Seeking to understand "slosh" (and proseal)

Louise Hose · #1 10-06-2011, 07:08 PM

Would one of you give me a primer explanation of "sloss". If I understand correctly, it is/was a fluid slossed around inside fuel tanks to help seal them. I had the impression this was done in the pre-proseal days, but maybe that was an assumption that I made. And, I've read the SB. I also understand that sloss is NOT used in the quickbuild tanks. Proseal does the sealing. But, now I've seen Andrew's thread and and he talks about the tanks he bought having both proseal and sloss. So, now I'm confused. Does proseal and sloss serve different purposes? Or, was using both a belts and suspenders exercise? Are there arguments for still using sloss?

Can anyone give a brief primer addressing my confusion?

Mel · #2 10-06-2011, 07:16 PM

Slosh was used to take care of any "small" leaks that remained around the pro-seal. The standard procedure for slosh is to pour it into the tanks and "slosh" it around covering the entire inside of the tank.

Van's recommended procedure was to complete the tank without installing the rear baffle, then to "paint" all seams with the slosh compound. Then install the rear baffle with pro-seal. Lastly, pour in more slosh compound with the tank held nose-up and simply "slosh" the rear baffle.

This procedure worked. However, as the "slosh" aged, it seemed to peel off in small sheets.

The later procedure is to be a little more generous with the pro-seal and forgo the slosh entirely.

Hope this explanation helps.

Kyle Boatright · #3 10-06-2011, 07:19 PM

Slosh is a belt and suspenders approach. Proseal is supposed to seal the seams and rivets in the tank. But, back in the day, it was felt that homebulders might not be thorough enough with the proseal, so sloshing the tank with another (second) sealer over the proseal was recommended to fill any remaining pinholes or voids.

It was a great idea except for the fact that slosh is subject to builder error (and chemical incompatatility) too, and sometimes comes loose after a few years, clogging fuel pick-ups and leading to engine stoppages.

So, all tanks have proseal. Some have slosh over the proseal, therefore the belt and suspenders.

Walt · #4 10-06-2011, 07:37 PM

The problem is not with the "slosh" topcoat but like most applications it's the surface preparation that will cause a defect in the coating.

Top brush coats are Class A compounds (as compared to fillet seal compounds which are class B) are routinely used over the B compounds in the military and on the heavy iron integral fuel tanks as the second barrier to leaks. Just like with proseal though, you have to properly prep the surface for proper adhesion.

http://www.bergdahl.com/PRC_PDF/PR-1005L_09-09_ba.pdf

HSANTIBANEZ · #5 10-06-2011, 07:46 PM

Did the new sealant that sells vans need the "sloshing" procedure, the sealant is no pro seal.

KatieB · #6 10-06-2011, 07:50 PM

Slosh is also used to seal fiberglass fuel tanks in composite wings. Wanna see something funny? When 2 guys have to reseal a tank that's built into a 15 foot- long composite wing, they use a forklift, a balcony, and the volume of the entire hangar as they rotate it around every conceivable axis to ensure complete coverage of the sealant! Thank goodness that doesn't happen very often...

L.Adamson · #7 10-06-2011, 08:05 PM

FWIW -- By the time I was building my 6 kit in 1996, slosh was done away with.

L.Adamson

Louise Hose · #8 10-06-2011, 08:36 PM

Thanks for the clear explanations. I think I've got it now.

TruTrakAndrew · #9 10-06-2011, 08:49 PM

What they all said!

Eddie P · #10 10-12-2011, 10:55 AM

I've got one other question about slosh that is from a second hand buyers perspective, if anyone would like to comment, I appreciate it.

If I were in the market for, say an RV-4 built in the mid 1990's, what sort of paper trail exists to confirm the tank was sloshed when built or during a modification? I see in the SB that a simple visual inspection is possible after draining the fuel, (that's good if it is that simple, I bet it isn't though!!). But what if slosh sealant is found? Are guys building new tanks outright rather than disassembling tanks and re-building? What would be the build time required for a new set of tanks on an RV-4, and more importantly, how many average hours to remove and replace the tanks and fittings? If one was not the original builder, can this work be done by the owner and then realistically signed off in stages by an EAA guy who is also an aircraft inspector?

I know these questions drift a little bit from the original one but I've quite curious as I may in fact be facing something like this down the road. Cheers!