Painting a Prop?

szicree · #1 08-15-2008, 06:28 PM

Any issues with stripping and painting a new Sensenich metal prop that I should know about. Obviously I shouldn't put 2 coats on one end and 19 on the other, but are there any other gotchas here?

RatMan · #2 08-15-2008, 07:34 PM

Have you checked out the Sensenich forum? They say don't do it. If you decide to do it let us know how it goes, I would love to do it as well.

gmcjetpilot · #3 08-15-2008, 08:47 PM

Quote:

Originally Posted by RatMan

Have you checked out the Sensenich forum? They say don't do it. If you decide to do it let us know how it goes, I would love to do it as well.

Don't do it? Why is that?

The 2 and 19 coat ratio? Really?

I would use a good epoxy paint and even coats. http://www.skygeek.com/epoxy-prop-paint.html

I've seen my Hartzell overhauled. They just painted it (even coats I recall). "HOW ITS MADE" on TV had a segment on making Hartzell props. They just paint the darn things.

As far as stripping, I'd just be careful. Chemicals need to be fully removed and/or neutralized. Mechanical removal (sanding or blasting) may change the shape of the prop.

For balance just apply even coats, but I could be wrong. I don't see any problem. The finish on the leading edge near tips can wear faster. There is not a lot you can do about that flying off of dirt, dusty and sandy conditions. They make those clear abrasion strips you can bond on the leading edge. I doubt the weight of the paint will make much difference unless you really way over did one blade more than the other.

I painted the back of my Hartzell once. It was chipped and worn. I used fine sandpaper to smooth out the chips in the paint (fine rock chips). Than using scotch-brite pads, I got it down almost to metal, smoothing chips in the painted surface more. Some dings went into the metal near the leading edge. I just blended them carefully with a tiny fine spoon file. I tried not to remove metal unless there was a nick. Cleaned with lacquer thinner, I used flat black rattle can to finish. I went over it with some fine grit sandpaper and painted a few coats light coats to get coverage. It looked good and was durable.

joeboisselle · #4 08-15-2008, 10:22 PM

Ya know, if you're concerned about weight, I've used postal scales under each blade to see what I'm working with. It's tricky to get the both blades in the exact position on both scales, but it's possible. ymmv

Rivethead · #5 08-16-2008, 12:20 AM

There's a prop shop I've used the services of in Troutdale Oregon. Personally if I wanted to paint my own prop I'd go talk to them about the process first. Then I'd give it a try. If it didn't turn out I'd have them redo it for me. It's worth trying at least once.

az_gila · #6 08-16-2008, 12:50 AM

From a Sensenich forum posting by their engineer...

I will assume that we are discussing an aluminum propeller here. We use both alodine and paint. The paint is a Sherwin Williams product called Polane. It is widely used in the propeller industry. All of the prop shops use it if your propeller needs refinishing.

The alodine is important... and unfortuneately the S-W Polane paint seems to be available in gallons only, and at many $$$$....

szicree · #7 08-16-2008, 08:57 AM

I'm thinking strip, alodine, two part epoxy primer and two part urethane should be pretty tough. Anybody out there paint their own prop?

CESSNADON · #8 08-16-2008, 09:42 AM

Painting a certificated prop is not permitted unless it is listed in the TC. Otherwise I guess it would be ok to paint. Paint could possibly hide a crack that was beginning to proprigate.

az_gila · #9 08-16-2008, 10:01 AM

Quote:

Originally Posted by CESSNADON

Painting a certificated prop is not permitted unless it is listed in the TC. Otherwise I guess it would be ok to paint. Paint could possibly hide a crack that was beginning to proprigate.

Actually, it is allowed for touch-up and is in the ICA (Instructions for Continued Airworthiness).
Sensenich has a bulletin on this... they actually want you to strip and remove small amounts of corrosion and re-paint.

If you own some of the FP McCauleys, they need a stripping and a crack check at the hub per an AD every 200 hrs, and then a re-paint. This can be legally done by an A&P mechanic.

These guys can do custom certified paint jobs on props....

http://www.americanpropeller.com/DESGINERPROP.html

Steve Z - this may be a $$$ option for you....

gil A - anyone want a McCauley Tiger prop that needs a 200 hr AD?.....

gmcjetpilot · #10 08-16-2008, 04:33 PM

We are NOT talking a substitute for a qualified prop shop required or recommended overhaul, but a repaint between prop recommended TBO. The way I did it was not strip totaly bare but have a hard time imagining that you can screw up so bad as to cause a hazzard. However I am sure there are some cases where DIY prop paint jobs went bad.

I agree you should do the alodine. Good point I forgot. Of course corrosion is pretty obvious on the blades but the hidden areas under the spinner, hub and bolt hole bores are critical.

The point about paint hiding a crack is a good one. The first step is a good visual inspection, but you do want a paint system that WILL telegraph a NEW crack to the surface for easy visibility. May be some paint systems are too good and could hide a new crack? Hummm interesting.

I suppose you can buy a zyglo kit and black-light and do your own look see. The kits are expensive (dye and blacklight) or hard to use effectively. Eddy current is the other NDT they use, but that is out of reach of the average individuals skill (training) and equip. I am not sure if they use any other advanced NDT (ultra-sound, xray). At the min get out bright lights and magnifier before and after striping and use the Mark IV eye-balls.

Is Polane paint needed? We are talking about experimental right. We can overhaul our own engine right. I am all for safety but we are just talking paint right. What about the rattle can stuff I posted above?