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Steve Thomas wrote:
Here is an update on the gasohol tests that I have been running. The witness samples that I have put into the test jars are all from either my own or the original factory layups, all using Derakane 411 of some sort. I used the -
45 for a long time, but switched to -350 sometime later as it was easier to get and wetted out better. I have three tests running as noted below:
1. The first test is with two samples in a jar with Jose Cuervo. Jose Cuervo is 40% ethanol. I have an original
What a terrible waste of perfectly drinkable Jose Cuervo.
I took the time to learn to weld aluminum and switched from the plans directions of a fiberglass tank to use an aluminum tank. The issue that concerned me most, and I really hope people using glass tanks will heed this closely, the most pressing issue is not ethanol (today's additive). The most pressing issue is, "What will the clueless politicians mandate that we add to our fuel in the future?"
You hope for the airplane to be flying in 20yrs. The government has clearly demonstrated that they are willing to go along with any boondoggle, no matter how much it harms the people they are claiming to help, as long as the right campaigns get a properly sized donation. Ethanol in gasoline is ridiculous by any reasonable measure, except for how much it enriches Monsanto and ADM; yet, there it is (and is increasing). There is absolutely no way to know what bright idea they will come up with in the future. The epoxies we use in our structures is an organic compound, which will have a measurable reaction to any organic solvents. All carbon based liquid fuels are organic solvents. Different types of epoxies will have different reactions with different solvents. There isn't a universal solvent, and epoxy that stands up well to the first, will melt in the second, while a different epoxy formulation will turn to goo by the second and seem to ignore the first. Someone has a rulebook somewhere that gives guidelines as to what solvents will affect which epoxies. I have only seen pieces of it, but I know enough to know that the rules are long, complicated, and hideously complex. People make careers of specializations within specializations within the various fields of organic chemistry, fer chrissakes.
So, we have an unknown future where clueless politicians get lobbied to mandate we pour various amounts of random chemicals into our fuel supply. You have fuel tanks built with organic chemicals that WILL have a reaction to these unknown chemicals, whether it be barely noticeable or instantaneously turning the entire tank to goo. You have a situation where a slight reaction can clog a filter and result in fuel starvation to the engine in flight, or a radical reaction resulting in the hangar floor below years of work being covered in volatile fuel. AAARRRGH!
If you're going to stay with aviation fuel, I'd say that you're reasonably safe with hand-laid tanks. The FAA is going to require a lot of tests to meet STCs before they let just anyone change the formulas. That has been demonstrated. We still have leaded fuel more than 30 years after it was mandated away everywhere else.
But IF you're going to be pouring gas from your local station into your tanks, either commission a roto-moulded tank from the same materials used to make plastic gas cans, or build one from aluminum. All fuel lines should be aluminum, or automobile approved materials (including O-rings and such). I'm not saying that going with the automobile gear will be a complete shield from trouble, but the politicians are more likely to fear millions of drivers being stranded when they push chemicals that are incompatible with autos.
I'm not trying to disrespect your experiment, Steve. In fact, I think that it clearly illustrates the point that all these interactions are funky, and not necessarily predictable. The point that bothers me is that they miss the most important point. All you can test is last week's/month's/year's formulation; but you will, by necessity, be flying with tomorrows.
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