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Toobuilder

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Wow Toobuilder, good catch !

Did you see a bulge in the header wrap when you got back, or did you remove it for a paranoid post-flight look-see?
Was looking up the cowl exit and gave each pipe a shake. This one was swinging in the breeze. Dropped the cowl and saw it was nearly burned through (wrap was blown away).

This same exhaust gave me no problems for 331 hour prior, and it's been wearing the wrap for the last 10, so it's fairly compelling evidence that the intense heat trapped by the wrap is the root issue. And that sucks, because I'm looking to maximize the heat delta between the exhaust stream and the cowl outflow. It's what makes the ejector work so well. Now I'm going to dump a LOT more BTU's into the lower cowl AND cool/slow down the exhaust velocity.

Flying tomorrow - will report back if there's a change in performance.
 

Bill-Higdon

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Was looking up the cowl exit and gave each pipe a shake. This one was swinging in the breeze. Dropped the cowl and saw it was nearly burned through (wrap was blown away).

This same exhaust gave me no problems for 331 hour prior, and it's been wearing the wrap for the last 10, so it's fairly compelling evidence that the intense heat trapped by the wrap is the root issue. And that sucks, because I'm looking to maximize the heat delta between the exhaust stream and the cowl outflow. It's what makes the ejector work so well. Now I'm going to dump a LOT more BTU's into the lower cowl AND cool/slow down the exhaust velocity.

Flying tomorrow - will report back if there's a change in performance.
I've heard of similar problems with exhaust wrap causing cracks, you might try ceramic coatings on both the inside & outside of the exhaust, I know some ATV owners who swear by them.
 

Toobuilder

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I've done the ceramic thing before and had great success. The wrap is essentially the same thing, but more effective and temporary. It allows evaluation of a configuration without much cost or permanent change.

It works great in theory, but not in practice. In the end, practice rules the day.
 

BJC

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In theory, ceramic on the inside keeps the gasses hotter and the metal cooler. I've not found actual measured, verified, data, so for me, it remains unproven.

Anything the blocks heat flow on the outside of the pipes makes the metal hotter.


BJC
 

Victor Bravo

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I agree, no data or long experience to base it on, but my gut tells me that the ceramic on the inside of the pipe should keep more heat out of the metal, without increased risk of cracking the pipe. Ceramic on the outside seems like a heat insulator, no matter how pretty it is.
 

TFF

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Done right it needs to be inside and outside. Performance, aesthetics, heat. The only way I would wrap an exhaust, would be after the ceramic coating. You don’t see either, it’s always together in racing for the last few decades.
Race cars only have to finish a race. A crack gets fixed for next weekend. I’m not saying it breaks on everyone, but in racing , you expect something will be broken every weekend.
 

Toobuilder

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The ceramic coating inside and out absolutely keeps heat in the pipes -dramatically so. My last experience was ceramic on the outside only of a mild steel header on the Hiperbipe. I got a few hundred hours of time with that exhaust and never got a crack.
 

Victor Bravo

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I'm confused... how can ceramic coating applied to the outside of the exhaust not be an insulator that slows the outbound heat radiation from the steel???

I understand how (on the inside) it behaves as a barrier, keeping heat from being absorbed by the steel. So if it's a barrier then it's a barrier.

To me, claiming that coating both sides (inside/outside) reduces the heat load on the metal is somehow claiming that the material is creating a barrier to heat flow on the inside but it is doing the opposite on the outside. A material can either prevent heat flow, or it assists heat flow.

I doubt that any material can do two opposing things. But even if it could, it would have to "know" whether it has been applied to the inside or the outside of an exhaust, and which function it should be performing on which side of the metal.. If such a material did exist, it would not be something you could buy on Amazon, or even discuss on this forum.
 

TFF

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There are a lot of companies that will not put it inside because it’s hard. One void and the pipe melts out. Most are for car for looks in the name of performance. Street car will not matter too much. You have to be your own QC to get what you want. A friend did a 6 cylinder Mercedes iron manifold. It looked great, but there was one spot on the inside, that would have driven me nuts.

I believe the outside ends up helping stabilize the metal. What heat gets in you don’t want to escape unevenly; the outside side to go cold and crack. Reject heat but then control what comes in. The extra on the outside still helps the compartment.
 

BJC

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Years ago, I corresponded with a person whose business included internal ceramic coating of exhaust headers for race car engines. Long story short: he would internally ceramic coat my exhaust, and charge a hefty fee for doing so, but he recommended against it.


BJC
 

TFF

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With racing if you are about winning, a race car is a consumable. You are after a trophy not after a race car. Some want to just own a race car and drive fast and finish a race ; participate. But that’s not winning unless it’s a soft class. A real race owner, within budget, does not care what blows up to win.

Airplane; attitude is,” Pretty Pretty Please Please, Don’t Blow Up On Me, Pretty Pretty Please.”

That is why race car technology is not always a good crossover. End game is different.
 

Toobuilder

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Flew 1.0 today and had my first taste of a comparison with another Rocket. This other Rocket (F-1) is a highly refined example, and he's the fastest in our group. For this one data point I have some encouraging results:. Head to head my CHT and oil temps are slightly cooler, my Pitot/static is very close, my airplane is a touch faster at high RPM, while he's faster at lower RPM - we expected that with the difference in props - I have a metal Hartzell 2 blade, while he has an MT 3 blade. FF at speed is similar, and MP is identical. This last part is disheartening a bit because I have the "perfect" airbox with the inlet way out in the prop arc, while he has the standard (and more streamlined) chin inlet. I have a lot more wetted area to no apparent benefit in MP. More testing to follow!
 

Toobuilder

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Did 1.0 in a racetrack pattern between PMD and TSP yesterday with no issues. tore into the wiring to figure out my ADS-b problems, and today did my first passenger flight with the boss (wife) in the back. Went to Big Bear for breakfast at 11k and hope to have a good PAPR from the feds as a result. Was happy to see all my CHT's sitting within a few degrees of each other at my perfect temp of 365 on the trip over and back.

Its starting to act like an airplane again.
 

pwood66889

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Rode out to look at my nose gear strut - found some issues = maybe a crack in the part just above the wheel, elongated bolt holes, and some bores a skidge too large. Good trip, but I gotta find that post here about some Ercoupe parts in HIO, Oregon.
 

Bill-Higdon

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Rode out to look at my nose gear strut - found some issues = maybe a crack in the part just above the wheel, elongated bolt holes, and some bores a skidge too large. Good trip, but I gotta find that post here about some Ercoupe parts in HIO, Oregon.
The parts were on Craigslist, sadly the ads are no longer present
 

Pops

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Rode out to look at my nose gear strut - found some issues = maybe a crack in the part just above the wheel, elongated bolt holes, and some bores a skidge too large. Good trip, but I gotta find that post here about some Ercoupe parts in HIO, Oregon.
I have bought Ercoupe parts from this man. Very good to deal with.
 

bifft

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Did some more climb/glide testing and the data was still bad. My test area is entirely desert and mountains so never get the cool windless mornings they books all say to test in. Still with enough data points you can average out the errors. So I'm calling it good. Signed it out of phase 1 at 44.2 hours.
However given the current conditions, gonna be a while before I go anywhere or give anyone I'm not living with a ride. And she's not that interested anyway. May to the condition inspection (also due this month) first.
 

Victor Bravo

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Took a magnifying glass to my newly welded (and repaired and re-welded) wing struts, spent half an hour just staring, to make sure the welds looked good enough. Not nearly show quality, a few very small issues, but they're plenty strong. Especially considering the (over 25) rosette weld holes I had drilled in the outer tube, out of abject paranoia.

Then took the miracle supersonic flap wheel grinder to it, to knock off small edges and weld nubs. I was NOT looking to grind the welds perfectly smooth, just to knock down sharp bumps. After an hour with the flap wheel, threw the struts on top of the old Volvo wagon roof rack, and rolled over to the powder coating place.

The powder coat is to protect against corrosion and damage, but not to serve as the outer cosmetic layer. There will be airfoil shaped fairings put onto the struts, and those fairings will get the final paint color. More than likely just flat black Aerospace-Oleum rattle can. It's a desert beater, not Thurston Howell's carriage :)
 
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