Fiberglass Fuel Tanks

Status
Not open for further replies.
I have Bill Hirsch's sealer in my steel Roadster tank, as treatment for surface rust that kept showing up in my fuel. For that, it's great stuff. Don't know how it'd fare in a 'glass tank.
 
NeilT49 said:

That is what I used in the fiberglass tank of my café racer, it was also relined with new fiberglass cloth and resin (regular polyester). It has been OK so far with gas (don't know if it has any ethanol in it though) in the tank for nearly a year. I also used it to line a tank that was cleaned up with new fiberglass cloth, but this time with vinyl ester resin which is supposed to be immune from ethanol (see fixing-fiberglass-tank-t6227.html?hilit=fiberglass ). I was told by Iron John that Caswell is better and he had a few instances of Hirsh sealer failing to do its job. I think that it should be OK provided it is coated everywhere and forced or allowed to dry completely before any gas in put in the tank. I used a small computer fan to force air in the tank for a couple of days before even thinking of putting fuel in it.


Jean
 
Just passed my 2nd year after Caswell treatment on my original Dunstall fiberglass tank. I contacted Caswell before I did the treatment and got a personal email back from Mike Caswell. The steps to a perfect seal is in the prep and the application technique. Per Mike's instructions, I put a handfull of drywall screws into the tank and swished & shook with Lacquer Thinner...drain and repeat...three times. Let it dry overnight. Mix up half the amount of Caswell that comes in the kit. The crucial step is mixing the 2:1 parts of Caswell EXACTLY. Important to find yourself a comfortable seat, pour into the tank. SLOWLY rotate the tank in your lap, tipping back and forth and thinking about the coverage. Be patient and rotate, tilting back and forth for at least a half hour or more...after that nothing should be sloshing around and when upended very little shoud pour out. Let the tank sit for about 4 hours and while the first applicatioin is still tacky, pour in the second mix and rotate, tilt until nothing seems to move when looked down in the tank with a flashliight. Let the tank cure for at least a week. This worked for me with no seeps or damage to the paint.
 
How do you seal the gas taps and the filler hole so you get coverage there and when it is dry you can put the taps and gas cap back on? I'd like to do the Caswell this winter.

Dave
69S
 
DogT said:
How do you seal the gas taps and the filler hole so you get coverage there and when it is dry you can put the taps and gas cap back on? I'd like to do the Caswell this winter.

Dave
69S

I inserted 1-inch bolts (1/2" UNC ??...can''t remember) into the petcocks...easy find down at the local True Value store. My tank was already painted so I had to first wrap in saran wrap....mummified actually. I left my gas cap on during the application. I placed a double layer over the filler hole and duct-taped to the saran wrap coverinig the tank...closed the cap and proceeded.

After the week of curing, I had to take a drill and ream a bit inside the petcock hole to get the petcock screen up into the tank....no big deal...minimal swarf just rinsed out with a couple of swishes of gasoline.
 
cmessenk said:
DogT said:
How do you seal the gas taps and the filler hole so you get coverage there and when it is dry you can put the taps and gas cap back on? I'd like to do the Caswell this winter.

Dave
69S

I inserted 1-inch bolts (1/2" UNC ??...can''t remember) into the petcocks...easy find down at the local True Value store. .

I am vary interested in this thread and how you and others have been successful. I like the description of how you applied the Caswell's in two coats. I would think that bolt selection is a vary critical choice. Too short and your tank threads are gummed up from the coating. Too long and when you remove the bolt you may now have a void in the coating between the top of the petcock and the tank lining. This uncoated area is susceptible to fuel deteration. Any thoughts on ensuring how to protect even these small areas?
 
Firstly the fact that many producers of GRP tanks use the cheapest possible materials and production methods, is something that means the quality of many composite tanks leaves a lot to be desired, both in terms of chemical resistance and durability/strength! Today even though the effects of ethanol bearing fuels on GRP are well documented, some producers here in the UK continue to use inappropriate materials and production processes, with many seeming to think that use of a chemically resistant resin system, will result in a chemically resistant tank!

Secondly the use of high cross link epoxy resin systems as tank sealers is highly questionable, as while these materials have a high level of chemical resistance, they are very brittle when cured. This combined with the fact that uniform film thickness of the resin after application, and proper preparation are both very difficult to achieve, means that such products can only be looked upon as a temporary solution to fuel tank problems.

Those who produce the various tank sealing products seem to have entirely ignored the fact that in service a fuel tank will be subject to high and low levels of resonant vibration, and that this in combination with less than perfect preparation and in most cases widely varying film thicknesses, will result in sealants cracking with failure occurring relatively soon afterwards in many cases.

Before the introduction of alcohol bearing fuels, if it were possible to prepare interior tank surfaces to the appropriate standard, then polysulphide type sealants which retain a certain degree of flexibility when cured, seemed to present the best possible option, but while such sealants are still appropriate for use within the aircraft industry (with no alcohol bearing fuels), they are not resistant to long term contact with alcohol type fuels.

At this moment in time it seems anyone with a GRP tank can only be 100% assured of it being fully resistant against Efuels, by sectioning it, then properly mechanically abrading the interior surfaces, and applying a chemical resistance layer comprising synthetic surfacing veil, a novalac vinyl ester resin with a flex agent added to all surfaces in contact with fuel, bonding parts together using the same novalac VE resin as a base, and finally appropriate post curing.

Some of the currently available tank sealers here in the UK fail after long term immersion tests using E85 fuel as a control, others based on high cross link epoxies are fully resistant to the E85, but as outlined earlier the brittle nature of these materials, will generally mean failure is likely to occur at some stage if they are being used on GRP tanks, which are much more difficult to prepare than steel, and tend to vibrate much more.

A product which was able to incorporate the positive points of polysulphide and novalac epoxy, would provide the ideal solution to problems with tanks, but as none of those producing tank sealers at the moment seem able to properly test them, or provide any sort of industry standard chemical resistance data, at the moment its very clearly simply a case of which one provides the most credible advertising blurb, and hoping for the best when pouring it into your tank!
 
It's true, you can't ignite gasoline with cigarette or glowing ember, I know, I've tried. What I would be afraid of in a crash, as far as a fire hazard, is the bike sliding along on its side making sparks and pavement can wear through a fiberglass tank easily. Of course, the same thing could happen to a steel tank. One thing about crashing on a road course or in the twisties is, the bike doesn't spend much time sliding on the pavement and usually goes off to the side into dirt or grass in the corners. If you crashed in a wide straightaway or in the middle of a freeway, you could be in trouble. Most of the time you would be thrown clear unless you are sliding along in its fuel trail. People have been racing with fiber glass tanks for decades and there has been a lot of hard crashes and few fires, so they're proven to be as good as metal tanks. If you have a tank that has never had gasahol in it, you're ok with nuts bolts, acetone and Caswell. But, if it has ever had gasahol fuel in it, you need to cut it open and hand sand with 36 or 40 grit to get all the damaged glass out and re-line with alcohol resistant epoxy as thick as you can get it. reassemble, and then Caswell treat it. If it's had gasahol in it long enough, it can weaken the structure. As an after thought, I wonder how liquid truck bed liner would work? Is it gas and alcohol resistant? If it is, it would form a kinda of fuel cell and be tough as nails.
 
Status
Not open for further replies.
Back
Top