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Jul 13, 2019, 04:25 AM
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Paint finishing advise


I have three models almost complete that need finishing, two of them are a combination of paint and film covering and one is all paint.
I would like to use a 2k clear coat on them and wanted to know if it is ok to use this over film?

Would I need to scuff or wet and dry sand the film parts for the adhesion of the clear coating....... (there are combined paint and film panels on different sections of the airframes) some are what looks like solar film and others look like a textured film covering that has been painted.

Lastly, after using fine wet and dry to cut the painted areas, how glossy do I need to try and polish the paint up before clear coating or could I just leave the matt sanded finish to gloss up using the clear coat?
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Jul 13, 2019, 07:05 AM
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The clear coat is the shine on paint. No need to polish paint. Can't help on clear over plastic.
Jul 13, 2019, 07:08 AM
PhoenixFlyer
PhoenixFlyer's Avatar
Not an expert here, except I have built many models with film wing and stab covering, and paint fuselage. Never thought about painting over film.

On the paint fuse, after all dry/cure, I wet sand with #2000, look for any runs, imperfections, the shoot clear over this. It also allows to sand off the ridges where you masked from paint color separation. Clear will make finish complete, if you take your time, light coats better then one heavy.
V



Quote:
Originally Posted by ChiliP
I have three models almost complete that need finishing, two of them are a combination of paint and film covering and one is all paint.
I would like to use a 2k clear coat on them and wanted to know if it is ok to use this over film?

Would I need to scuff or wet and dry sand the film parts for the adhesion of the clear coating....... (there are combined paint and film panels on different sections of the airframes) some are what looks like solar film and others look like a textured film covering that has been painted.

Lastly, after using fine wet and dry to cut the painted areas, how glossy do I need to try and polish the paint up before clear coating or could I just leave the matt sanded finish to gloss up using the clear coat?
Jul 13, 2019, 09:04 AM
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Thread OP
Thanks for the answers, the problem I have is the models were built by my father in his latter years and have now come to me, it looks like he was trying to use up materials that he had left and this has ended up with, for example a wing that has paint over sealed skin on one part, paint over textured film on another section and gloss film on the last section of wing.

It looks like I will have to clear coat over the whole wing to get an even finish, I think scuffing the gloss film a bit would be a good idea, what do you guys think?
Jul 13, 2019, 11:28 AM
Registered User
I've painted Monokote and scuffing is not essential, but if you do I would use very fine grade automotive paper 600 to 1000 grit. What is critical for good paint adhesion to plastic film covering is thorough cleaning with a solvent. If you are painting with epoxy, for example, use epoxy thinner.
Good Luck!
Jul 13, 2019, 12:58 PM
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Thread OP
All good info, I have tied a little bit of cleaning on the film using isopropyl alcohol and it pulls the dirt off nicely (over 10 yrs worth on one model and at least 20 yrs on another) but the paint does not like it so much (car rattle can)
luckily pops had cans of matching colors left over for touching up, thankfully only one ( a Curare) needs any significant paintwork, it had an old Super Tigre G60 bluey in it to hold the prop and spinner in place, absolutely mint condition internally apart from having no piston and rod !!
again luckily I managed to source another one in tip top condition.
The old motor had leaked residue down the non fuel proofed fuselage and as soon as I started to rub it down for coating I could see the paint around the nose and underneath had been affected, so a respray is going to be done here.
Jul 13, 2019, 05:22 PM
DavidsPlanes
doxilia's Avatar
I’d also suggest the same as Will when it comes to sanding mylar film. Some films like MK will actually “bead”
if the sandpaper is too coarse. A coarser cut is fine for initially texture if colour paint is going over an open frame wing. However, if you just want to uniformly spray 2K CC (SprayMax is best if using rattle cans) over the entire model, you want to preserve there integrity of the base colour of the covering and coarse sanding can cut too deeply. 1000-2000 grit should provide all the texture you need for good adhesion providing it is thoroughly “debburred” and cleaned prior to the CC. The CC is actually pretty good at going over just about anything but since it’s essentially a layer of plastic that’s being shot, anything on the subsurface you’re dissatisfied with will be locked in permanently.

Follow the acrylic urethane SprayMax can directions to the letter and it will be amazing once fully cured a week later. Remove the curing “grease” after a week with a mild liquid car polish and hand buffing.

David
Jul 13, 2019, 06:26 PM
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Thread OP
Ok, fine grit it will be then, as for the 2k clear I have a friend in the auto body repair line, he has agreed to do the clear coating for me at cost, probably a much better job than I could do with cans , I just have to do the prep work.
I dont expect show type quality as the models have been knocking around in the basement for a long time and have some hanger rash/faults that I will attempt to rectify/hide but I dont have the time to do full restorations as they are not that bad and this has put my own Curare build on hold as well.
Heres a picture of the model in the best condition, smarty points to whoever can i/d it or its roots, the wings and tail are made from Curare cores with a glass fuzz dad picked up at a show but even my dad doesn't know what the model is and he built it! back in the 80`s, before anyone says it, yes we know the ailerons are real small, the motor is an old HP 61 and "clapped out" as my dad put it.
Thanks all
Greg
Jul 16, 2019, 04:55 PM
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Thread OP
Well a few ups and downs, I re did the green and yellow on the Curare, amazingly the green came out good! (10yr old spray can remnants) The yellow however had a sneaky surprise in store, part way through painting, the spray decided to change into a water pistol effect, no amount of cleaning the nozzle or even changing the nozzle would stop it, so more sanding tomorrow.
Had to get a new shade of yellow as the one my dad used was for a british car manufacturer that went out of business at least 10 yrs ago, so racy Fiat golden yellow it will be instead.
Almost finished sanding down the unknown model ready for clear, it needs touching up in places but i dont have any matching paint as it was built at least 20yrs ago, so it will have a few rough spots rather than a miss match of paints.
Aug 05, 2019, 01:31 PM
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Roguedog's Avatar
Some years ago when i worked at an autobody shop we used scotch brite pads to rough up truck beds and door jambs.

It put enough of a scratch so the new paint would adhere to old.

Later when I started painting my own cars I found a paint adhesion promoter called Bulldog.

It was specifically made to get auto paint to stick to the plastic parts the auto manufacturers started putting on cars when they stopped using chrome on side mirrors and bumpers.

It works so well I found that I didn't even need to scuff up doorjambs with the scotch brite pads.

All I had to do was scrub down the door jambs with Dawn dish soap and water, air blow it dry, then just spray the 2 recommended coats of Bulldog. Each coat is fully dry in 15minutes. When dry I could shoot the paint directly over the Bulldog and it would stick as if I had sanded it. Awesome time saver!

The surface of Monokote is plastic so scuff the surface with a scotch brite pad where you want the paint to stick, spray it with 2 coats of Bulldog, and it's ready for color or clear coating.

Bulldog comes as liquid that you can put in your own spraygun or you can get it in an aerosol spray can. Here's a link to Amazon for the liquid
Bulldog


Regards

Bryan
Last edited by Roguedog; Aug 07, 2019 at 01:36 AM.
Aug 05, 2019, 03:10 PM
Registered User
This Rustoleum product - Xim Uma - is another bonding agent that allows just about any overcoat to be applied to just about any surface:
https://www.rustoleum.com/product-ca...logy-uma-white

Read the technical data sheet for detailed use instructions:https://www.rustoleum.com/~/media/Di...White_TDS.ashx


It comes in a spray can as well as quart/gallon can formats, is water based and easy to work with. Although the can says "white", it dried clear when I applied it to a dark surface (haven't yet tried it on piece of clear glass) and the safety data sheets give the UPC Color as "clear". The spray can is priced at just under $11 U.S. at the Paint Store.


Michael in Ontario, Canada
Aug 08, 2019, 08:26 PM
Registered User
hook57's Avatar
Great info, will most likely try this! Thanks Michael!
Aug 14, 2019, 09:18 AM
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Thread OP
Thanks all for the help, the models are all ready for clear coating now, the Curare has been virtually completely repainted and I will put up some photos after they are done in a couple of days.
One last question, (sorry) I have a couple of stickers to put on the Curare, should I put them on before the clear coat or after? Im thinking maybe after as they can then be changed if needed even though they might not last as long.

I was visiting my father on the weekend with my brothers and sister to help clear out his house (he is now in an old folks home) and I showed him a picture of a model that I spotted from the last UK Classic aerobatic meet up at Huddersfield and I thought (99%) it was one that he had built, he knew it straight away and confirmed he had indeed built it and this made his day to see it again. I know which model it is, but do any of you guys from across the water know?

While clearing out the basement I also found this bad boy (no I wont be sticking it on the Curare)
Aug 17, 2019, 09:13 AM
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Thread OP
Well the clear coating has been completed, unfortunately not to a very good standard and to say I am disappointed would be an understatement.
I wish that I had taken some pictures after painting and before the clear coat was done, there were no runs at all and also no specks of dust etc, just a couple of minor dings that I should have fixed better. Now the models have runs, dust and dirt under the clear coat and even blisters in the clear in some places
To be fair the guy who did the clear coating was quite upset at how poor a job he had done and cut the cost so low that it did not even cover the materials used and offered to re do the clear for free if I sanded the models down again, not sure I could face doing that again.
To add insult to injury when loading the planes into my car, the sprayer dude dropped the wing of the unknown model onto concrete and damaged it

I followed the advise given here and the paint went on great no problems with adhesion at all, one thing I would add is that premium masking tape is essential.
Once again thank you all for your help, advice and tips.

Here are a couple of pictures of the Curare before and after.

Ohh and before I forget, the model in the previous post is called the "Challenger" by Terry Westrop, some of you may of heard of his better known "Loaded Dice" design.
I still have no idea what model that red, green and gold one is, I will stick a couple of pictures up when Im able.
Now I can crack on with my own Curare build!

Thanks all.
Greg
Aug 17, 2019, 09:27 AM
Registered User
Sorry to hear. But all is not lost. On the runs and drips you can wet sand using 3000 grit sandpaper followed by buffing compound. You can use the same technique on the blisters as long as it doesn't go down to the paint. You can wet sand these and spray clear on top to recover. Then take down with a 2nd wet sanding and buffing. As for the debris in the clear coat, I'm afraid you're going to have to live with it.. The plane looks fantastic and there aren't too many more of these around. Meant for flying and not a museum!

PS: make sure the paint has cured first...


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