Howdy, Leviathan Build, and some questions

Discussion in 'High Power Rocketry (HPR)' started by KDA, Jan 1, 2019.

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  1. Jan 1, 2019 #1

    KDA

    KDA

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    Happy New Year everyone. This is my first post to the forum. So first, introductions. I live in the Denver area and I've been out to the C.R.A.S.H launch at Bear Creek with my son's scout troop a few times over the years and in the process I've built quite a few small rockets and one true Mid power. (Aerotech Arreaux that suffered a chute failure on a single use G70 last time we were flying, that'll be a discussion for a different thread)

    I decided that I'd like to try to get L1 certified at Bear Creek and then build a slightly larger rocket with the scouts and launch it at the Hartsel launch this summer. Bear Creek is an un-waivered site with a 52 oz lift off weight limit and a 125 g propellant weight limit. Given those parameters and the fact that I had an un-built Leviathan kit in the basement I decided to attempt my certification flight on that.

    I started the build process and I'll try to post a couple of pics before I get to the questions.

    IMG_20181231_162042.jpg

    I peeled the motor tube and decided on Titebond III

    IMG_20181231_185739.jpg

    I also decided I would fully build the fin and motor assembly outside the rocket and then extend the fin slots to the end of the tube and insert the entire thing into the lower tube. Not sure it was the best idea, but that ship has sailed.

    Next I decided to use a length of kevlar cord so I notched the top centering ring, run the cord through it, and super glued a knot. I glued the green spacer on the top of the motor tube since it seemed like and easy and light weight way to secure the kevlar cord. I'll epoxy the short end of the cord to the motor tube when I get to the epoxy stuff.

    IMG_20181231_194249.jpg

    Next step was to start on the fins. I sanded the leading edges a bit and used an MDF jig to center the fins on the motor tube. Still using Titebond III for all of this stuff.

    IMG_20181231_185812.jpg

    I'm going to hit submit now and see if all the pics upload. Hopefuly back in a bit with more pics and the questions.
     
  2. Jan 1, 2019 #2

    rharshberger

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    The Leviathan doesn't have a motor block does it (I have all the PSII builders kits but haven't built them yet)? If it does make sure and leave it out so you can use the longer Aerotech and Cesaroni casings.
     
  3. Jan 1, 2019 #3

    KDA

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    Next step was to start attaching the fins.

    IMG_20181231_202701 crop.jpg

    IMG_20181231_233753 crop.jpg
     
  4. Jan 1, 2019 #4

    KDA

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    The kit came with a motor block, but I did leave it out. Thanks for the heads up.

    Ok, next step was to try my hand at some epoxy. Mostly this was just to see what it was like to work with it since it seems most folks agree it's probably not nessesary on a paper and wood model. Here is started on the fillets and attaching the kevlar cord. I had some West Systems Gflex in the basement from some past project or another, so that's what it'll get. I also felt that there where some gaps in my wood glue but joints, so hopefully this will fill those. I think need to change up how I'm using the MDF jig to get a better glue joint.

    IMG_20190101_104435 crop.jpg
     
  5. Jan 2, 2019 #5

    KDA

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    Finally up to the questions and thanks in advance if you've stuck with it this long. Probably some fairly standard pics for this forum. Ha.

    I downloaded Open Rocket and found a nice looking Leviathan on Rocket Reviews. I should have no problem staying under the 52 oz limit but I'm a little concerned with the CP / CG relationship since I feel like I'm going to be adding a fair bit of weight to the tail with the epoxy and a small H motor. Now the dumb question part. Center of Pressure is purely a function of the shape of the parts and not the mass correct? So CP should not change with a larger motor? My plan is to take the CP from Open Rocket, mark it on the body and then balance the completed rocket and motor to verify that the two points are far enough apart to be stable. I'll be doing this with a few scouts so I kind of wanted some of the testing to be "in the real world". I also don't have a good way to weigh all the individual components to accurately figure CG with Open Rocket. Does all that sound reasonable?
     
  6. Jan 2, 2019 #6

    K'Tesh

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    Welcome to TRF!!! Happy New Year!

    Nice looking build!!!

    RocketReviews files are highly subject to the accuracy (or lack-thereof) of the person who did it. The file for the Leviathan I found there had the rocket listed as a "Ventris" (look at the name of the rocket in the top left side of the window with the rocket displayed in it), as well as problems with fins that were not shaped accurately..

    I have a .ork file of the Leviatian with accurate fins, and other measurements, save for weights (which you can mass override yourself in OR).
    https://www.rocketryforum.com/threads/kteshs-openrocket-files.123564/page-2#post-1441817

    [​IMG]

    Here's a link to my actual files thread: https://www.rocketryforum.com/threads/kteshs-openrocket-files.123564/
    And one to the index file for it: https://www.rocketryforum.com/threads/kteshs-openrocket-files-index.148212/

    Again, Welcome! And Happy New Year!
    Jim
     
    Last edited: Jan 2, 2019
  7. Jan 2, 2019 #7

    crossfire

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    Looks like your off to good start. You said you peeled a layer of paper off MMT. Make sure you do a test fit when you go to slide body tube over the fin can section. It might be a tight fit at the point where body tube slides under the part of the fins.
     
  8. Jan 2, 2019 #8

    Rex R

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    welcome to the forum. the CP shouldn't change unless your larger motor sticks way, way out the back end :). measure your cg both with and with out motor (otherwise ready to fly) and use the w/o cg for your cg over ride. completed mass to the nearest gram is good enough for the mass over ride.
    Rex
     
  9. Jan 2, 2019 #9

    K'Tesh

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    As for weighing each individual part... I wouldn't... It's going to change with all the glues, paints, and decals (as well as other treatments (such as fiberglass, or wood hardener) that you're going to do to the rocket.
     
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  10. Jan 2, 2019 #10

    rharshberger

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    Or you can weigh each part, and still do a overall rocket mass and cg override, its what I do, each to their own. I find it easier to plan my build if I have a rough idea of whether or not I need to add noseweight ( a Leviathan shouldnt need any BTW). As KTesh said the weight will change as you build but it works well for me to weigh and enter the parts prior to building.
     
  11. Jan 2, 2019 #11

    KDA

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    Thanks for the link to the .ork file, I'll use that one to figure the CP.

    I'm starting to look for a single use 29 mm H motor that I can use at our site. I'm thinking an Aerotech H125. Thoughts? I'm also comtemplating a Jolly Logic Chute Release to try to increase the chances of recovery. Hopefully the Leviathan will be large enough to see.
     
  12. Jan 2, 2019 #12

    dhbarr

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    Did you mean h115 or h135? The 115 is a sparky IIRC, don't know if your site has restrictions.

    h97 is a fine smokey barely-H reload if someone will Lian you a case.
     
  13. Jan 2, 2019 #13

    dmgrime

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    I cert'd L1 on a "stretched" (added 34" of balsamachining.com 3" tube and made mid-break with a baffle) leviathan and an AT H128W. Have since flown it on most 29mm AT H loads up to and including the I200W (29/360 case).

    The DMS H115DM (sparky) is awesome as well ... was first flight motor for my MDRM.

    Good luck on your L1!
     
  14. Jan 2, 2019 #14

    Nytrunner

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    Love the leviathan! Built 3, (only possess 1 still :( )

    A chute release is a great idea for getting it back,e specially around orchards or wooded areas. It gets up there on H's
     
  15. Jan 2, 2019 #15

    Bat-mite

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    Ditto. I have seen too many people show up for a level 1 attempt with a beautifully built rocket that they obviously spent a lot of time on, launch it to 3000', deploy the chute at apogee, and watch it sail away over the trees never to be found. Not only a failure, but the loss of a nice rocket on its maiden flight.

    Chute Release is your best bet.
     
  16. Jan 2, 2019 #16

    BayouRat

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    I would use the smallest H you can get. Here is a quick list of the Aerotech Single use H motors. If you can fly a Sparky the H115 will be your best bet.

    [​IMG]
     
  17. Jan 2, 2019 #17

    DRAGON64

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    The Leviathon and Executioner are two of my all-time favorite Estes rockets.
     
  18. Jan 2, 2019 #18

    KDA

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    I'll have to ask about the H115DM motor. I think I was looking at a similar chart of the Apogee website and came to the same conclusion regarding the Single Use H motors. Figured I'd try to avoid the HazMat shipping as well as support a local guy and make the drive down to Apogee in Colorado Springs. Hopefully I can get the Jolly Logic Chute Release and some rail buttons there too. I was thinking about using the conformal / glue on buttons. It seems like it may be easier than trying to reinforce the screw on type.

    In an earlier post Crossfire mentioned that the lower body tube may be difficult to slide on over the completed fin can and he was right. Going to have to sand down the underside of the fins a tad to get them to slide over the cardboard tube. All the epoxy seems to be pretty well set-up so I'll work on getting the fin assembly into the lower tube next.
     
  19. Jan 2, 2019 #19

    Bat-mite

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    Conformals need to be glued on absolutely, perfectly straight. If you get standard buttons, you can use wood screws. Screw them in, extract them, harden the hole with CA, put a little CA on the screw, and screw them in. You could also use expanding well nuts.
     
  20. Jan 2, 2019 #20

    Nytrunner

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    If you can swing it and keep it class 1, try a motor with a little more oomp than a baby H (my opinion). You're building it strong to take high power motors right? Give it a good run!

    Or the rail button and weld nut combo Apogee sells while you're up there. (Lol, the idea of Apogee as a "local guy" makes me chuckle)
     
  21. Jan 2, 2019 #21

    swatkat

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    I certed on a stretched Leviathan as well. H165R, weighed 25.5 Oz dry, flew to 1859'. Easy recovery. Should be no issue. 6E5A0440-tiny.jpg 6E5A0441-tiny.jpg
     
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  22. Jan 2, 2019 #22

    swatkat

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    And the Sim files if you need them.
     

    Attached Files:

  23. Jan 2, 2019 #23

    boatgeek

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    If you are planning on flying a fair amount of HPR, you might want to get a case. I can see not wanting to for your cert flight, but it'll save around $10/flight for these sizes of motors. HazMat is a non-issue since Apogee is local to you. I personally like the Cesaroni starter kit ($66 at Apogee) which will cover virtually all 29mm motors from F to I. Cesaroni also has a lot of variety in their reloads and are nearly as easy to use as single-use. In their 3-grain motors, you have the option of H in white, blue, classic, and IMax. Going up to 4 grains will get you red and smoky propellants. Aerotech reloads and cases are also a great option that many people love, but you would probably want someone to look over your shoulder the first time you assemble a motor because there are more bits and pieces to keep track of.
     
  24. Jan 2, 2019 #24

    KDA

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    Thanks for all the input. A follow up question on conformal vs buttons. I was leaning conformal becasue I like that they are surface mount and the fairly large gluing surface seems like it would spread the load out a bit. The cardboard body tube on the Leviathan seems fairly flimsy and the centering rings seem a little thin to screw into. I'm intrigued by the button and backer nut set that Apogee has, looks like it's make by Madcow? Will those work with the cardboard or should I plan on a backing board of some sort? One fairly straight forward solution may be to add wood blocks to the centering rings to screw into, any other rail button / guide tips or suggestions?
     
  25. Jan 2, 2019 #25

    smugglervt

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    Wood blocks on the CR is my preferred method with cardboard rockets. I use 1/4" to 3/8" plywood depending on what I have handy.
     
  26. Jan 2, 2019 #26

    KDA

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    I do like the idea of a case and reloadables, but I think I'l like to build a 38mm or 54mm rocket to fly at the Tripoli Launch at Hartsel CO this summer so I may try to get a case system in a larger size. I'm the Scoutmaster of my son's troop and after doing a few low power launches with the boys at Bear Creek I was hoping to have them "help" or at least follow along on a bigger build and then we can camp somewhere near Hartsel so they can see some of the big guys launch.
     
  27. Jan 2, 2019 #27

    Andrew_ASC

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    I certed on a 3.34 pound Wildman RB-05A apogee deploy at 2,520ft with an AT H123W. It has a 24” IriS drogue. The field we flew at Rembert, SC had a massive turf farm. There was a thunderstorm approaching. So yeah. Apogee deploy can be done with motor eject at the right field if you launch with little wind. You will sprint nearly half a mile to get the rocket back. The forum will shriek. I wouldn’t push it over 3,000 ft without a tracker or dual deploy. We all had visual the entire time. Important is to maintain visual and not watch other rockets, kept track of where yours landed. I wanted to keep it simple as simple got. I’ve seen one JLCR failure which is very rare.

    The only time I really regretted apogee deploy was a student college multistage MIn diameter H that deployed at 11,563 ft and then drifted 1.4 Miles last year, but it landed in a swamp, then we won a national competition after getting it out of swamp. So you can multiply the altitude by 0.64 if you want a rough idea of how far it can drift laterally from a real world experience. The winds at higher alts are not ground wind speeds and often exceed 30mph even when it feels calm on ground.

    A JLCR or dual deploy or smaller chute reduces drift significantly. The problem with wind drift is you do not control where the rocket lands.
     
  28. Jan 2, 2019 #28

    kevindcornwell

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    I used the Apogee buttons with the backer nut. I symetrically bent the sides of the backer nut to conform to the curvature of my 4" bluetube body. Then just epoxied them in place with epoxy completely covering the backer nut (with a small tape over the threaded hole). It made an extremely strong and very streamlined attachment for the rail button. It would destroy the body tube if it every pulled out.

    Also, I L1 & L2 certed on my scratch-built. And, I'll likely not fly it again without a chute release in it. On my L2 it reached 4600' then descended to 400' on a drogue, then CR the 60" main with a landing just 20' from the launch rail. All in conditions where other (similar altitude) rockets were drifting up to a mile away. Gotta' love that CR :)
    stil2.jpg 20180530_130606.jpg :)
     
  29. Jan 3, 2019 #29

    KDA

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    Ok, did a bit more on the Leviathan last night. I think now it was a mistake to build the fin assembly and open up the tube slots all the way to the bottom. I couldn't get the body tube back it's correct shape. I don't think it's a deal breaker, it'll just require a bit more epoxy in the tail and it will probably look a bit goofy in the end. Here is a pic of the gaps around the bottom centering ring after I got it on.
    IMG_20190102_195702.jpg

    I sliced about a 1/4 inch off the coupler to make a cardboard splint.

    IMG_20190102_195728.jpg

    then I glued the splint in with a bit of wood glue and decided to try my hand at epoxy fillets. Again, probably overkill, but I'd like to try a few of these techniques. I taped off small fillets and mixed up a little bit of the West Systems GFlex. I smoothed it out with a small stirring stick (think small tongue depressor) and got a pretty nice shape. Peeled the tape off after about an hour and this morning at least one of the fillets looked great. On the other some of the epoxy ran down into the gap at the base of the fin, so I'll try to touch it up this evening.

    IMG_20190102_220651.jpg
     
  30. Jan 3, 2019 #30

    Nytrunner

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    Overkill indeed, but experimentation and learning is always good!

    Any decision on a paint scheme? It's a good size and masking isn't particularly tricky.

    [​IMG]
    [​IMG]
     

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