Sean's Glasair Sportman Build: Intercooler

Intercooler, plenum and ducting moving along slowly.

Spend the day yesterday getting the brackets, plenum, etc all ready for paint. Finishing up all the drilling, deburring, fastener prep, 3" holes for the ducts, acid etch, alodyne, etc. I thought it would take an hour... 4 hours later... Everything is primed and paint is going on now.

I decided to use epoxy primer this time rather than zinc chromate. What a difference... the primer sticks better, and the paint goes on REALLY well on top.

Next is riveting...

Intercooler bracket all riveted with nutplates installed.

Plenum and flanges riveted. Test fit on the bottom bracket. All good.

Test fit on the intercooler. Snaps right into place. One tiny interference issue on the intake tube. Fixed.

Bonded in place using leftover firewall silicon goop. I also put a small bead of the goop on the seam on the inside of the plenum. It shouldnt leak much, but every little bit helps.

Installed...

Its a bit of a puzzle to install. The intercooler (minus the plenum) fits right in no problem. But to get the plenum in, the intercooler needs the bottom mounts free, and the top mounts loose.

So onto the intercooler inlets. My plan is to use the outside of the cylinder inlet D and feed it to the intercooler. My first attempt at this was MDF and dry wall mud - dont do that. It worked, but took forever to dry and cracked a lot. I finally finished it weeks later.

For the other side, I used foam - 1/2" foam to be exact, and cut / laminated it. Here are the two of them side by side. The white one is the MDF / drywall mold (starboard side), and the foam one is in its early stages (port side).

I am going to lay it up in three separate pieces, and then bond them together - top, rear and bottom. I know this is not ideal, but I dont want to destroy the mold.

First piece laminated up.

Part extracted from the mold with only minor mold damage.

Next: I chopped off the rear flange (which was not usable... all the cloth was gathered there from the sides). Put the part BACK on the mold (after some minor repair), and layed up 3 layers of glass on the rear, plus another layer on the top 2" to bind it all together. Then another 2 layers on the leading edge to make it stronger as it will be sitting in the airflow at the front and want it super stiff.k

Part came back out of the mold with a little bit of poking and prodding. It now has a new back and reinforced front. Next is to make the bottom.

My plan is for the bottom to slip over the top. I will bond them together with resin / cabo and cleco. Once dry, I will put another layer or two of glass over the seam.

To make the bottom fit over the top, I have to build out the bottom slightly. The glass thickness is about .04. 4 layers of tape is about .012. So I need around 10 layers of tape to build up the edge enough that the bottom will slip over the top. The only place this is critical is the rear as the back has structure. All the rest of it will just conform, but figured I would try to do it right since I was already at it.

Bottom layed up.... fingers crossed.

Back extracted from the mold after lots of gentle nudging.

The sides need to be trimmed down obviously.

The first mold is very heavy and strong, which made it easy to get the part out. I am somewhat worried about the foam mold. It is fairly strong, but much more fragile than the first one.

Top and bottom temporarily fit together. I think this is going to work out just fine.

I have been staring at how to mount this to the side of the plenum for quite some time. I want it to be removable. Since the beginning have been planning on using 2 of the 3 bolts that hold them plenum sides on. Dawned on me the other day to use the holes that hold the top on a well.

So the plan will be an aluminum bracket (probably 0.063) that will go between the top and bottom mounts. Then I will position the intercooler plenum, and both bond and rivet it in place.

After a lot of staring and wondering what to do, and talking to a hanger mate about his project I thought about 3D printing the forward plenum. Talked to a friend that used to teach 3D modeling and printing at a local high school. He accepted the challenge to design these up for me.

Ordered a test part through Xometry - which claims to be the uber of 3D printing. Ordered on a Sunday with their slowest / cheapest option. Shipped Thursday from MI via ground. The top and bottom were $297 USD including shipping. I checked a number of Canadian 3D printing shops, and the cheapest price was $500 CAD.

Parts arrived...

There is a small amount of interference at the front between the bottom and top of the plenum. This should be easy to fix.

Rough positioning to see how it fits. There will be a 0.063 plate that the entire assembly is attached to, so it will be offset outboard. Also planning on an air gap to protect it from the heat after shutdown.

Plate made and clecoed in. Duct clecoed in. Nothing is final final, as I need to make a few filler plates to make everything be perfect.

Honestly, I think its pretty good. You cant see it in the photo, but there is an air dam that comes out from the duct into the fiberglass inlet to channel the air either to the intercooler or cylinders. I like this way more than my crappy fiberglass parts. Need picture with cowl off.