View Full Version : SB819 related question ( corrosion)

10-11-2011, 10:36 PM
I'm building an experimental shortwing (along the lines of a 2-seat clipper, or a lycoming powered pa17 with clipper controls, or.....)

Anyway, the airframe is nearly ready for cover and I just discovered SB819. My fuse has the typical sheetmetal over tubing in the door and windshield areas... The same areas addressed in this bulletin. It is all new construction, not a re-used piper fuselage.

Is there an effective eay to add corrosion protection to my nearly finished fuselage in these areas? I will likely have it powdercoated.... Meaning i am not sure how either linseed oil (poured into the blind areas) would react to the powdercoat heat (but i would bet the powdercoat wont like the oil!). Perhaps i could apply the oil after powdercoat?

Another option.....Not too late, but a TREMENDOUS pain to remove the sheetmetal, add 3m weld-through primer, and re-attach. I fear i will loose location of all the boot cowl and windshield holes. Same uncertainty about the powdercoat with the primer.

Not totally commited to powdercoat vs paint.. Just sounds easier.

Looking for advice!

10-12-2011, 02:41 AM
I would get a rattle can of 3M weldable primer, drill a 1/8" hole near the top of the sheet metal and a tiny drain hole at the lowest point on the bottom (you have to be extra careful not to drill into the tubing underneath).

Attach a short length of plastic tubing to the nozzle on the rattlecan (same sort of thing as a WD40 pressure pack), poke it into the top hole and give it a wriggle around as you spray to cover all the inside areas. This should coat both the inside of the sheet metal as well as the tubing. Allow it to drain and dry, and plug the top hole with a rivet. It will be covered by fabric so will not be noticeable.

If you want to get it powder coated, the temperature should not affect the weldable primer as it will be bugger all compared to the actual welding temps. I would not put any linseed oil or similar inside the fuselage tubing until after it is powder coated. Sealed struts bend like pretzels during powder coating as there is nowhere for the gasses formed by the heat to vent.
(Clyde Smith the Cub Doctor, does not like powder coated fuselages. He prefers epoxy paint - as it's easier to inspect for cracks.)

Steve Pierce
10-12-2011, 07:04 AM
John has a good idea. You could also take a Rotbroach hole saw and drill some larger holes in the wider areas and get primer and paint into the hidden areas. I like primer and paint better because I can get into all those cracks and crevices.


10-12-2011, 08:58 AM
Thanks for the input guys. The concensus seems to be that leaving it as-is (trapped bare metal) would be really bad... If that is the case i think my best bet is to remove the sheetmetal, prime (weldable) and reweld. At least i have good jigs for positioning.. The boot cowl and some interior panels (across the top of the door).

Thanks for the heads-up on powdercoating the struts. I am all set up to paint, but not for sandblasting large parts unless i do the outdoor, small blaster, hope to beat the rust routine. Can have the fuse blasted and powdercoated at the same place. No matter what, i will paint the struts.

10-12-2011, 09:29 AM
Curley mentioned that clyde smith doesn;t like the powder coating. I can also say that alot of people in the old car hobby have steered away from it too. They report adhesion problems and flaking off due to vibration on frames etc. Just my opinion, but I would not do powder coating on an airplane. It just hides to much.


10-12-2011, 04:12 PM
Well, I bit the bullet and did it the hard way.. removed & primed, then re-attached. Like most jobs, agonizing and dreading it took longer than the actual project. A dremel cutoff wheel is a great weld remover, and by not grinding the final weld remnant smooth I had a perfect means to re-align everything without a sweat.
thanks for the help everyone!

10-12-2011, 07:28 PM
Hey - proud of ya! It always feels good when you do it "the right way".

My friends reckon I am anal (because I would have done the same thing) but I really don't care what they think. I only have to satisfy a couple of people - myself, my dear old Dad who taught me "the right way" before he dropped off the twig, and a couple of blokes on this site (you know who you are) just in case they ever get a chance to look at my work.:icon_wink:

mike mcs repair
10-13-2011, 01:07 AM
always amazes me how people talk down powder coating in the lower 48....

is there no quality control down there, or???

our powder coaters here are FAA repair stations, and at least the one in big lake I use, his main thing is aircraft.... and I have had no issues like I keep hearing down there....

only bad thing is just like paint where you ream a bolt hole out to bare metal, it might crawl underneath, just like paint....

been using it on ALL the rebuilds since early 90's.........

Steve Pierce
10-13-2011, 06:50 AM
Kime, I have not found a quality powder coater here. I looked at an Airframes fuselage that was brought to Oshkosh back in the late 1990s. After a year of sitting in the hanger it had some red spots in the cracks and crevices. Easy to deal with but I would have to haul a frame 100 plus miles and take a gamble on the right job being done. You are close an excellent powder coater.