Can improved manufacturing prevent spirals?

Discussion in 'Techniques' started by Funkworks, Nov 14, 2019.

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  1. Nov 14, 2019 #1

    Funkworks

    Funkworks

    Funkworks

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    This is the body tube from an Estes Honest John I purchased a few weeks ago. The packaging is stamped 2015.

    IMG_0831.jpg

    Question 1: Do you see spirals?

    Q2: Would you apply putty, wood filler or Bondo to fill the spirals?

    Q3: Do you think sandable primer is sufficient?

    Q4: How about just a little sanding and regular primer?

    Q5: How WOULD you prepare this tube?

    Q6: Why aren’t all tubes this smooth?

    Q7: Is this a sign of things to come? Did Estes recently find a way to make tubes with negligible spirals?

    I had reached a point where I was looking forward to trying out new spiral filling techniques. But now I see this and I’m stumped.
     
  2. Nov 14, 2019 #2

    mbeels

    mbeels

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    I would suggest sliding your fingernail up and down, and see if catches on any spirals. If your fingernail can "see" it, it will likely show up visibly after painting.
     
  3. Nov 14, 2019 #3

    Scott_650

    Scott_650

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    Another tip is any groove you can run a pencil along will probably show up - the pencil line also makes it a little easier to follow the spiral when you’re filling it.
     
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  4. Nov 14, 2019 #4

    BEC

    BEC

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    Estes doesn’t make the tubes, of course. As far as I know they still come from the same source (Euclid Spiral Paper Tube Corporation) as they have since Gleda Estes stopped rolling convolute tubes herself. Bob Sanford (Initiator001) would likely know for sure.

    Your HoJo tube looks like some much older tubes I have from old kits/parts stashes (circa late 1960s, early 1970s). Perhaps they are returning to the particular process/approach they used “back in the day” at the behest of the new ownership at Estes. One could hope.
     
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  5. Nov 14, 2019 #5

    David Schwantz

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    I never use bondo for this, always rusty sandable primer.
    Sand tube 220grit
    spray primer
    let dry lots
    sand with 220 and block, I use a foam as it will conform to tube a bit.
    clean with windex
    spary again if needed.

    this is Estes Saturn V with a replacement LOC 4" tube done the way above.
     

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  6. Nov 14, 2019 #6

    caveduck

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    My methods, YMMV

    Glassine outer wrap: *do not sand*. One heavy coat of Klass Kote or similar 2-part epoxy primer using a cheap detail gun. It's 100% sandable in 6-8 hours. Sand with #150->220->400. Done. Ready for color coat in 1/2 a day, fairly insensitive to temp/humidity.

    White outer wrap with relatively shallow and narrow spiral gap: Light sand with #220 or #320. First coat of 2-part primer, sand lightly with #220. Then fill gap with 3M or similar automotive spot putty. You want primer under the putty for better adhesion. In 1/2 hr or so you can sand with #220-320 as long as it's not too thick. Then 2nd primer coat, sand with 320 -> 400. Cheat mode: make the first primer coat really thick and *maybe* you can get away without a 2nd one. Less suitable for light top coats as the putty may show through.

    With large spiral gap (blue tube is probably the worst): Start with primer coat as above. I use 2-part pink Bondo for the gaps. PITA to use until you get used to it b/c working time is like 2-3 minutes, but sticks much better. Be sure to use enough hardener (somewhat more than recommended) or it stays gummy for days. Sand spiral with sanding block. Block is totally required b/c putty is tougher than paper tube. Then primer as usual. Blue tube is so rough away from the spirals you may need multiple primer coats.
     
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  7. Nov 14, 2019 #7

    jqavins

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    I fill with spackle and really should give CWF a try. I've tried filling tubes like this and found I couldn't get the filler into the grooves. I can feel them with a fingernail, but can't force filler in so that it stays.

    My answer: screw it. Prime, sand, repeat, and tiny grooves like that are gone.
     
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  8. Nov 14, 2019 #8

    Bill S

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    I find that Bondo spot putty stays in the shallower grooves better than CWF.
     
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  9. Nov 14, 2019 #9

    neil_w

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    That's why the CWF must be sufficiently thinned, so it will flow all the way into the grooves and stay there. I have rarely had any problems after a single good application of CWF followed by one heavy coat of filler/primer.

    And again, nowadays (if the tube is not too large) I just slather the CWF over the whole tube with my fingers, rather than trying to direct it only into the grooves. Since I've been doing it this way, filling spirals is no longer my least favorite rocket-building task.
     
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  10. Nov 14, 2019 #10

    Steve Shannon

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    Back to the original question: In manufacturing almost everything has a cost associated with it. A spiral paper tube is probably the least expensive tube available. Tightening tolerances to make the seam between the spiral wraps indiscernible would cost money. Convoluted tubes don’t have spiral seams. I’m sure for a price a tubing manufacturer would be willing to provide a tube that has no discernible seam.
     
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  11. Nov 17, 2019 #11

    Funkworks

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    I've never noticed catalogs highlighting convoluted or seamless tubes. My idea of the market is distorted as I still haven't gone to very large gatherings, but perhaps it could be a good selling point.

    And thanks everyone for the great tips and info. I'll surely be considering everything, along with whatever material I currently have in stock, or can easily find.
     
  12. Nov 17, 2019 #12

    hcmbanjo

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    The old Estes BT-30 was a convoluted tube. The more recent MPC (re-branded Chinese Sky brand) kits have convoluted tubes. They seem to be
    plastic impregnated.
    Here's a mix ratio for the CWF: http://modelrocketbuilding.blogspot.com/search/label/E Interceptor
    That ratio of water to filler is a starting point. I add just a little more water now.
    And how I fill the spirals: https://modelrocketbuilding.blogspot.com/2010/07/mx-774-kitbash-part-6-seam-filling.html
     
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