Clear coat question

[Doug Moon]

I have used 2 part polyurethane clear for a long time. It is very resistant to nitro and it doesn’t seem to care about nitro. The guy at the paint shop is telling me acrylic urathane will work for my application. It is about half the cost. Does anyone have experience with acrylic clear? Is it oil resistant? Shine?

[Lauri Malila]

Doug,

I think that modern car clearcoats are polyacrylic urethane. Chemical resistance is about the same as with polyurethane (at least according to my experience with polyurethane paints): no problem at all with methanol, nitro or acetone.
Again according to my experience, polyurethane is slightly easier to sand & polish, but propably there are differences between different brands.
For example, untill now I have used (Acrylic clear, that is)  the Italian brand Sestriere. After spraying I sand everything with #2000 and then polish by hand with Farécla G10. It’s hard work because it’s impossible to respect the 24h after spray -polishing that is recommended. But it’s doable anyway, we have a long winter.
Now, I tried a PPG clear (D800) and it’s clearly more difficult to sand and polish than the Sestriere, even though they share a similar chemistry. Maybe it's because of the very high solid content of PPG? I think I’ll have to go with PTG style and sand with a little rougher paper and then spray one more highly diluted coat of clear and continue finer sanding & polishing from there.
I really like the polyurethane (cheap industrial 2-component) for base colours. I prefer them from 2-component car paints as they have no plasticizers, meaning they are really nice (hard) to sand and polish too, if necessary. L

[Doug Moon]

Thank you!

[frank williams]

Doug
I have used the ShopLine 660 Acrylic Urethane (two part).  I think John Hill uses this also.  Its cheaper than the top of the line PPG.  I'm not as good a painter as John by any means.  You might try to contact him.  It seems to be very fuel proof.
Frank

[Jim Kraft]

I have been using Krylon Crystal clear to refinish wood props for years. It seems to be impervious to about everything. Never gets sticky or dull. I have no idea what it would add for weight. Flows out nicely. It says it is acrylic, but that is all. Never tried it on a plane. It does have great revues.

[Tim Wescott]

I haven't tried it yet, but the locals on the West Coast who can Akshully Paint (TM) tell me to use KBS DiamondFinish clear.  It's some sort of "one part" urethane that's activated by the humidity in the air (so, really two part, but mother nature supplies the water vapor).

[Claudio Chacon]

Doug,

I think that modern car clearcoats are polyacrylic urethane. Chemical resistance is about the same as with polyurethane (at least according to my experience with polyurethane paints): no problem at all with methanol, nitro or acetone.
Again according to my experience, polyurethane is slightly easier to sand & polish, but propably there are differences between different brands.
For example, untill now I have used (Acrylic clear, that is)  the Italian brand Sestriere. After spraying I sand everything with #2000 and then polish by hand with Farécla G10. It’s hard work because it’s impossible to respect the 24h after spray -polishing that is recommended. But it’s doable anyway, we have a long winter.
Now, I tried a PPG clear (D800) and it’s clearly more difficult to sand and polish than the Sestriere, even though they share a similar chemistry. Maybe it's because of the very high solid content of PPG? I think I’ll have to go with PTG style and sand with a little rougher paper and then spray one more highly diluted coat of clear and continue finer sanding & polishing from there.
I really like the polyurethane (cheap industrial 2-component) for base colours. I prefer them from 2-component car paints as they have no plasticizers, meaning they are really nice (hard) to sand and polish too, if necessary. L

Hi Lauri,
Do you remember how much weight was added after applying the 2k PU clear on this ship?

Later,
Claudio.

[B Johanson]

Take a look at Summit Racing clearcoat acrylic urethane.

https://www.summitracing.com/parts/sum-up200q

I have used it for many years on racing planes with good success. They have many choices reducers and activator. Don't forget the the fish eye eliminator.

Regards,
Bill

 

[Lauri Malila]

Hi Lauri,
Do you remember how much weight was added after applying the 2k PU clear on this ship?

Later,
Claudio.

I remember for sure, that the base colour, aluminium polyurethane for whole model was 15g. It covers very well and weights allmost nothing.
The clear polyacrylic added 25..30g once sanded and buffed.
It’s all about base work quality. L

[Mark Scarborough]

Acrylic Urethane is softer, easier to polish, easier to spray, and not as strong as the other alternatives, that said, if you keep the plane clean I would expect it to hold up well enough to fuel,,