sanjoh

I'm looking at building some "cans" for my ZDZ120 twin. After seeing the cost and weight of the aluminum ones, I thought I would try to make some out of fiberglass.

I've been having trouble finding the right resin for this application. I figure it should take 500F. The cans will be exposed so some cooling will take place.

Plan on laying up over foam then wash with gas to remove foam.

Target weight in the 4-6oz range

2.5"OD x 11"L

Any ideas or suggestions?

rpmtech

My Feedback: (6)

Hi, thing you might be able to use for exhaust is some type of carbon prepreg for hi temp,and the only ones I know of are only good to about 400 F or so, and are prepregs so are harder to keep in place while laying up and work with in general. I have seen carbon tuned pipes, But I dont know what they are using, so you might want to get in touch with someone who makes em and ask. Maybe someone else here knows a resin you could successfully use for this, But due to the higher EGT of gas engines I really dont see any practical way to make something that would be reliable. I hate saying something cant be done, because it is possible to do what you want, but it would take alot of time and experimenting and frustration. I will be interested to hear other peoples solutions on this one.

Mike James

I haven't done this particular composite task myself, but would love to read about it. I've done several projects that could benefit from lightweight, composite mufflers or exhaust systems.

martyg

My Feedback: (42)

The pattern guys do this.
That would be a good crowd to engage with that question.

I have a couple of guys in my club who have made CF pipes.
Will find out what kind of resin and header they use.

TOYMAKER

My Feedback: (6)

I have a homemade c.f pipie I run in my pattern plane.
You have to have a good high temp resin. We had failure of the inlet pipe because of the high temp so we started using 3/4 scrap aluminum wing tubes for inlets and with good results. See attached photo. The pipe laying on the ground is the one I am talking about. It weights 4.7 oz and has 3 baffles in it. Very quiet, so quiet that all I really here is intake and prop noise. We are still in the testing stages. If you are going to go with a gasser they develop much higher temps so I'm not sure how they would hold up to your application. Its worth a shot, with the price of this stuff it sure dont hurt to experiment. I know a guy that made a muffler out of 2 Glade airfreshner cans brazed together an it was really pretty quite and cheap too.

sanjoh

Are the pattern guys running gasoline engines?

I will be using the ks stainless headers so the "cans" will be some distance 4-6" from the exhaust port.

I wasn't thinking of cf but the much less expensive fiberglass.


Toymaker,

What resin did you use for the pipe and how did you lay it up?

thanks,

John

TOYMAKER

My Feedback: (6)

My buddy who is a composite expert did it for me so I'll have to get back to you on the resin thing.

Go to this website on how to make the metal can muffler. I think these would hold up better to the higher gasoline exhaust temps.

www.rcaerobats.net

fw190

My Feedback: (37)

How about this site for HI-Temp Epoxy?

rated at 550 degrees...



http://www.hottec.com/Bondceram/e660.html



fw190

Craig-RCU

JB Weld is essetially a high-temp epoxy. I did a small experimental layup of JB Weld and fiberglass with the intention of making my own exhaust system parts. The JB Weld bonded well to the glass. I haven't made any parts yet but it looks promising. The fiberglass gives the normally brittle JB Weld good strength. Since it is a little thicker than epoxies it does take a little forceful squeegeeing to work it between the glass fibers. Regular JB Weld (not JB Kwik) gives you about 40 min work time or longer in cooler temperatures to do this. Give it a shot and post back here.

rpmtech

My Feedback: (6)

If im not mistaken I think JB weld is Epoxy with aluminum powder and a few othe additives. Maybe you could LIGHTLY thin it with some acetone to get it to wet out a little better.

fw190

My Feedback: (37)

I don't think JB weld will hold up over 300 degrees. You need one better at 500 plus degrees.

fw190

sanjoh

JB weld will take up to 300C (572F). It can get expensive.

I found a product called "muffler mender". Its used for plugging leaks in exhaust systems on autos. Looks promising.

Had a friend bring over a mousse can that was 7"l x 2"od, made of aluminum. A 60cc would need something roughly twice as long in 2" OD. But, IT ONLY WEIGHS 1.3OZ. The intake on the can fit the output on my headers (1"). Looks like I'm going to the hair salon! Let see I need a 14"l x 2" od mousse can!

sanjoh

Went to the hair salon! They gave me some empty cans from hair spray.

Heres a pic of the baffle (tail rotor tube from a crashed raptor)which fits inside the the short alum, which goes inside the can. A teflon adapter will join the header to the can.

sanjoh

Here's the finished product (before paint). It weighs half as much as most "production" cans at 3.3 oz. and cost me some jb weld!

I'll follow up with a report on performance once the plane is flown

Darrinc

My Feedback: (5)

There is no sense in guessing what resin to use until we know what temp we are dealing with.

Could someone with one of those infared temp guns give us some real numbers please.

I believe using a braid would be a great idea. I'll be using a Carbon/Kevlar braid from A&P myself.

If it ends up being a fairly high temp cure, there are resins that you can do a room temp cure, then post cure at operating temperature, which you could do in a standard kitchen oven.

The ideal setup for anyone that really wants to do composites would be making your own autoclave.

Regards,

Darrin Cash

JasonS

I don't know about gas aero engines, as I run glow, but motorcycles and auto engines run as high as 1400 degrees exhaust temps 6-12 inches from the port. I don't think you will find an unclassified resin for composites that will work for a gas motor exhaust system unless you use a really long header.

trailingedge

My Feedback: (1)

Check out www.cotronics.com. They have a lot of high temp expoxies. I don't know if they would fit your need, but it's worth a try. Have you thought of a thin ceramic layer for insulation? It could be a real pain, but it may be exactly what you need. Hope this helps.

bestrcpilot

I have tried to make a pipe for a G-62 out of fiberglass. But it did not hold up to the high temp exhaust, the fiberglass itself did, but the Epoxy did not. I was seeing temps of 900 dergees at the exhaust port. I'm am now trying out a new design using High Temperature Ceramics with a CF outer skin. This is working out so far but the "cans" are a bit on the heavy side. The weight is in the ceramics and in order to get the ceramics thiner I have to make a new mandrel, which I hope to have done on Monday and hope to have a new "can" ready Friday for testing.
Let me know if you want to hear more.
Scott

paperairplanes

My Feedback: (10)

maybe try talking to the jet guys, most of their bypasses for turbines are of composite materials. Maybe they could shed a little light on the subject. I know that the surrounding area around a turbine is not as hot as the exhaust, but it might give you a few ideas anyways. Just a thought......