Painting the beast

[Marty_d]

A very generous pilot recently gave me 100m of plastic and an industrial drum fan.

I plan to set up a spray booth inside the shed that my plane currently sits in, duct the fan outside and use it to suck the air through from a filtered (probably Hessian) inlet hole on the other side.

 

What I would like is any hints or tips, things you did (or wish you did!), or things you wouldn't do if you knew what you know now.

Lights? Are LED strips good? Breathing systems? Did you use tack paint inside the booth? Etc etc.

 

Thanks in advance!

 

Marty 

 

[Moneybox]

We would always hose the booth out and paint with the floor still damp. Everytime your spraygun points down it stirs up dust. Insects are a real problem too. They tend to land and manage to struggle along for quite a way before getting bogged down. It leaves a unique pattern in the gloss finish.

[IBob]

Hi Marty, I have very limited spray painting experience and set about it with real trepidation. I managed to get a good finish, though I did have to wash off one wing side that went on too dry. My setup was as follows:

 

A Supercheap car parking tent set up inside my workshop, with the bottom edges duct taped to the floor. 
At the far end, two 150mm domestic extractors (as used in kitchens and bathrooms). These had no ducting, went straight out through the tent and (ply) workshop wall. The pilot who donated these had used them with a long length of ducting and said they were useless like that. I had no trouble, so I think it's worth noting that spiral ducting may greatly reduce airflow over any distance.
I painted in winter, so at the near end I had a hole in the tent where I placed an oil filled radiator. I would turn on the fans, which provided a very gentle airflow, turn on the radiator and watch the temp rise in the tent where I had a cheap thermometer. When the temp rose to about 23' I would suit up, turn off the radiator, go in and mix the paint and spray. The temp would continue to rise a bit due to the residual heat in the radiator.

For lights I had fluoro strip lights all down one side , with DIY foil reflectors behind them. I thought this would be more than enough in a white tent, but it wasn't. The only way you can see how you are doing is from the reflection of bright light in the surface, and to get that without having to walk round the job and view it at various angles, you need lights on all sides. Simply put, you can't have too much light. 

 

I made simple tilting mounts for the wings so that the surface was angled towards me at about 45'. This is a big area to spray, and I found it far easier to work the gun with the job tilted towards me that way. I did not have the confidence to spray both sides , so the wings were each done in two sessions, one side then the other. I partly rotated the fuselage for the same reason, and that was painted in 4 sessions.
I found with the colour on the fuse it was really easy to see the finish, compared to the white on the wings etc, where I had to paint then walk round the job squinting at odd angles to get a good reflection. You haven't got much time to be doing this, and the less you move around the less dust you disturb.
For all the smaller parts, empennage etc, I also went to some trouble to set them up so I wasn't trying to use the gun at odd angles. 



 

 

[facthunter]

Runs and dust are the problem. Paint is also heavy. Keep the thickness to a minimum. Thick Paint chips. Something like acrylic Lacquer is easy to touch up. If you can rotate the fuselage it would help. Don't spray on cold days.  Keep everything clean and have no water in the  airlines. Have clean guns and no blobs in the Paint.  If paint has fully dried you have to light sand  before the next coat. The lights I use warm up the surface. Wear a proper mask. Nev

[IBob]

Some other bits and pieces for those coming at it for the first time, as I did:
My assembly priming was done with a cheap gun, but when it came to the final job, I bought a good quality gun. They just do work better.
The wing side I had to wash back and repaint went on too dry, and the reason was too much air. I bought an air pressure gauge that goes on the gun, as the pressure at the compressor is not the same as at the gun once you start spraying. This allowed me to set the pressure at the gun correctly.
I had a mixing table in the booth, with a DIY stand for the gun. For mixing I used straight sided pots and a measuring stick to get precise mixing ratios. The measuring sticks are available at spray shops. I then used fine mesh disposable filters (also from spray shop) to filter the mix.
I wore a (disposable) lightweight suit, with hood, and neoprene (?) gloves.
My mask was 3M full face with Organic Vapour cartridges. This has a neat setup whereby incoming air comes via the face, but outgoing air does not, so there is no misting up. I also bought disposable particulate filters: these go on the outside of the cartridges and catch the overspray, which will otherwise quickly block the (expensive) cartridges.
Also from the the spray shop:
Tack cloths. 
Masking sheets (for masking off big areas). These come in a dispenser with adhesive tape attached to one edge and are far quicker and neater to use than DIY solutions.

 

Edited Tuesday at 10:23 PM by IBob

[IBob]

Also this: the polycarbonate in my doors still had it's protective peel-off coating. I then added a thick layer of paper, fastened round the edge with masking tape.
This turned out to be totally inadequate, as when I removed those, the surface of the poly was lightly fogged. Presumably paint solvents had made their way through.
I believe what the professionals do is mask this stuff with some sort of metal foil and tape. No doubt someone here can tell us?

 

It gave me a bit of a scare: the door is basically two poly panels with a huge number of rivets round the edges and across the middle.
But I was lucky (that time): the fogging was 'only' surface and I was able to remove it using a Meguires smooth surface clay kit and a great deal of elbow grease.

[sfGnome]

Hi Marty. I haven't had a great experience attempting to paint - hopefully things will turn out better for you. I bought rolls of clear builder's plastic and lengths of conduit and constructed removable walls that hung from the roof of the shed. I put an extractor fan down on the ground at a door with the rest of the door blocked off so the air was drawn over the tops of the plastic walls and down to the floor level at the fan. That aspect seemed to work well. (I can add photos if you'd like, but at the moment I'm on a PC which doesn't play nicely with the format that the iPhone produces. Yes, I know how to deal with it, but I'm being lazy...). 

 

I painted the cabin interior, but decided that the results, though ok, weren't really good enough for the outside. Maybe I just got frightened and it would have been alright? I don't know. I did show some examples of my work to my paint supplier (an ex-spray painter) and his response was "Not bad, but doing the outside would be a bridge too far", so I gave up and have sent it to a commercial shop recommended by some other blokes in my SAAA group. Sadly, it's been there for a couple of months, and it's still not finished. There's always some "big commercial job" that he's had to do and it's always mine that gets bumped. 😞 Whinge over.

 

If I was trying again, I think I'd leave the interior until I'd built up some skills. Trying to work inside the box that is the baggage area was difficult as I kept bumping the gun against other recently painted surfaces. I'd suggest doing lots of practice sweeps without pulling the trigger until you're confident that you'll get the coverage without the contact.

 

Oh, and I had a couple of worksite lights hung at different angles, but like iBob said, too much light is never enough.

Edited Wednesday at 02:16 AM by sfGnome

[skippydiesel]

My spray booth under construction:

Cheap timber, builders plastic wrapped, cheap pedestal fan (extracting) at one end and air-conditioning filter (blue stuff) at the other. Preloved window rattler reverse cycle air conditioner in centre to warm booth for paint curing. Doubled the floor plastic to hold water.

Pr loved Fluro's hung all around. Whole system driven by 3.5Kva Honda generator (no 240V power)

 

[skippydiesel]

[skippydiesel]

Extensive use of packing tape.

Double doors for large component entry exit. Fan & cowling went into small square on right hand door.

Edited Wednesday at 06:38 AM by skippydiesel

[skippydiesel]

[skippydiesel]

Probably should have made it .5 M wider & higher - bit squeezy when fuselage being painted.

Used the Stewart System for paint & fabric - worked a treat.

Most materials recycled for other projects.

 

😈

Edited Wednesday at 06:45 AM by skippydiesel

[IBob]

Other things keep coming back to me:
The manufacturer's printing on the 6061 needs to come off, or it will bleed through. Thinners will do this, but MEK does it far quicker and cleaner. However, MEK is nasty stuff, so needs handling with care.

[Marty_d]

3 hours ago, IBob said:

Other things keep coming back to me:
The manufacturer's printing on the 6061 needs to come off, or it will bleed through. Thinners will do this, but MEK does it far quicker and cleaner. However, MEK is nasty stuff, so needs handling with care.

Fortunately after stupidly doing the rudder with the printing on the outside, I learned my lesson and built the rest of the plane with printing on the inside.

[skippydiesel]

5 hours ago, IBob said:

Other things keep coming back to me:
The manufacturer's printing on the 6061 needs to come off, or it will bleed through. Thinners will do this, but MEK does it far quicker and cleaner. However, MEK is nasty stuff, so needs handling with care.

Did you try isopropanol ?😈

[IBob]

1 hour ago, skippydiesel said:

Did you try isopropanol ?😈

I didn't, Skippy. I know MEK is just about instantaneous compared with thinners. Is isopropanol similar?

[facthunter]

Genthin thinners will do. I think it has acetone in it. Nev

[skippydiesel]

1 hour ago, IBob said:

I didn't, Skippy. I know MEK is just about instantaneous compared with thinners. Is isopropanol similar?

Iso (about 75%) is the stuff they wipe your arm with before giving you a jab. The yanks use it (100%) a lot for pre painting prep.

 

Its supposed to be less toxic than most every other thinner/degreaser/Acetone/ etc that you might use to clean a surface.

 

I found out about it when I started using the Steward Paint System (US)

 

I use it quit a lot. These days mostly for removing belly oil & petrol stains.

 

You can make a great glass cleaner with it - from memory, dilute ,with H20, to 75%  to make a litre, add a few drops of concentrated washing up fluid, shake well and dispense with a spray bottle.

 

In Au you can a pay an arm & leg for a small (300ml) container from Bunnings Aerospace or go down to a wholesale cleaning supply shop and purchase 5 L for about the same price.😈

[facthunter]

Why paint ALL of the surface IF it's alclad? Nev

[facthunter]

Isopropanol is an ALCOHOL and won't mix with Wax, Petrol or oils other than Castor. It's a solvent for shellac. But that's not much help. Nev

[Marty_d]

37 minutes ago, facthunter said:

Why paint ALL of the surface IF it's alclad? Nev

It's 6061-T6 which has some anti corrosion properties but still benefits from paint protection.

Polishing is an option but doesn't really look good on big square slab sides - great on curvy planes like Ryans, Ercoupes and that new Spirit.

 

 

Edited yesterday at 01:49 AM by Marty_d

[facthunter]

The primer should probably be an etch or use some other al  preparation for aircraft. I would NOT recommend any soft surfacer that must be sanded. I'll look up a couple I still have some of Here, later today. Nev

[facthunter]

Alumiprep and allodine are the two treatments. Leaves it looking slightly yellowish. I got them from Aviall. Nev

[Marty_d]

I'm going with the Norglass system Nev - a mate in Canberra has built 2 CH750's and used that, is happy with it.

Part of that system is a metal prep and then etch coat for bare aluminium.