filling spirals

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KEN R

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do you fill the spirals before or after you glue the fins on?
 

crossfire

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What do you guys use to fill the spirals? After many years of trying I still not satisfied how mine turn out.
 

prfesser

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What do you guys use to fill the spirals? After many years of trying I still not satisfied how mine turn out.
Adding to that question, what satisfactory combinations of the following have been found?

Cardboard tubing and rattlecan primer
Cardboard tubing and other primer/ spiral filler
Phenolic and your favorite spiral filler of any sort (can be wet-sanded)

Cardboard tubing usually must be dry-sanded, and most rattlecan primers I've tried do not dry-sand well even after weeks of drying; constant, rapid clogging of sandpaper. I tried drywall sanding screen, no better. I think some have mentioned wet-sanding cardboard but it's not worked for me. (ruined one rocket)

Best -- Terry
 

Spitfire222

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I usually spray the entire body tube first with filler primer, then use either Carpenter's Woof Filler (CWF) or Bondo Spot Glazing Putty. Some people only use multiple coats of primer. I find that the filler primer does two things: 1. It covers the glassine to help prevent "fuzzies" from future sanding, and 2. helps to begin filling the spirals. The CWF or Putty do the rest to my satisfaction. I only do one round of filling, while others do several, it depends on the kind of finish you're after. For me, one application is sufficient, keeping in mind future coats of primer, color, and clear.

With regards to the rattle can primers, I've never really had an issue with them. Yes, they clog sandpaper when used dry, which is why I have huge stashes of sandpaper and throw them out as they become clogged while dry sanding. Used wet, it's different, but still I'm not shy about discarding a piece of sandpaper and grabbing a fresh one often.
 

Bill S

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Definitely before you put the fins on. I use Bondo Auto glaze (red stuff), and thin it some with lacquer thinner. The thinner evaporates quickly so you have to work fast. I use an old credit card to smear the body tubes, let dry, sand off leaving it in the grooves and low spots in the tube. Only issue is that it is red, so if you are doing a white rocket, you need to cover it with a non-white primer (I always use grey primer unless its to be a white rocket anyways).

I end up sanding each coat of primer as the one I use is somewhat rough - a quick sand-down with some 400 grit sandpaper (very lightly mind you) does the trick.
 

neil_w

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Before the fins, 100%.

I apply thinned CWF to the entire body tube... then sand. I slop it on and spread it as thin as I reasonably can with my fingers. I find this to be easier and quicker than trying to confine the CWF and sandpaper just to the spirals. Then I apply filler/primer and sand.

Using this method, a bit of spiral shows through on occasion; if it does I don't worry about it.

Largest piece of tubing I've done this way is my current build, 24" of BT60. At some point a tube might become large enough that it's just too much to CWF the whole thing, but I haven't hit that point yet.
 

afadeev

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do you fill the spirals before or after you glue the fins on?
100% before the fins, unless I screw something up (e.g.: wanted to apply vinyl wrap, had to give up on that, now have to go back and fill those #$%^ spirals).

What do you guys use to fill the spirals? After many years of trying I still not satisfied how mine turn out.
I'm using the following, sometimes interchangeably, sometimes depending on the depth of spirals involved.
Listed below are the options in the order in which I resort to them as of this season:
  1. 3M 907 Bondo Glazing & Spot putty.
    1. Pros: inexpensive, quick and easy application (squeeze out of the tube), dries quickly, easily sandable.
    2. Cons: a little stinky, wasteful in application on shallow spirals (hard to apply small quantities).
  2. Paint primers, Krylon Industrial Tough Coat (KITC) in particular.
    1. Pros: inexpensive, dries quickly (unlike other primers), sands VERY easily, doesn't clog sanding paper (true for KITC, not true for other paint primers). KITC has a rubber-like component to the paint that fills spiral valleys way quicker than other primers.
    2. Cons: a little stinky, requires multiple (3+) passes to "build up" enough material in the spiral valleys. Can't be applied precisely, thus requires more sanding cycles.
  3. Tamiya Putty (white).
    1. Pros: the easiest to sand, dries quickly, can fill-in 1/8" of a valley in one pass.
    2. Cons: expensive, comes in small 32g tubes. Impractical for large airframes.
  4. Elmer's WoodFiller (white).
    1. Pros: cheap, can be dissolved with water and "painted" into the spirals.
    2. Cons: requires multiple (3+) passes to "build up" the filler in the spirals. Takes a while to dry. Can be hard to sand. Doesn't stick to glossier tubes, and will fall out during sanding unless you pre-sand the spiral valleys before application.
  5. HobbyLite balsa filler - not anymore.
    1. Pros: cheap, can be dissolved with water and "painted" into the spirals. Easy to sand.
    2. Cons: requires multiple (5+) passes to "build up" the filler in the spirals. Far too fragile (falls out of spiral in chunks), doesn't stick to tubes all that well unless you pre-sand the spiral valleys before application.
For shallower spirals I go with #2.
For deep spirals I go with #1.

YMMV.
 

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MALBAR 70

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Put me down for the Bondo Glazing & Spot putty as well. Works great on spirals and plastic nosecone seams too.
Lately, I've just been giving the rocket a couple of heavy coats of Rustoleum 2 in 1 Sandable Filler Primer, sanding it down and calling it good.
Nothing is more irritating than spending a couple of hours filling and sanding spirals, only to have sections pop out after the top coat has been applied.
 

Mike Haberer

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Bondo on nose cones (sticks best to the plastic)..
Thinned CWF on spirals, then thinned Duplicolor Filler and Surfacer (plus sanding) before paint.
Deft Laquer Sanding Sealer on balsa.
 

Jozef

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Cardboard tubing usually must be dry-sanded, and most rattlecan primers I've tried do not dry-sand well even after weeks of drying; constant, rapid clogging of sandpaper. I tried drywall sanding screen, no better. I think some have mentioned wet-sanding cardboard but it's not worked for me. (ruined one rocket)

Best -- Terry
I

Try Duplcolr filler primer. It will not clog your sandpaper.
 

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hcmbanjo

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With regards to the rattle can primers, I've never really had an issue with them. Yes, they clog sandpaper when used dry, which is why I have huge stashes of sandpaper and throw them out as they become clogged while dry sanding. Used wet, it's different, but still I'm not shy about discarding a piece of sandpaper and grabbing a fresh one often.
Years back I tried to wet-sand a body tube . Never again!
I dry sand body tube and fins filled with CWF and then sprayed filler/primer with 400 grit.

You can extend the life of your sandpaper pieces many times over by (circular) brushing out the clogs
with a soft brass brush under a stream of water in a sink.
First picture shows the brass brush I got from Home Depot.
Second picture is clogged 400 grit before and after the brushing under running water.


S. Block 3.JPG S. Block 5.JPG
 

Philip Tiberius D.

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Adding to that question, what satisfactory combinations of the following have been found?

Cardboard tubing and rattlecan primer
Cardboard tubing and other primer/ spiral filler
Phenolic and your favorite spiral filler of any sort (can be wet-sanded)

Cardboard tubing usually must be dry-sanded, and most rattlecan primers I've tried do not dry-sand well even after weeks of drying; constant, rapid clogging of sandpaper. I tried drywall sanding screen, no better. I think some have mentioned wet-sanding cardboard but it's not worked for me. (ruined one rocket)

Best -- Terry
 

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Philip Tiberius D.

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Or this... I have no problems sanding the medium grey... white seems to work on the Rustoleum but it’s hard to find at my Lowe’s. I usually do a couple of coats 30 or so minutes apart then sand after a few hours. I try to fill spirals with minwax wood filler otherwise you end up burning through a lot of primer.
 

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Greg Furtman

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Off Grid Gecko

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Good info in this thread. I've found spackle or drywall mud to be particularly effective on spirals. The stuff is made to look like your walls were made out of one continuous sheet, after all, and after doing my small house, I can spot a terrible drywall job a mile off.
I have a couple of questions to add to the OP if nobody minds. Was thinking of making another thread but saw this and figured I'd not contribute to the endless supply of spiral filling threads.
Do you seal your tubes before trying to fill spirals? I find that sanding, especially wet sanding, will raise fuzzies from the depths in silly places all over the tube. What can penetrate well without interfering with the glue bond later? I'm thinking just mask the fin tab areas as those will be filled in with fillets later anyway. Shellac spray is my new favorite sealer and seems to work well. On my current build, I applied it immediately after attaching the fins and lugs, and now I have spirals to get at (I was hoping it would gloss them over after seeing the initial test results.
I can't bring myself to use spot putty anymore. It dries far too fast (maybe my climate?) and makes a mess of my fingers and clothing every time. It sands into some type of rouge that colors everything.
On that note, what about application? @neil_w mentioned coating the tube with his fingers, but how do you avoid built up spots and blotches? I too would like to do the whole tube as these Estes deals are full of tiny dents and dings that drive me batty more than the spirals do. Luckily, I think the first coat of primer took care of those, but still annoying to see them on the naked tube. Like orange peel on a show car.
Filling a flat surface, fine. I have those putty knives. Filling a 2" tube however, that's a trick to get the surface smooth. Maybe better to do one half of the tube at a time to avoid fingerprints and blemishes, but even then, is there an easy-scrape method that any of you use to get some CWF or other material to drop a smooth surface that's easier to sand clean without little hard nuggets? I don't want flat spots all around the spot I'm trying to take down.

Just some more questions that I don't see discussed as often. What are the tools and techniques that you use for application of whatever filler, be it bondo or spot putty or CWF? I think the primer method is pretty self explanatory, but in that case I wonder how you avoid raising fibers from the substrate while sanding.
 

neil_w

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@neil_w mentioned coating the tube with his fingers, but how do you avoid built up spots and blotches? I too would like to do the whole tube as these Estes deals are full of tiny dents and dings that drive me batty more than the spirals do.
I can only tell you what I do. I slather with my index finger, and when there’s a coating on the tube I keep running my finger over it to smooth it out until the layer is very thin, or until the CWF is dry. The remaining very thin layer is quick and easy to sand with 400 grit paper.

I have not tried (yet) anything as lashed as a 2” tube, although I have an upcoming build with a section of BT70 that will be my first.
 

Jozef

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Try using a maroon ScotchBrite pad. They are around 320 grit. And they are about 3/16-1/4" thick. Think 3D sandpaper. They don't fill up very fast & when they do you can rinse them in mineral spirits and blow them out.
T

They work great.... but only issue is they do not level the surface imperfections on cardboard tubes. I use the fine gray pads before applying finish coats, but leveling the surface beyond filling spirals requires alternating primer coats and block sanding.... and time
 

Greg Furtman

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T

They work great.... but only issue is they do not level the surface imperfections on cardboard tubes. I use the fine gray pads before applying finish coats, but leveling the surface beyond filling spirals requires alternating primer coats and block sanding.... and time
@Jozef I've taken pieces of body tube a little larger than the one I'm working one, sliced them in half, glue the two halves together and then glued a block of wood on the outside as a handle. Then I put a piece of ScothBrite pad on the inside and use the assembly to sand. Works pretty good.
 

Jozef

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@Jozef I've taken pieces of body tube a little larger than the one I'm working one, sliced them in half, glue the two halves together and then glued a block of wood on the outside as a handle. Then I put a piece of ScothBrite pad on the inside and use the assembly to sand. Works pretty good.
Thats a great idea. I'll have to give its try....
 

BABAR

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For the creatively lazy rocket builder, there is always the AFTER painting technique.

By the way, if you ever just WANT to make colored spiral stripes on a rocket, vinyl/electrical tape now comes in many colors and because it stretches, it can make true helical configuration.

2B8F1AC1-55E2-468E-8742-40890A55F5EC.jpeg
 

tomsteve

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T

They work great.... but only issue is they do not level the surface imperfections on cardboard tubes. I use the fine gray pads before applying finish coats, but leveling the surface beyond filling spirals requires alternating primer coats and block sanding.... and time

take a piece of BT the same size and cut it in half/third. length of mine are 3-4" for most.glue a grab block on the high point of the arch. 3m make s sandpaper that has a light tack back that works great in the new body tube sanding block ya just made.
 
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