Heater flue dorade rebuild

[Tree]

I am in the middle of rebuilding a leaky dorade that is specific to venting a heater. I've had a bit of water ingress from this, hence the project.

The sides of the dorade appear to be solid and made out of several "donuts" of teak like ply. They appear dry and solid. I have sanded them down to bare wood and plan on an epoxy seal coat and then painting them.

Capping the dorade was a pice of material that is in bad shape.... into this cap piece there was a bronze fitting that has a 3" screw in cap that can be replaced by a medal cowel when the heater is being used.

About this material that is in bad shape.... It appears to be a pressed board type of material. It almost looks like masonite but less dense. It's about a 14 inch thick. Many years back there was a homebuilding material called cellotex that was used in northern climates as an insulation board. This piece looks a bit like this.

My question is..... does this seem right? This stuff sure doesnt' look like it could (and obviously didn't) stand up to a marine invironment. Was it used because there is a need for something that will not conduct heat? Is it some special material that is fire proof? Or is it more likely that some PO used what was on hand and they were not thinking through what they were using? Anyone out there know what I should replace it with?

I was thinking perhaps a piece of stainless or aluminum would be a lot more bomb proof.... but, it would probably conduct any heat from the cowl back down to the dorade..... any help or thoughts on this matter would be greatly appreciated.

[sailingdog]

Tree-

In situations like this, photos are very useful. I don't think this is actually a dorade, which is a specific design of a boxed vent that prevents or reduces water intrusion, which usually appears as a rectangular box, with the vent over one half of the rectangle.

How hot does the piece get?? Post some photos if you can...

[Tree]

My question is about what material would be good to use to replace what in this picture has white flakey stuff pealing off.... this piece acts as the top of the Dorade.... It will have the bronze piece that the Hood screws into mounted onto it and it sits on top of the round (dark brown) dorade box. It could be teak... but I'm looking for low maintanence and something that heat won't affect. Most importantly, I want to know if the material is something "special" because the heater vents here.

[sailingdog]

It really depends on how hot the piece gets. If it gets really hot, then you might try using a sheet of mica, which is very temperature resistant. Mica is a mineral that is often used for furnace view ports. The one problem you may have with it is that it can be rather brittle. You'll have to be rather careful cutting it and shaping it, and since it has relatively low tensile strength, you'll need a fairly thick piece for the plate.

However, if it doesn't get that hot, you might as well use a piece of marine plywood that has been coated in epoxy and then painted or varnished. My guess is that the plywood would be fine, since the exterior of the vent structure is wood.