Alcubierre Upscale a Neil_W design)

Discussion in 'Scratch Built' started by SDramstad, Oct 10, 2019.

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  1. Oct 10, 2019 #1

    SDramstad

    SDramstad

    SDramstad

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    I have been hanging around here for years but have never done a build thread. Well here goes. I have been following Neil_W's builds for awhile and his Alcubierre really caught my eye. Started playing around in Open Rocket with it and finally decided to go with a 3 inch tube. That gives me a ring fin of close to 12 inches and the other dimensions looked right to me. I have been doing a lot of builds with mostly fiberglass. Rolling my own tubes and cutting my own fins.
    So step one is rolling a 3 inch body tube. In the past I have used blue tube couplers as a mandrel. Those worked pretty well but for this build I am going a different way. I bought a 3 inch diameter aluminum pipe 3 inches in diameter with quarter inch walls. Spent a lot of time smoothing it out and filling minor dents but its finally looking good.

    workbench-mandrel.jpg

    I wrap the mandrel with 2 mil mylar from Hobby Lobby. The epoxy wont stick to it and it allows me to slide the finished tube off fairly easily. I am using 8.8 ounce e glass fiber glass material. 3 wraps gives me a fairly light tube that is still pretty strong so a bit of math pluss a few inches and it turns out to be about 33 inches of material.

    fabric.jpg

    Was home alone when I was working on this so unfortunately I wasn't able to get pictures of the rolling process but will try to document rolling the motor mount in more detail later. Here is the tube on the mandrel while it is still wet.

    rolled-tube-wet.jpg

    I let it set up for about 4 hours and pulled it off of the mandrel.

    dry-tube.jpg

    More later.
    Steve
     
    Last edited: Oct 10, 2019
  2. Oct 10, 2019 #2

    neil_w

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    That's a fine looking tube ya got there. Fiberglass tubes look especially impressive when you're accustomed to working with paper.

    <insert popcorn emoji here>
     
  3. Oct 10, 2019 #3

    Bruiser

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    This is very interesting.

    What is the mylar from Hobby Lobby and how do you attach it to the mandrel?

    -Bob
     
  4. Oct 10, 2019 #4

    SDramstad

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    It's clear mylar in a roll about 18 inches wide. You can get either 2 or 5 mil thickness. I prefer the 2 mil. Just wrap the mylar around the mandrel and use scotch tape to keep it from unrolling. Just use the tape to keep the mylar from unrolling. Do NOT tape the mylar to the mandrel. You will never get it off....
     
  5. Oct 10, 2019 #5

    SteveNeill

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    West Systems epoxy is my favorite. Always sets of thoroughly and the next day non tacky and ready to sand and sand well.
     
  6. Oct 10, 2019 #6

    mbeels

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    Ooooh, very nice, following this thread with great interest.
     
  7. Oct 10, 2019 #7

    Bat-mite

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    Nice job on the tube. I really need to try rolling glass someday.
     
  8. Oct 10, 2019 #8

    SDramstad

    SDramstad

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    Thanks Everyone. I was alone in the shop when I rolled the body tube so was not able to get any photos of the process. When I roll the motor tube I am thinking about setting up the Go Pro and making a video of the process.
     
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  9. Oct 10, 2019 #9

    Nytrunner

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    Sounds similar to the technique John coker uses in his video on glassing, except you're not reinforcing a tube, you're making your own!
     
  10. Oct 10, 2019 #10

    SDramstad

    SDramstad

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    When I started working with fiberglass I had all sorts of problems. Then I found John Cokers posts. Made a huge difference. I learned the basics from his posts and that really improved what I was doing. We owe a lot to John.
     
  11. Oct 10, 2019 #11

    neil_w

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    What's the wall thickness, out of curiosity?
     
  12. Oct 10, 2019 #12

    SDramstad

    SDramstad

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    I haven't measured this one yet but in general 3 wraps of this cloth gives me just under 1 mm. Will post exact numbers and weights later
     
  13. Oct 11, 2019 #13

    SDramstad

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    So did some measuring last night and the body tube came out with a .9 mm wall thickness is 42 inches long and weighs in at 11.something ounces. Now thats not finished out so that will add an ounce or 2 to it. Next step is to cut out the fins and roll the motor mount tube. Have to work this weekend so sometime next week probably.
    Steve
     
  14. Oct 11, 2019 #14

    jqavins

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    Did I miss it: what size motor mount?
     
  15. Oct 11, 2019 #15

    SDramstad

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    I am putting in a 38 mm motor mount. Thought about a 54 mm but ring fins dont like too much oomph......
     
  16. Oct 11, 2019 #16

    Tobor

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    Yes Please!!! And thx in advance.

    >>Subscribed<<
     
  17. Oct 17, 2019 at 3:55 AM #17

    SDramstad

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    Okay, so some progress has been made.

    parts-laid-out.jpg

    I have cut out the 2 wings from some fiberglass sheet I had sitting around. I ended up deciding to run the through the wall fin tab the full length of the fins. There is no way I could have cut out that long skinny pointed fin with the tools I have. This also means my motor tube will be 29 inches long....... Speaking of which, I rolled the motor tube the other night and ran the go pro camera to document it. Will need to edit it and put it up on youtube. 2 things I have never done before. Its pretty crude but should show how I make these tubes. the body tube was rolled awhile back and I got in the nose cone, couplers and boat tail from Madcow.The ring tail is going to be a 2.5 inch wide piece of concrete form tube from Menards. I plan to fiberglass the inside and outside of the ring with a layer of 8.8 ounce fiberglass. Once that sets up I will split the ring in half, feed a length of carbon fiber sleeve onto the ring. Glue the ring back together and then epoxy the carbon fiber all the way around the ring. First time for this so we shall see. Only other major parts are the other fins and the ebay. I want to use rail guides on this rocket so instead of 2 wings and 2 fins at 90 degrees to each other I will do two wings and 3 fins. 2 wings at 180 degrees to each other, then the other 3 fins 120 degrees from each other with one of them vertical. That way I can put the rail guides along the bottom and it wont look cockeyed on the rail.
    More later
    Steve
     
    Last edited: Oct 17, 2019 at 3:36 PM
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  18. Oct 17, 2019 at 4:59 AM #18

    mbeels

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    Oh. my. goodness.. This is starting to look serious. Looking forward to your tube rolling video. That ring sounds like it will be solid!
     
  19. Oct 17, 2019 at 4:28 PM #19

    neil_w

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    Wow.

    Do you have nose cones for the pods? Those would be about 2" from my reckoning.

    Also: will there be room in front of the stuffer tube for the recovery materials, or do you expect you'll need to stuff into the stuffer?

    Bonus question:
    What's the thinking behind glassing it, then cutting and sleeving it? Why does it need the glass *and* the sleeve? (I am composite-ignorant so this is all black magic to me...)
     
    Last edited: Oct 17, 2019 at 4:43 PM
  20. Oct 17, 2019 at 5:13 PM #20

    SDramstad

    SDramstad

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    I want the ring tail to be good and strong. I dont care if its a little heavy because I am not going for speed or altitude with this build. Once the ring has been fiber glassed I should have an easier time squaring off the edges and rounding the edges before putting the carbon sleeve around it. I also want the ring stiff enough to maintain its shape while I am putting the sleeve on. First time I have tried this. Will see how it works.
    I am bouncing between two ideas for recovery. One the traditional dual deploy where you split the body tube for the drogue and blow the nose for the main. The other idea is to use an altimeter to blow the drogue and main at the same time out the nose cone and use a chute release on the main. Still debating this one, have had good luck with both. If I go traditional I will probably have the drogue inserted into the motor mount tube.
    The pods are going to be a bit smaller then scale shows them. Madcow has a balsa nosecone for a BT-55 that is a Ram Jet cone. Been looking for a good place to use one and this is it. I covered a BT-55 tube with a carbon fiber sleeve and will use that for the pod. Will have the ramjet nose cone on the front and maybe the back of the tube. Will have to see how it looks.
     
    Last edited: Oct 17, 2019 at 5:25 PM
  21. Oct 17, 2019 at 5:20 PM #21

    neil_w

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    Ah, that's the "little" black tube in the middle of the table. Got it!
     

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