I am making a very special exhaust pipe. It is very much like a F-117 pipe, which will bifurcate, and the ends will be flattened. I am planning on making the inner pipe from SS, however I would like to make the outer pipe out of carbon fiber. It will allow me to keep the pipe's shape better in the rear, and also allow for easy disassembly or inspection ( would have top/bottom bolt together) I do not think the outer pipe will be getting hot at all, however i would like to have the carbon laid up with something that would also if need be heat resistant. AC composites sells a high temp laminating epoxy that is intended for the making of tuned pipes, and exhausts, i though of using that ... anyone have any other products you could recommend ?

also I may be wrong, but i think the old BVM F-4 pipe's outer wall was composite .... ???




http://www.acp-composites.com/acp-ez.htm


thanks !



Voy

just found out EZ-lam is good up to 200c .... hmm .. i don't know if that would be enough ?? also, it needs to becured at a similar temp... anyone know of anything that would not need to be cured at such a high temp ? and/or that can withstand higher temps ?


Voy

I was involved, a few years back, with some aerospace high temp resins. I think they were BMI resins (can't remember what the BMI stood for). The big problem with using these for modeling was that they needed to be cured at elevated temperatures of like 250 to 350 degrees F. Any they were only good up to 350 degrees.

BMI = Bismaleimide. I posted before your second post. I see that you've discovered that the elevated temp composites normally require elevated cure. Bummer.

I could tell you the answer, but I will have to charge you $20.

is $20 what you need to finish your next foamy Curtis ??




I guess i will need to find somewhere with a big oven for curing whatever i end up using ... ( don't think my wife would let me use the one in the kitchen, but maybe i could try when she is out


thanks ...



Voy

Hi Voy,

In my experience, a specialty resin's hi temp performance is only as good as it's post cure temp level. So you need to build an oven first!

Good luck,

http://download.r-g.de/handbuch/en/kapitel02.pdf
page 36

and/or

http://shop.ezentrum.de/1786376/ZdfC...engruppen#2568

guys, all good info here ... i think instead of puting the effort into ovens, etc, i might just make a plug and send it off to Tad at Golden West to lay up in carbon / high temp epoxy. I know he has experimented with composite pipes in the past himself ... ( even for inner pipes i have heard .. )


Voy

Inner pipes!!????!! Whoaaa! Any intel at all of what materials he was using and what level of success?

What about laying up the carbon in resin and then coating the inside with ceramic material or BVM Heat Shield?

I am using a plain, home made epoxy glass pipe as the outer on my Skyhawk with MW44 and Wren stainless steel inner pipe. The outer pipe is made from one layer of 200gram cloth cured flat, painted on the inside with BVM heatshield then rolled into a tube. It only has approx 5mm gap to the hot jet pipe, so far it has not shown any problems even with extended ground running with barely any airflow through it.

H

Most resins that will take that temp won't cure with out a oven. Then you need a tool or mold the will take the temp's also. It can be done but it will be very expensive. At the size you are dealing with I think the carbon and resin pipe would be heavier than a SS pipe. Butch

Remember guys: the BVM Heat Shield stuff is just a fire resistant coating. It offers almost no insulative capability. It just does not support combustion. It will not keep anything that it is coating from getting hot, just from burning. The thing it coats will still get just about as hot with or without it. It may insulate enough to give a delta of a few degrees F, at the most. It just keeps direct flame away. So if the glass/epoxy pipe will get real soft at the temperatures it gets to without the Heat Shield, it will still get that way.

Try some JB weld it works with high temps and it has different heat tolerances for each application.

P. Richards aka Swat Team

you can not lay up carbon cloth with JB weld ....


looks like i will be looking for a used electric oven in the clasifieds ... make a few pipes, and then get rid of the oven ...

thanks for al the good info guys ..

Voy

Wojy, how about using some of that pube poxy that you used in your video here on rcu ?

Great idea! The moisture in the pubes could act as an active cooling system as it boils off, keeping the pipe from getting too hot.

Now all you have to do is get Tracy to sign up the Bunny-donors, wet them down, and harvest the fibers!!! [X(]

Yup! That has worked for me so far.........no "pipe" over-heats!

John

PMR15....or Carbon/Carbon you can get rid of the inner SS pipe.
Mr. Composites

no problem Wojtek
our L-39 has a composite outer pipe over the ss steel pipe
the lenght is over 800mm
never had a issue .

i found the spec sheets on this stuff .. cool !! ( uhhh, i mean HOT ! )


where can i buy this ? is Mr.Composites a reseller ? if so i was not able to pull up an web sites or contact via web search ..


regards,


Voy

Isnt that a polyimide?

Sorry Wjotek, for getting you excited. We did some testing/evaluating on these Hi Temp composites back 20 years ago in Phantom Work and that is where I started little more than 23 years ago.... It banned from use few years latter due to carcinogens....I don't think you can get to it now. We got much better stuff now, But......
No, I'm not a vendor. I just been heavily involved with Research and Development in Composites for many years....It's so funny that stuff that we were developing or evaluating and testing don't get to general public or commercial use at least 10 years latter....
Col Tomb