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Message-ID: <4AA07AEB.6060303@canardaviation.com>
Date: Thu, 03 Sep 2009 22:26:51 -0400
From: John Slade <jslade@canardaviation.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Help for John Slade
References: <list-3835554@logan.com>
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First of all, thanks to the many people who responded to Buly's 
message.  I'm sorry I wasn't able to call everyone back. I was on the 
phone for a couple of hours with various helpers, but failed to explain 
to all of them that I was an idiot. In my own defense it had been a very 
long day.

With regard to mogas, epoxy tanks and filters, let me try to clear up 
any misunderstandings and provide whatever information I can to assist 
others avoid the same issues....

Yes. My MGS 335 built tanks failed to hold up to ethanol in mogas. The 
symptoms of failure are (or were in my
case) fairly benign. After about 4 years there was evidence of softening 
of the inner strake skin. This first showed up as faint lines along the 
curve of the strakes where we bend the skin. There were no leaks or 
"gummy stuff" found in the fuel or filters. At about 5 years, reaching 
through the filler holes to squeeze the inner skin proved that the inner 
skin has significantly softened. I decided tht the tanks needed to be 
rebuilt. I removed the strake tops and discovered that the entire inner 
skin was soft. Interestingly, in the areas where there were 2 BID tapes 
the tapes were soft, but the skin under them was undamaged - it seemed 
to me that the ethanol had weakened the skin very gradually, and had 
just about got through two layers. A leak was clearly imminent.

To cut a long story short, I removed the bulkheads and removed the inner 
skin down to foam. I then rebuilt the strakes from the inside with plans 
layups using EZ-poxy and built and installed new bulkheads. When this 
was all cured I constructed inner tanks in each of the three sections of 
each strake using vinyl ester resin and 1 UNI. These inner tanks have 
lids which were added to the underside of the strake tops prior to re 
installation. Perhaps the inner tanks may be superfluous based on others 
experience with EX-Poxy (Perry Mick, for example). I just didn't want to 
do this (roughly 80 hrs) job again so a I used a "belt and braces" approach.

The strake "lids" were reinstalled and taped. Last week I completed the 
refinishing of the strake tops filled the tanks, taxi tested, and 
cleaned the filters. There was very little crud in the filters. I then 
test flew the airplane for 1.5 hrs and cleaned the filters again prior 
to my planned cross country flight from Rhode Island to Florida. I made 
a fuel stop for mogas at SFQ in VA, then topped up again at BNL in SC. 
On my first use of the right tank after the BNL fillup The engine 
immediately ran rough at reduced rpm. Switching off the right tank did 
not rectify the situation. (each tank has a separate pump & filter. The 
feed is T'd at the rail and I always switch both on, then switch off the 
one I'm moving from). This means that the engine was never running on 
just right tank. Theoretically it should have been getting fuel from the 
left. Apparently it was not.

The engine ran rough at around 3500 rpm max throttle from then until 
touchdown at 17FL. Switching fuel pumps and injectors had no effect. 
I'll cover the emergency landing in another post. After landing I turned 
to back-taxi on the 7500' runway and found that the engine ran 
perfectly. I suspected filter blockage, but was puzzled as to why 
running on left tank did not solve the problem. On inspecting the 
filters I found the left one to be clean, and the right one completely 
blocked with about a cubic MM of epoxy dust material. Failure of the 
engine to start after filer cleaning was simply my error in forgetting 
to switch the manual tank isolation valve. Once I switched this valve 
the engine started and ran as normal on the last leg from 17FL to LNA.

My guess is that the pressure surge from initializing the right pump 
cause some epoxy dust to be forced through the (post pump) Earls 
stainless filter and on to the injectors' screens. This is the only way 
that the left pump would have failed to correct the problem. As for the 
sudden "arrival" of the crud after finding clean filters twice - Here's 
my theory, for what it's worth - When at the hangar I fill the tanks 
from 5 gal fuel containers. At SFQ and BNL I used the airport pumps. 
These pumps are VERY high volume / high pressure. You can fill a Cozy 
tank in just a few seconds. I think that the high volume fuel insertion 
caused turbulence in the tanks that hadn't occurred with my normal 
filling method, and forced crud out of the corners into the sumps.

Anyway, thanks for all the good wishes. I'm safe & sound back in South 
Florida, and apart from this inconvenient little incident, the engine 
purred like a kitten the entire way.

John Slade
Turbo Rotary Cozy N96PM