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  • October 25, 2020, 07:05:51 PM

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Author Topic: CA ridges showing through paint top coat?  (Read 418 times)

Offline Dennis Toth

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CA ridges showing through paint top coat?
« on: October 13, 2020, 10:52:03 AM »
Guys,
Am working on finishing a top color coat over the fuse/wing center planking joint. I got the fuse in place, added some epoxy/fiberglass flower filler then used Elmer's wood filler as smooth coat. This came out very smooth, I used some CA to seal the sanded the filler by applying and wiping off. This I sanded with 400 and thought I was ready for the black color coat. I seemed to have missed getting all the CA that got wiped onto the planking area sanded totally flat. The paint is Design Master acrylic lacquer and goes on very smooth (electric don't need fuel proof). Now for the bad news. Once the paint dried there were streaks down the center planking where the CA wipe was applied. It looks like where the CA wipe went over the planking it was not totally flat. I sanded the streak area flat with a block to get it totally flat. Then after wiping down, re-sprayed the DM black. It is very nice paint and goes on very nice. BUT, when it dried there were the streaks. OK, sanded it down again and re-coat, same result. On a test piece I wiped on CA just as I did the fillet, let it kick and set for a few hours then sprayed the DM black over it, no problem.

I called Design Master customer service, which is very good. They said they never ran across this issues but admitted they didn't work with modelers that much. We discussed an option of using a primer first then top coat. I have done some test pieces and it goes over the primer with no problems. I will try this on one panel on the bottom.

Having said that has anyone had this kind of experience with any type of paint going over CA sealed surface (I know Windy used CA to seal lots of small pieces before painting with no trouble)? If so how did you solve the issue.

Thanks,   DennisT

Offline Randy Powell

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Re: CA ridges showing through paint top coat?
« Reply #1 on: October 13, 2020, 12:44:39 PM »
I've had weirdness happen. Never this particular weirdness. No idea unless there is some sort of chemical reactivity going on.
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 Randy Powell

Online Avaiojet

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Re: CA ridges showing through paint top coat?
« Reply #2 on: October 13, 2020, 01:50:16 PM »
Primer?
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Offline Dennis Toth

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Re: CA ridges showing through paint top coat?
« Reply #3 on: October 14, 2020, 08:02:46 AM »
I did the test with the primer on one section on the bottom. The primer is a universal sandable solvent based material that I have used under dope and other paints. After sand down the black DM paint to where I could not see or feel any ridges I applied the spray primer of a section that had previously had the ridges develop. The primer went on smooth with no bad reaction. Let it dry several hours. When I came back to check how it was doing a problem developed in that as the primer dried and I assume shrunk a bit it formed gaps in the film surface down to the bottom surface paint. Some places adhered well but the surface was uneven. The prep I did was to sand down the DM black paint with 150 grit dry until smooth with no ridges. Then a light sand with 400 dry. and spray area with the primer. My thought was to not get it super smooth so the primer had something to grab to.

I am working with a test piece now and trying to apply a clear coat (Diamond Clear) seal to the DM paint that can allow a smooth coat. So far the DC went on smooth, will check in a few hours to see if it can be painted over with the DM.

Best,   DennisT

Offline Dennis Toth

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Re: CA ridges showing through paint top coat?
« Reply #4 on: October 15, 2020, 06:23:52 AM »
This is becoming a real pain. For something that should have been a 15 minute deal it's taking four days of time to sand, test, sand again, test. Still no clear answer. The Diamond Clear went on and dried hard but in the areas were the CA ridges were it is not smooth and the ridges are still there. For some reason the area where the CA streaks are will not seal nor will it allow a fill in to get it to sand smooth.

Best,    DennisT

Offline Ken Culbertson

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Re: CA ridges showing through paint top coat?
« Reply #5 on: October 15, 2020, 07:23:59 AM »
This is becoming a real pain. For something that should have been a 15 minute deal it's taking four days of time to sand, test, sand again, test. Still no clear answer. The Diamond Clear went on and dried hard but in the areas were the CA ridges were it is not smooth and the ridges are still there. For some reason the area where the CA streaks are will not seal nor will it allow a fill in to get it to sand smooth.

Best,    DennisT
Fresh CA?  I use it to seal all over, especially on fillets.  Never had an issue.  Wierd.

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Offline Dennis Toth

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Re: CA ridges showing through paint top coat?
« Reply #6 on: October 15, 2020, 08:07:50 AM »
Ken,
I too have used CA to seal small parts and never had a issue. What did you apply over the CA? I'm looking for something that will go over the CA/acrylic lacquer that is on the surface. Normally I would use primer but I don't know what type will go over the acrylic lacquer that is on the surface (I can't seem to get down to raw dope without sanding through the covering.

Best,   DennisT

Offline Ken Culbertson

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Re: CA ridges showing through paint top coat?
« Reply #7 on: October 15, 2020, 01:51:41 PM »
Ken,
I too have used CA to seal small parts and never had a issue. What did you apply over the CA? I'm looking for something that will go over the CA/acrylic lacquer that is on the surface. Normally I would use primer but I don't know what type will go over the acrylic lacquer that is on the surface (I can't seem to get down to raw dope without sanding through the covering.

Best,   DennisT
I don't have the budget for the automotive paints so I mostly use rattle can.  For primer I use the gray automotive stuff.  I get it at AutoZone but for the life of me I can't remember the name.  Never had any luck with the black or white.  I think you have a bad batch of something.  Have you considered sanding down and covering the area with tissue to seal in whatever is causing the problem.  I have done that once on a nose section that had something that just wouldn't paint.

Ken
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Offline Dennis Toth

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Re: CA ridges showing through paint top coat?
« Reply #8 on: October 16, 2020, 04:10:21 PM »
Well, still working on this issue. Is there a particular type/brand of sand paper or technic for sanding these ridges? I have been using dry 3M 400 purple with a flat block (1/2 sq block). I have been sanding in a circular motion over the ridge areas. So far, I am working on one section to see if I can get a solution rather then going over the whole thing then having to strip it all off. It seems that the CA is very difficult to sand. but it's coming along. In one area I think it is very smooth but looks like it needs some type of overcoat to avoid the dry spot look. Since I went down the path of using the acrylic lacquer so can't go back to dope, what type of seal primer will go over it?

Best,    DennisT

Offline Ken Culbertson

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Re: CA ridges showing through paint top coat?
« Reply #9 on: October 16, 2020, 08:30:34 PM »
Any chance you can shoot a picture of what it looks like.  Might help..or not.

Ken
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Offline Steve Berry

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Re: CA ridges showing through paint top coat?
« Reply #10 on: October 17, 2020, 09:10:28 AM »
Just a thought here, probably wrong, but here goes. The CA hardens up the wood it soaks into. The surrounding balsa is still, comparatively soft. Are you perhaps sanding ridges into the softer balsa? I'm pretty sure I've heard Windy mention this very thing in several of his videos.

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Online Dan McEntee

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Re: CA ridges showing through paint top coat?
« Reply #11 on: October 17, 2020, 09:30:11 AM »
   I still don't understand the need or desire to stack so many different materials on top of one another, least of all making the CA the last in the stack?  I see no need for that at all, and as Steve Berry mentioned, it dries so hard that it is easy to sand away material from around the glue. I almost never us CA to glue anything that will need a lot of sanding, especially things that are compound curves. This example that you present here is a perfect argument against using multiple materials in a finishing system. The forums are full of threads made made people looking for help to solve issues caused by this practice.
  Type at you later and good luck with it,
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Offline Dennis Toth

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Re: CA ridges showing through paint top coat?
« Reply #12 on: October 18, 2020, 07:14:55 AM »
OK, after quit a bit of sanding I seem to have gotten through the ridges and it is now flat. I sprayed on a light coat to seal then a second and all seems good. There was a few dry spots so I assume at this point I just need to let it gas off for a while, lightly sand the dry spot and recoat.

Dan, the reason for the different layers was me just trying to get this project done quicker. When I installed the wing into the fuse because this was a rescue ship that I had to remove the wing (to get the controls and center planking corrected), there was a little more gap to fill in at the fuse/wing joint. I did this with strips of balsa to get the fuse tight and in alignment with the stab correctly. This left some areas that needed additional fill to smooth over the joint. I did this with Epxoy/fiberglass flower (similar to micro balloons but stronger). Once this was sanded there were a few rough spots that I added the Elmer's wood filler over and sanded smooth. The Elmer's is a very good filler, light, easy to sand. To speed up the process I wiped the CA over the joint. This worked but I didn't see the ridge streaks on the planking, got it on the fuse side just missed on the planking. Then did the first spray of the DM paint. That's when the ridges showed up. I did try to sand and figured it would fill in between the ridges and would just take a few extra coats. Seems the Design Master paint goes on very thin and it didn't seem to build like dope would (reason for the DM paint was the LHS didn't have any black dope and I only needed less then 1/4 oz, had the DM in the house, its electric so no need for fuel proof).

Best,   DennisT

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