Insulating a sliding hatch

[blackrose]

My sliding hatch is basically a steel plate with about 5mm clearance from the roof to the underside of the hatch so difficult to insulate it effectively. I originally stuck some cork tiles on the underside of the hatch and while it stopped a bit of the condensation it wasn't very good.

 

The only way to do it is insulate it from the outside, so when I originally bought this boat about 14 years ago I stuck some foam underlay on top of the hatch and made a wooden cover to go over it which I treated inside and out with GRP epoxy gelcoat. It did a good job and lasted pretty well but it was starting to look a bit tatty and I could see the epoxy splitting in places, so about a week ago I ripped it off and started again. I took the outside of the hatch cover back to metal and gave it a couple of coats of Jotamastic 87 before starting to insulate it again.

 

This time I stuck a sheet of 25mm celotex on top of the hatch with Stixall and then covered the celotex with 3mm aluminium sheet and angle, also stuck on with Stixall.

 

I know there are thermal bridges and it's not perfect but I'm quite happy with the result. It just needs painting now. The job was made a bit more difficult as the steel hatch is slightly curved (convex from outside) so the celotex ended up curved too, but I more or less levelled it out by putting the aluminium angle on the two sides of the hatch on first and then stuck the aluminium sheet on top of the angle. The front piece of angle went on last 

 

I ended up going through nearly 3 X 300ml tubes of Stixall. I don't think it's ever coming apart! The whole assembly is rock solid.

 

Edited September 3, 2019 by blackrose

[Drayke]

I also have a Liverpool boat so same hatch as yours with same problem of condensation, just stuck some carpet tiles on mine, been ok for the past 8 years or so.

[blackrose]

15 minutes ago, F DRAYKE said:

I also have a Liverpool boat so same hatch as yours with same problem of condensation, just stuck some carpet tiles on mine, been ok for the past 8 years or so.

 

But have you covered the carpet tiles with anything? If not don't they just get wet and horrible and lift the paint off the hatch?

 

Sorry you mean you stuck them on the inside? Yes that will stop must of the condensation, but it's not much in the way of insulation.

Edited September 3, 2019 by blackrose

[sharpness]

Doesn't he mean on the inside where you used cork tiles?

[blackrose]

Just now, sharpness said:

Doesn't he mean on the inside where you used cork tiles?

Yes I think you're right. I just edited my post

[johnmck]

I used that dense self adhesive foam sheeting. Cut to size, remove the backing and apply. No more condensation  and has lasted several years now.

Edited September 3, 2019 by johnmck
Add picture

[Drayke]

18 minutes ago, blackrose said:

 

But have you covered the carpet tiles with anything? If not don't they just get wet and horrible and lift the paint off the hatch?

 

Sorry you mean you stuck them on the inside? Yes that will stop must of the condensation, but it's not much in the way of insulation.

Yes on the inside, Not much insulation but NO condensation.

[blackrose]

Mine hatch is a big area (3'3" X 2'6") so it really needed proper insulation not just something thin to stop condensation. I guess on a smaller hatch it's not such an issue.

[Drayke]

5 minutes ago, blackrose said:

Mine hatch is a big area (3'3" X 2'6") so it really needed proper insulation not just something thin to stop condensation. I guess on a smaller hatch it's not such an issue.

Same size hatch as yours, my boat is 11ft wide. I just wanted to stop condensation as we have a utilities room at back with door to bedroom.

[system 4-50]

37 minutes ago, F DRAYKE said:

...a utilities room at back with door to bedroom.

that would be beyond the swimming pool and opposite the gym?   A utilities room?  I am not jealous, I am not jealous, no not a bit....

[blackrose]

42 minutes ago, F DRAYKE said:

Same size hatch as yours, my boat is 11ft wide. I just wanted to stop condensation as we have a utilities room at back with door to bedroom.

 

Ok, but if there was condensation then there was warm air in your utilities room that was meeting the cold surface. That's still happening and heat is still escaping through the poorly insulated hatch, it's just that you've stopped the moisture condensing out of the air as it meets the cold surface.

 

I take the view that the fewer uninsulated areas a liveaboard boat has the better.

Edited September 3, 2019 by blackrose

[Drayke]

22 hours ago, system 4-50 said:

that would be beyond the swimming pool and opposite the gym?   A utilities room?  I am not jealous, I am not jealous, no not a bit....

Thats what you can have with a widebeam, SPACE?

[Drayke]

23 hours ago, blackrose said:

 

Ok, but if there was condensation then there was warm air in your utilities room that was meeting the cold surface. That's still happening and heat is still escaping through the poorly insulated hatch, it's just that you've stopped the moisture condensing out of the air as it meets the cold surface.

 

I take the view that the fewer uninsulated areas a liveaboard boat has the better.

Need it cool, helps with the freezer.

[blackrose]

My freezer works fine without uninsulated cold spots.

[WotEver]

15 hours ago, F DRAYKE said:

Need it cool, helps with the freezer.

Many freezers won’t function in a cold space. They need a minimum temperature for the evaporator to work.