Replacing unusual roof vents

[simonebb]

I have 4 vents on my roof that consist of 115mm dia steel tubes that project through the roof, these are covered over by a curved rectangle of steel that is welded on at the corners. The problem is that is is impossible to maintain the roof section underneath and subsequently these areas are very corroded. I want to remove the covering steel, clean up the roof and fit something more suitable but I would rather not have to cut out the tubes. Any ideas?

Simone

[Grace and Favour]

Hi Simone,

 

It would help if you would take some photographs and download them on here so we can see whate we're dealing with........

[simonebb]

Hi Simone,

 

It would help if you would take some photographs and download them on here so we can see whate we're dealing with........

Will have a go at taking some pics tomorrow, it should make more sense then....

[The Bagdad Boatman (waits)]

would brass mushrooms slide over the tubes?

[simonebb]

would brass mushrooms slide over the tubes?

[simonebb]

I'm not sure if mushroom vents will fit over because of the way the tube projects above the roof.

 

I am trying to upload some photos for clarity but do not know how to attach them to the post - help!

[simonebb]

Okay hope this works...

https://www.flickr.com/photos/96201195@N07/

Hopefully you should now be able to see images of the vents!

[Tony Brooks]

I suspect angle grinder, a fair amount of time and fit mushroom/flying saucer vents. Flying saucer vents do not foul ropes like mushroom ones.

[IanM]

Linked to the photos for you.

 

image by Artyfartybartyboo, on Flickr

 

image by Artyfartybartyboo, on Flickr

 

image by Artyfartybartyboo, on Flickr

[Grace and Favour]

Thanks for the pics.....

 

Now - would you please measure the diameters (inside and outer edge) of the tumes please.

 

(with a little luck) It may well be that these can be ground off and mushroom vents fitted inside

Edited September 16, 2014 by Grace & Favour
Sp: - I can't spell mushroom!!

[David Mack]

Thats a pretty unmaintanable detail. There's no way you could properly prepare and paint that steel, even if the rust and pitting hadn't got a hold.

 

As others have said, take an angle grinder to the edges of the tunnels, and grind down flush with the roof. I woudl be inclined to do the same with the tubes outside and inside so you just have circular holes which you can then fit conventional vents over.

 

You could leave the internal tube as a sleeeve through the cabin lining/insulation, but I suspect a steel sleeve would be prone to condensation, and a separate plastic tube or a brass liner not in intimate contact with the shell would be better.

[blackrose]

It may well be that these can be ground off and musroom vents fitted inside

 

Ground off? I think they will have to be cut off with a cutting disc and then the rough edges ground flush with a grinding disc and lapping disc.

 

If the OP is not confident with an angle grinder then this is not a job I would encourage her to do herself, but assuming there are four or five tunnels then somebody who knows what they are doing should be able to cut them off and grind them flush within a couple of hours. Just make sure they don't cut through the roof!

Edited September 16, 2014 by blackrose

[simonebb]

Thanks for the pics.....

 

Now - would you please measure the diameters (inside and outer edge) of the tumes please.

 

(with a little luck) It may well be that these can be ground off and mushroom vents fitted inside

Int dia = 105 mm

Ext dia =115mm

 

 

Thats a pretty unmaintanable detail. There's no way you could properly prepare and paint that steel, even if the rust and pitting hadn't got a hold.

 

As others have said, take an angle grinder to the edges of the tunnels, and grind down flush with the roof. I woudl be inclined to do the same with the tubes outside and inside so you just have circular holes which you can then fit conventional vents over.

 

You could leave the internal tube as a sleeeve through the cabin lining/insulation, but I suspect a steel sleeve would be prone to condensation, and a separate plastic tube or a brass liner not in intimate contact with the shell would be better.

Not the answer I wanted and the one I was hoping to avoid but I suspect you are right and this will prove to be the only sensible course of action, good point about the inner tube, best get rid of the lot!

Edited September 16, 2014 by simonebb

[Ally]

Never seen anything like that before. Have them cut off and mushroom vents placed instead.

[simonebb]

Ground off? I think they will have to be cut off with a cutting disc and then the rough edges ground flush with a grinding disc and lapping disc.

 

If the OP is not confident with an angle grinder then this is not a job I would encourage her to do herself, but assuming there are four or five tunnels then somebody who knows what they are doing should be able to cut them off and grind them flush within a couple of hours. Just make sure they don't cut through the roof!

I'm not a fan of grinders but have had to use mine a lot recently ! Might well get someone to cut them off and then finish them off myself with a grinding disc, alternatively if they are as lightly welded as the rest of the boat I might just be able to remove the weld and tap them out!

 

On a related matter, the cabin is predominately 3 mm, consequently any remedial welding causes it to curtain, also welding a plate in the roof repair a hole has made the roof dip, has anyone else experienced this, if so any tips?

 

Linked to the photos for you.

Thank you!

Edited September 16, 2014 by simonebb

[IanM]

I'm thinking that perhaps that arrangement of vents is meant to be temporary to allow fitting of mushroom vents later.

[markgregoryuk2000]

Looks more like what I expect for the flew from a coal fire if you remove the curved plate over the top.

 

Would a china mans hat work once the plate is removed, perhaps adjusted to sit close to the top of the pipe.

[bizzard]

I think they're rather sweet, they look like little Nissan huts dotted about don't they. Why not play war games on the roof to pass the time of day with toy soldiers and yes! the Dinky toys Centurion tank ect.

But as they won't snag ropes like stupid mushroom vents do you could retain them with a simple modification that will allow you to treat and paint underneath whenever you want.

Cut through each side close to the roof clean and straight with a slitting disc in an angle grinder, remove Nissan huts, level off the old welds with a stone in the grinder flush with the roof. Weld hinges to one side of each Nissan hut , place back over the vent pipes and weld all hinges to the roof. You can now just lift and hinge them back to see and deal with what's going on underneath.

[AndrewIC]

Has anyone considered having the equivalent of the tubular base of a mushroom vent fabricated in welded steel, then fitting a conventional mushroom dome on top? That way there is no sealant joint to leak.

[Batavia]

Has anyone considered having the equivalent of the tubular base of a mushroom vent fabricated in welded steel, then fitting a conventional mushroom dome on top? That way there is no sealant joint to leak.

The vents on Batavia are like this -ish.

 

Each vent consist of a length of 4" steel pipe welded through the roof and a bar, with a tapped hole in it, is welded across the top end of the pipe. The mushroom part is a 6" butt weld cap, with a length of studding welded in the centre. The studding is screwed into the tapped hole in the bar and and is secured at the desired point with a lock nut. Mine are painted, but you could always use stainless caps for a bling finish.

 

This would be a relatively easy solution to the OP's problems (the main challenge being trying to buy 6" weld caps at a sensible price!).

 

Chris G

Edited September 17, 2014 by Batavia

[BlueStringPudding]

What fascinating vents. Never seen anything quite like them. Sure you can't get in there with a small wire brush or hand drill attachment to grind away the rust, then Vactan the metal and paint it using a long handled artists brush?

 

If those amazing contraptions were on my boat and were in any way salvageable I'd try to keep them and make a feature of them.

[simonebb]

Thanks everyone!

Some really interesting, helpful and creative suggestions ... I will let you know what we decide to do.