Primers, spiral filler and airframe filler--what do you use?

Finishing has never been my thing...I can make a rocket look decent but I stick to the basic krylon spray jobs and basic fillers. My rockets definitely look decent but they're not that perfect paint job--up close you can see filler lines here and there along with your occasional glue glob. I'm not looking for automotive finishes here but I would like to improve my spray can technique so...

What do you use for filling spirals? I know this routine pretty well and use elmers wood filler or even spackling but I'd like to hear what other stuff you may use.

What do you use for primer? Good 'ol krylon? I know a lot of guys used to use Killz. Any good high-build primers out there that might negate body filler on a rough finish?

Finally, what do you use on a fiberglass job when the whole airframe needs filling, particularly a job that's a little rough? I've primarily used bondo body filler...but I can never get a perfectly smooth surface with it. Perhaps it just takes some practice? Any lighter, better suggestions?

Thanks.

You pretty much covered the options...

I'd throw in Bondo Glazing and Spot Putty... the stuff in the tube... basically REALLY THICK (toothpaste consistency) primer with enough lacquer thinner to make it a paste. Best stuff I've found for tube spirals.

Lightweight and sands easily, and smooths on easily as well (so long as you don't let it get too dry) and works great.

Later! OL JR

marcusSRG said:

What do you use for filling spirals? I know this routine pretty well and use elmers wood filler or even spackling but I'd like to hear what other stuff you may use.

Click to expand...

I haven't found anything that works as well as Elmer's CWF, thinned to the consistency of thick paint, and then painted onto the spirals. I pre-prime the tubes first with a coat of primer, sand most of it off and then apply the filler. I have also used Bondo Glazing and Spot Putty, but in my experience CWF has the edge in overall performance.

marcusSRG said:

What do you use for primer? Good 'ol krylon?

Click to expand...

RustoLeum Painter's Touch Ultra Cover 2x. No one makes a better rattle-can primer (or paint, for that matter).

marcusSRG said:

I know a lot of guys used to use Killz. Any good high-build primers out there that might negate body filler on a rough finish?

Click to expand...

In some situations I use Dupli-Color High Build Filler/Primer, but I use it to augment other fillers rather than entirely by itself. It can get the job done by itself but it requires a lot of spraying, which gets expensive. (The stuff ain't exactly cheap.) It also produces Dust Bowl-levels of dust when it is sanded, but yeah, it works.

Nothing to contribute re: fiberglass, because I haven't worked with that material yet.[/QUOTE]

I use elmers cwf as well... i thin it out and coat the entire rocket... it gets messy and takes a little longer to sand... i also dont let it set up over night... lately ive been using the ace brand primer... ill sand the rocket with a rough grade sand paper first then move on to less course grades till i am happy with how smooth the primer is... from there i paint my entire the base color then sand it down and give it a light respray.... from there ill move onto the other colors...

Depends on the type of tubes/fins that I'm filling.

Wood fins and paper tubes I use Elmers CWF. Easy to sand, fills the spirals and grain well.

FG, Blue Tube and Magna Frame, I use the Bondo Professional Glazing Putty (2 part). It stinks to high heaven, but it sands very well and is reasonably strong. It makes getting a smooth, blended finish easy when put over your primary fillets.

For primer, I like Duplicolor Sandable Primer. It's a lacquer and comes in a variety of colors in both regular and high build thickness. There might be compatibility issues if you put a lacquer over enamel, so test first.

I use the Rustoleum Filler Primer you get in the automotive section at Walmart. They make other types of primers so make sure it says Filler Primer. I started using that when I couldn't find any of the Duplicolor high build primer around. It works very well.

The secret to filling with primer is you have to sand each coat down and only leave what is filling in. Even after the third for fourth coat, if you need that many, you will be sanding down to the fin or tube in most places. Only the final coat gets a light sanding where none of the BT or fin shows through. If you don't sand it down between coats, the grooves and indentations have to be filled to the depth of the groove or indentation, plus the thickness of the paint you leave on the flat areas.

It really doesn't matter what you fill with, Elmer's CWF, spackle, bondo, etc. You have to sand away what isn't actually filling in something. The prep is 90% of what it takes to get a great paint job.

I also do what MarkII does and pre-prime before filling. What I do differently is I'll use a very thin coat of white lacquer first. It drys hard, makes the grooves, grains and marks show up, and gives you a white layer to sand darker primers down to. You'll know when you have the primer sanded off the flat areas. Sometimes I'll put a second coat of the white lacquer on between primer coats just to get the color contrast.

As for fiberglass, I've used Bondo to fill tubes I glassed with 6 oz cloth. This last time I added a layer of 2 oz glass cloth as a sanding vail. I'll used a vibrating sander and just sand it smooth this time. The quick set up time of the Bondo, and the stink, makes it a PIA as far as I'm concerned. Anything left after the vail is gone will be filled with Elmer's CWF, spackle, etc. and then primed. The good thing about fiberglass is you can wet sand the primer and paints without worrying about wood or cardboard tubing getting wet and swelling.

I want to learn the best way to use Elmers CWF, how do I treat a balsa fin sheet so it doesn't warp. Thanks.

Handeman said:

The secret to filling with primer is you have to sand each coat down and only leave what is filling in. Even after the third for fourth coat, if you need that many, you will be sanding down to the fin or tube in most places. Only the final coat gets a light sanding where none of the BT or fin shows through. If you don't sand it down between coats, the grooves and indentations have to be filled to the depth of the groove or indentation, plus the thickness of the paint you leave on the flat areas.

It really doesn't matter what you fill with, Elmer's CWF, spackle, bondo, etc. You have to sand away what isn't actually filling in something. The prep is 90% of what it takes to get a great paint job.

Click to expand...

I think that's it pretty much right there...

I use the FnF for spirals. I know some others use bondo spot glazing putty. I'm sure that works well. The whole secret to a nice finish is the prep work and to a certain degree the type of primers you use. I prefer Duplicolor primer and paints. After filling in the spirals and sanding the body tube I spray a couple coats of primer. I sand in between each coat until I'm happy and don't see any imperfections. The last coat I wet sand until it's glass smooth and then laid down my paint. usually end up with a pretty decent paint job. Sometimes you just have to practice find out what works best for you.

Hi Marcus,
Everybody has their own methods. All the posts have great advice.
If you take the extra time you'll get great results whether it's sanding sealer, balsa fillercoat or Elmer's CWF.

For me - filling balsa grain using CWF:
https://modelrocketbuilding.blogspot.com/2010/09/carpenters-wood-filler-mix-ratios.html
For filling body tube seams, the mix is thicker:
https://modelrocketbuilding.blogspot.com/2011/11/cwf-filler-mix-ratio-for-body-tube.html

I still hit the filled parts (body tube seams or filled and sanded balsa) with Dulpicolor Filler/Primer.
Then sanding to surface again.
That'll fill any grain or seams left.

CWF won't really seal the wood or body tubes. It's still water soluble after it dries.

For GeorgeB,
Right now I'm building the Quest Aerospace One. Lots of balsa to fill!
I'm filling the balsa before gluing to the body tube with CWF.
After the first side was dry enough, I brushed CWF on the other side.
The large wing fin was warping but most of that will go away when you brush CWF on the other side.
I'm letting the large fin dry on a flat countertop with a weight on top. That should straighten any warp.
You should catch and correct the warping wood before it totally drys.

I use primer - duplicolor high build red and gray - to fill spirals.

Duplicolor primer for final coat before painting - red, gray or white depending on the top coat color.

Duplicolor lacquer for color. You really can't go wrong with Duplicolor.

Trim Monokote is a really nice way to add details or even cover the rocket.

Fins? I recommend replacing the balsa with basswood. Couple shots of primer and you're done.

Bones

Primer is what I use, but there is another type of "bondo"like filler called icing. I have done fillets and filling with it. It is very light weight.

Thank you Hcmbanjo,my current build is an Estes Photon probe.