siclick33

I have a Jetarrows A-10 (EDF) that I am just about to paint and have a question regarding the surface preparation.

The whole model is composite and the glass work is excellent. It has quite subtle panel lines moulded into the surface. I am not after a museum quality finish, just something simple that looks ok from a couple of feet away, so was planning to spray it with thinned Humbrol enamels.

Do I need to do anything to prepare the surface for the paint?

invertmast

My Feedback: (23)

I have always washed it with warm water and a little liquid dish detergent to get rid of any mold release, and then roughened the surface with some 320 grit paper

ChrisPetersen

My Feedback: (3)

I have been asking around on the same question for my A10 and the general consensus is that at a minimum you are going to want to use scotch brite to give the paint some kind of surface to adhere to. The beauty of those is that it wont take off your rivets or panel lines. Just do enough to take off the shine. The big pain is the seam lines.

FILE IFR

I may not be the only one, but after the surface prep for a good paint bite, I wipe it down with a moist lint free rag of naptha to rid the surface of anything that may give it a 'fish-eye' paint problem.

bidrseed2

My Feedback: (2)

I read a paint manufacturers guide book once and they specifically stated NOT to wash the fuse with any form of soap or detergent-( I seem to recall thats an old airfix model suggestion) the reason being you add another layer of grease to the surface, which is almost impossible to remove.
They suggested using a rag with the strongest thinners you could find and wipe down with a three fresh rags. The first stage merely dissolves any mold release or grease and moves it around, the second wipe removes most of it and the final stage should leave you with a clean rag, with all the grease having come off in the second stage.

I used Urethane thinners on my modellbau mirage, which seems to clean easier than white spirit.

I cant comment on what grit of paper to use.

dvs1

Personally on composite or gel coat finishes I scuff the surface with the red scotch pads as they will roughen the surface but wont remove surface details, then clean with a mild dish soap, then rinse off with clean water. If you really want to you can hit it with a tack cloth right before painting. I just use a clean cloth as I'm not painting an automotive finish.
I always use an automotive primer before paint no matter what type of paint I am using. If your really concerned about the primer sticking to the surface you can use a self etching primer as that will etch itself to the surface. the primer will also give a good surface for your paint to bond to.

bidrseed2

My Feedback: (2)

I use tack cloths too which are available from halfords.

dvs1,
I thought etch primers were for metal?

InboundLZ

My Feedback: (10)

When I painted my Habu I sanded down most of the paint. I wanted to get rid of paint lines. Everything worked great but I did learn one lesson whenit comes to red paint, you have to remove ALL of it or it WILL bleed through.

If you have decent glass and paint on it now, just sand it downto remove most of it but not so much that you get in to the raw glass and you are good to go.

siclick33

If I use a Scotch Brite pad will I not end up with massive scratches on the surface?

I'm worried about sanding it too as the surface is so good at the moment and I don't want to damage it. I've been reading through so old posts so, armed with that info, might try a bit of sanding with 800 grit and then painting with no primer.

I'll let you know how I get on

bidrseed2

My Feedback: (2)

I ended up sanding out some of the detail on my Mirage.
If it helps, I used a very light coat of halfords plastic primer on mine and Im quite happy with the finish on mine.

PHIL GREENO

After you have roughened the surface either with scotchbrite or fine wet and dry paper used wet it is best to clean the the surface with panel wipe.

This is what is used by all auto body repair shops to clean the surface after rubbing down and before spraying.

You can buy a gallon of panel wipe from any Auto paint outlet for a few pounds and it lasts you for years.

Also ideal for cleaning/degreasing of any kero stains at the end of a days flying.

Phil.

Chris Leese-Wood

It all depends on which release agent they use. The release I use, cannot be washed or wiped off with solvent.

I would always recommend 1200 wet and dry used wet, then wipe down with a lint free cloth. This will avoid the paint lifting later.

Chris

schroedm

My Feedback: (1)

If your glass finish is beautiful and shiny then the paint will just fall off!!

You need to flat it back so that when you hold it under a light and try and 'reflect' the light, you can't. It should be dull. You don't need to use horrible coarse grit paper for this or even do it 'wet'.

Two of the best model painters I have dealt with (Ray Habgood and Ralf Schneider of Tailormade) both recommend this approach and use the Mirka Abralon range to achieve it.

http://www.polishedbliss.co.uk/acata...scs-cat11.html

Once flat, panel wipe or tack cloth off any dust and prime/etch prime away. If you use etch primer then everything sticks like poop to a blanket!!

Geoff White

FWIW.

On my Hunter, the whole model was scuffed with Scotchbrite to remove the shine. As Mark says unless you do this the paint is not going to adhere very well. A coat of etch primer was then applied, followed by 1K primer, rubbed down. Then base coat colours , weathering and then finally a 2K matt clearcoat.

Geoff.

HarryC

My Feedback: (1)

The grey scotchbrite pads are not as severe as the red ones and should scuff the surface enough. I have the mirka pads but they are small and not easy to hold for scuffing large surfaces. Very fine grain sponge pads from 3M work well and are about A5 size and easy to hold. Then as per Phil Greeno does, I always wash with panel wipe (sometimes labelled as "pre-paint" to remove grease, silicon, finger print grease etc. Finally wipe with tack cloth seconds before painting. I use either Halfords plastic primer aerosol cans, or Klass Kote epoxy primer to get a really good grip onto epoxy glass. From then on handle the parts with gloves on to prevent finger print grease on the primer, sand back with 1200 or scotch grey pad, then again tack cloth immediately before painting.

One "gotcha" to avoid - many people measure out their paint and thinners using a medical syringe, and then get fish-eye on the model indicating silicon contamination despite scrupulously cleaning the model prior to painting. The contamination comes from the lubricant in the syringe so if you do use a syringe wash it out thoroughly first.

Washing composites with soapy water to remove grease, mould release etc can contaminate the model as much again, for example I live in a hard water area and after a water wash the model has lots of fine deposits of limescale on it, so nowadays I only use thinners, panel wipe etc.

Xairflyer

My Feedback: (1)

There are many methods, but from advise from a friend and tips picked up this works for me.

You need to get rid of the shine, I use 400 wet and dry used wet with luke warm water and a tiny drop of washing up liquid (stops the paper snagging) You are only looking to get rid of the shine, you can also use a grey scotch-brite if you wish.

Wipe it clean then with Panel wipe, Using Panel wipe is probably the best tip I was given, it is a must if doing any painting, since using it I never had any paint fisheye/reaction issues.
I then blow it all off with the airline and just before spraying I wipe once more with panel wipe and give the whole thing a good blast of my hot air gun.
I have used the plastic primer you get in Halford's and it goes on very well for an aerosol.

Warbirdguy

Being in the business of fiberglass molding. I will tell you what I recomend and the reasons why.

1. It is correct to wash the model with water and a detergent. There is a reason why. The mold release, if PVA was used, is only water soluable. Nothing else will remove it. Wash with warm soapy water and the rinse several times. Then use a quality tac cloth to clean up with. When you sand the model, any residue from the soap will be removed.

2. I suggest using 3M 600 grit paper WET and LIGHTLY sand all the surface. Anything heavier grit than that will remove any details , and leave sanding marks. I cant stress enough, lightly sand. If you press hard or stay in one area longer than others, you stand the chance also of sanding through the finish coat of resien and into the fiberglass itself. Then you have a mess on your hands.

I would also use a really good quality primer sprayed lightly before paint. As would many professional paint people would agree, Use the same brand of paint from primer to finish coat. Then you have NO issues with compatability.

My two cents. And good luck with it

WBG

dvs1

They are but they can be used for composites. It is the light amount of acid that etches the surface, It will work for composites as I have done it in the past.


Back to the question about the red scotch pads hurting the finish, they will not. I am finishing up on a fiberglass, carbon fiber composite plane and used my method in my last post.
I used denatured alcohol to remove any surface contamination, then scuffed surface with scotch pad, washed with soap and water, rinsed, dried, primed with auto primer, lightly sanded with 320-600 grit sandpaper, cleaned surface again and painted.
It turned out great. The scotch pads will remove a very, very fine amount of material but will only roughen the surface enough to let primer adhere to. It will not remove surface detail unless you get crazy with them. Remember you just want to roughen up the area enough to get rid of that glassy smooth surface to allow paint to stick, otherwise it will flake off, especially if you mask with tape and remove the tape. Paint will depart the plane quickly.

2walla

My Feedback: (10)

Glad to see you getting your A-10 going.. When I did mine I washed it with warm soapy water. I wiped it down lightly with denatured alcohol- be careful.. I scotchbrited and hit it with primer.. I used krylon on mine- I extracted the paint from rattle cans and mixed the colors I wanted. Then I put some rattlecan krylon matte finish on it..

2walla

My Feedback: (10)

Oh ONE IMPORTANT THING. Don't let it set out in the sun- the plastic canoopy will melt.. My buddy found out the hard way.. It curled up on the edges, the unpainted areas stayed ok, but the edges got really wavy..