decent rates.

    I don't know how but I stumbled on the dimensions and design of the Viking 7 sounding rocket. I then figured out I can do a 1/4 scale version with 8" diameter tube, 143" tall, 4 fins with a fin span of 27.5", with the "Tab" on the fin corner.

    I pulled the wax layer from the inside of the tubes and plan to sand the outside. I am going to double layer the airframe, I will cut a strip out of the 8.325" od tube and glue that to the inside of the 8" od tube.

    I will have the inner tube stop 8" before the top of the booster and start 8" into the payload so the coupler will sit on the inner tube.

    I also double walled the coupler, and the av bay lids will sit down inside the coupler on top of the inner tube.

    I am going with a 98mm mmt and have a 98mm Slimline retainer.

    I have 1/2" plywood to cut centering rings, and make the fins, do a layup of fiberglass or figure out stronger material if needed.

    I will be making the nose cone as well, it's only a 2.6:1 so I will make a plywood x structure and hobby foam pizza slices to make up the shape. Then fiber glass over the top. I will have a spot in the nose for a tracker and room for weight, up to 50-60oz and a HD video camera of some kind.

    OR and thrust curve are showing a all up weight of 55lbs with a 98mm L, it could fly on a 54mm AT K1275 est 1150' apogee. The AT L1500T or AT L2500ST will be what I am building this for, looking at 3700'.

    It will be dual deploy, with a large drogue and main chute. I loaded up the OR file also, I did find the spot to adjust the launch parameters.

    ~John
     

    Attached Files:

    Last edited: Jan 13, 2020
  2. Jan 6, 2020 #2

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    More pictures and the start of the building process.

    I show the fin tab in the OR file but I think I will make them removable so the fin is less likely to be damaged during recovery.

    The paint scheme is fairly simple white and black so I will try to mimic that the best I can.

    I have been picking up parts in the yard sale and other places, I will gather all I have and update with another large post outlining the build material, recovery components, electronics etc.

    ~John
     

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    Last edited: Jan 6, 2020
  3. Jan 9, 2020 #3

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    I was working on the booster section. I have the tubes cut to length, wax peeled and I just need to start gluing the air frame together.

    I was test fitting the 4' inner section that will connect the lower and upper tubes making the 6' booster and my cut was not very straight and not wide enough so the tube became stuck.

    After a while of trying to pull it out I ended up stepping on it and it tore on the spiral seam and I pulled it out.

    I learned the tubes are not that strong in this area and the coupler I made being double layer the seam does not line up and the structure feels a lot stronger. So as I glue the other split tubes into the 8" OD tube I will look to make sure the seam does not line up.

    I then marked 1/2" up the inside of the bottom booster tube and glued the 24" section inside the bottom of the tube. Next I will glue a 38.875" section, then the 24" top tube to make the complete booster tube.

    I also glued the 2.625" wide switch band onto the coupler.

    Here are a few pictures of the parts I have been gathering: 1/2" plywood, I will look at aircraft quality plywood for the fins, but this 1/2" interior plywood will work well for the centering rings, bulkheads etc. I have a jigsaw I bought and will either make or buy a hole cutting fixture for it. I also have some thin wood strips if I feel the need to brace between the mmt centering rings and or make fin tab pockets. I did buy a whole gallon of TB2 wood glue, I will be using a lot on this project. 98mm Slimline retainer.

    5/8" tubular Kevlar, 5/8" tubular nylon, nomex squares, drouge: 144" sphere chute, main: Skyangle Cert 3 XXL, copper caps and pvc caps, I have a hand full of electronics and will use a ARTS 2 altimeter, and a MW RRC2+, MW T3 GPS tracker, and or Communication specialist RF tracker. I plan to split the airframe in the middle at apogee, and backup at +2 seconds, then main at 1000', and backup at 800'. The payload tube will be attached to the eBay lid with SS screws, 8 total, and I will use 3-4 nylon sheer pins to hold the nose cone on.

    I will do a Kevlar Y harness off the mmt to a HD swivel, then the 5/8" tubular nylon 36', then another section of Kevlar, about 2' hooking up to a 3/8" SS U bolt on the eBay. The drogue will attach 8-10' down from the ebay, the main will attach to the quick link on the nose cone end of the main harness. I will be getting 2 deployment bags.

    The main will also have a Kevlar harness, 6' long, hooked up to a 3/8" SS ubolt on the top of the ebay. Then another section of 5/8" tubular nylon, 36', that will attach to the nose cone base with another 3/8" SS ubolt. I will use my sewing awl to stitch the loops together. And use 3/8" SS quick links into the booster, eBay and nose cone.

    ~John
     

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  4. Jan 13, 2020 #4

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    I started on the nose cone base. I cut a 10" length of the tube that fits inside the 8" od payload tube, then glued a piece to the in side of that making it flush on the bottom.

    I then glued a 2" chunk of the 8" od body tube towards the top of the nose cone base, having 8.125" slide into the payload tube, the same for each end of the Ebay coupler. This will be my transition for the 2.6:1 nose cone. I also cut out a cardboard mockup to slide into the nose cone base.

    I also took a stab at the dimension on the fin tab sticking out of the bottom corner or the fin and cut a cardboard mock up, then setup the rocket to get a feel for the scale, and looks so far.

    I will be setting up to cut centering rings and bulk heads this week. I will do research on the size of the recovery mounting gear, but I am thinking: 3/8" SS U bolts (2) for the booster mounts, then a single 3/8" SS U bolts for the Ebay bulk heads, and nose cone base.

    I have updated the OR file with a more scale version of the fins, based on the pictures or the actual rocket, and the pictures of the model rockets available on the market. The Fin tab is a little higher up, and a notch on the trailing edge of the fin. In the pictures the outboard edge does not look to run parallel with the air frame, but angles out slightly.

    I will keep looking at pictures and try to figure out the external details on the rocket and add them the best I can.

    ~John
     

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    Last edited: Jan 14, 2020
  5. Jan 18, 2020 #5

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    I was able to get the main body tubes glued together, I had to add 1 1/4" to the inside of the payload tube as I somehow missed the mark for the length on the inner tube to have the Ebay lid and nose cone base sit on the inner tube.

    I stacked about 100lbs on top of the booster tube as the glue setup. I have used 3 TB2 squeeze bottles so far.

    I will be adding a 1/2" thick plywood centering ring to the top of the booster tube to help the structure stay in shape over time and flights. It will be about 3/4" wide and sit on top of the inner tube.

    I trimmed the card board fin mock up for the updated OR file.

    I also started cutting the pieces to make the nose cone structure, 1/4" thick ply wood. I need to sand to shape, cut some holes, setup 2 nose cone compartments and start cutting hobby foam pizza slices to make the shape to be covered in a couple layers of fiber glass. The 2 compartments will be in the nose cone shoulder area opposite each other in the X structure. One will be for GPS or other tracking solutions and the other will be available for other electronics or video down the road.

    I marked and started cutting centering rings, I need to cut the hole for the 98mm mmt, and sand to fit the rings, bulk heads.

    ~John
     

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    Last edited: Jan 18, 2020
  6. Jan 18, 2020 #6

    gna

    gna

    gna

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  7. Jan 18, 2020 #7

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    Thank you. I did find the 2 threads you linked when I started research on the viking 7, that and seeing others work with sono tube I figured out the 1/4 scale option for the viking 7.

    There are a few more months of winter here in Mn, I could have this flight ready early in the rocket season.

    I have the AT 54/2560 motor
    Ellis Mountain 75/7000 snap ring motor
    Options to loan 75mm CTI hardware

    I will save money to get a AT 98/5120 motor

    I will be going to menards later today to look at the aircraft 1/2" plywood to make the fins.

    ~John
     

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  8. Jan 19, 2020 #8

    Ez2cDave

    Ez2cDave

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  9. Jan 23, 2020 #9

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    I finished cutting out the MMT centering rings, interior spacer rings and bulk heads.

    Now I just need to true up the OD of the CR's then mark and cut the hole for the 4" shipping tube that will make the first thick layer of the MMT, they are 24" long and I have a 4" x 31" MC body tube on order to make it the 3.9"/98mm MMT. I also picked up a 75mm mmt to make an adapter.

    I also started gluing the nose cone structure together, then I will sand to shape and glue into the nose cone shoulder.

    I glued a ring in the bottom of the payload tube, the Ebay lid should sit on the ledge, I will make all the attachment points and charge wells smaller then the 6" hole in the ring. I realized I could not do this to the top of the booster or payload tube as the recovery gear would have an issue coming out.

    So I will do a layer of fiberglass on the top inside of the booster and payload tube. This will help fill the gap from the ebay and nose cone shoulder, and help with the nylon shear pins as well.

    I decided to glue the bottom bulk head into the ebay coupler, I figured this would make for a more ridged anchor point as the rocket separates at apogee and descends on the large drogue.

    The payload tube will come off the ebay with some screws and the top lid of the ebay will be removable to gain access to the electronics

    Thank you for the photos they look amazing.

    ~John
     

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    Last edited: Jan 23, 2020
  10. Jan 25, 2020 #10

    GalantVR41062

    GalantVR41062

    GalantVR41062

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    I was working on the nose cone, cut and fitted a few bulk heads, made a centering ring that the bottom bulk head will bolt to, making a large area for nose cone electronics with no threaded rod to affect GPS or RF tracking.

    I cut 4 slots in the top of the nose cone base, slid the x structure in and spun it in the lathe at 70rpm, it looks fairly symmetrical.

    I started to cut the foam wedges, then I will use construction adhesive to hold them in place for the fiberglass layup on the outside.

    I also cut one of the 24" 4" shipping tubes so I will have a total of 42" of motor mount tube, then the 31" body tube will be glued inside these, with about 3/4" sticking out to attach the 98mm Slimline retainer.

    I also updated the OR file to reflect the changes in the nose cone.

    ~John
     

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  11. Jan 25, 2020 #11

    Ez2cDave

    Ez2cDave

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    Dave F.
     
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  12. Jan 31, 2020 #12

    GalantVR41062

    GalantVR41062

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    I cut the 4" shipping tubes to length and glued the 31" long 4" mmt inside. It almost made it to the mark but stuck, so I had to cut 1.5" off the bottom of the inner mmt. I needed 3/4" sticking out for the slimline retainer to sit in a 10ga aluminum thrust plate I will fabricate and attach to the aft CR.

    I think I will be doing 4 aluminum threaded rods to go from the thrust plate to forward CR, I can tie in the 2 U bolt anchors to distribute recovery loads to the majority of the lower air frame.

    The fins will be through the wall and I will be making a trough for the fin root to sit in on the MMT. I am still thinking the process on MMT assembly and instillation, I plan to glue and fillet the CR for the top of the fins, and the one in the middle top of the MMT, this would leave the top and aft CR off for interior fillets etc. I will try and plan to add the threaded rod after the MMT is glued, but before the forward and aft rings are glued in.

    I have been cutting foam for the nose cone shape and hope to be getting into fiberglass work this next week.

    I cut the 4 fins out all at once, minus the fin tab detail, I then used the jigsaw for the detail cuts. I am happy with the look and shape. I will be doing a simple airfoil shape for the fins, and am leaning to cutting the fin tab off, then fabricating aluminum airfoiled fin tabs that bolt on and are adjustable for the scale look, or try them to help with the roll of the rocket if its predictable.

    I made some more adjustments to the OR file, I have the rocket setup for dual deploy and single deploy for the smaller motors, the stability was high at 2.8 calibers on the AT K1275R motor. Adding a 54mm reducer for the MMT and moving the main to the booster and just have it single deploy with a JLCR if I feel I need to delay the main deployment, other wise the deployment bag and a slip ring on the main shroud lines could help get things deployed smoothly and moved the CG back to 2.2 calibers of stability. I think the 2.8 calibers of stability on the AT L1500 and L2500 will be alright as the motors will be hitting a little harder and getting it up to speed, is there a issue with running this high of a stability margin at subsonic speeds?

    I also removed the fin tab on the single deploy and it looks like that will move the CP and result in a 1.7 calibers of stability on the smaller motors.

    ~John
     

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  13. Feb 13, 2020 #13

    GalantVR41062

    GalantVR41062

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    I decided to use 1/4" zink coated steel threaded rod. It was cheap, available at Home Depot and will help move the CG back a little.

    I used the rods to mock up the rings, and glued the 2 centering rings in the middle. Leaving the top and bottom rings removable for now.

    I used my electric drill to thread the first nut to the middle, then did the others by hand. I used super glue to lock then into place. And tightened the nuts down on just the middle 2 rings putting the rods into tension a little. I secured the inside nuts for the top and bottom rings with super glue and just need to tighten the outside nuts once the top and bottom. Rings go on for the last time.

    I then marked the booster tube with the locations of the centering rings. I did this so I could tighten a strap around the ring as the glue dries, and I plan to run a few wood screws into the centering rings.

    I stood the booster up, slid the mmt in and covered 2 centering rings with a lot of wood glue and pounded the motor mount into place, then cinched down the aft ring to help hold things square and at the right depth.

    I will be doing a wood block backer for the 1515 rail guides I have. Just above the aft ring, and just below the top ring. I will be attaching the 2 5/16" SS U bolts to the top CR before I install that. I will use construction adhesive on the body tube and mmt when installing the top and aft rings, then use wood glue on the plywood ring OD and ID

    I did sand the nose cone plywood structure to shape, and I might make a solid wood nose cone tip, this would help to have a nice shoulder at the base, and the tip to start/stop the fiberglass.

    Up next: get the fins ready to install. Cut off the fin tab and airfoil the fins, mark fin slots and notch the booster tube, glue fins in, internal fillets, rail button mounts, top and aft centering rings install. Fiberglass nose cone and finalize recovery harness attachments. Start to plan out the Ebay.

    I also had a friend take my picture standing next to the rocket mocked up again with the plywood fins and nose cone.

    ~John
     

    Attached Files:

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