1969 Chris Craft Roamer 46 Refit: More Exhaust Riser Insulation

I wish everyone (myself included) a happy and productive 2017, which for me would entail getting this boat done enough that I can finally splash it and take it around to my home port!

With the exhaust risers welded up and the starboard riser insulated, I bought some high temp epoxy resin with the intention of making a hard shell to cover the insulation. But the more I try to make a hard shell, the less convinced I am that I can pull it off. I welcome any suggestions or comments about how to proceed.

DeAngelo riser I bought by mistake has a nice hard shell

DeAngelo riser I bought by mistake has a nice hard shell

I dissected this riser to see how DeAngelo makes them. It’s just a shiny fiberglass layer over dense blanket insulation. But this riser doesn’t have the sharp mandrel bends that mine does, so wrapping it would have been pretty easy. Then there’s the shiny coating, which appears to be just tinted resin that’s heavily saturated the fiberglass cloth below. The more I think about it, if I wet out fiberglass that much, gravity will take over and it’ll end up dripping onto the floor. All I can come up with is that I’d need to mount the riser in a low speed part rotator that kept moving until the resin set up to get a nice, uniform surface like DeAngelo does. Otherwise, I’d need to use the same approach as we did when we made the cabin top bullet-proof, and do the FRP layer, then top with fairing compound, THEN come back and sand, prime, and paint later. But fairing compound, epoxy primer, and urethane paint aren’t high temp products…that can’t be the right way to do it.

When last we talked about my risers...

When last we talked about my risers…

The 1″ ceramic blanket I’m using as primary insulation is outstanding to work with, and the Inferno Wrap is much, much easier to use than any fiberglass strip product I’ve seen. But after thinking about this over the last couple of weeks, I decided that if one layer of ceramic blanket is good, two would be even better. So…off came the Inferno Wrap and out came the scissors.

Two full inches of ceramic blanket insulation

Two full inches of ceramic blanket insulation

The mandrel bends are the tricky part

Where there's a will and spray glue...there's a way

Where there’s a will–and spray adhesive–there’s a way

Inferno Wrap locks the ceramic in place and looks good

Inferno Wrap locks the ceramic in place

I wasn’t going for a nice, uniform wrap because I was still planning on doing a fiberglass hard shell at this point. Even without uniform spacing, the Inferno Wrap looks good and holds everything securely. The Inferno Wrap manufacturer recommends the use of straps to permanently hold their product in place.

Ready for a test fit of the FRP layer

Ready for a test fit of the FRP layer

First, cut the 1708 into thin strips

First, cut the 1708 into thin strips

Heavy 1708 biaxial cloth cut into strips wraps very nicely

Heavy 1708 biaxial cloth cut into strips wraps very nicely, but only on the straight sections

At the sharp bends, the heavy cloth leaves high ridges at every overlap. At the exhaust flange, I never was able to get it to lay down nicely in full contact with the substrate, even though  I spent two whole days trying. Maybe if I overlayed the 1708 with a lighter fabric…

Overlaying the 1708 with 9oz fabric...epic fail

Overlaying the 1708 with 9oz fabric…epic fail

It turns out that the lighter 9 oz fabric lays down even worse around the tight mandrel bends than the 1708. It looked worse with the added layer. So, then I thought maybe I should use the 9 oz fabric as the base layer, and top that with pre-pregged 1708. So I gave that a couple of dry test fits…total failure.

At the end of a long and frustrating weekend...

At the end of a long and frustrating weekend…

I tried every permutation in wrapping the FRP, but none of them worked. Now I have a bunch of strips of fiberglass fabric with tattered edges from being handled too much, especially the lightweight stuff. I realize that when wetted out, fiberglass fabric can become quite pliable. But these mandrel bends are tight, and I don’t know how to keep everything in place and smooth until the resin cures.

It did occur to me that I could try wetting out the Inferno Wrap with resin and applying it. I also suspect that DeAngelo isn’t using straight fiberglass to get that nice, smooth finish. But then another thought occurred to me: why not just forget the hard shell? Granted, it’s prettier than fabric insulation blankets, and the hard shell would tend to reduce the possibility of corrosion under the somewhat permeable insulation. Plain Inferno Wrap would eventually get dirty, but if it does (and it bothered me) I could just put another layer on over the top. And there’s still that question of how to keep the resin dripping off until it cures.

I’m leaning toward abandoning the hard shell and just using the double ceramic blanket topped with Inferno Wrap, secured with stainless straps. Feel free to make suggestions/comments below.

Next up on our 1969 Chris Craft Roamer 46 Refit: Priming the V-berth Head

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21 comments on “1969 Chris Craft Roamer 46 Refit: More Exhaust Riser Insulation

  1. boatnut23 says:

    I thought I saw a zipped on exhaust cover in the engine room of a big sport fish I was on once. If I remember right it was silver/ gray material with metal zippers. I remember thinking how can that handle the heat! Thanks again for the Blog.

  2. Chris Kiefer says:

    Could you vacuum bag it?

  3. Steve (warby12!) says:

    There is always the possibility of a leak in the S/S at the welds too, very unlikely but if so you will have to do it all again. I had that once but was using a second hand flexible bellows.

  4. John says:

    I know very little about fiberglass work but don’t they use fiberglass to wrap broken arms. That stuff sets up rock hard over a thin fabric blanket. Is there something to be learned there?

    • 1969roamer46 says:

      Hi John. That’s an interesting observation, but every product I’ve seen for high temperature applications like this have pretty complicated cure schedules. For example, the resin I bought won’t even fully cure until it undergoes three-hour exposure to 300°F. Also, I suspect cast fiberglass would not stand up to the abuse of an engine exhaust system. The vibration, the heat, and potential for getting smacked by large wrenches…it’s a tough environment.
      But it’s an interesting thought. I’m going to look into it a bit more. Maybe I could adapt whatever application technique they use to get around my mandrel bends.
      Cheers,
      Q

      • Steve says:

        We used that broken arm stuff, was fine, but of course collects grime. Simple and neat to apply 🙂

        • 1969roamer46 says:

          You used casting tape for an exhaust system? With the ceramic blankets, I could see where that wouldn’t be a problem through the straight sections, but the turbo flange near the tight mandrel bend will get up to 900°F. It looks like casting tape is just a fiber product pre-pregged with polyester resin. I could see that getting charred.
          But using the same idea, in the article I mentioned that I could wet out the Inferno Wrap with the high temp epoxy I’ve got. Thing is, as another commenter noted, the hardshell is perhaps just a cosmetic thing. Another commenter on the web indicated that he’s been using Inferno Wrap for 10 years and it still looks and works great. So…do I really need the hardshell?
          Cheers,
          Q

  5. Reed Martin says:

    If/when the Inferno Wrap gets dingy, consider occasional freshening up with header paint? Time not wasted in trying out all the possibilities, nice work!

  6. Pat Colins says:

    First off, thanks for the excellent ongoing blog.

    Just a couple of thoughts for you to adapt
    – oil burner mechanics use a wet ceramic blanket to line the firepots of some oil burners. Should be good to about 2000 degrees. I’ve used them a number of times. Easy to form into shape then after heating (drying out) it would be like your blanket insulation. It might be easier to work with.
    – many high temp industrial piping jobs use a canvas wrap over the insulation then a wash of “white stuff” I don’t know the name of to seal the canvas and hold it all together. It won’t give you the hard shell, but would give the insulation protection and is very easy to repair. Check out pipe insulators in your area. I’ve been on jobs where tis method was used over 600 degree piping and the canvas covering was barely warm to touch.

    Good luck.
    Pat

    • 1969roamer46 says:

      Thanks Pat!
      Believe it or not, the ceramic blanket insulation I got is the 2,600°F version used for wood stoves…basically, the same stuff as what the oil burners use. It really is excellent stuff.
      From other comments I’ve gotten on the Inferno Wrap, I think it’ll hold up fine all by itself, so long as I secure it with stainless straps.
      Cheers,
      Q

  7. Peter Hitchcock says:

    Not sure what the point of the hard wrap is apart from cosmetic, if you want to make it dirt resistant I’d be tempted to wet out the inferno wrap with resin, give it several thin coats that won’t run, recoat as soon as the first layer is green until you have a smooth hard shell… I think this would work with the fiberglass as well but can’t see the point…!!!

    Happy new Year to you, I hope this is a good boat year for you (and me) and that she finally gets wet….

    • 1969roamer46 says:

      Thanks Peter….you’re thinking like me. The only additional benefit of the hard coat beyond cosmetic is that it would be impermeable to water vapor. Word has it corrosion under insulation (CUI) is a problem that pipeliners deal with all the time. Then again, I’m not using iron pipe, so I suspect I don’t need to worry about it so much.
      Happy new year to you and yours, too!
      Cheers,
      Q

  8. Kent says:

    custommarine.com

    Why not just put a “Water Jacket” on them?? Just kidding– That would be a whole other Project!! Wrapping them sounds easy and I’m sure when you figure it out your Exausts will look FAB..

  9. Joe Ruttger says:

    Wet out the fiberglass with epoxy, then wrap the outside diameter with shrink wrap plastic. When the epoxy sets you can then remove the shrink wrap. There may be some areas that need light sanding but the shrink wrap will hold the soaked ‘glas until it cures.

    • 1969roamer46 says:

      I like it, Joe!
      But is there an 8″ diameter shrink wrap product that can smoothly bend around a mandrel bend with 4″ radius?

      • Colin says:

        How about vacuum bagging it?

        • 1969roamer46 says:

          As I understand it, vacuum bagging would pull resin into the ceramic blanket and also compress it. That would reduce it’s insulating properties. Also, I don’t have a vacuum bagging setup, and I’m not sure if it would turn out as pretty as I’d like IF I continue on the hardshell path. Interesting idea, though.
          Cheers,
          Q

        • 1969roamer46 says:

          As I understand it, vacuum bagging would pull resin into the ceramic blanket and also compress it. That would reduce it’s insulating properties. Also, I don’t have a vacuum bagging setup, and I’m not sure if it would turn out as pretty as I’d like IF I continue on the hardshell path. Interesting idea, though.
          Cheers,
          Q

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