filling body tube lines

Chuck Gassert · May 1, 2019

Good morning,
What is the best material to use for filling the spiral seams on body tubes.
Thanks
Chuck

Jim Hinton · May 1, 2019

I like the Elmer's (or similar) water based wood doughs. These use a carpenters glue as a bonding agent. I thin them down to a slurry with water and apply it to the seam lines. One application gets lighter spirals. Ther 'death valley' spirals (LOC, Aerotech, some Estes) require two or three applications, sanding between applications. The current production stuff is kind of a pink-purple out of the tub. As it dries the color changes to a natural wood tone. Easy to tell when it's dry and ready to sand. Also pretty good as general filler and for fillets on low to mid power.

Jim

Chuck Gassert · May 1, 2019

Jim Hinton said:
I like the Elmer's (or similar) water based wood doughs. These use a carpenters glue as a bonding agent. I thin them down to a slurry with water and apply it to the seam lines. One application gets lighter spirals. Ther 'death valley' spirals (LOC, Aerotech, some Estes) require two or three applications, sanding between applications. The current production stuff is kind of a pink-purple out of the tub. As it dries the color changes to a natural wood tone. Easy to tell when it's dry and ready to sand. Also pretty good as general filler and for fillets on low to mid power.

Jim

Thanks Jim

dr wogz · May 1, 2019

2 or 3 coats of a sandable primer once the rocket is built. spray, sand, spray, sand, spray, sand.. I'll even spray colour and sand a lot of it off..

Chuck Gassert · May 1, 2019

dr wogz said:
2 or 3 coats of a sandable primer once the rocket is built. spray, sand, spray, sand, spray, sand.. I'll even spray colour and sand a lot of it off..

Thank you Dr.

neil_w · May 1, 2019

Based on a recommendation here recently, I've just started applying very thin CWF to the entire body tube, rather than attempting to confine it to the spirals. So far I'm very happy with this approach, which has multiple advantages:
1) Quick to apply: just use your finger to slather it on to the whole body tube, and then run your finger over it all a few times more to remove excess. No fine application tracing spirals or careful squeegeeing off excess.
2) Easier to sand. Even though there's *more* to sand, it's easier because you don't have to worry about staying off the uncovered tube.
3) Fills irregularities in tubes beyond just spirals. Tubes treated this way feel noticeably smoother across the entire surface.

The only disadvantage I can see is that it uses more CWF, but that's really in the "don't care" territory as far as I'm concerned.

Disclaimer: I've tried this on modest-sized LPR tubes only thus far, can't vouch for using it on a large MPR or HPR tube.

Chuck Gassert · May 1, 2019

neil_w said:
Based on a recommendation here recently, I've just started applying very thin CWF to the entire body tube, rather than attempting to confine it to the spirals. So far I'm very happy with this approach, which has multiple advantages:
1) Quick to apply: just use your finger to slather it on to the whole body tube, and then run your finger over it all a few times more to remove excess. No fine application tracing spirals or careful squeegeeing off excess.
2) Easier to sand. Even though there's *more* to sand, it's easier because you don't have to worry about staying off the uncovered tube.
3) Fills irregularities in tubes beyond just spirals. Tubes treated this way feel noticeably smoother across the entire surface.

The only disadvantage I can see is that it uses more CWF, but that's really in the "don't care" territory as far as I'm concerned.

Disclaimer: I've tried this on modest-sized LPR tubes only thus far, can't vouch for using it on a large MPR or HPR tube.

Thanks Neil!

Banzai88 · May 1, 2019

If, and only if, they're too big to deal with with the filler primer, I get filler in a toothpaste style tube and put it only in the spirals. Dry overnight, quick sand to knock out the big stuff, then filler primer handles the rest of it.

Chuck Gassert · May 1, 2019

Banzai88 said:
If, and only if, they're too big to deal with with the filler primer, I get filler in a toothpaste style tube and put it only in the spirals. Dry overnight, quick sand to knock out the big stuff, then filler primer handles the rest of it.

Thank you sir!

GlenP · May 1, 2019

I have not tried this yet, but was thinking of just using the spray primer, spray it in a cup and brush it on the spirals, with a fine tip brush, or even a toothpick. Let that dry then spray the whole rocket. Sand it down to knock down the brushed on ridges in the spirals. Crazy enough?

Chuck Gassert · May 1, 2019

GlenP said:
I have not tried this yet, but was thinking of just using the spray primer, spray it in a cup and brush it on the spirals, with a fine tip brush, or even a toothpick. Let that dry then spray the whole rocket. Sand it down to knock down the brushed on ridges in the spirals. Crazy enough?

I have thought of that also Glen. Haven't tried it yet but just might experiment a bit. Thanks

Banzai88 · May 1, 2019

GlenP said:
I have not tried this yet, but was thinking of just using the spray primer, spray it in a cup and brush it on the spirals, with a fine tip brush, or even a toothpick. Let that dry then spray the whole rocket. Sand it down to knock down the brushed on ridges in the spirals. Crazy enough?

The solids rapidly settle out of the solvent, and you end up with runny gray paint and a thick film of yuck in whatever you spray it in.

For under $5, you can have a handful of universal spray heads that will go as small as a 1/4" spray spot if the standard spray head produces too much of a fan pattern for what you're doing.

GlenP · May 1, 2019

I have mainly only used the spray can in a cup technique with paint, not primers, to touch up those small spots after masking when you have to clean up the mask line. So, yeah if the primer has a heavier solid mix to it, might not work as well as regular paint, maybe in small quantities. but could also just use a bottle of paint as well to brush in the spirals, as long as it blends well with the spray paint, I guess.

slohand · May 1, 2019

Automotive glazing putty is super easy to work with. Dry's very fast, sands easily and takes primer/paint beautifully.

mbeels · May 1, 2019

GlenP said:
I have not tried this yet, but was thinking of just using the spray primer, spray it in a cup and brush it on the spirals, with a fine tip brush, or even a toothpick. Let that dry then spray the whole rocket. Sand it down to knock down the brushed on ridges in the spirals. Crazy enough?

I've heard that KILZ primer is a brush paintable primer that builds up well for spirals, but I haven't tried it.

Chuck Gassert · May 1, 2019

slohand said:
Automotive glazing putty is super easy to work with. Dry's very fast, sands easily and takes primer/paint beautifully.

Thanks Slo

prfesser · May 1, 2019

slohand said:
Automotive glazing putty is super easy to work with. Dry's very fast, sands easily and takes primer/paint beautifully.

I've diluted glazing putty with enough lacquer thinner to make a thick paint, then apply with a brush or even a gloved finger.

Event Horizon · May 17, 2019

My concern about using automotive based spot fillers, like red spot putty, is that I don't believe that these fillers are very flexible. I'm currently working on 2.6 inch diameter tube (Aerotech white) and I realized right away that this diameter tube is very easy to deform with light finger pressure. There has to be something a bit more flexible?
Am I thinking correctly? or worrying for nothing? Does the motor mount, the ejection baffles and couplers stiffen up the tube a lot?

rharshberger · May 17, 2019

Event Horizon said:
My concern about using automotive based spot fillers, like red spot putty, is that I don't believe that these fillers are very flexible. I'm currently working on 2.6 inch diameter tube (Aerotech white) and I realized right away that this diameter tube is very easy to deform with light finger pressure. There has to be something a bit more flexible?
Am I thinking correctly? or worrying for nothing? Does the motor mount, the ejection baffles and couplers stiffen up the tube a lot?

Spot and glazing putty is more of a very high solids lacquer primer than a filler like bondo, unless really caked on thick I have had few issues with it cracking. Its also recommended to use it on top of the primer.

Marc_G · May 20, 2019

For Kraft paper tubes e.g. Estes, I first spray filler primer and get a good coat covering the glassine surface. Many times, two coats of this is thick enough to sand down and eliminate the spiral.

If not, I use Brodak sanding sealer thickened with talc (real talk, not cornstarch) painted onto the spiral with a thin detail brush. Let dry, sand, spiral gone.

Advantage of this approach is no scuffing of the glassine layer. This has been key for me, using the sandable high build filler primer first before the Brodak.

I might do a white primer coat over the sanded, spiral-fixed rocket at this point.

AfterBurners · May 20, 2019

There's numerous article in this forum on this topic along with prepping fins for flight sanding etc.

jqavins · May 22, 2019

For some tubes I've found the grooves so small that I just can't push any filler into them. For those, prime, sand with 320, prime, sand with 400, paint.

When they're wider, I've used wood putty and foamed DAP spackle with equal success and ease. Lately I've been using 3M foamed spackle + primer for filling balsa grain with great success, better than the other two products I mentioned. I haven't tried it yet for spiral grooves, but I'm very hopeful.

I don't remember what wood putty I used, but it probably wasn't the CWF that so many swear by. I'll have to try that some day.

filling body tube lines

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