New Cabin Top- Steel or wood?

[JohnP]

Hi All- I am working on a small steel Colvin designed trawler. The existing forward cabin top is plywood, and needs to be replaced. It is 3/4 with polyester and glass. The cabin sides are steel. I am trying to decide whether to replace with plywood again- would probably do 2 layers of 1/4, with glass which should provide plenty of strength, especially arched. Or... skip the wood and do steel sheet to avoid the wood to steel issues. If I did that, I would probably go 1/8 or 3/16 with bracing underneath as needed.

Thoughts or guidance?

Thanks-

JP

 

[Barry]

1/8 inch steel sheet weighs about 5.1 pounds per square foot, compared to the 3/4 inch ply with fibreglass that you are considering which would weigh about 2.5 lbs per foot. (an estimate only due to the fact that the fibreglass laminate weight is not known.

3/16 inch plate would be weigh (sic) too heavy for your application. With the 1/8 inch, you would need minimal bracing if you get a camber rolled into it as the spans are minimal. If you went to say a 12 gauge sheet, .105 inches thick, you would need more bracing which would add more weight.

For the ease of attaching the roof to the sides of the cabin with steel, welding, and the
additional strength and the fact that you would not need a bolted joint, steel would be the way to go

 

[JamesG123]

Also need to worry about insulating the underside of a metal roof.

 

[JohnP]

Thanks- the cabin currently has an overhang, which is nice looking, but is also one more maintenance item. I am thinking with steel I would just go flush to the cabin or do an overhang with some round stock welded to the edge for looks/safety. Am I overthinking this?

 

[JamesG123]

Your boat is the way it is because of literal centuries of experience building and using boats.

 

[JohnP]

Your boat is the way it is because of literal centuries of experience building and using boats.

Not sure what you mean- are you saying I should go wood? Or are you saying I should keep the overhang either way?

 

[Barry]

the overhang with round stock would look nice or even a flat bar style ridge to channel the water from rain to where ever you want it to go.

 

[JSL]

stay with what you had- it was probably plywood for a good reason. Steel (sheet, stiffening, beams, etc) will likely weigh more and 1/8" can be prone to weld distortion and need fairing (more weight) compound.