fiberglass thread epoxy

[PeoriaCommando13]

I'm installing the steel threaded inserts (that the petcocks screw into) into the fiberglass threaded holes in a fastback fuel tank. Question is what is the best
goop or epoxy to use on the fiberglass threads?? Suppose you want to
not only seal but structurally strengthen the joint so you wont strip the
weaker f/g threads when tightening the petcock lock nut, etc.
Much appreciate a reliable answer!

 

[dynodave]

I've made repop fastback tanks and studied the originals, both early 68 and the 2 later ones. Check to see if you might have an original tank. Fastback tanks came with 3/8 BSP steel molded in bobbins. Then the outside 1/4 BSP-3/8 adaptors were glued in. A good epoxy would work but unless you have cut it open (demanufactured the tank half joint) and novalac epoxy painted the inside after a blasted prep, the tank may not give you much service. E-10 always wins against old GP resin.

My yellow tank 20 years ago when I still younger and stupid. This was my 2nd tank...
http://atlanticgreen.com/ntfbrgls.htm

 

[PeoriaCommando13]

Thks, sounds like a very knowledgeable reply. I just bought
this 71 fastback 2 months ago and dont know the history.
Ive cleaned up the parts now and they are brass inserts that
thread into the fiberglass base of the tank. The petcocks then screw into the ID threads of these brass inserts/bushings.
Im redoing this because i had leaks between the brass inserts
and the fbrglss base. im considering jb weld to give both
structural strength to the fiberglass threads and a decent seal.
But just wondering if theres a better option? cheers!

 

[Tornado]

In the repair of glass fiber polyester resin sail boats, the best secondary bonding achieved with West System epoxy. These can be mixed with a number of different fillers to achieve desired strength or adhesive properties. This epoxy is available in small blister packs for small jobs like this appears to be. Recommend roughing up the insert surfaces with steel or brass brushing and the glass holes to provide better mechanical hold. After an overnight curing it can be gently heated with hairdryer of thirty or more minutes to maximize the epoxy crosslinking reaction.

 

[Danno]

Marine Tex is about the same thing, but not sure if it's fuelproof (no pun intended).

 

[MexicoMike]

I have a lot of marine experience with the West system and it's great stuff though I have NOT used it where it will be submerged in gasoline so can't say about that particular application. I HAVE extensively used JB Weld in submerged gasoline applications for sealing Quadrajet carburetor castings (the original factory-designed self-leaking carburetor) and it works fine. West may work as well but absent any personal experience in the gasoline application, I'd go with JB Weld.

 

[Tornado]

Any epoxy will be fine in gasoline. It's the the polyester resins that are more susceptible. Jb weld is a pre thickened epoxy which is ok for general use. The advantage of unthickened is you can select specific types and the amount of thickeners for the desired properties the specific job needs. More thickener generally gives better structural strength but lowers the bonding strength for example.

 

[PeoriaCommando13]

In the repair of glass fiber polyester resin sail boats, the best secondary bonding achieved with West System epoxy. These can be mixed with a number of different fillers to achieve desired strength or adhesive properties. This epoxy is available in small blister packs for small jobs like this appears to be. Recommend roughing up the insert surfaces with steel or brass brushing and the glass holes to provide better mechanical hold. After an overnight curing it can be gently heated with hairdryer of thirty or more minutes to maximize the epoxy crosslinking reaction.

Good, thanks much!

 

[PeoriaCommando13]

I have a lot of marine experience with the West system and it's great stuff though I have NOT used it where it will be submerged in gasoline so can't say about that particular application. I HAVE extensively used JB Weld in submerged gasoline applications for sealing Quadrajet carburetor castings (the original factory-designed self-leaking carburetor) and it works fine. West may work as well but absent any personal experience in the gasoline application, I'd go with JB Weld.

Great, think i’ll just go with JB since i already have some and of course it has to be fuelproof!
Thks much!

 

[PeoriaCommando13]

Any epoxy will be fine in gasoline. It's the the polyester resins that are more susceptible. Jb weld is a pre thickened epoxy which is ok for general use. The advantage of unthickened is you can select specific types and the amount of thickeners for the desired properties the specific job needs. More thickener generally gives better structural strength but lowers the bonding strength for example.

Great info, thks much!

 

[PeoriaCommando13]

Any epoxy will be fine in gasoline. It's the the polyester resins that are more susceptible. Jb weld is a pre thickened epoxy which is ok for general use. The advantage of unthickened is you can select specific types and the amount of thickeners for the desired properties the specific job needs. More thickener generally gives better structural strength but lowers the bonding strength for example.

Great info, thks much!

 

[dynodave]

For over a decade I researched chemical resistance charts for all possible resin candidates. "excellent" gasoline AND ethanol resistance was virtually impossible to find.

Norton tanks originally made from general purpose polyester was totally unsuited for E-10. My first repop tanks were made with a vinylester resin, supposedly OK for E-10, did not withstand ethanol.

The resin discussed in the other thread, "found in europe "...won't export to USA...was found to be the ashland chemical novalac epoxy/vinylester resin.