Best technique for filling-in spiral groves on cardboard or phenolic tubes??

Please offer your experience and thoughts on the best filler material and technique for filling-in the spiral groves on cardboard or phenolic body tubes? I was thinking of using some of the Elmers Wood Filler material, that can be applied with a putty knife and then sanded once it dries. Thanks for the help!

PTP

op:

This has been heavily discussed before-- I'm sure you can find more information in a brief search of the forum.

To directly answer your question, yes, the Elmers Carpenter's Wood Filler is one of the recommendations you'll hear. Personally I've never had much luck with it. It all seems to "go away" when you sand it down level to the tube surface leaving as much of a spiral as when I started.

I prefer to use autobody spot putty. It comes in a tube from the local auto parts store. A common brand name is Bondo Spot Putty. It's a thick red paste, essentially a VERY thick primer with LOTS of solids and just enough lacquer thinner to make it a paste instead of dust. I daub it into the spirals and let it dry about half an hour or so and then sand it down flush to the surface of the tube with 220 grit sandpaper-- fills perfectly.

I'm sure you'll get plenty of recommendations, such as Fix-It Epoxy Clay from Apogee Components, which also looks like a good material. You'll probably also get a lot of naysayers telling you not to use this or that, or citing reasons why this or that is a lousy option (including the spot putty). I'm speaking from my experience and I suggest the spot putty. Ultimately it's up to you to follow whatever recommendations you choose.

Later! OL JR

I'd second the automotive spot putty. I've been using the green stuff...like this:
3M Acryl Green Spot Putty

I like to thin the auto spot putty with lacquer thinner then paint on spirals with a qtip or fine brush. Then 220 grit as previously described. Works a treat.

Many have stopped using all forms of "fillers" preferring to use Cheap (buck a can or less) Auto primers to do the filling. Since we're sanding off the majority of the primer anyway this adds little to the mass of the model, while speeding the building process. Personally haven't used a body tube filler or balsa filler on a model (MMX to BT-80 Upscale) in the last 20 years or so. Still producing babies butt smooth finishes on all surfaces.
Draw back if there is one. is it does create some overspray mess that needs to be controlled in a spray painting booth, Chamber, cabinet or cardboard box big enough for your model. in some places a dropcloth in front of the box also limits the cleanup.

First up, I'd never claim to have the right or only technique but this is what's working for me right now.

A while back I expirmented with thinning Carpenter's Wood Filler and found out a ratio for a good brushable mix for filling balsa:
2 1/2 parts CWF to 1 part water

I used this same mix trying to fill body tube seams but it was inconsistant.
Seam widths are different between tubes (or batches of tubes) and more often than not, some filler would pop out when sanding.
For the tube seams, I changed my filler to water ratio making it a little thicker.
4 parts CWF, 1 part water.

The thicker CWF stays in the seams now!
I use the thinner CWF mix for balsa and the thicker mix for seams.

Any leftover seam lines are filled during primer.
I find with this new seam mix I only have to apply CWF filler once and sand to surface.
Where I used to do a few heavier coats of primer (loading up and throwing away too many pieces of sandpaper)
now I only do one lighter coat of primer and sand.
Now filling is quicker with less steps.

The whole story is on my blog at:
https://modelrocketbuilding.blogspot.com/2011/11/cwf-filler-mix-ratio-for-body-tube.html

Good luck! In the end you'll end up with a technique that'll work best for you.

luke strawwalker said:

yes, the Elmers Carpenter's Wood Filler is one of the recommendations you'll hear. Personally I've never had much luck with it. It all seems to "go away" when you sand it down level to the tube surface leaving as much of a spiral as when I started.

Click to expand...

Do you mean the hardened stuff just comes out of the groove?

I've never worried about spirals with Estes and LOC tubes, but now I'm working with a couple of phenolic tubes that have big obvious spirals. So far I have put the Elmers stuff on the grooves and smoothed them off with a plastic scraper.* I haven't done any sanding yet but it looked like the smoothing off might take some of the material out of the groove leaving the top of the material slightly below the top of the tube. And then I'm wondering if the sanding process will remove the softer material below the level of the tube. Maybe using fine grit paper and a hard sanding block would help there. I've also wondered if the stuff shrinks a bit when it dries.

*I have a few of the plastic fake credit cards that get sent out in the mail, I've saved them for hobby use and they work well as scrapers to clean filler off of fins and such.

Here is an idea that I had recently- sand a very shallow curved notch in the edge of the plastic scraper, and when wiping off the excess filler center this notch over the groove so that rather than scraping off material more or less flush with the surface of the tube, it leaves a slight raised area over the ridge. Then sand this ridge down to the surface of the tube.

bjphoenix said:

Do you mean the hardened stuff just comes out of the groove?

I've never worried about spirals with Estes and LOC tubes, but now I'm working with a couple of phenolic tubes that have big obvious spirals. So far I have put the Elmers stuff on the grooves and smoothed them off with a plastic scraper.* I haven't done any sanding yet but it looked like the smoothing off might take some of the material out of the groove leaving the top of the material slightly below the top of the tube. And then I'm wondering if the sanding process will remove the softer material below the level of the tube. Maybe using fine grit paper and a hard sanding block would help there. I've also wondered if the stuff shrinks a bit when it dries.

*I have a few of the plastic fake credit cards that get sent out in the mail, I've saved them for hobby use and they work well as scrapers to clean filler off of fins and such.

Here is an idea that I had recently- sand a very shallow curved notch in the edge of the plastic scraper, and when wiping off the excess filler center this notch over the groove so that rather than scraping off material more or less flush with the surface of the tube, it leaves a slight raised area over the ridge. Then sand this ridge down to the surface of the tube.

Click to expand...

Well, I've tried using CWF on regular Estes-type paper tubes (various manufacturers/sources of kits/tubes) and I can thin it down, brush it into the grooves so that the groove/tube is COMPLETELY COVERED about 3/8 inch wide stripe over the groove, let it dry, and then sand it down level with the tube with 220 grit. When I'm done, it looks like I haven't done a blessed thing... the groove is just as evident as when i started. I tried it several times and found it just didn't do what I wanted to do.

The red autobody spot putty-- that I can take a little dollop on my fingertip, daub it onto/into the groove and on either side of it as I work my way up/down/around the rocket filling the spiral, let it dry a half-hour or so, and then sand it down with 220 grit, and it looks fantastic. No problems whatsoever and the spiral is GONE.

SO, I'll be sticking with the auto spot putty...

That's my experience anyway...

later! OL JR

PS. saw a neat vid on the Apogee website about filling spirals-- Tim was using the Epoxy Clay product he sells, daubing it into/onto the spirals as I do with the autobody filler, but then he used a RAZOR BLADE as a "squeegee" to get most of the filler off the tube on either side of the spiral and force the epoxy clay down into the groove filling it COMPLETELY... VERY neat idea! I'm going to have to dry it on my next build...

When it comes to filling phenolic tubing (at least the PML stuff i`ve used) and sometimes BlueTube ,those spiral grooves can be pretty deep ,in a relative way.

For me,it`s Bondo Red Spot putty in a tube ,although I have heard the 3M Acryl Blue is wonderful stuff also ,I just can`t seem to buy it at local shops (may need an automotive supply store)

Using an overspray of primer to fill these grooves would not be very effective at all ,and must be filled prior to prime/paint.

I remember years back ,I used a light ,fluffy looking "spackle" type filler on my first PML Phenolic project ,and it worked very well and was water clean up with minimal shrinkage.

On some cardboard tubes ,the spirals can be very minimal ,so a watered down woodfiller or as Micromeister mentioned ,several coats of high solids primer may be all that`s needed.

But alas ,I`m stuck on spot putty now and have been for a few years.It`s easy to apply ,dries fast and has minimal shrinkage when applied properly and it sands very very easily.If you use a good quality sandpaper ,it won`t clog too badly ,just check the paper once in awhile and tap out the dust often.

Paul T

I use the wood filler on raw tubes most of the time , if there is still filling to do after primering, I use the bondo spot putty.

something of note..bondo spot putty was designed to go on top of ,and bite into a primer coat ,, not under it.

I know it works either way for rockets but I always put it over primer to further ensure there is no future cracking ... so far, so good

Stymye said:

I use the wood filler on raw tubes most of the time , if there is still filling to do after primering, I use the bondo spot putty.

something of note..bondo spot putty was designed to go on top of ,and bite into a primer coat ,, not under it.

I know it works either way for rockets but I always put it over primer to further ensure there is no future cracking ... so far, so good

Click to expand...

Both times I tried to use the spot putty (un-thinned, by the way) on top of primer, it melted the primer and didn't seem very well adhered compared to when I put it directly on the tube. The primer was Rustoleum auto filler primer.

I like putting primer on top of the spot putty, as the filler primer fills any tiny imperfections in the spot putty and/or its junction with the tube. :wink:

Marc

Marc_G said:

Both times I tried to use the spot putty (un-thinned, by the way) on top of primer, it melted the primer and didn't seem very well adhered compared to when I put it directly on the tube. The primer was Rustoleum auto filler primer.

I like putting primer on top of the spot putty, as the filler primer fills any tiny imperfections in the spot putty and/or its junction with the tube. :wink:

Marc

Click to expand...

The spot putty I have uses lacquer thinner as a carrier, so it only makes sense it would eat up a regular enamel primer...

I've never had a problem with using it directly on the tube...

Later! OL JR

Marc_G said:

Both times I tried to use the spot putty (un-thinned, by the way) on top of primer, it melted the primer and didn't seem very well adhered compared to when I put it directly on the tube. The primer was Rustoleum auto filler primer.

I like putting primer on top of the spot putty, as the filler primer fills any tiny imperfections in the spot putty and/or its junction with the tube. :wink:

Marc

Click to expand...

well maybe contact 3m bondo corporation and let them know that their procedures are wrong ... no one said you can't put primer on top of bondo .. I just related that it's designed to go on top of an automotive filler/ primer base,
I read it on the bondo website.

Stymye said:

well maybe contact 3m bondo corporation and let them know that their procedures are wrong ... no one said you can't put primer on top of bondo .. I just related that it's designed to go on top of an automotive filler/ primer base,
I read it on the bondo website.

Click to expand...

:lol:

I can imagine being the customer service person at Bondo or 3M, and I get an email:

Dear Bondo,

I was using your product the other day to smooth the fins and body tube on my rocket...

:trashcan:

:jaw:

I think it often works fine either way. Probably just a specific incompatibility with the stuff I was using. I think either way makes sense so it becomes a preference and experience thing.

Marc

....lol..