Louise Hose

Louise Hose

Well Known Member
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? :confused:
 
Slosh Primer; No, not that kind of primer.

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.
 
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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.
 
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
 
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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...:rolleyes:
 
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!
 
Eddie P said:
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!
Click to expand...

Eddie,
I am speaking from purely a 2nd owner standpoint. I did not build my plane, and I am sure that you will get more experienced folks to reply.
You can see the slosh even with fuel in the tank. It is a white film against the aluminum that is readily apparent.
Knowing what I know now, I would probably look for a plane without the sloshed tanks, as it is just that much less to worry about. That having been said, my -6 has sloshed tanks which I watch carefully through visual inspection inside the tank, and checking the fuel screen every few months. So far, I have had no problems, and the fact that my aircraft was assembled by a very well known RV guy, I am pretty confident that the process was done correctly.
From what others have stated here, it sounds like it is simpler to just build new tanks and replace the sloshed tanks versus going through the agony of opening the tank and using MEK to get the slosh off.
YMMV
 
To Eddy P

You can send your tanks off to have the Randolph Slosh removed for about $1500 plus shipping and all the down time of 4-5 weeks turn around. There is a tank builder who will build new tanks but you have to fit them to your a/c upon return and paint them to match your plane and he is about $2500 plus shipping just for the tanks. You can do it yourself like I did and it's a messy horrible job and spend 300-400$ for materials and tools and building fixtures plus 100+ hours of your time trying not to asphyxiate yourself with the solvants.
The slosh was still attached very well in my tanks except in the bays where the fuel nozzle scraped it loose during fuel fill ups before I bought the plane.
 
Slosh...aka dirty rotten crud peeling off in my fuel tanks!

Eddie,

I can only respond based on my personal experience with slosh...but here is what I know:

In my tanks a visual inspection (simply looking through the fuel filler) was enough to show two things.
A. I had slosh in my tanks.
B. It was peeling off in LARGE sheets.

Now...I then began trying to decide what to do about it. As you know there are pretty much two options.
A. Clean it.
B. Build new ones.

I had my mind set on the new ones. Several phone calls to Van's and with the amazing help of Gus, determined that I had the old style tanks on my 4. (Don't remember the year that they changed them, but I think early 90s). This meant that building new tanks would be a MUCH larger undertaking...remove wings and blah blah blah. I was looking for a fairly quick solution if possible. So I decided on cleaning. If you have the new style tanks (flange on the rear baffle pointing back), the prepunched tanks can be used.

Now to the cost. I was busy trying to get other things finished up on my -4 so I called John Nys and asked if he wanted to undertake the job of cleaning out my tanks. He accepted the challenge. I now have no peeling slosh in my tanks, and some nice large access holes in the rear baffles (not that I care about the holes, but they MAY come in handy later!) Total cost for the fix was $1800. Don't know if that number will vary depending on the amount of trouble...but it was my cost. From what I have learned it will cost about the same to build new ones.

Hope this helps a little!
 
Building new tanks

My -4 has an orange slosh in the tanks. My flying is 100% in mountainous areas and I am not interested in worrying about when the fuel lines might plug up every time I fly. I never seriously considered trying to clean the slosh out, I just purchased a tank kit and will build new tanks. My old tanks had some weeping anyway, and one of the senders needed replacing. The time to remove the old tanks was a couple hours - easier than I thought.

I have the old style tanks ('87 build) but don't expect to pull the wings to fit the new ones. I intend to use the old ones as a pattern for the new. Will see how it goes.
 
Replacing the tanks

If your choice is to simply replace the tanks, contact Evan Johnson in Redding, CA. He is in the business of building new and replacement fuel tanks for RV's. Once you determine RV type, year, and vintage, Van's can ship the tank kit parts direct to Evan.

Web site link:

http://www.evansaviationproducts.com/

BTW, the RV-4 tank design changed slightly in 1986. The change affected the direction of the flange on the rear baffle and the rib lengths. Pre-86 tanks had the baffle flange pointed forward.
 
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