How do I paint swoopy stripes with smooth edges?

[TomSmith58]

Folks I tried out this paint scheme

And I got lumpy edges. They wandered and weren’t smooth curves. I used CAD to create a template. Unfortunately it was a male template. A female template might have been better.

I covered the nosecone and payload section with blue tape first. I put double sided tape where I wanted my template. Then I hand aligned my template and stuck it to the double sided tape. I cut around the edges of the template with an Exacto knife freehand. That caused the wandering edges. I then peeled off the TE molars and tape underneath. And I painted. I used white primer and fluorescent green paint.

After the paint dried I peeled off the remaining tape. I saw the wandering edges. I carefully scraped the borders of the green until it was more of a smooth curve.

The used of an Exacto leaves scratches on the carbon. Also the paint was extra thick at the edges. I think this is called a paint dam. I used 600 grit to take the edges off and of course the white showed through.

Does anybody know a better way to mask off a complex shape? It is especially hard on a compound curved item like a nosecone.

Does anyone know how to prevent paint dams?

Thanks
Tom

 

[les]

For the main tube you could try using friskit film. Put your template over the film and cut it to shape before you apply the film to the rocket

For the curving nosecone I would try using some fine Tamiya tape. Use some thin stuff (2mm) for the edge of the curve, and apply more using wider tape to get width, then you can finish off with blue masking tape for the balance.

For paint dams you can try to make sure the top paint is a thin as possible by doing very light coats. Otherwise try to very lightly wet sand with a 600 grit (or higher). Don't try to get it all - just the worst high spots and then clear coat.

 

[Nathan]

Don't use painter's tape. Mask the edges of the curves with 1/4" 3M Fine Line tape. Then finish the masking with 3M Precision masking tape, and also plastic sheeting if necessary.

I don't prevent paint dams. I wet sand and polish my paint jobs (1000 grit then 2000 grit), and the wet sanding also removes the paint dams.

 

[mikec]

+1 to all of those recommendations. If you're cheap and/or don't have ready access to speciality hobby tapes, regular Scotch tape can be used to mask and leaves a cleaner edge than blue tape. See https://www.nar.org/educational-resources/model-rocket-building-techniques/masking-painting/

 

[TomSmith58]

Thanks guys, this is really helpful.

 

[GrouchoDuke]

It's tough to get a smooth edge if you're going from an unpainted surface (i.e. awesome looking carbon) to a surface with both primer & paint over it. Like others have said, cutting your paint mask before you put it on there or using a thin flexible tape is the first step. I haven't had good luck removing tape once the paint's dry because the paint always gets little chips & leaves a thick edge. I remove the tape (or mask) as soon as the paint is tacky (i.e. if you touch it, it'll still leave a fingerprint). For a case like your Mongoose, there might be a paint that'll stick to the carbon without primer. That'd let you have a thinner edge & dodge that pesky primer line after wet sanding.

For rockets that are completely painted, I start with a filling primer, then sand most of it off. If there are high spots or other abnormalities in the finish, it may take several prime/sand iterations. After that, I spray the base coat. I like starting with the lightest color first, as long as the paint scheme allows for that.

Once the base coat is dry, I put on the mask. For masks that wrap all the way around the rocket, this seems to always take 4 or more hands to do - get help. For cutting masks, my favorite is to use a vinyl cutter. We have a Silhouette Cameo 3 and it works like a champ for cutting rocket paint masks. I really like Enduramatte vinyl for spray paint masks.


Sanding in between coats can work really well to get a great final finish, but follow the directions on your paint on how best to do multiple coats. If nothing else, you can wet sand everything once it's complete. I like to start with 1000 grit for wet sanding, but that depends on how smooth your paint went down, how thick your paint is, etc. Watch out though - it's really easy to sand through your color.

So, take your mask off as soon as the paint is tacky. I use an x-acto knife. You have to be ultra-careful not to touch any of the fresh paint while you're removing your mask. You'll probably want help for this step too. Once all the mask is off, the paint should smooth out (flow or whatever you want to call it) a little bit on the edges.

In this photo, you can see one bit of mask removed and another one still in place.



After it's completely dry, wet sand carefully to get it perfecto. Depending on your rocket weight & how the paint looks, you may or may not want to clear coat it.

 

[TomSmith58]

Groucho
Thanks! That was great. That rocket looks awesome...and the little girl doesn't look too bad either.
Thanks
Tom

 

[JohnCoker]

What I do to get razor-sharp lines is paint a light coat of the base color after masking. That seals the tape edges so the next color doesn't bleed underneath.

jcrocket.com/simple-painting.shtml

 

[Rob702Martinez]

got to feather the edges... do you want it to look just like it does now, but with a nice paint job/finish? You are in CA? How big is that thing? I use many ways to do stuff like this.