Tam,
My tailpipe only last one flight! Unfortunately, it was in my FEJ F-18 when it crashed on it's first flight. I was able to get some money for it at the scrap yard. It seems that a custom bifurcated pipe after 1 ride in a FEJ plane is worth about 3.00

I should twist your arm harder to throw out that pipe.
Sorry to hear that.

What a life saver this thread is. I was going to fly tomorrow for the first time this season. I was checking over my viper and after reading this thread I decided to pull my pipe out and give it a good look over. To my dismay I discovered that my pipe had failed and had a 2" long opening in the seam. I'll be calling tam tomorrow to order another pipe, but thankyou for the save.

Smart move.
Pipe need to check regular to see any open seam or dark purple spot.

I think FEJ did the same thing as CARf. My f16 pipe is very heavy.

I had a MB f86D and the pipe in that was very light, very small. I had some wet starts. Never collapsed after 100 flights.. Must of been luck?

Would love to see some ideas on how to align the pipe and turbine.

Would love to see some ideas on how to align the pipe and turbine. Good eyes are all that's needed...

Gotta admit, I was wondering if someone had a better way to do it than using the good ol' Mk1 Mod0 Eyeball

Sluggo

Sluggo and All,
Several (many) years ago I designed a simple tool to align the turbine to the tailpipe. This was documented the JPO newsletter, CONTRAILS, Volume 18, Issue 1 /Winter 2006, pages 9-10.The article is entitled "Turbine Alignment Tool". Fortunately, this issue is available on the JPOwebsite, www.jetpilots.org. Scroll to: CONTRAILS and open the Winter 2006 issue forthe article, found at the 2nd year up from the bottom and on the left.

While you're at the site check out some of the other issues for valuable jet tech hints and consider joining JPO, an application is located within.

Art ARRO

Thank Art!

In terms of a hot start, if you get a blue flame out the back of the pipe for a few seconds, kinda like a butane wind proof lighter, is that considered a hot start?
Also, with most pipes today, would you guys agree that smaller turbines (100N or less) are probably ok assuming there are not numerous hot starts or severe misalignment? Seems the issues come with bigger turbines these days with modern pipes.

BTW The FEJ pipe I have is very thick, and very big. It always weights a ton. Hoping it doesnt leave me burnt.

How are jet legend pipes? I have a 1/9 GJL F-15 should I be concerned other than checking it? Thanks

George,
I just binned the OEM Jet Legend pipe in my ongoing JL Mirage2000 assembly and replaced it with a new Tam pipe.
Never even installed the JL one; it "appears" to be constructed OK (decent looking welds and reasonably heavy gauge inner sheet) tho there is no way to know the quality of the steel.
I went with Tam's pipe because:
1) unknown quality of JL pipe
2)<span style="background-color: rgba(255, 255, 255, 0);">the JL one was a tapered (convergent) design 85mm tapering to 75mm at the exhaust which can up the temps and hurt thrust.</span>

<span style="background-color: rgba(255, 255, 255, 0);">Tams is a straight parallel wall front to back, weighs within 3 grams of the JL, and is a known quality.</span>

-<span style="background-color: rgba(255, 255, 255, 0);">sorry......probably doesn't really answer your question.</span>
<span style="background-color: rgba(255, 255, 255, 0);">Mike Warren</span>

Hi George

Yours is fine. I have over 200+ on each F15 before I replace the pipe.

Check the divergence Y for any holes or crack and replace the pipe if you find them.

One of the outer wall pipe sections at the junction will break loose if there is a leak of hot gas. Then it's time to replace it right away. This acts as a telltale for me to replace it before it fails.

Also put some heat shield around the servos and top section of the rear fuselage as precautions.

Out of hundreds of F15 we have sold so far we have no report of pipe collapses so far.

Mike

Thanks Mike The pipe looked good and the thickness was fine.

Was he injecting smoke into the pipe mouth?  That can cause premature failure as well...

Tam,
Where do u recommend injecting smoke OK into the pipe? Near the turbine or by the exit?
Thanks

Yes, I'd like to know this as well ^^^^^^^^^^

I asked this question at TopGun, and there was disagreement about causing damage to the pipe from "cold shocking" if the smoke oil is injected just aft of the engine exhaust nozzle (i.e. like on a Bobcat or Boomer) vs having to be injected at the end of the exhaust tube.

Sluggo

Never inject cold fluid into a hot exhaust pipe with hot gas traveling at 500-600mph or 0.7 Mach or higher. It will induce back pressure, acoustic compression and thermal shock in the flow. Normally a jet factory will void the warranty instantly the moment you put smoke fluid in the tube. Try to do that on full scale and you will have a biggest fireball in the sky.

The best way is to preheat the fluid and inject it 1/2 in away from the exhaust pipe's exit.

Mike

All this talk about collapsing pipes got me paranoid. I had a hot start on a bandit with a p100 on a brand new bvm pipe. What do you guys think about the color? Am I still ok? Flame was not blue.

Another pic

Here are some pictures of subsonic transverse injection and shocks created in a wind tunnel test.

Dr.V. It's about time to replace that. The pipe had already discolored on the outside, so it has become more brittle and lost 1/2 of it's strength. The welding spots at the mid section seem to be pulled apart. Most of the pipes are over engineered so they will hold for a while but why take chances when you know the risk has formed.

Mike

Well, this pipe has been ran only once. The engine has been started only once. I primed it without taking the fuel line out and was not fast enough to stop the flow of fuel. It was brand new from bvm. Hot start was 2 seconds or less. Amber flame. The weld spots do not pull apart and not soft at all. The pipe is very solid. Some of those purple spots are my finger prints so the picture is deceiving.

DRV

The best way to test it at home is to press it lightly and listen to the sound. It should feel solid and no buckling sound, then it's fine. If you have repeated hot starts a few more time, and press the pipe again, you will feel the difference in sound. It will become brittle over time. Just inspect it before each flying day.

Mike

DrV, I'd hit the rear of the bypass with some additional ceramic paint though. clean it up and brush some on there. my2c.

+1
prep with 80 or 120 grit so that the ceramic can stick and then 3 coats.
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