Top coat - Fabric painting

rtl_flyer · Post by **rtl_flyer** » Mon Aug 11, 2008 11:43 am

Using Ceconite & Randolph process. There are two possible top coats.

Butyrate & Polyurethane (Ranthane). So far I have been happy using the Butyrate dope to silver. Now it's time for top coat.

Butyrate:
+ Easier to spray and fix any mistakes.
+ Have used it already
- I want a very shinny gloss finish Butyrate not as gloss as Polyurethane.
- More coats required (heavy?)
- Fabric paint different to metal paint finish not quite the same.

Polyurethane:
+ Two coats required
+ High gloss (what I want)
+ Same paint for fabric and metal
- Not used it before and hear it is thinner (have not had runs with butyrate but hear possible with Polyurethane)
- Not easy to fix (MEK will not touch it, needs to be rubbed down/off).

So anybody have experience of one or both. Very undecided what route to go. Think I may order a small amount and do tail surface and see how it goes, could always recover it if I have to!!

Comments please.

Tim

tnowak · Post by **tnowak** » Tue Aug 12, 2008 8:20 am

Your observations are correct regarding the two finishing techniques. I had my wings recovered last year and used the more "traditional" Butyrate finish. I still achieved an excellent shine on the wings after using polishing compound and wax polish.

My main reason for sticking with Butytate was for ease of maintenance, long term. Also, I believe Polyurethane is much more toxic than Butyrate (good mask/breathing equipment required) and possibly is more difficult to apply.

TN

alant · Post by **alant** » Tue Aug 12, 2008 10:15 am

Your descriptions are spot on and yes two pack polyurethane is nasty stuff. Butyrate is easier to spray and is touch dry in minutes and not the 1/2 hr + of polyurethane. Whatever you you go for good luck.
Alan

Andrew Leak · Post by **Andrew Leak** » Wed Aug 13, 2008 12:55 pm

Having been a paint sprayer on vehicles& boats (and the odd aircraft) until a few years ago, I found the majority of metal frame/rag & wood/rag aircraft finishes had quite a stark difference if sprayed with polyurethane. If your aircraft is near PERFECT in it's construction and covering you will get away with poly. If you go for a darker colour (blue, black dark reds, greens etc) every detail tends to show. However, there will be some readers who will say their aircraft came out OK in poly with a few imperfections hardly showing, that's great, but I would tend to go towards Butyrate and cut/polish after. The 'wet look' is nice on a metal panel and as long as you stick to a colour , say, white - as dents and the odd slight imperfections don't show. This is always going to be a case for argument but to give you an idea I am in the process of restoring my aircraft and intend to use butyrate purely because of the flexibility of the paint and finish and also because the aircraft was covered in the stuff when new! Poly was not an option as I felt that it would not benefit the overall finish and not enhance it to the degree I want it to. Over to you.

Andrew

G.Dawes · Post by **G.Dawes** » Thu Aug 14, 2008 6:34 pm

There is another way and that is to roller the polyurethane cot on, I have done this with my fuselage and it is as good as anything I have sprayed,You must use the correct roller for it though and they are meant for International paints range and ae a hardish foam that doesn't melt with the tinner or paint.
The advantage is that there is a very thin coat which doesn't run or sag easily but the paint has the ability to creep into a smooth level coat.That cuts down on the amount of paint,cost and weight involved. I am about to cover the wings and will top coat the silver butyrate coats with rollered poly.

mike newall · Post by **mike newall** » Thu Aug 14, 2008 8:13 pm

The change from nitrate to butyrate is only appropriate if you are continuing through butyrate as a finish coat. If you intend to use 2 pack as a finish system, stay with nitrate - it works better and the top coat will bond better. The swap from nitrate to butyrate was twofold - the butyrate is more flexible and resisits cracking and also is less flammable.

Pro's and Con's.

Butyrate - good, traditional finish, easy to rejuvenate and keep tidy as further coats melt into the previous coats. Cheaper than 2 pack by a long shot. Can be cut and polished to a good shine. Sticks OK to metal substrates provided base primer is good and keyed prior to covering. No need for air fed mask - carbon mask is OK. Runs and mistakes can be easily rectified.

2 Pack - gloss finish, heavy, difficult to repair and touch up, needs flex agent which can result in a soft surface finish, expensive compared to butyrate.

You don't say what aeroplane it is.

If it is an older type, I don't think there is any decision - butyrate through to finish.

If it is a new type and you have a good fabric and structure, then I would probably go nitrate/2 pack - that is what we did on our Christen Eagle G-IXII. On my mate's Tiger Moth, I recovered the tail and stuck with butyrate, mainly 'cos of gap seals but the colour match and finish were superb (Thanks Ray @ LAS )

rtl_flyer · Post by **rtl_flyer** » Fri Aug 15, 2008 9:56 am

Mike,

I have sprayed to silver, the Polyurethane is going to be Ranthane to 'optional' coverying from Randolph. As such it is approved and does not require flexing agents as it's already mixed for fabric.

The aircraft is a Great Lakes, its not the series I it's a 78 series two. So I am going for a modern 'aerobatic' finish! I already have the airfed mask.

Cost wise I don't see much difference. Butyrate is around £30 a gal plus thinner but requires more coats. Polyurethane is £100 a gal but requres (as I understand) only two coats.

How is the Pol' heavy if it requires less coats?

Regards,

Tim

Andrew Leak · Post by **Andrew Leak** » Fri Aug 15, 2008 1:07 pm

How is the Pol' heavy if it requires less coats?

I don't think that G.Dawes was saying that Poly is heavier, merely that it saves weight! The thing is; butyrate is more flexible and is about the same amount of hassle if you need to repair as is poly. The overall problem is whether or not the 'sprayer' is confident in using poly+airfed mask etc and PATIENT between coats. Two coats can be achieved, but it depends on the pigment of the paint and the prep work beforehand, if it's your first paintjob I would (IMHO) use butyrate as it is easier to recover from mistakes - heavier, probably, as more coats are required for low pigment colours but can all end up as 'swings and roundabouts'. To give you an idea, the first aeroplane I painted arrived in my bodyshop and the chap wanted it sprayed in white ICI 2K with a plasticizer additive. It was probably one of the most easiest substrates I had painted (a bit like a commercial vehicle) all those flat(ish) metal panels, but getting the wings mounted to be painted, needed a bit of imagination. I believe the a/c is still around somewhere and it took 3 coats to cover it and emptied my mixing scheme of white base!!!

Andrew

ivanmanley · Post by **ivanmanley** » Sat Aug 16, 2008 11:55 am

Butyrate tends to be lighter even with many coats, as most of the "dope" evaporates off. With poly, it virtually all sticks, so whilst fewer coats are needed, they are heavier.

Ivan
________
M06

gasax · Post by **gasax** » Wed Sep 17, 2008 9:25 am

For a real gloss then Poly is the answer. But and it is quite a big but - get some practice or help from someone with the appropriate spraying skill.

Even using a dust coat and carefully controlling the amount of paint Poly has a real tendency to run. If it does run then the necessary rubbing down is a little nerve racking on fabric. It can be done but requires great care to ensure the fabric is not touched.

It can be done - it just needs a bit of practice - and great care around all the fittings which break up the plain surfaces.