Tip Tank coating

Hi,
I recently purchased a 2002 RV 8 with tip tanks. These tanks are labeled as 10 gallons each and run through their own sumps directly to the engine through their own fuel selector valves. They are equipped with their own fuel level gauges.
My question is; These tanks are coated inside with a shiny gray hard substance. Looking through the fuel cap filler holes I notice there are a couple of small cracks in this coating. I can lift it with a screw driver and see the fiberglass of the wing tip. Would anyone out there know what coating this might be and how to fix this issue? Or, is it an issue? Will the fuel eat the fiberglass? I only use 100LL.
Just going through the aircraft fixing any discrepancies. Your help is appreciated. Thank you, Ed

N781RV RV8

Might be Slosh? Here is Vans Slosh Service Bulletin.

Service Bulletin 11-9-13
Date: September 13, 2011
Subject: Fuel Tank Slosh Inspection
Affected Models: All
Required Action: Inspect for the presence and/or condition of fuel tank sloshing
compound.
Time of Compliance: Before further flight
Synopsis: Van’s has discouraged the use of fuel tank sloshing compounds
since the early 1990s. However, some standard RV fuel tanks currently in
service contain sloshing compounds applied by the original builder during
assembly or after completion. While sloshing compounds have never been used
during the initial assembly of QuickBuild tanks, these tanks may have
subsequently had sloshing compounds applied by the owner. The safe service
life of slosh can vary significantly depending on many factors including initial
preparation of the interior of the tank, type of slosh, type of fuel used, etc. Failure
of fuel tank slosh can cause in-flight power loss leading to injury or death.
Periodic inspections should be performed to assure that slosh, if present,
remains in airworthy condition.
Corrective Action:
If you are not the original builder of the fuel tanks or otherwise are not certain if
fuel tank sloshing compound is present in the fuel tanks, complete the inspection
described in 1) below:
1) Before further flight, visually inspect the interior of all fuel tanks to determine if
sloshing compound is present. This can be done by removing the fuel caps
and visually inspecting for the presence of slosh on the inside tank skins
and/or ribs. The most common colors for the slosh are white and red,
depending on the brand used. If any type of slosh or sealer is observed other
than the dark gray polysulfide sealer (Proseal) used during initial tank
assembly, perform the inspection described in 2) and 3) below. If no slosh is
found, perform any normally scheduled inspections on the fuel system as
required.
If sloshing compounds or non-polysulfide sealant are present in any fuel tank,
perform the following inspections before further flight. Visual inspection of the
interior of the tank(s) described in 2) should be performed each time fuel is
added to the tank. Entire fuel system inspection as described in 3) should be
performed before further flight and at intervals not to exceed 25 hours thereafter.
2) Visually inspect the condition of the slosh/sealer through the fuel cap opening.
If any flaking, blistering or otherwise loose slosh or sealer is detected, the fuel
tank should be removed from service until it can be repaired or replaced.
3) Inspect the entire aircraft fuel system including, but not limited to, all filters,
screens, finger strainers, selector valves, fuel lines, gascolators, carburetors,
injection servos and injector nozzles and lines for any contamination or
obstructions. If any contamination or obstruction is found, corrective action
should be taken to return the fuel system to an airworthy condition.
Contact Van’s Aircraft with any questions concerning this service
bulletin.
503 678-6545
[email protected]

Hi Ed,

What you are seeing may be Hysol. It is gray and shiny. It is commonly use to seal fiberglass surfaces like the inside of cowling for example. I have no idea how to repair it but you may find information from other sources.

Hysol

Definitely not Slosh. Hysol looks to be a very good possibility. It looks like good stuff besides the crack I see. About a gallon of fuel has been sloshing around in one tip and it does not look bad in anyway (besides the crack in the coating).
Has anyone else out there used Hysol for a fiberglass fuel tank coating? Second question. Would anyone know if the original fiberglass in the tip would be damaged if 100LL came in contact with it? Tips are dry now and will remain dry until I figure this out. Thanks, Ed

Resin type is the key

You may want to check on the resin type used to produce the fiberglass tip tanks. They may be polyester resin based. If so, the fiberglass is impervious to the 100LL. The Glasair wing is built using polyester resin based glass. The plane has a wet wing with no coating inside the tank areas beyond a resin rich build to ensure no exposed glass fiber. As such, the coating in your tip tanks may be just insurance but not really necessary which would explain why you have seen no issues from the area with the split. The epoxy based glass used in the Lancair and others is not fuel resistant.

Hysol comes in many colors. The gray is EA9394 which is an excellent adhesive. It's gray because it's aluminum filled. Its pretty viscous and expensive; a quart can is over $100.00. Not something you would want to seal a tank with unless you got a whole bunch for free. Is the entire tank coated? Could be the Proseal that you can brush on. Are the tanks leaking at all?

So far, since I have owned it, I have not filled the tip tanks yet. One side had a gallon of fuel in it as I flew it across the country last week with no signs of leaks. The previous owner did not use the tanks so I don't want to use them until I make sure everything is right.

If it is not going to hurt the fiberglass then maybe I will put a couple of gallons in the tips and monitor.....but, I would really like to seal the cracks first just for good measure.

Maybe I will attempt to contact the original builder to see if he remembers. Ed

The tip tank coating in my wingtips turned out to be the same stuff that the Lancair guys use in their fiberglass fuel tanks. It is called Jeffco 9700 FCR and is an Epoxy coating. It is sold by Rhino linings. I plan on calling them soon to learn more about it. The phone number is 1-800-422-2603. I only need a little bit and from what I hear they sell it in 5 gallon buckets for several hundred dollars. If anyone knows someone local that is not going to use all of theirs, let me know. Thanks, Ed 360-380-7337

Are there any composite builders in your EAA chapter? Contact them and have them take a look.

The good news is you are dealing with fiberglass. You can remove both wing tip, cut into the baffle where it won't be seen, address whatever issue you are dealing with, fiberglass it backup, seal it, and put the tip back on.

If you protect the paint on the tip-tanks, you might not have to repaint anything.

Other than that, I would say to contact the builder and see if he remembers what he used.