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Joe,
Thanks for the response - I need to qualify
some points.
There are about 4 resin ( as in epoxy resin)
manufacturers in the world - so the BASIC resin is pretty standard.
I take you point, indeed there are different
fillers and colours in different resins, but this doesn't make such a
big difference, but they still have to matched to the
hardener.
The real difference is in the hardener. Hardeners
are very complex, and the more complex the more expensive. It could very well be
the better the hardener the better the molecule to molecule mix ( higher
density?). If This is true than Al's statement is true, but he hasn't said that
- WHAT HE IS SAYING isn't clearly defining these
points and could be misunderstood by others. I quite obviously have trouble with
what he was saying.
George ( down under)
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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