Minimum Diameter F Rocket

Discussion in 'Mid Power Rocketry (MPR)' started by HStuart18, Aug 14, 2019.

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  1. Aug 14, 2019 #1

    HStuart18

    HStuart18

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    Is it a bad idea to design a minimum diameter F-class rocket? My concern is the structural integrity of the rocket. I intend on 3D printing (PLA) it with a wall thickness of about 2-3mm. Does anyone have any experience with 3D printing minimum diameter mid-power rockets?

    Thanks
     
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  2. Aug 14, 2019 #2

    Nytrunner

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    Bad idea? Don't think so. many have done it before. The real challenge is finding the thing after you launch it

    PLA can get a little....melty. As a young club member discovered recently (below). PETG has better thermal properties

    Plus at 3mm, it'll be much heavier than a paper tube which can survive an F motor normally with little to no reinforcement (well, the F250 is an exception)

    upload_2019-8-14_9-21-17.png
     
  3. Aug 15, 2019 #3

    HStuart18

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    2mm has been sufficient in my experience, but I wasn't sure whether it would be sufficient for a more powerful motor. I guess I could always put a couple of internal "reinforcement-rings" in if necessary. I am using 3D printing as part of the project. I'll see if I can use PETG, but if I have to use PLA, is thee some sort of heat-absorbing paste or resin I can coat the inside with? Is this concern regarding more the heat of the engine casing as it thrusts, or the ejection charge? Could I just stuff the tube with heaps of thermal padding if the latter?

    Thanks
     
  4. Aug 15, 2019 #4

    BryRocket

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    It really helps to throw a cardboard thick wall motor tube inside the rockets. And as mentioned, petg will hold up better.
     
  5. Aug 15, 2019 #5

    manixFan

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    You can also just do several wraps of the heavy brown construction paper (the Home Depot kind, not craft store) to line the inside of the rocket. No structural benefit, but it will insulate from the ejection charge.

    I would not use PLA at all, in Texas it would not survive the car ride in the trunk to the launch. I had an iPhone mount I printed out of PLA and it warped before the temps even got into the 90's. (Of course, the interior of the car got a lot hotter.) PETG is just a much better material for rocketry.


    Tony
     
  6. Aug 19, 2019 #6

    jqavins

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    What about ABS?
     
  7. Aug 19, 2019 #7

    cwbullet

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    PLA is not a good choice if you plan of flying it in the summer. Go with PETG.
     
  8. Aug 19, 2019 #8

    Nytrunner

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  9. Aug 20, 2019 #9

    wrad

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    To make PLA more heat resistant, print/ paint in white it makes a huge difference. And 2/3mm is overkill in my opinion, for most printers that’s between 5 and 8 perimeters, or 2 + infill, I have flown many 3D printed parts and rockets and only go that thick for parts I want to be very heavy and durable for bigger rockets, most of my mid power stuff has wall thicknesses of about 1mm
     

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