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  1. #1
    Join Date
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    EAC Viper XL build

    Like many of you, when I was a kid I was a member of the Estes Aerospace Club. I even made it to Skill Level 5! The rocket kit that came with membership was the EAC Viper. I've decided to build an upscale of it, based on 3" tubing. It'll be about 45" long, have 1/4" fins, and a 29mm motor mount. I'm building it with a zipperless design, that separates in the middle. It will also have a triple baffle system.

    You know, it dawned on me that a lot of my builds are very similar, with a lot of the same techniques used. But I'll keep posting build threads until you all get totally bored and disinterested in them.

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    NAR 91107, Level 2

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  2. #2
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    As usual, I started by cutting out the centering rings with a 3-1/4" hole saw. I cut three, two for the motor mount and one for the baffle plate that will go in the coupler. I mounted them on the wood lathe, and cut them to their final diameter. I cut the center holes for the motor mount rings with a 1-3/16" hole saw, and sanded them to fit the motor tube with my Dremel.

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    NAR 91107, Level 2

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  3. #3
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    I marked and drilled holes in the aft centering ring for the tee nuts that will be used for motor retention. I epoxied pieces of 1/8" plywood over the tee nut holes, because the tee nuts are 1/4" high. I also epoxied a piece of 1/4" plywood to the ring for the rail button to screw into. I pressed the tee nuts into the holes, and covered them with epoxy.
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    NAR 91107, Level 2

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  4. #4
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    I printed out a drilling guide for the baffle plate, and marked the holes with a center punch. I drilled the holes with a 5/16" bit. The center 1/4" pilot hole will get the eyebolt for recovery attachment. The baffle plate was epoxied into the coupler, about 1/2" from one end.
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    NAR 91107, Level 2

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  5. #5
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    Another of my favorites. I have fins cut for an original clone & an upscale in OR for Aerotech size (1.88").

    Watching with great interest!!
    Terry

    NAR L1
    L2 is on hold, maybe never

  6. #6
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    I had epoxied a piece of 1/4" plywood to the forward centering ring for the rail button. The ring was then epoxied to the motor tube, using a 1/2" piece of plastic pipe as a spacer to keep it level.
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    NAR 91107, Level 2

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  7. #7
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    Quote Originally Posted by T-Rex View Post
    Another of my favorites. I have fins cut for an original clone & an upscale in OR for Aerotech size (1.88").

    Watching with great interest!!
    Yeah, I loved the Viper when I was a kid. I remember it had a 13mm motor mount, because the mini-engines as they were called were less expensive. I wished at the time that it had an 18mm mount, but I wasn't clever enough then to modify it. The 29mm mount in this version should serve me well.
    NAR 91107, Level 2

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  8. #8
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    As I've done on my last several builds, I drilled and pinned the fin blanks so I could cut and match sand them all at once. It's been working out well, for 1/4", 5/32", and 1/8" thick fins.
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    NAR 91107, Level 2

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  9. #9
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    I pinned the canard fins and cut them out as well. After match sanding them, I cut off the scrap with the pins. The canard fins won't have tabs.
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    NAR 91107, Level 2

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  10. #10
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    I sanded all the main fins on the stationary belt sander. I ended up hand sanding the canard fins because of their small size. The two half moon shaped baffles were epoxied in the top of the motor tube.
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    NAR 91107, Level 2

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  11. #11
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    I flooded one end of the coupler with CA, then mounted it on the lathe and polished it with a sanding sponge and polishing pad.
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    NAR 91107, Level 2

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  12. #12
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    I also flooded the inside of the body tube with CA and sanded it smooth. Because I put the forward centering ring too close to the end of the motor tube, I cut an inch off the bottom of the coupler.
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    NAR 91107, Level 2

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  13. #13
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    Looks like a medium woodworking lathe is a requirement for building model rockets. Who knew?

    Gonna have this upscaler ready for Saturday after next's launch at Snow Ranch?

    Cranky Kong, Certified Rocket Monkey
    "But we were promised jet packs!"

    Total Impulse in 2017: 605.77 Ns (Equivalent to an 89% I motor)
    Total Impulse since 2010: 13,872.11 Ns (Equivalent to a 35% N motor)

  14. #14
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    I've discovered that since I've been a BAR, I've become very anal about some small details. I'm always worried about eyebolts coming loose. In this case, I used a toothed lockwasher and a locknut. But because the hot ejection gasses will hit the nut on the eyebolt, I was afraid to use a nylon insert locknut for fear the nylon would melt. I found some all metallic locknuts at Ace Hardware, and used one of them. To hold the nut in the socket while I started it on the eyebolt threads, I put a strip of paper in the socket.
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    NAR 91107, Level 2

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  15. #15
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    Quote Originally Posted by o1d_dude View Post
    Looks like a medium woodworking lathe is a requirement for building model rockets. Who knew?

    Gonna have this upscaler ready for Saturday after next's launch at Snow Ranch?

    No, you could probably use a mini lathe. LOL

    I want to get it ready for paint by Wednesday, which should be a warm sunny day. So yeah, I'm hoping it'll be ready for Snow Ranch.
    NAR 91107, Level 2

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  16. #16
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    Quote Originally Posted by qquake2k View Post
    You know, it dawned on me that a lot of my builds are very similar, with a lot of the same techniques used. But I'll keep posting build threads until you all get totally bored and disinterested in them.
    As long as you're talking about rocket, count me interested. Beats the heck out of bigfoot, gas prices or former economic advisors that are all the rage on some other rocket forums.
    NAR 79563

    2014 motor usage: 60 flights: 1/4A - 2, 1/2A - 2, A - 23, B - 24, C - 1, E - 3 = 257.287 Ns
    2015 motor usage: 122 flights: 1/4A - 10, 1/2A - 14, A - 50, B - 16, C - 19, D - 5, E - 8, F - 2 = 825.3574 Ns

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  17. #17
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    Quote Originally Posted by Fishhead View Post
    As long as you're talking about rocket, count me interested. Beats the heck out of bigfoot, gas prices or former economic advisors that are all the rage on some other rocket forums.
    Hey, Bigfoot would be a good name for a scratch build. Hmmm...
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  18. #18
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    Got the coupler epoxied in the lower body tube. The masking tape is to keep it from "creeping" while the epoxy sets.
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  19. #19
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    The motor tube was a little long, so I cut it shorter with the bandsaw. I cut the fin slots with an Xacto knife.
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  20. #20
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    Using my homemade fin alignment guide as always, I got the four main fins epoxied on.
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    NAR 91107, Level 2

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  21. #21
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    The canard fins are too narrow for the fin guide, so I epoxied them on the old fashioned way. Because they're 1/4" wide, they sat up straight on the body tube by themselves.
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  22. #22
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    I like it!
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  23. #23
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    I seem to recall discussing the possibility of making the main fins 10% smaller because they looked better. What did you decide?
    Terry

    NAR L1
    L2 is on hold, maybe never

  24. #24
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    Quote Originally Posted by T-Rex View Post
    I seem to recall discussing the possibility of making the main fins 10% smaller because they looked better. What did you decide?
    No, I went ahead and made them bigger. I decided it looked better.
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  25. #25
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    Quote Originally Posted by qquake2k View Post
    You know, it dawned on me that a lot of my builds are very similar, with a lot of the same techniques used. But I'll keep posting build threads until you all get totally bored and disinterested in them.
    Quote Originally Posted by qquake2k View Post
    I like it!
    Jim, keep these build coming. I pick up something new all the time.

    P.S. The rocket looks great.

  26. #26
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    Wow, a 3 hr. build. You are getting fast Jim. Your builds always put me in a building mood.

  27. #27
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    Quote Originally Posted by bill2654 View Post
    Wow, a 3 hr. build. You are getting fast Jim. Your builds always put me in a building mood.
    I actually started on it several days ago. I did get quite a bit done on it yesterday, though.
    NAR 91107, Level 2

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  28. #28
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    Quote Originally Posted by azgreg View Post
    Jim, keep these build coming. I pick up something new all the time.

    P.S. The rocket looks great.
    Thanks Greg!
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  29. #29
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    I used Titebond molding glue for the internal fillets, like I did on Who's Your Daddy. I also got the aft centering ring epoxied in, along with a piece of 3" coupler. The coupler will hopefully strengthen the bottom.
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  30. #30
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    24th April 2009
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    That's looking great, Jim! I have used the coupler doubler at the aft end on several rockets and it seems to make quite a difference in durability, especially on a rocket like this, where the fins won't be the first thing to hit the ground. Also, I hadn't thought of putting the baffle elements in the motor tube. I always have put all three elements, the two half moon pieces and the forward, drilled bulkhead in the coupler. I have been wanting to build one of these bigger vipers for a while now. Yours is just about the perfect size. Do you have the markings for it yet? John.


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