24mm Near Min-Diameter Scratch Build Thread

Discussion in 'Mid Power Rocketry (MPR)' started by Zertyme, Mar 17, 2019.

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  1. Mar 17, 2019 #1

    Zertyme

    Zertyme

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    Hello,
    First of all, this is my first post on this forum and English is not my primary language... So their's might be some spelling errors.

    For this build, I want to start experimenting with a dual deployment technique that the France Tripoli prefet teach me. Here is how it works.

    When the apogee is reached, the parachute is ejected but still hold close by a nylon string. At 100m, the E-Match is ignited which melt the nylon string and deploy the parachute. Seem pretty simple..

    I will also use this rocket to test the GPS that I'm working on with a friend. It will use LoRa to communicate to a ground station and track the rocket.

    Here is a screenshot of the OpenRocket design.
    upload_2019-3-17_21-37-59.png

    This rocket will be made out of Carbon fiber and the nosecone will be made with fiberglass and a custom made nosecone mold.

    Boat-Tail:

    The boat tail will simply be made of 2 parts: one 24mm int.dia cf tube and one 26mm tube.
    upload_2019-3-17_21-52-43.png

    I had to sand down the boat tail by hand. To prevent delamination, I applied a thin coat of JbWeld on the inside. The boat-tail part will also act as motor retention. The motor ejection charge will not be used so friction fit might be enough but this is what I did.

    I added some JbWeld on the inside to add materials for the screw to bite on. A simple screw is used to hold the motor in place. This work with Cesaroni and Aerotech hardware.
    upload_2019-3-17_21-59-11.png

    Fins:

    The fins are made out of 2mm thick carbon fiber plate. A Jig Saw with a small teeth metal blade do a perfect job at cutting carbon fiber plate without delamination. It's a bit hard to get a perfectly straight line but once you get your hands on it, it becomes pretty easy.
    upload_2019-3-17_22-3-57.png

    Now time for the airfoil. I first marked a line at 7mm from the fins edges. This will be my reference line for the sanding. Simply by using 120 grid sandpaper and a sanding block, you can get the rough shape.

    upload_2019-3-17_22-6-36.png

    and here is the final fin!

    Now 2 left to do...


    Fins Slots :

    Fins slots were pretty tricky to do because I don't have the right tools to works with carbon.

    Here is the setup
    upload_2019-3-17_22-21-54.png


    Just a simple drill press...
    After drilling pre-holes, I used a Dremel diamond sanding bit to finish the slot. And here is the result without sanding.
    upload_2019-3-17_22-20-29.png
    As you can see, it is not perfectly smooth but it will help when I will be gluing the fins in place.

    I was able to get a near perfect alignment without even holding the fins in place!

    upload_2019-3-17_22-25-46.png


    upload_2019-3-17_22-31-44.png

    Here is the final picture of the progress for today, I will keep this thread updated on my progress as soon as I have time to continue this rocket!

    Stay Tuned!



    PS: I still haven't found a name for this rocket, so if you have any ideas, let me know!
     
  2. Mar 19, 2019 #2

    dhbarr

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    This is lovely!
     
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  3. Mar 19, 2019 #3

    grouch

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    Nice work!
     
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  4. Mar 19, 2019 #4

    Scotty Dog

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    Name... Spelchek. The way I just spelled it
    Looks really good. I like this use of diffrent tools to get the job done. We call that "Yankee Ingenuity "
    And thats another name for the rocket
     
  5. Mar 20, 2019 #5

    Theory

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    very nice, and I like your drill press slotting idea. fantastic ingenuity; what this hobby is all about!!!!
     
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  6. Mar 20, 2019 #6

    ksaves2

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    Make sure your GPS antenna is fully encased in the fiberglass nosecone or there could be some decreased range.
    Also avoid black colored fiberglass as carbon black is used as a colorant. Doesn't attenuate as much as carbon fiber but if you want to recover as many positions as possible, optimize as much as you can. Also avoid metallic paint. Regular white should be OK. Kurt
     
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  7. Mar 20, 2019 #7

    Zertyme

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    I'm back at it!

    First of all, thank you for all your support and suggestion!

    Here is the progress:

    I cut out the fins guide out of a simple cardboard
    IMG_20190320_115330.jpeg
    I hope this is precise enough to align the fins...

    Now time for the boattail/retainer
    I first applied Jbweld all around the connector to make sure there is no air bubble
    IMG_20190320_120019.jpeg

    Then I just removed the excess: I don't really care about the finish for the moment, this part will be covered by a tip-to-tip lamination. IMG_20190320_120250.jpeg

    Jb weld dries very nicely over a heater: only 2 hours for it to dry!


    Then It was time for the fins
    First of all, I use 100grid sandpaper to make the surface rough for the Jbweld.
    IMG_20190320_131826.jpeg

    Then I use the Jbweld to your the root of the fins
    IMG_20190320_133705.jpeg

    For the moment I haven't encountered any major problem! (Except getting the fins to be exactly the same)

    I will try to do the fillets tonight if I have time.
     
  8. Mar 20, 2019 #8

    Zertyme

    Zertyme

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    Like I said, here are the first 2 fillets!

    First of all, I used masking tape to protect the other part from the epoxy.
    IMG_20190320_192512.jpeg


    I then mixed normal epoxy ( YatchCare Epoxy) with a lot of microballons to get the epoxy to the right thickness. I then use a wood dowel to get apply the epoxy correctly.
    IMG_20190320_193908.jpeg

    Turned out pretty well!
    IMG_20190320_211507.jpeg

    And here is the side view
    IMG_20190320_211724.jpeg

    I'm done for today, I will continue as soon as I have time to.
     
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  9. Mar 21, 2019 #9

    Andrew_ASC

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  10. Mar 22, 2019 #10

    jqavins

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    For a name, the ratios of length, diameter, and fin span are suggestive of a dart, a javelin, or some such. You might use one of these but in you native language (French, I assume?). "Javelot" has a nice sound to it. Or "Flèche". Of course, a nice sound is subjective, and what's exotic here is mundane somewhere else, so perhaps "Javelin" would have the exotic sound for you.
     
  11. Mar 22, 2019 #11

    mbeels

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    Beautiful work, and very nicely documented!
     
  12. Mar 22, 2019 #12

    Zertyme

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    Thank you for the proposition. I already did another rocket that I name Athena for the same reason here are some pics.
    IMG_20190301_175607.jpeg
    IMG_20190301_175551.jpeg
    It actually never liftoff the pad... The E18 were a bit humid causing them to not ignite. This rocket was for a school rocket but it was a bit rushed so their is some defect...

    (And yes I'm french!)

    Progress:

    I finished all the fillets!
    JPEG_20190321_200819.jpeg

    Same mix, same method but it still need some sanding before the tip to tip lamination.
    I won't make any progress tomorrow because I go to the ARGOS meeting! Maybe tonight!

    I really love the support from this community!
     
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  13. Mar 22, 2019 #13

    Tim51

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    Cool build - very nice work!
     
  14. Mar 22, 2019 #14

    blackjack2564

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    You really don't need anyT-T with this size rocket, especially with carbon plate fins.
    Will only create thicker fin profile.
    I've flown 3in minimum diam. rockets with M's and no T-T fins always stay on.......

    Very nice work on build.
     
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  15. Mar 22, 2019 #15

    OverTheTop

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    Welcome to the forum Zertyme. Nice build.
     
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  16. Mar 22, 2019 #16

    Zertyme

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    Yeah... I just tried to do one but failed because my food vacuum pump was not powerful enough to create a full vacuum.
    IMG_20190322_235606.jpeg
    IMG_20190323_001944.jpeg

    Took me like 30mins to clean everything up...
    So I guess I will abandon the tip to tip for the moment.

    I will try to do the nosecone mold Sunday and also the finish on the rocket bottom part.
     
  17. Mar 23, 2019 #17

    OverTheTop

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    As CJ said, you should have no problems if you don't do tip-to-tip. The slotting of the airframe for the fins does wonders for strength.
     
  18. Mar 23, 2019 #18

    Zertyme

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    I just realized that my fillets where all smaller than the dowel are used...

    IMG_20190323_064715_BURST001_COVER.jpeg
    Except for one set.
    IMG_20190323_064658.jpeg

    I guess I will add another lawyer of epoxy for most of the fillets.
     
  19. Mar 23, 2019 #19

    cbrarick

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    looks nice.

    to do good vacuum bagging you really need to have a proper pump. When I first started out I tried to use a cheap oil style vacuum pump, which was inconsistent and eventually the pump died. It really wasn't designed to pull a big vacuum for a long time.
    I then ebay'ed a nice Gast pump which will run forever at 29 mm Hg and not get hot.
    The products I create now are much better....
     
  20. Mar 24, 2019 #20

    Zertyme

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    Update

    I added epoxy to all the fillets, making sure they are all the same diameter
    IMG_20190324_131452.jpeg

    I then drilled all the holes for the altimeter switch etc...

    I used 800 grid sandpaper to sand everything down, even the carbon fiber tube to get a nice mat finish
    IMG_20190324_132932.jpeg


    Even with sanding, the fins part still has some defects so I used primer and some polyester filler to fill all the defects.
    IMG_20190324_143106.jpeg
    IMG_20190324_163120.jpeg
    You can see here that the transition between the 2pieces was not perfect: the polyester resin did a perfect job.

    I then apply 2 coat of white paint (Montana black )
    IMG_20190324_180319.jpeg
    The surface is still a rough so it will need some wet sanding before the finish.
     
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  21. Mar 27, 2019 #21

    Zertyme

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    Update

    IMG_20190324_192611.jpeg
    The paint was way to rough for my liking so I decided to remove everything using paint stripper and some sandpaper....

    Here is the av bay design
    IMG_20190326_063429_01.jpeg
    Ans here is the av bay printed.
    JPEG_20190326_125216.jpeg

    One of my friend printed it out for cause I don't have a 3d printer.


    I also did the separator
    IMG_20190324_221327.jpeg
    I glued 3 nuts for screws

    IMG_20190325_063246.jpeg


    I also received the GPS that I'm going to use for the first few fly:
    JPEG_20190325_190707.jpeg
    I will upgrade later with something like an eggfinder.
     
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  22. Mar 29, 2019 #22

    Zertyme

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    Small update on the paint



    I bought some car paint to redo the bottom part of the rocket.

    I first made a test on a spare tube of carbon
    IMG_20190327_182232.jpeg

    It turned out pretty well.


    Here is the painting setup
    IMG_20190327_195523.jpeg

    And the final result
    IMG_20190329_220726.jpeg


    I will most likely add a thin coat of epoxy on the entire part to seal everything.
     
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  23. Mar 30, 2019 #23

    Zertyme

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    Time for the tricky part: the stencil

    I first cut the stencil
    Out of vinyl
    IMG_20190330_173358.jpeg
    IMG_20190330_181514.jpeg

    I then use some painters tape to hold the design in place while sticking it on to the rocket
    IMG_20190330_191301.jpeg



    Then paint using the same paint used on the bottom part of the rocket
    IMG_20190330_210652.jpeg

    And here is the result after removing the stencil
    IMG_20190330_211534.jpeg

    There are still some defects that I sand down tomorrow
    IMG_20190330_211628.jpeg

    But overall it looks great!
     
  24. Mar 30, 2019 #24

    Bill Morrison-Bates

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    Great work my friend...almost up to British Standards......haters queue here
     
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  25. Mar 31, 2019 #25

    JPVegh

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    She a real thing of beauty!
     
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  26. Mar 31, 2019 #26

    Zertyme

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    Yes she is!

    Here are two more pictures before a bit of sanding. I will then use a clear coat.
    IMG_20190331_170302.jpeg
    View attachment 378876

    The whole fuselage is 135g without the final clear coat!
    IMG_20190331_150632.jpeg
     
  27. Apr 3, 2019 #27

    Zertyme

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    Update
    Clear coat is on!

    I first sanded down the entire rocket with 2000 grid sandpaper.
    I used an old can of automobile clear coat (can't find any link)

    Here is the first coat on
    IMG_20190403_192858.jpeg
    IMG_20190403_192901.jpeg
    You can see how gloss this clar coat is.


    After 40mins the clear coat was dry to the touch so I proceed to wet sand the entire rocket with 2000 grid again.
    IMG_20190403_192909.jpeg

    Then I reapply another coat
    IMG_20190403_205228.jpeg

    I will see tomorrow how it turned out...
     
  28. Apr 3, 2019 #28

    timbucktoo

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    Hammer time!
     
  29. Apr 4, 2019 #29

    boatgeek

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    Looks great!
     
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  30. Apr 9, 2019 #30

    Zertyme

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    Update

    The clear coat has been cured and polished!

    On the left the not polished tube and on the right the polished one
    IMG_20190404_183000.jpg

    The text is a bit crooked but that's OK...
    IMG_20190405_084411.jpg

    IMG_20190405_084427.jpg

    Here is a nice reflection I got
    IMG_20190404_184255.jpg

    Now time for the Nosecone!

    I asked my friend to print the mold for it but turned out really bad. I don't know what happened but I will not use it...
    JPEG_20190409_110452.jpg

    I will make a male mold on my lathe then directly wrap the fiberglass over it.
     
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