Filling in body tube spirals...

Discussion in 'Beginners & Educational Programs' started by ewomack, Sep 17, 2019.

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  1. Sep 17, 2019 #1

    ewomack

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    I've built about 8 rockets in the past few months and I still feel like a beginner, but I still have not mastered filling in body tube spirals. I have used a substance called "Wonderfill," but either I'm not using it correctly or I'm not using it for the right purpose. When using it, I always see spirals in more places than I would expect with such a product. Again, it might be me and me alone.

    What do you use to fill spirals? Or do you use different things for different types of spirals?
     
  2. Sep 17, 2019 #2

    les

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    Elmer's Fill and Finish
     
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  3. Sep 17, 2019 #3

    dr wogz

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    "how" should also be asked...

    What is your technique to filling them?
     
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  4. Sep 17, 2019 #4

    samb

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    When I want to fill paper tube spirals I use Elmers Carpenters Wood Filler and I follow this technique from a master model builder to the best of my ability.

    http://modelrocketbuilding.blogspot.com/2011/12/filling-body-tube-seams.html

    Elmers Carpenters Wood Filler.jpg



    Searching this forum using "filling body tube spirals" will returns pages and pages and pages of tips, tricks, techniques and materials you can review and try till you find what works for you.
     
    Last edited: Sep 17, 2019
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  5. Sep 17, 2019 #5

    JohnCoker

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  6. Sep 17, 2019 #6

    beantownJPL

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    I find the easiest way is to use a high-build sanding primer ... my preference is the Rustoleum product. It builds up fast, very run/drip resistant, dries fast and sands very easily.

    I seal any balsa with Titebond thinned with water to a "brushable" consistency. Then quickly knock down the "bumps" with 220 grit once dry (about 30 minutes or so). Be careful not to re-expose the grain by sanding too much, it doesn't take an awful lot of sanding to be "smooth enough" for the primer to take over.

    Then I'll blast the whole model with a fairly heavy coat of sanding primer and let it dry for about 20 minutes. I'll take MOST of it off again with 180 grit. I stop sanding when little "bumps" of cardboard on the body tube are visible, and I can just start seeing the grain coming through on the balsa parts.

    At this point, I'll use CWP to fill any larger voids. The primer coat will really help you see these. Then I sand them smooth with 220 grit (I'll also usually go over the the whole model at this point with the 220 grit to reduce the sanding scratches).

    Now, I'll spray another coat of sanding primer, let dry completely and then sand it "thin" with 220 grit. Things should be pretty smooth at this point. If you find anything unsatisfactory, fill-spray-sand again ... repeat as many times as necessary.

    If I'm just going for a "good enough" finish, I'll spray a couple coats of color coat, let it dry, apply decals and shoot the clear coat.

    If I want a glassy finish, I'll spray the first color coat, let it dry (stay within the recoat time, or you may wrinkle), and then wet sand lightly with 400 grit and then 800 grit. I'll take this coat down to the point that I might see some primer peek through here and there. Then I'll shoot another color coat, let dry as above, and hit it with 800 grit and then 1000 grit.

    Now, I'll apply 2 coats of my "base" color, tape off my design elements, and add a coat of my top color ... and a second if it seems necessary.

    Once the paint is dry to the touch, I'll add any decals and shoot a coat of clear and pray that I'm still in the recoat window and that nothing wrinkles. If I don't have confidence it won't wrinkle, it's best to wait AT LEAST a week before shooting the clear (far too often, I turn out to be over-confident).

    If it does wrinkle ... you either "live with it" or get out that sandpaper, order a new set of decals and go back to square one, making sure the kids aren't around to hear your choice words.

    If you are shooting a multi-color design, you often get a visible difference at the tape lines due to the thickness of the upper coat. You can either resolve this by letting the paint harden at least overnight and lightly wet sanding with 1000 grit before adding decals and clear, or you can shoot multiple coats of clear, sanding between each coat to feather the edges. Either technique has its pluses or minuses, but you're less likely to mess up any "fine" details with the multiple clear coat approach.
     
    Last edited: Sep 17, 2019
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  7. Sep 17, 2019 #7

    neil_w

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    Many methods work.

    As of late, my preferred method is to cover the entire body tube with thinned CWF, applied with the most useful and versatile tool I possess:
    upload_2019-9-17_12-12-33.png

    That's a side benefit of the fact that CWF is water based and extremely benign.

    The reason for doing the whole tube is that I find it is much easier to deal with the entire tube at once rather than just focus on the grooves. This applies both to applying the stuff, and then sanding. Using my finger, I slop it on and then run my finger over is to remove as much excess as possible. Usually you only get one or two passes before the stuff starts drying from the friction, but that's OK.

    One coat of filler/primer follows. Occasionally I find a bit of spiral that still shows; if I cared I would probably just do another coat of filler/primer (but I usually *don't* care, if it's minor).

    Anyway, this technique has made me no longer dread filling spirals.

    On the occasions when I'm using CWF for balsa filling (I paper almost all my fins these days, but still have occasion to use CWF) I also use my finger to apply thinned CWF in the same manner. So much less fussy than using a brush that gets all clogged up with the stuff, *and* it's easier to remove excess to reduce sanding.

    Disclaimer: I'm doing this in the LPR domain, with tubes that aren't that big. I don't know how large a tube it would scale to before covering the whole tube really becomes excessive.
     
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  8. Sep 17, 2019 #8

    Charles_McG

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    You are also doing it on tubes with the glassine intact. My homemade tubes respond very poorly to water contact until they are painted.
     
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  9. Sep 17, 2019 #9

    neil_w

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    Yes, good point, although that presumably applies to using thinned CWF in general, not just the "smear it over everything" approach.

    How are the spirals on your homemade tubes compared to commercial?
     
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  10. Sep 17, 2019 #10

    Charles_McG

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    When I'm paying attention, very similar. I get a little big of a center ridge sometimes, too. I alternate wind directions to try to avoid it. Mixed success.
     
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  11. Sep 17, 2019 #11

    Winston

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  12. Sep 21, 2019 #12

    gna

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    There is a spiral that you can see, and one you can feel. Run your thumbnail along the tube, and it will catch on the spirals that are hard to see. If you look at them in the light you can see them. That's the one you need to fill.
     
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  13. Sep 21, 2019 #13

    neil_w

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    Often there are two spirals that need filling.
     
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  14. Sep 21, 2019 #14

    hcmbanjo

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    Here's an article wrote for the Apogee Peak Of Flight:
    https://www.apogeerockets.com/education/downloads/Newsletter448.pdf

    It covers body tube seams, launch lug seams and nose cone mold lines.
    Ideally I try to do just one pass of each -
    1. One fill with thinned Carpenter's Wood Filler (CWF) and sanding to surface,
    2. One moderately heavy coat of Duplicolor Filler/primer and sanding almost to surface.

    Color coats follow with light sanding between coats.
    Final color coat is heavier, but not enough to result in drips.
     
    Last edited: Sep 21, 2019
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  15. Sep 21, 2019 #15

    Sooner Boomer

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    You *can* just slather (or spray) filler all over the body tube, and then spend a lot of time SANDING the entire body tube, OR you could mask off the spirals , leaving a small margin on either side before filling. I peel off the masking (I use blue painter's tape) before sanding, but you can leave it on for most of the sanding. You still have to pull it off to sand down flush to the body tube.
     
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  16. Sep 21, 2019 #16

    kuririn

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    Depends on the tube. Most commercial tubes have two spirals. Then there are these:
    0920191812.jpg
    One deep brown spiral, dozens of spirals in between. This was in a TLP kit.
    In this case, Neil's method would be my method of choice.
     
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  17. Sep 21, 2019 #17

    neil_w

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    For what it's worth: I have found that it takes less time to sand the whole body tube than to just sand the spirals. This is for at least two reasons:
    1) I don't need to try to be "accurate" with my sanding, or follow any sort fo spiral pattern to avoid scuffing the glassine. Just run sandpaper up and down the tube willy-nilly.
    2) Applied with my finger, I can really remove the bulk of the extra CWF, so there's not much left to sand.

    Anyway, I'm just sayin' that I have found it quicker and easier to do the whole tube than just the spirals. This may be counterintuitive but it is my experience for the above reasons, at least for LPR-sized tubes. The smaller the tubes, the bigger the (relative) savings in time and effort.
     
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  18. Sep 21, 2019 #18

    beantownJPL

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    Personally, I have just never bothered with CWP for filling spirals. I find sanding primer can handle it all by itself. ...at least on tubes that already have tight spirals.

    I have occasionally touched up a few spots here and there that the first prime/sanding cycle didn't take care of with CWP, but then it's only a little bit. Saves a ton of work IMHO.
     
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  19. Sep 23, 2019 #19

    cerving

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    I've used spackle on GLR tubes with the wide and deep grooves, it works fine. With any of these fillers, putting in the filler is the easy part... it's sanding them down that's a PITA.
     
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  20. Sep 23, 2019 #20

    mbeels

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    This is what I do as well. There isn't that much sanding to do, and CWF sands down very quickly. I first go over it with 150 grit to knock down the high spots, and then switch to 220. That leaves it smooth enough for priming.
     
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  21. Sep 25, 2019 #21

    Nytrunner

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    Did someone say...spirals?

    [​IMG]

    I've used the CWF trick, but find myself using Bondo spot and glazing putty more these days. It doesn't require thinning so saves a bit of time, but does give off some VOCs so a mask and fresh air are recommended.
     
  22. Sep 25, 2019 #22

    beantownJPL

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    I'd also recommend some gloves.

    I've been tempted to try glazing putty, but haven't had need to be in an auto supply store of late. I've used it for its "intended purpose" many times in my fender-bending youth, very easy to work with and sands quite easily.
     

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