Scuffing Tank Skins and Ribs

[sglynn]

What do you guys (with no leak tanks) use to scuff up your skins and ribs for Prosealing. I've used Scotchbrite and a plastic wire wheel, but I've heard I should be much more severe and use #40 sand paper and really scruff them up so the Proseal will stick and never leak. So what did you use and how deep did you make your scratches. Thanks

[Dan Langhout]

I just used the normal 7447 Maroon pad by hand. I actually taped mine off with masking tape to keep the scuffing where I wanted it but that's just my obsessive nature. I did scuff two directions at 90 degrees to each other so I had a sort of cross hatch pattern but I don't know if that was really necessary.

I think the real key is CLEAN! I wiped and wiped and re-wiped the contact areas with MEK until the pad came up clean (no gray aluminum scuff residue) and made sure not to touch the areas afterwards. You really don't want any oils or grease where the sealant goes.

Both of my tanks were leak free. (Well . . . Ok the first one had a small leak in the rear inboard corner by the baffle where I didn't put enough sealant - fixed through the fuel pickup access hole. )

[Robert M]

Originally Posted by Dan Langhout

I just used the normal 7447 Maroon pad by hand. I actually taped mine off with masking tape to keep the scuffing where I wanted it but that's just my obsessive nature. I did scuff two directions at 90 degrees to each other so I had a sort of cross hatch pattern but I don't know if that was really necessary.

I did the same thing, taped them off with masking tape to keep the scuffing where I wanted it and cleaned it alot with lacquer thinner - tanks sealed. Well the second one sealed - learned alot about placement of proseal during the first tank build.

[szicree]

Maybe the instructions have changed, but my plans said to use a stainless steel bristle brush. I think I got it from a welding supply, but I can't remember for sure. Gotta use stainless so as not to embed particles of dissimilar stuff into the alum. (i think)

[Kyle Boatright]

Originally Posted by sglynn

What do you guys (with no leak tanks) use to scuff up your skins and ribs for Prosealing. I've used Scotchbrite and a plastic wire wheel, but I've heard I should be much more severe and use #40 sand paper and really scruff them up so the Proseal will stick and never leak. So what did you use and how deep did you make your scratches. Thanks

A moderate scuffing with scotchbrite worked for me. There is no need for a more aggressive treatment of the material.

The other keys to leakless tanks are:

- Properly clean the tanks before applying proseal. Naptha was recommended back in the day.

- Butter every rivet before you insert it.

- Butter the end ribs before you insert them.

- Apply a fillet of proseal along the transition between the end ribs and the tank skins.

- Be generous with the proseal when attaching the rear baffle.

It ain't rocket science. Its just attention to detail.

[Hawkeye7A]

On my first tank I did the Scotchbrite scuff. Had a couple small leaks in the corners of the baffles. On the second I used a bead blaster (one of the cheap HF ones; only about $15 IIRC) with #30 silica beads and the air pressure turned way down. Left a great rough surface. Make sure the skin is well supported laying flat on a table/bench. Did the same on the rib flanges inside and out. Second tank, no leaks! Of course, as mentioned by a previous poster, you will learn more about how to apply the proseal and will invariably do better on your second tank.

[NYTOM]

Originally Posted by szicree

Maybe the instructions have changed, but my plans said to use a stainless steel bristle brush. I think I got it from a welding supply, but I can't remember for sure. Gotta use stainless so as not to embed particles of dissimilar stuff into the alum. (i think)

That's the same thing I did Steve. I was really scared of leaks with all the talk about them on this site. I also cleaned the mating surfaces as best as I could with Acetone. As a result, my tanks tested OK.

[AF_Alan]

Masked the second tank to keep scuffs where I intended them. I used both scotchbrite pad and an aluminum oxide type sanding sponge. It was about 1" wide and on edge made a clean pass where the ribs were to go. Removed tape, cleaned really well with lacquer thinner and/or acetone, and remasked. Generous with the sealant and no leaks in either tank.

Alan
RV-9A Wings
N984AW Reserved

[panhandler1956]

I used a pretty aggressive rotary wire brush on a cordless drill. No leaks during the test, although they haven't flown yet.

[Flying Scotsman]

We used a coarse grade sandpaper "flapper" thing in the cordless drill, and pressed down on it to make a good, heavily scuffed path along all rivet lines.

2 tanks flying on my buddy's -8, 2 more ready to go on my -7A. So far, no leaks in the -8's tanks after 150 hours or so.