How to fill spirals with the least amount of sanding?

[Bill S]

I use this stuff, available from Walmart: Bondo glazing and spot putty.

https://www.walmart.com/ip/Bondo-Glazing-and-Spot-Putty-00907ES-4-5-oz-1-Tube/16927984

I used to coat the entire tube to get the small dings and defects in the tube, and it worked well. BUT it was a ton of sanding. I now just use a gloved finger and put it on the grooves, and sand that down, using a second coat to ensure all of the areas where it shrank are filled in. I also use it for filling in balsa grain, after using some Duplicolor filler primer. Best way to do that is to use some lacquer thinner. I use a 3" or so bead on a piece of plastic, and use 1.5-2 standard eyedroppers full of lacquer thinner, mix well and use quickly. The thinner dries fast so make small batches and work fast, using a credit card to apply and scrape off as much as you can.

 

[DES]

Well, the Bondo, err plot, thickens!

I have the "Professional Glazing and Spot Putty." It includes the red hardener. It smells slightly less than Bondo Body Filler, but pretty much behaves the same. Are you saying there is another "Glazing and Spot Putty" that does not require mixing in a hardener? If so, then 3M has a horrible marketing department.

This is what I have:

View attachment 447830

Yes indeed, it does seems 3M has two versions of Glazing and Spot Putty. In nearly identical packaging. Suggest you give the #907, solvent based version a try. It works very well for minor filling.

 

[afadeev]

More product info in this thread:
https://www.rocketryforum.com/threads/ca-soak-fins-how-where-why.161021/#post-2030295

 

[roytyson]

I wouldn't be filling anything more than just the spirals as you're drastically increasing the amount of work. I refuse to build anything made of cheap cardboard with spirals, see my signature.

I feel you! Not one person will ever see a spiral on any pad, not even the low power pads. Build it, paint it, stuff it, light it.

 

[Pem Tech]

Not directly related to filling spirals but filling still but how in the hell do you get a nice surface on the inside of the Kraken tube fins? I tried once and it was a disaster.

I used wood filler, an old hotel key card, lots of primer and a butt load of sanding. Mine just have the first couple of inches filled, you can't see the rest unless you get all up in its grill. What went so horribly wrong?

 

[neil_w]

I feel you! Not one person will ever see a spiral on any pad, not even the low power pads. Build it, paint it, stuff it, light it.

As always, it depends on whether you fill spirals more for *others* or for *yourself*.

 

[Buckeye]

As always, it depends on whether you fill spirals more for *others* or for *yourself*.

Of course it is for me. In each new rocket, I try to do something new or better as compared to my previous builds. That's why I don't have swappable electronics bays, recovery gear, etc.

This time, I learned about Bondo!

 

[Woody's Workshop]

Red putty is lacquer based. I can't believe they still make that stuff. I guess there is a huge market for it in the hobby industry. No one would ever use that stuff in auto body repair anymore. Lacquer based products were out dated in the 70's.
It's known to swell, shrink and crumble during heat and humidity cycles. Especially under Lacquer paints.
EverCoat makes a much better, 2 part creamy polyester filler.
It's like plastic auto body filler (Bondo) but much, much less dense and easy to sand.
No air bubbles or tough skin of resin to break through after applying.
I use to use a skim coat over your plastic filler to fill in deep scratches and air pin holes and sand with 220 and your ready for a couple light coats of catalized primer.
Come's in a small metal cans. Last I knew you could get it in 8oz, 16oz and 32oz sizes.
Working with all kinds of fillers and putty's over the years, that Red Putty is just awful.
The dust stains your cloths and hands.
But if it works for you...

 

[Bill S]

EverCoat makes a much better, 2 part creamy polyester filler.
It's like plastic auto body filler (Bondo) but much, much less dense and easy to sand.
No air bubbles or tough skin of resin to break through after applying.
I use to use a skim coat over your plastic filler to fill in deep scratches and air pin holes and sand with 220 and your ready for a couple light coats of catalized primer.
Come's in a small metal cans. Last I knew you could get it in 8oz, 16oz and 32oz sizes.
Working with all kinds of fillers and putty's over the years, that Red Putty is just awful.

Could you mention the product name, or a link? It seems they sell lots of products, mainly in larger containers (ie, expensive).

 

[SkyFire]

Could you mention the product name, or a link? It seems they sell lots of products, mainly in larger containers (ie, expensive).

 

[SkyFire]

I use #907 Bondo for small imperfections and pin holes. Won't use it on large areas because it does crack like mentioned before. Should be fine for spirals. I use the Evercoat filler for larger areas (RC aircraft). Bondo Glazing and Spot putty dries very quickly! Sometimes I put it in a small cup and thin a bit with lacquer thinner. Spread it with small metal blade artist spatula. Sands very easily.

 

[AfterBurners]

You must be getting old, or turning into a perfectionist, or a bit of both!




I've switched to using Bondo for spirals, exclusively. Both for the ease and speed of application, and the durability.
Wood filler takes too many applications, and occasionally falls out of the spirals during sending, requiring a complete multi-step redo.

Once spirals are filled, I spray sandable primer over the body tube, and sand everything even.
They key is getting a quick drying primer, as all Krylon and cheap WM/HD primers clog up the standing paper unless you wait 1-2 days to let them fully dry.
For this purpose, the best I've found is "Krylon Industrial Tough Coat Light Gray Sandable Primer".
It dries in under 15 minutes, sands easily and quickly. You can apply and sand multiple coats in under one hour.
https://www.ebay.com/itm/KRYLON-IND...029447?hash=item48f3173407:g:O7QAAOSwPKpf-UhL


Epoxy would add a lot of weight.
If that's not a concern, you would go with fiberglass tubes to begin with.

Have fun!

I haven't used Krylon products in years. I've always used Duplicolor. A fantastic product, but expensive and not too many choices when it comes to colors, but their primer sands like butter. I agree some of the primers on the market today really do a nice job of coating the surface, but clog the sand paper if you don't wait long enough. Working with card board is another challenge in that you can't get too aggressive with, because the results would be a body / airframe that has a lot of imperfection and abrasions caused by over sanding one area too long. The epoxy theory above is a good idea, but maybe another option would be epoxy clay. It will allow you to press the clay into spiral and using a straight edge blade you can scrape the excess clay off. Let it dry and come back and sand it. No masking or mess with epoxy running everywhere. Dries like concrete. Not sure how deep the spirals are you are sanding, but you could try a small area and see how it works?

I'm with you on the sanding. I dislike sanding even wet sanding. At one time I was okay with it because I knew for a really nice paint job 90% is in the prep work. Anyway stick with it. Its the necessary evil when it comes to building rockets. I bought a couple PML kits and love the fact that there's no sanding on the tubes, aside from roughing them up with 220 to allow the primer to stick.

Good luck and hope it works out for you.

 

[Bill S]

Skyfire, thanks.

 

[afadeev]

I've switched to using Bondo for spirals, exclusively. Both for the ease and speed of application, and the durability.
[...]Once spirals are filled, I spray sandable primer over the body tube, and sand everything even. For this purpose, the best I've found is "Krylon Industrial Tough Coat Light Gray Sandable Primer".

I haven't used Krylon products in years. I've always used Duplicolor.

Completely agree - I've also switched to Duplicolor or Tamiya paints for top coats. The latter is even better, but yet more pricier than the former.
Tamiya primer is also fantastic, but is expensive and comes in tiny 180ml/6oz $11 cans. It almost hurts to spray the entire can onto one rocket, just to sand it off 15 minutes later.

That's where Krylon Tough Coat Primer comes in.
It's the only Krylon product I now use. You wont find it in HD/WM, so mail order is the only way to get it.
Krylon Tough Coat is an enamel primer that has some rubbery compound mixed in. Takes 60+ seconds of shaking to mix it all up. It dries fast and very even, fills gaps nicely, sands super easy, and stinks to high heaven. No matter how many doors I close, my wife smells it from 2 floors away. In the winter, I only use it late at night, after she goes to sleep

The epoxy theory above is a good idea, but maybe another option would be epoxy clay.

Epoxy clay is an all-around crap product.
It's heavy, messy to work with, and being non-liquid, neither penetrates nor sticks to the cardboard tubes very well.
It is also a total nightmare to sand. There are exactly zero use-cases where I would ever recommend using epoxy clay. After offering my package for free a few years back to anyone on TRF, with no takers, I threw mine away.

For me, right now, it's Bondo 907 for the spirals, then sanding, then a coat or two of Krylon ITC sandable primer.
On smaller or super nice (e.g.: Fliskits, Zooch) models, I might use Tamiya primer and paints exclusively. They dry fast and even, don't run, and never EVER wrinkle.

YMMV,
a

 

[RobertH3]

I'm sure the polyester product is better but will the vapor melt things, including you? The last time I was around polyester paint being used I ran from the vapor! Pure evil and you would need a VOC filter on a respirator to apply. Crazy good metal bond though.
I think Bondo lacquer putty, cut with lacquer thinner may stink for cars but is a nice alternative for spiral filling. It's a small fill that gets loaded with primer. Just be careful not to breathe dust when you sand.

Cheers / Robert

 

[Buckeye]

Epoxy clay is an all-around crap product.
It's heavy, messy to work with, and being non-liquid, neither penetrates nor sticks to the cardboard tubes very well.
It is also a total nightmare to sand. There are exactly zero use-cases where I would ever recommend using epoxy clay. After offering my package for free a few years back to anyone on TRF, with no takers, I threw mine away.

Now that is a perfect 1-star review!

TVM is always pushing the epoxy clay, and he did a video showing how to fill spirals with it. The spirals were very wide and deep. BlueTube, maybe.

 

[AfterBurners]

Now that is a perfect 1-star review!

TVM is always pushing the epoxy clay, and he did a video showing how to fill spirals with it. The spirals were very wide and deep. BlueTube, maybe.

I use it on fillets with no issues. No runs or drips. Can do a complete set without having to wait. Dries hard in 24 hrs. Also good for fixing quarters and other change to sidewalks. Very entertaining to watch pass byers trying to pick them up. Has many uses.

 

[DES]

I'm sure the polyester product is better but will the vapor melt things, including you? The last time I was around polyester paint being used I ran from the vapor! Pure evil and you would need a VOC filter on a respirator to apply. Crazy good metal bond though.
I think Bondo lacquer putty, cut with lacquer thinner may stink for cars but is a nice alternative for spiral filling. It's a small fill that gets loaded with primer. Just be careful not to breathe dust when you sand.

Cheers / Robert

None of the vapors are any good for you, and you really should use a respirator when working with any of the styrene or polyester resins, no matter how good your ventilation. Much, much more toxic that epoxy. But the thing you really need to look out for is the hardener.
The hardener for polyester is methyl ethyl ketone peroxide, and this is one of nastier chemicals you can run into. Organic peroxides, super reactive. That is why you need so little of it for polyester.

MEKP carries a Danger rating. Keep if off your skin, and out of your eyes. Instant eye damage. The crème versions probably a bit safer than liquid, less likely to get it in your eyes. The SDS says it can explode if you heat it. I suggest not finding out.

In simplest OSHA terms [... if you fail to follow the instructions...],

Caution - this product can hurt you;
Warning - this product can kill you;
Danger - this product will kill you.

 

[Buckeye]

I have had really good luck with the "smear and wipe" technique using the Bond Glazing putty. Basically you smear a thin film of the solvent based glazing putty over the body tube, let it start to dry a bit so it gets thicker, then quickly wipe it all off with a paper towel, scrubbing across the spirals. It leaves the filler in the groves, but very little on the surface of the tube. The putty dries fast, so you have to do a section at a time and not get carried away. You can repeat the process a couple of times if the groves are deep, or you can apply the putty directly to the grove, and use a plastic scraper to level it off. It goes really fast.

Then you sand and prime. Two coats of a primer, with sanding between usually fills all the spirals. This will depend on your body tube and how deep the groove are. I don't like "spray fillers". They are soft and gummy, don't sand well, and don't really seem to fill spirals well.

View attachment 447621View attachment 447620
View attachment 447622View attachment 447623

View attachment 447625

^^^This^^^^

I just tried this method. Nice and easy!!!! Thanks for the tip!

The "secondary" spirals, or whatever you call them, don't get filled very much, however. I can still feel them when I run my fingernail across. Maybe the filler primer will take care of them.

 

[DES]

^^^This^^^^

I just tried this method. Nice and easy!!!! Thanks for the tip!

The "secondary" spirals, or whatever you call them, don't get filled very much, however. I can still feel them when I run my fingernail across. Maybe the filler primer will take care of them.

The "secondary" spirals are under the surface of the paper, and the primer will fill those. Some builders going for the ultimate finish will open those up and fill them too, but I have never found it necessary. Maybe on larger diameter tubes if they are deep.

Once you have filled the spirals, sand the tube lightly to knock off any high spots and cut the gloss. Follow with a coat of a medium body primer. Once dry, sand again until you have "leopard spots", maybe 30% of the tube peaking through the primer. Wipe off all the dust, hit with one more coat of primer, and you should have a nice, clean tube.

It really isn't that much sanding, and it goes fast if you use a good primer, and let it dry. Lacquer based primers work well, like the Rustoleum grey automotive primers. They dry fast, and sand easy. Avoid enamel based primers and "high build primer fillers". They take too long to dry and tend to be soft and gummy.

Incidentally, the Bondo 970 works well to fill grain on balsa too. Smear it on quickly with a bit of pressure using a putty knife, then scrape it all off with a plastic epoxy scraper. It will stay in the grain. Easiest to do before you glue the fins to the rocket.

 

[tomsteve]

It really isn't that much sanding, and it goes fast if you use a good primer, and let it dry.

i took a technique from sanding on auto body work and applied it to sanding body tubes. in auto body, long hard blocks are used for sanding.
first rocket i tried it on was 3" dia so i took a 3" length of 3" by and cut about a 1/3 to 1/2 out. then glued a grab block on the outside. then took some 220 grit sticky back snadpaper and put it on the inside.
that was for sanding the body filler i used to fill spirals. when in primer i switched to 600 grit.
makes sanding real easy.

 

[Marc_G]

Another product, that works for me when I bother to use it, is Brodak sealer. I have two jars. One is plain, the other has a bunch of talcum powder mixed in to make it fill more. I apply with a fine brush carefully along the cardboard tube seam, let dry, spray the tube with filler primer, let dry, then sand down the seams. The primer helps prevent scratching up the glassine, and takes some of the sweating out of the process. After it's smooth, I spray the tube with a coat of Bullseye 123 white sealer primer. Lightly sand that and ready for top coat.

https://brodak.com/sanding-sealer-4-oz.html

 

[thom9894]

I'm a wood filler guy. Spent 5 hours filling and sanding my 4" LOC Nike Zeus so far. I fill the spirals so when I am building it it looks pretty at a foot away. Will be only my 3rd HPR, so I'm going to take my time and put some love into the build.

If you'd told me as a teenager that I'd be worried about spirals I'd ha e laughed. But I really enjoy spending time with my kits.

 

[Angel_of_the_Skies]

+1 on masking the spiral and filling it. I brush on filler primer for shallow spirals. Wood filler or automotive glazing putty for deep ones. Very little sanding required after.

This is something I’m curious about. This seems easy and straight forward. Why would one try a different method than this. To me this is more simple.

I’m about to start building the Apogee Zephyr Jr. and im trying to figure out how to fill the seems. As far as sanding, do you sand while the tube is still masked ? Do you run the risk of sanding the tube and pulling fibers ?

 

[H_Rocket]

If you want a really easy to use, almost zero shrink filler with none of the polyester fume problems try this stuff. Sands like a dream, is very lightweight, and sticks to most anything.

https://www.aircraftspruce.com/catalog/cmpages/superfil.php

 

[Angel_of_the_Skies]

If you want a really easy to use, almost zero shrink filler with none of the polyester fume problems try this stuff. Sands like a dream, is very lightweight, and sticks to most anything.

https://www.aircraftspruce.com/catalog/cmpages/superfil.php

For a MPR, does clay putty really affect the weight drastically?

Looking to build an MPR for sport, so I don’t think it would really matter, but I’m very curious

 

[H_Rocket]

For a MPR, does clay putty really affect the weight drastically?

Looking to build an MPR for sport, so I don’t think it would really matter, but I’m very curious

Depends on how much you glop on. If you’re just filling spirals, you could use almost anything without adding a noticeable amount of weight. I go for things that are easy to use. I personally go for the lightest possible and don’t use anything for spirals. To me. It’s just not worth the effort.

 

[bjphoenix]

I've only filled a couple. For normal Estes and LOC tubes I just leave the spirals.
I had a piece of tube I bought somewhere that wasn't really cardboard, maybe it was phenolic, but it had big enough spiral grooves that I wanted to fill them. I already had some JB Weld epoxy putty leftover from another project so I used it. I agree that it was hard to work with. People have mentioned plastic hotel key cards, I did a similar technique but I used a single edge razor blade. I rolled the putty up into small diameter "snakes", pressed them into the spirals, and scraped off the excess. Very little sanding was required. Teh surface wasn't perfect, when scraping off the excess it might pull off a little bit too much. A couple of coats of primer and some sanding and it looked good enough for me.

My wife had a big paint project recently in our house. Her painter did some repair on dented door frames and with the red bondo glazing putty. That stuff has a very strong smell. The next day he sanded and painted. I use Elmers wood filler for various things but it is hard to get it the right consistency and it doesn't spread very well. I would like to try the red bondo.