fuel vapor seperator - follow-up

[Gary S.]

[Patrick H.]

Re: fuel vapor separator - follow-up

Gary,

I'm in the middle of the test.

I found an excellent professional site regarding adhesives. I, too, am trying to get some additional professional advice. Since these little tanks are not (I think) constantly exposed to gasoline, I'm not sure how "stringent" the requirement be.

We may need to repair as we discussed on the phone and as I have repaired, and then use an internal sealant like is used for gas tanks to seal the bottom.

Better yet, once we figure this short term issue out, I'l be looking into a much more correct and permanent fix. I'll keep you posted.

Patrick

[Joe L.]

Re: fuel vapor separator - follow-up

Patrick-----

They're not exposed to LIQUID gasoline all of the time, but they are pretty much constantly exposed to gasoline VAPORS. Either way, the effect on the plastic (or adhesive) is going to be the same.

[Gary S.]

Re: fuel vapor separator - follow-up

Patrick, the only caveat that this fellow would mention was that the aerospace industry had some pretty cosmic sealants for fuel tanks that may work. I know just a little bit about aerospace "stuff" and I know that these products are typically VERY expensive, have a limited shelf life (typically in the weeks category) and are highly controlled.

For those not in the know on aero stuff, most modern commercial aircraft have fuel tanks that are integral to the wing. That is, the fuel tank does not have a bladder or anything to contain the fuel other than the metal structure of the wing or tail. The fuel cell is typically sealed with some rather unique substances to prevent the fuel from migrating to the outside.

Gary

[Gary S.]

Re: fuel vapor separator - follow-up

Good point, Joe. However, I would think that the solvency of a vapor would be much less than that of something continually exposed to a liquid. Didn't I read recently in some NCRS publication that the N06 (big tank) cars had issues with their fiberglass tanks degenerating over time? Mostly thinking out loud and using common sense.

Gary

[Joe L.]

Re: fuel vapor separator - follow-up

Gary-----

There might be some "accelerated" decomposition with respect to contact with a liquid as opposed to the vapor of that liquid. However, I don't think that the difference is going to be very much.

As far as the N-06 tanks, yes, they will degrade over time as a result of the contact of the gasoline with the fiberglass. In fact, fiberglass resin is less resistant to gasoline than linear polyethylene, polyethylene or polypropylene. As plastic go, the 3 foregoing are about the best, but even they will be degraded over time. Teflon is the best, though.

[Jim T.]

Re: fuel vapor separator - follow-up

What was used in the SR71 for sealing its fuel?

[Gary S.]

Re: fuel vapor separator - follow-up

Heat!

Obviously you know that the SR-71 leaked JP7 and hyrdraulic fluid like there was no tomorrow. There wasn't any way to keep the bird dry on the ground when the skin grew by several inches during flight. The titanium skin stretched during high speed cruise and sealed itself. If you ever saw an SR up close during an air show or in the hangar they always had drip pans to catch the stuff that ran out. In addition, I carried JP7 several times for the SR (to some "undisclosed" locations) and it was alleged to have the consistency of semi-melted jello.
Gary

[Joe L.]

Re: fuel vapor separator - follow-up

Gary and Jim-----

I believe that the A-12/SR-71 were the very first aircraft to use the "integral" fuel cells. However, there was a sealer used in these tanks notwithstanding the fact that the tanks leaked fuel when the aircraft was in ground or low speed configuration. As a matter of fact, when the Air Force and NASA brought back a few of the SR-71s to operational status a few years after their general retirement in 1990, the biggest problem was obtaining the tank sealer. The sealer, which was unique to the A-12/SR-71 application, was out-of-production and it was not practical, at all, to put it back into production. They finally found a supply of it in some government warehouse and it was determined to still be usable. They did, however, establish the fact that they could only keep the fleet operational as long as the supply of the sealer held out. When it was exhausted, they would have to retire the aircraft permanently. The Air Force only kept a few aircraft flying for a few more years, anyway, and before the supply of sealer ran out. I believe that NASA may have 1 or 2 still flying out of Edwards AFB. The fact that the Air Force decommisioned their fleet and, consequently, "freed up" the remaining supply of tank sealer may enable the NASA aircraft to fly for a longer period.

Incidentally, the "#2 Guy" on the A-12/YF-12A/SR-71 project was a fellow by the name of Ben Rich. Ben took over at Lockheed ADP for the "#1 Guy", Kelly Johnson, after Johnson retired. Eventually, Ben ended up being the "#1 Guy" on the F-117A Stealth Fighter. Ben's brother Ray was a VERY good friend of mine for many years. Ray passed away of a massive heart attack (in the waiting room of the emergency room at the hospital) about 10 years ago, shortly before Ben died of pancreatic cancer. There's hardly anyone in the world that I miss more than Ray. I think of him all the time. He was a truly lovable and utterly unique character. I cherish every moment I spent with him.