Tuned Pipe Construction

Has anyone here made there own tuned pipes? I'm not concerned with the dimensions or "tuning", that's a another discussion, just the physical process of actually making the pipe. What method is used? Do you make molds and lay it up or use a mandrel and wrap with CF tow or braided sleeve? What sort of resin?

I'm not really sure I want to try making my own, I'm just interested in the process.

I think the preferred process involves a mandrel, a braided sleeve, and a high termperature resin.

And, no, I don't think you want to enter into that picture, unless you have a real good reason.

Windy Urtnowski would share some info with you-he probably has a video showing how he makes them. He uses turned mandrels as forms and I know that he cures them in a autoclave.

Len,

You're right. I'm just interested in the process of how they are made. Not that I wouldn't mind tackling it, but I don't think the tooling needed is worth the effort to make pipes for myself and I'm not interested in going into business <grin>.

Who knows, I might decide to make my own. I doubt it, but I wanted to know how it was done.

If you use a turned mandrel, how do you get it out after cure? Is it made of foam or other "melt-able" material?

I presume that a release agent is applied to the mandrel first. PVA, probably.
K

The shape of a tuned pipe would not allow the removal of a solid mandrel no matter how good the release agent. Is the mandrel not mechanically locked in? Do the pipes have a seam?

Several pieces, several seams.

Windy has been down this road a couple of times. He uses a mandrel made of a teflon material..... no release problems at all. He has also done a ton of work on the binding agent.

Not as easy as it looks!

See Ya

>... Do the pipes have a seam?

The ones I've seen show one obvious external seam where the forward end joins the rearward piece, which are designed to land this seam on the point of maximum diameter. George had a box of these to unpack in his shop while I was there on two separate occasions. He sells them for the GMA/Jett stunt engines.

Kiwi

As long as you didn't have to use "Pre-Preg", you could make an aluminum mandrel, cast a plaster or epoxy 2-part mold, and use that to make wax patterns. You'd probably want to cast the wax patterns with a steel rod down the center. Then you could mold your pipe in one piece and melt the wax out, remove the tube, and you'd have a single piece pipe, unless there are baffles inside? We used to use high-temp epoxy at Boeing in the Mockup Shop. I don't recall the temp rating, but it was actually cheaper than the standard stuff. Also, we used a lot of paste floor wax for mold release, and sometimes a shot of spray. I don't recall if it was silicon or teflon, tho. A mind is a terrible thing to lose.
Steve

Yes, and a waiste is a terrible thing to mind.

There are baffles in the typical pipe. Also, some of the newer ones have the eshaust outlet aimed down--in effect another chamber. All of which adds up to...that's why we let the other guy do it, unless we have a special need for a special pipe and know what we are doing (or are willing to spend the time and money learning).

My original interest started because I needed a special pipe to fit a particular airplane. None of the standard sizes were going to work and I figured I'd probably end up having to make my own. The project was abandoned (at least for now) until I could work ot this and a couple of other issues.

Seems the best route is to make the pipe in 2 pieces. This would allow you to insert a baffle and would make molding a bit easier. I have an early Smith pipe that was obviously made in 2 halves and joined right down the middle, front to rear. Another is pretty clearly also made in 2 pieces but as a front half and and back half. Another, more recent one, I can't figure out how it was made. Seems to be one piece.

Randy:

I know that Winfred will hammer together a custom unit for you.... just send a sketch.

See Ya