1969 Chris Craft Roamer 46 Refit: Insulating the Starboard Exhaust Riser

Good news! The truck transmission is rebuilt!

Bad news! My wallet is significantly lighter, and now the catalytic converters are tripping codes! I may have to think about monetizing this blog!

Props to commenter Tom aka Florida Boater for reminding me about this hilarious song from the TV show Hee Haw in response to my last post lamenting my life as an old-school country western song. I hadn’t heard that song in decades, but it’s absolutely perfect for this refit! 🙂

That said, I finally wrapped up the welding on the stainless exhaust risers. Next is insulation on the dry sections. I initially planned to use Inferno Wrap from Heatshield Products, and bought 200′ worth of the 2″ wide version. But when I test wrapped one riser, I decided it just wasn’t thick enough to hold in the heat. A fellow on boatdiesel.com said that with 3/8″ of fiberglass wrap, he was seeing 400°F on the outside of the wrap during a run at high cruise speed. I want these things insulated well enough to be able to touch the exterior shell without getting burned. I considered using dry  fiberglass cloth since I’ve got lots left over and could easily build it up to a 1″ wrap or more. But then I found ceramic fiber blanket material. This  stuff is commonly used in the manufacture and installation of wood and pellet stoves. It’s rated for 2,600°F continuous, which is 2x what it will ever see, can easily be cut with professional-grade scissors, and comes in various thicknesses. I got a 1″ x 24″ x 50′ roll and gave my idea a go. It turned out pretty good, I think.

The mandrel bends are challenging

After doing some rough measuring and cutting, I snipped wedges out of the insulation so it would be able to have 100% contact with the the tubing around the mandrel bends. I used el cheapo spray adhesive to stick the center of the wrap to the tube, then snipped additional bits off of one section at a time to get just the right fit. Then I hit it with more spray adhesive, stuck the section in place, and moved on to the next. The spray adhesive isn’t heat rated. I’m only using it to keep the insulation in place until I do the second layer wrap. The adhesive is going to stink when I first run the engines, but once it cooks off I don’t expect it to be a problem.

Use Inferno Wrap as the second layer

In retrospect, I didn’t need the Inferno Wrap at all. I could have just cut a bunch of fiberglass strips from the rolls of cloth I’ve got leftover. But since I’ve got it, might as well use it.

Also, I found it was easiest to use a separate piece of the insulation blanket on the inside radius of the mandrel bends, then form a second piece on the outside radius and sides of the tubing. Doing it all in one go is unnecessary and much more difficult…just gotta make sure there’s 100% coverage.

That’s much, much easier doing the mandrel bends with two pieces

That’s 1″ of ceramic fiber topped with Inferno Wrap

That should keep the heat in

It looks like this approach will work. Next I’ll slice a bunch of strips off the 54″ rolls of fiberglass cloth I’ve got and wrap the riser again, then apply a final layer wetted out with high temp epoxy for the hard shell. Sounds like a good project for this weekend, but only after I get the catalytic converters swapped out in my truck.

Merry Christmas to you all!

Next up on our 1969 Chris Craft Roamer 46 Refit: The Safety Rail Stanchions (again)