Composite intake manifold


Help Support HomeBuiltAirplanes.com:


Jul 15, 2014
North Carolina
Even that is a bit low for an intake manifold, especially with turbocharging. I'd recommend PTM&W 2080, which post-cures to a Tg of about 260F.
Any suggestions for quart quantities of high Tg epoxy? I seem to find gallons, which is more than a I need for engine stuff


HBA Supporter
Aug 15, 2013
Western US
Any suggestions for quart quantities of high Tg epoxy? I seem to find gallons, which is more than a I need for engine stuff
Just call PTM&W and order the gallon. The quart pricing is about twice as expensive, so you're not saving much that way. You'll eventually find things to use it all on. Ignore the shelf-life spec; if you keep the cans sealed (especially the hardener) they're good for at least ten years. If they do get cold and crystalize, just heat them to 150F until they are clear liquid again.

Some notes about using PTM&W 2080:

* Parts cure to the touch under room temperature, but they are very delicate in that state. Do not demold them, or even remove peel ply, until you've post-cured them to 100F for a couple hours. For most parts you can easily achieve that with a heating pad or folded electric blanket.

* As a demonstration, take the leftover epoxy in the bottom of the cup where you mixed the 2080 and allowed to cure at room temperature, and strike it with a hammer. It shatters like glass. Repeat with a cup that you post-cured to 100F, and you find it much tougher.

* This system is more viscous than most laminating systems, so it is harder to get good wet-out without using lots of resin. Expect to get lots of breather saturation when you vacuum bag it.

* Be sure to have a thick absorbent pad under the vacuum tap. If the epoxy fills the aperture of the tap, that slug of solid epoxy will cure before the epoxy in the laminates, blocking the vacuum line, after which leakage removes the vacuum from your part. That's bad, because the vacuum had already squeezed all the extra resin through the peel ply and perf ply into the breather, so now you have a resin-starved part that finishes cure under ambient pressure.

* In my shop we generally do an ambient temperature cure under vacuum followed by post-cure in the mold to 100F with heating pads. Then we peel and demold the parts. For bonded assemblies we make bonding paste using 2080 plus flox and cab. When the assembly has cured at room temperature we handle it very carefully. We post-cure assemblies in our hot box with a two-hour ramp to 170F and a four-hour hold at that temperature, and then unplug the heaters and allow a two-hour ramp back down.

* This system uses a rather strong hardener that is probably more sensitizing than most. Be very careful to minimize personal exposure to it.


Well-Known Member
Nov 17, 2014
Any Rutan builders reading this thread?

As a data point, I looked at a medium-time VariEze that was for sale back around 1992. The O200 had cooling baffles made of fiberglass. According to the owner, that was standard technique on VEs. Now, that's not a truly structural area, but it does see considerable force/pressure, and the heads are going to be in excess of 300 degrees. I have no idea which epoxy was used to make the baffles, but I suspect it was pretty primitive stuff compared to today. I also have no idea whether they did any post cure on the parts, or just let the heads post cure them. I wouldn't bet my life on an intake manifold made with the same layup thickness as the baffles, of course; pressures on intake tubes are several times greater than on the cooling plenum.

Above is *not* a response to Bob's recommendation, and I really don't know if the VE owner was just shooting me a line.