How can I check if my roof is steel or fiberglass?

[Mslondon]

This seems obvious but I have heard of GRP being overplayed on the roof with steel 

inside the boat there are 2 metal wedges that I was told indicate that the roof was replaced (it’s a harborough)

however there are a couple of leaks which come in under the gunnels which I was told might indicate fibreglass roof still

want to sort some rust patches out in the summer but unsure what I’m dealing with 

anyone with a similar boat got any advice?

thenk you 

[GUMPY]

With a magnet?

[Mslondon]

I did that but it can’t differentiate between replaced roof and overplating... 

[Flyboy]

6 minutes ago, Mslondon said:

This seems obvious but I have heard of GRP being overplayed on the roof with steel 

inside the boat there are 2 metal wedges that I was told indicate that the roof was replaced (it’s a harborough)

however there are a couple of leaks which come in under the gunnels which I was told might indicate fibreglass roof still

want to sort some rust patches out in the summer but unsure what I’m dealing with 

anyone with a similar boat got any advice?

thenk you 

You could remove a light fitting if you have flush mounted ones or a roof vent liner and have a look up from inside.

[Iain_S]

1 hour ago, Mslondon said:

I did that but it can’t differentiate between replaced roof and overplating... 

I'd think overplating, as opposed to replacement would be fairly hard to do. Welding would be a distinct no-no!

1 hour ago, Mslondon said:

This seems obvious but I have heard of GRP being overplayed on the roof with steel 

(snip)

I see you've got the same speed checker I have

[Mad Harold]

You might drill a hole through the roof to see a section of it.You can plug it with filler or Stixall.

Because of different expansion rates fibreglass (or ply) tops on steel hulls don't stay watertight for long.

I have heard that there is a way of ensuring fibreglass tops stay watertight,perhaps someone here has experience of this and can advise.

[Sea Dog]

13 minutes ago, Mad Harold said:

 

I have heard that there is a way of ensuring fibreglass tops stay watertight,perhaps someone here has experience of this and can advise.

Mate them to fibreglass bottoms? Seems to work on quite a few vessels I've been on.

 

[Boater Sam]

There are a few wood or Glass Fibre cabin boats that have had a complete steel cabin welded on over the existing superstructure. One I know of is/was Lazy Moon

 

So you have steel all over outside but suspect the existing cabin is inside?

 

If you have a leak then the steel top must be leaking UNLESS its condensation on the inside of the steel running through the old cabin top.

The steel will not be insulated inside.