Composite Pipe Repair

[Edward Skorepa]

Hi Gray,
what a nice educational post! However, while most of what you've wrote is right on the money there are some points which are misleading or inaccurate IMHO.

"That is why half off you guys say never had a problem and the other half burn up your inlet tube"
This looks like 50% of our pipes have problems. In reality, out of over 3000 sold 68 failed including 40 made with wrong mislabeled hardener. That's only 2.27%. The main reason why some people are having problems with melted neck is they installing pipe too close to the engine. There are no problems with two strokes pipes not just because 2 strokes produce cooler exhaust but mainly because pipe must be in exact distance from the engine. With introduction of high performance AAP header which is BTW very hard on pipe due to lack of heat dicipitation by Teflon connecting tube it suddenly become very easy to fit pipe in airplane by whacking off the Teflon tube. I have seen our pipe mounted directly behind the header with only 1.5" long Teflon tube.

"sanded outer surfaces exposing the fiber"
will NOT soak up oil on our pipes.

"Hats off to Bolly" they use..........."
Nothing against Bolly pipes, but they will burn out just like any other cf pipes if you try hard. Also, they do not use BMI resin. I'm not sure for 100% but I think they are made in one step. They pull over the wax mandrel saturated cf/Kevlar sock then they wrap it with Kevlar thread to hold it on. This kind of technique will produce zillions of pinholes so after initial cure the whole body is several times recoated before putting it in over for post curing which will melt out the wax. I've seen advertising somewhere"triple coated for pinhole free surface". They don't sand outer surface because they can not do that. They would expose those pinholes if they did. We were also in the past making unsanded pipes. They were ugly, cost $15 less and nobody wanted buy them.

All that talk about inlet failures is now history. We have switched to material you were describing in your post. You were damn right about all those problems with wetting and curing. After 18 months of frustrating testing we can now produce every time relatively easily without need of any special expensive equipment flawless, pinhole free body which will hold up to 850 deg.
All of our glow pipes are now made from that resin. Since April, we have made and sold 180 pipes and so far no problem of any kind. Our gas muffler is going thru severe durability test. Mounted on test stand behind ZDZ 40 running wide open for 3 min then 15 sec at idle till fuel runs out. Total time at full power so far 26 hours 12min and no sigh of failure.  The exhaust temp. in 6" long header just before gas enters the pipe - 812 deg F. On 12" long header temp. drops to 600 deg. You can check out all set up at  http://www.escomposites.com/test_stand.htm

Regards,
Ed Skorepa/EScomposites
  ----- Original Message ----- 
  From: Gray E Fowler 
  To: discussion at nsrca.org 
  Sent: Wednesday, September 24, 2003 8:14 AM
  Subject: Composite Pipe Repair



  The answer.....do it the way the B-2 was done.....epoxy-aromatic amine (or bismaleimide or cyanate ester)  prepreg cured in an autoclave.....Now can you afford this? Perhaps.  To avoid blatant advertising I will stop here. Anyone interested please email me offline at  Aeroslave at comcast.net.


  Gray Fowler
  Principal Chemical Engineer
  Composites Engineering
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