Fuselage tubing - what brand expoxy primer after blasting?

[McRay7ac]

Re: Fuselage tubing - what brand expoxy primer after blasting?

I like soda blasting better than sand, soda gives a better finish - also I do a punch test on the bottom of tubing have found tube that is rusting out and weak places that need replaced - I also agree with Ray
and Hank on small airbrush and foam brush or 1in brush I have use both they do a good for me

[Scott]

Re: Fuselage tubing - what brand expoxy primer after blasting?

Of course we wouldn't use sand on aircraft.

Soda works great for me on engine and other parts where relatively gentle non-abrasive cleaning is desired, but for paint and corrosion removal I prefer something more aggressive. I settled on 80 grit aluminum oxide media for both steel and aluminium parts.

For painting all my smaller parts and tubing I use a Finex HVLP gravity feed gun. Its small enough to get in all the tight places and It will spray like an airbrush if you want it to or can spray up to 5" pattern.

[Kim]

Re: Fuselage tubing - what brand expoxy primer after blasting?

Thanks for all the replies and encouragement.

The wings (disassembled) are put away someplace, so I cannot get any pics. Right now we are trying to get the fuselage primed and get some momentum on this project. The next step after the fuselage is primed will be to look at the wood around the doors, and the doors themselves. I have looked a little around this forum on the doors, but will have many more questions when we get to that part of the project.

McRay7ac - one of the bottom longerons was replaced from the clusters on back, along with other tubing. I will see if I can find pics.

[Hank Jarrett]

Re: Fuselage tubing - what brand expoxy primer after blasting?

The doors are a major pain. Some really intricate cabinet making. I have the drawings, but you will really need to build a jig to get them right. I would suggest you build the door frames onto the fuselage and use the frames as the jigs to get the doors to fit tight and close smoothly.
When I rebuilt mine I cheated just a bit by taking Carbon unidirectional tapes and gluing them between the frames and the plywood skins. It added almost no weight and made the doors MUCH stiffer. They sound like a 1950s Buick when they close. They SOUND really heavy, but aren't.
When you get to that part I will get you a bunch of the photos I made and the drawings. What you should do is photo document the whole process (I didn't and could kick myself not for not stopping and taking more photos). It is a process we should really document.

Hank

Wish you were closer to SE Virginia! You might need to plan a vacation down this way next summer. Virginia Beach is great for vacations and has lots of aviation things to see.

[astjp2]

Re: Fuselage tubing - what brand expoxy primer after blasting?

I would also make sure everything fits before you cover, I just fixed an airplane that had the elevator cables wrapped around the trim cable....and it flew that way..

[Kim]

Re: Fuselage tubing - what brand expoxy primer after blasting?

An update:

We tried blasting the fuselage to remove old primer and paint (possibly original).

Process took a lot longer than we thought and we did not finish. Got a lot of front of the fuselage bare, but ran out of time, so applied a temp coat of spray can primer. The back half was done by hand before and covered with a temp coat of spray can primer at that time, it is still that way. I have read concerns about blasting being too aggressive, our system may not have been aggressive enough. The old primer (green zinc cromate??) and paint was slow to come off and underneath there were spots of black, which we assume is corrossion that needs to be removed. See pics. The black spots took a lot to remove, and we just worked on removing the primer/paint leaving most of the black spots.

- We did not have a problem with air supply, see attached pic for our air compressor setup. I do not know the size of the larger compressor.
- One of our group thought that the nozzle we were using was large and this may have been part of why the old stuff was slow to come off.
- Not sure what sand we used, but it was not the 'black diamond' stuff we used to initially inspect the clusters when we got the project.
- Recovering media eats up time
- Easy to miss spots, either blasting or applying primer/paint
- The non structural channel pieces around the instrument panel seemed to be the worst with having the black corrosion, it may be easier to just replace them (???).
- Watching the other guys put on the temporary primer coat after we quit, I can see how easy it would be to miss spots.


- Is there a way to do this in 'pieces' instead of the whole go at once?
- How long can the bare metal sit before it needs to be covered? We had planned on blasting and applying primer
in one day.
- Is there a coating that can be applied once the metal is bare, but then painted right over at a later date? What are 'metal ready', 'metal prep'??? I am new to this.
- Anyone have a commercial place blast a fuselage? We got an estimate from a place, and the cost was way more
than we could afford. And there is always the concern that they may be to aggressive.

- We bought PPG DP50L04 (epoxy primer light), DP48F04 (Epoxy primer white) and DP402LF04 (catalYst). So two coatings (1 quart each). Cost was almost as much if we had bought enough for three coats (3 quarts total) of Polyfiber from our local supplier who only had white even after 3 weeks notification that we would want white and
green (dark). We still have it. It is good for a few years so we should be ok.

Any thoughts or suggestions? Some of our group were quite discouraged.

[Kim]

Re: Fuselage tubing - what brand expoxy primer after blasting?

pics

[Robert Lees]

Re: Fuselage tubing - what brand expoxy primer after blasting?

Good quality pictures! Black spots certainly look like corrosion. Your blasting media looks adequate, because it has turned the good metal grey, and it may be rough enough to pick lint off a cotton cloth.

It is possible that you are not spending enough time on eash tube (and I know...it took me four weekends of both days = 8 days) to do mine.

I blasted a section, then sprayed with two-pack etch primer. Next weekend I blasted the next section and sprayed that.




At the end, I went over the WHOLE fuselage again, but very lightly, to remove the previous weekends worth of etch primer (it is hygroscopic) and then re-etched and epoxied all in one day.





4 hours is the recommended max time for bare metal, but it depends how humid your location is.

Next time, I'd pay someone else to do it!

Hope that helps,
Rob

[Scott]

Re: Fuselage tubing - what brand expoxy primer after blasting?

there is no easy path, but you can save time by using a good paint stripper first. Clean Strip is usually available at hardware stores. I have not had success with the water-based products but others may have.

Looking at the photos makes me ask what size media you're using. I recommend 80 grit aluminum oxide. I understand that many people use silica/sand based media but the residual sand promotes corrosion.

Yes the black is corrosion. 80 grit should clean it off, but again you can let chemicals do some of the work for you. Stripper, scraper, corrosion remover and then media blast. Remember the media blast works on about 1/2 square inch at a time whereas stripper will slowly work on a relatively big area all at once. After stripper you'll see the blasting goes much faster.

Make sure you air hoses and fittings are adequate inside diameter. Also long hoses cause problems... drag increases at the square of distance in a tube. Install a gauge at the gun, you may be surprised to see less than half the pressure you have at the compressor.

No point in messing around with spray bombs. Mix up some epoxy primer, do a section of fuselage, clean it, and apply the epoxy. Put any leftover in the freezer and use the following day. Depending on the amount of moisture in the air where you are, clean steal starts oxidizing immediately.

[N95334]

Re: Fuselage tubing - what brand expoxy primer after blasting?

I don't see a water separator on your air compressor rig setup. Water in the line can cause the dark spots also.
Really need a great water separator for blasting and painting.
I used sand to blast a PA-12 fuselage. I used the small spray gun that sells for $25. Don't hold much but it adjust down to a very fine spray like an model airplane airbrush to a wider spray. Also have the fuselage on stands at each end so you can rotate the fuselage 360 degrees.
FYI I used Stitts yellow-green primer for first coat that left a flat finish and Stits Epoxy in grey for final coat that came out gloss.
Just my two cents worth.
Dennis McGuire
Jacksonville Fla

[astjp2]

Re: Fuselage tubing - what brand expoxy primer after blasting?

I take mine down to the media blast guy and for 3~500 its done in 2 days. Then I buy the Grizzly HVLP gun that holds 4oz of paint with the .8 or the 1.0mm tip and go to town with variprime and top coat with epoxy. I am hoping to try yellow zinc plating someday without paint and see how it fares....Tim

[astjp2]

Re: Fuselage tubing - what brand expoxy primer after blasting?

http://www.grizzly.com/products/Delu...ce=grizzly.com $28.50 and when you are done, throw it away and buy another if it wont clean up.