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George –
Al knows full well the strict ratios for
epoxy reaction. He built and is flying a Cozy. What he is saying is that
epoxies that use a higher resin to hardener ratio “TEND” to be more
resilient to fuel & alcohol. Al pointed out that this is coming from a
couple of epoxy experts that have been on the canard forums for years. An epoxy
with an 80/20 or 100/40 ratio “tend” to be more non-reactive.
Epoxy quality can’t necessarily be
defined by ratio – BUT – most epoxies use the same basic chemicals
and reactions (also pointed out by the “epoxy experts”). So, “quality”
is generally a matter of fillers, colorants, etc. supplied by the mixer of the final
product being sold. Depends on the fillers used.
Strength and chemical resistance are
unrelated. I’m guessing there are epoxies that are strong – but that
will dissolve in fuel and/or alcohol. So, strength is not the only criteria
when selecting an epoxy. If one is going to use epoxy in the fuel tank –
that needs to be researched and tested.
A couple of years ago I met the MGS epoxy
representative for North America. I
asked him about fuel resistance. His basic answer was that no epoxy company will
tell you their epoxy is “fuel proof”. That’s because they don’t
know what constitutes the word “fuel” – could be lots of
things including rocket fuel. His only firm answer was “I build a
composite plane 20 years ago with MGS and it’s still flying today with the
same composite gas tanks”.
Regards,
Joe Hull
Cozy Mk-IV #991 (preping for DAR inspection
- details, details)
Redmond (Seattle),
Washington
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of george lendich
Sent: Wednesday, January 18, 2006
1:02 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Auto fuel
Just so we are talking about the same thing here, I've asked
some questions in the body of your e-mail.
No, I wasn't speaking of polyester. You can buy epoxies of different
ratios. I'm told by expert (Gary Hunter) that all epoxies which use ratios like
80/20 have significantly better mechanical and chemical properties.
Better properties to what?
1. All epoxies uses strict ratios, as I
explained!
2. The ratios are set by the manufacturers.
3. There are different quality Epoxy Resins
- I agree, but the quality can't be quantified by the ratio of the resin to
hardener alone, to my knowledge!
4. The dearer resins are quite obviously,
better quality!
5. The Quality resins are those most often
used in Aviation and there is comprehensive information available on
structural strength etc.
6. If someone where to use a
cheap Epoxy without researching it's properties - I would be very
concerned.
7.Are you suggesting that people may use a
cheaper (non structural) resin to line fuel tanks and my therefore see a
break-down of the material sooner?
This is measurable, and agrees with my and other peoples
tests. Like I say, I tested all of the fuel tank components in
various batches of alcohol fuel for years (you know how I don't like
design assumptions). None of the components were affected. The only exception
was when I exposed 50/50 epoxy mix to fuel. It slowly got mushy.
I have seen fuel tanks destroyed, leaking like a sieve from exposure to
alcohol fuel. One reportedly had old version of proseal inside. It completely
peeled off tank inside. Clogged fuel port. Forced landing. If memory
serves me correct, it also had poly that degraded by erosion. It looked like
someone had etched the poly out of the tank.
You must be speaking about Polyester as Epoxy must
absolutely maintain a strict ration mix, as per manufacturers
instructions, to allow proper molecule to molecule bonding of the
hardener and the resin. Polyester on the other hand has flexibility in that,
more hardener promotes hardening sooner.
I tested the hell out of that. No effect. Years of exposure to
different batches of known alcohol. I understand that if you use a resin of
high proportions of hardener to resin, it's resistant. If you use 50/50, it
isn't. I had 50/50 get soft from fuel exposure.
This info consistent with all the other guys that did the same test.
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland,
Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
It will make it less attractive for those with fiberglass
tanks. Alcohol/gas mixes are more aggressive than either gas or alcohol alone.
Bill Schertz
KIS Cruiser # 4045
----- Original Message -----
Sent: Tuesday, January
17, 2006 8:17 PM
Subject: [FlyRotary] Auto
fuel
By the Farm Bureau Paper it is stated that Wisconsin has passed a law that all 87 no
lead will contain 10% alcohol and that nine other states are considering
it. It didn't mention the other no lead grades. Here in Michigan it is under
consideration at this time, and there is a good chance it pass. Other
than cutting the power some what, is going to effect the operation of the
rotary in some other way. JohnD
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland,
Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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