Light Aircraft Association

Good afternoon,

Could someone give me the low down on overpainting Ceconite? What will work?

I've applied 2 clear and 2 silver cross coats of non-tautening nitrate dope to my re-covered control surfaces.

I'd planned to paint the top coats with ICI 2pack but have read some 'stories' about it not working and cracking. I've purchased a flexing agent which I can add to make the paint more pliable.

Also can I use 2k high build primer on these surfaces prior to colour coating?

Any thoughts (first hand experience if you have it?)!


Regards

Martin Harvey

I would suggest you stay well clear of the 2pack paint and stick with recognised aircraft materials.

2pack was used on my Jodel for the final gloss coat and even with the appropriate flexing agent started to crack after six or seven years. Another Jodel at our strip was painted some years previously to mine using aircraft materials all the way through and is still in pristine condition.

Thanks John,

Ok so if I steer clear of the 2pack can I use normal automotive cellulose high buildd primer/topcoat paint being that this is the same type of paint as Non tautening Nitrate dope that I've used thus far?



Regards

Martin Harvey

automotive cellulose

Can you still get that? I thought it was now effectively a banned substance under EU H&S laws.

Hi Harv, from the longevity viewpoint, cellulose would be worse than a polyurethane two pack paint. You can add a plasticiser to cellulose but that ceases to do its job after a few years and the surface will crack and ringworm.
I do not know what you are painting, is it a microlight for instance where weight is perhaps really critical? If it is a typical light aircraft then I would brush on a first coat of slightly thinned nitrate dope to ensure that the fabric is fully encapsulated in the dope (it will go translucent when it is), then spray on maybe two cross coats (four total) clear nitrate, then 2 cross coats of silver, then two cross coats of butyrate colour dope. this will give good UV protection and should produce a decent finish. All coats will need thinning to get a decent spray cosistency depending on the equipment you are using, and an HVLP system will use less paint and make less mess. If you know what you are doing you can thin the final colour coat further still to get a better finish, but don't do that unless you have good gun technique or you'll get more runs than the London marathon. Some colours (particularly yellow) may need more coats to get good depth as they contain fewer solids than say a blue. Good thing with Butyrate is that you can use very fine wet and dry and cutting compound to get rid of runs and polish up dodgy areas. This type of finish should last at least twenty years.

Hi again Harv. I should add that you can use 2 pack poly on supported areas ( on a leading edge for instance, or a ply covered fuselage) and cracking won't be an issue, it is on unsupported fabric where the problem lies. Two pack generally does not react with paints that you are covering, so if you had an aircraft with an already painted leading edge, in a dope scheme for instance, you would be unlucky if a new coat of two pack over it caused a reaction. Doing it the other way around though (butyrate over a two pack) is likely to lead to the paint reacting rather like if you'd got some paint stripper on it. This is always a risk with Butyrate and Nitrocellulose type materials so when overpainting with them always do a test area first and don't lay the first coats on too thick.
I should add that regarding weight, although the traditional dope schemes sound like they will be heavy because you are putting lots of coats on, these materials dry through their solvents evaporating off, and each coat carries a relatively small amount of solids. Two packs (and there are proper aircraft two packs such as Polyfiber's Aerothane) rely on a chemical reaction between the two constituents, and fewer coats are required because the solids content is much higher. It is generally considered that a two pack finish will weigh a bit less but on a typical light aircraft the difference is hardly worth worrying about.
On a microlight you can get away with fewer coats, and some even do away with putting on the silver. This will reduce the weight of course but UV protection will be compromised so the fabric will degrade over time. I have no personal experience of how quickly this degradation takes place, but for an aircraft that doesn't live outside in a sunny climate, it ight be a reasonable length of time and the weight saving on a microlight might be considered worth the trade off.
Should also mention Oratex of course which Paul HS sells. Effectively a lightweight pre-coloured fabric; great product and should be easy to use but it does come at a price.
Some guys in the States have experimented with what they call Latex paints. These are emulsion paints like you and I would use around the house. You can get emulsions that are OK for external use. Various unofficial tests have been carried out, and there is a view that UV protection is present in the colour, and people have simply used the paint directly onto the fabric with no dopes etc being used. This is a system that intrigues me (no I'm not tight, just poor), and at some point in the future I intend trying it on an SSDR. You would need approval to use it on a certfied or permit aircraft.
Anyway, I've rambled on long enough. Why haven't I written an article about this in the mag? Mainly because though I can spray and have a reasonable amount of experience, I do not consider myself to be as knowledgeable as the many experts that are out there who could do a better write up on the subject. Unfortunately though I have yet to find one willing to commit pen to paper. If such an expert is reading this then please get in touch and we could work on something together.

Further to above,


I have done 2 jobs recently, one was recover, nitrate clear, silver then straight to 2 pack with plasticiser. Worked really well and lasted well.

Second was a recover of a Tiger Moth tailplane - in yellow. Had all sorts of problems sourcing the dope due to the high chromate content, however Ray at LAS was very helpful, we sent a sample of the old fabric, that went to Randolph's in the States, they matched it perfectly and LAS mixed it.

If you are using coloured dope, the top coats change to butyrate because it is more plastic, is less flammable when dry and is more resistant to cracking. The butyrate does not stick well to Ceconite - hence the nitrate build up coats.

If you are going into 2 pack, you don't need the butyrate as the 2 pack sticks like the proverbial.

2 pack is still readily available via eBay from several sources - most will match colour for you and give a great service.

My understanding is that paint types are restricted for road vehicles. If you are not painting a vehicle (or you are painting a really historic type) you have more choice of paint technologies. If they can be convinced that you are painting an aircraft (show them some photos of the rebuild) the paint suppliers will sell you almost any technology you need.

Rans6....

What hasn't been mentioned are the safety aspects of the various systems. Dopes (nitrates and butyrates) are significantly safer to use than most of the 'old' two pack systems. the former may get you a bit stoned if you breath too many of the fumes, the latter contain isocyanates which are carcinogenic and do you a power of no good. You will need an air fed mask to spray them.
As a general rule, the motor trade has moved to water based paints that require baking spray booths to cure them.
The point with using car paint (cellulose or two pack) is that you are taking a chance. Odds are, certainly with cellulose, that even with plasticiser it will probably crack and ringworm in time, may be five years, could even be sooner. There is no practical cure, it will be a recover job. Two packs may survive longer, but I have also seen them break down in five years or so and again there is nothing you can do with it. Aircraft quality paints are expensive, some ridiculously so, but they will last for years if you put them on properly. My money's on dope schemes for the amateur painter - they are far more tolerent of b*lls ups, safer to use, straightforward to repair, and despite what the ads tell you, cheaper.
All the above applies to painting fabric, as that is what this thread is all about but if you're painting an aluminium or plastic aeroplane then a car based material is fine. In fact if you are painting the cowlings etc of a fabric aeroplane then dope is a non starter and these parts too need an alternative system. Various etch and primer systems are available, and for colour probably a two pack is best as unlike cellulose systems, the gloss will not fade over time. But do take precautions; use an HVLP system to keep over-spray down to a minimum, and wear coveralls and an air fed mask.

I have painted my jodel with an international two pack that is meant for glassfibre boats and I rollered it on using their own special rollers and although it is not as smooth as I would like it is passable and very tough, I used it on my previous D120 and I think it is still there after twenty years without ringworm, just dont make it too thick.
Graham

After my previous comments, I forgot to add.

My next project after the RV7 is a re assemble of a Piper J5. That will almost certainly be going into butyrate as a final colour as it is easier for me to apply in my workshop and when properly done with Randolph glossing thinner as a topcoat gives a lovely 'original' finish that can be polished and will last for years.

Thanks for all your tips and experiences.

After considering the options I've opted for 2k with the plasticiser. Its a paint system that I know well and having seen and spoken to a Harvard owner who's used this over a long period of time (8 or so years) I felt happy to try it.

Once the colour coats go on I'll report back with the results,


Thanks

Martin Harvey