Cutting a hole in my roof

[Wanted]

I didn't want to hijack the stove fitting thread however I need to fit a new collar tomorrow which will mean cutting a bigger hole. Any tips on the best way or is a jigsaw with a load of metal blades the way to go?

 

Also, the new collar has a slant to allow for the roof but I don't think it's enough, what should I use to pack it out?

 

Cheers in advance

 

Rob

[Ray T]

Could you use a burr on a electric drill to enlarge the existing hole?

 

The yard that fitted our stove used a block of shaped hardwood, teak I think to enable the chimney to be mounted vertically. They cut the hole in the wood former about an 1/2" diameter larger than the chimney collar and filled the void with fire resistant expanding foam.

 

I keep a check on the wood block and after 18 months of having the fire installed there is no sign of burning or scorching.

 

Edited October 27, 2012 by Ray T

[Rebotco]

I didn't want to hijack the stove fitting thread however I need to fit a new collar tomorrow which will mean cutting a bigger hole. Any tips on the best way or is a jigsaw with a load of metal blades the way to go?

 

Also, the new collar has a slant to allow for the roof but I don't think it's enough, what should I use to pack it out?

 

Cheers in advance

 

Rob

 

There was quite a useful thread recently about drilling holes in metal boats. This should be helpful My link

[bizzard]

If the hole only needs enlarging a bit, an angle grinder with a stone in it might be the quickest.

When in a hurry a couple of times in the past i've packed out under the collar with car body filler P38 but only an inch wide wall around the edge of it with silicon ladled on in the middle space between the hole and body filler wall to obtain the vertical and surprise surprise they've been excellent and weather tight ever since.

[Wanted]

The hole is currently five inches and needs to be six, Maybe a grinder would be best, it looks as if car filler has been used previously so I may try and use some of that.

 

Cheers all, I'll report back.

[Grace and Favour]

The hole is currently five inches and needs to be six, Maybe a grinder would be best, it looks as if car filler has been used previously so I may try and use some of that.

 

Cheers all, I'll report back.

 

I'd use a jigsaw, on a slow speed with a fine "metal" blade, and plenty of cutting fluid.

 

Scibe a good 6" circle, take your time - the result will be good

[alan_fincher]

I'd use a jigsaw, on a slow speed with a fine "metal" blade, and plenty of cutting fluid.

 

Scibe a good 6" circle, take your time - the result will be good

Another vote for jig-saw.

 

I'd say trying to grinding away the difference between 5" and 6" is optimistic, and you are better cutting the new line.

 

Just hope your roof is less than the 5mm thickness that our shell has!

[Wanted]

Another vote for jig-saw.

 

I'd say trying to grinding away the difference between 5" and 6" is optimistic, and you are better cutting the new line.

 

Just hope your roof is less than the 5mm thickness that our shell has!

 

Same builder I believe (if you are talking about Chalice) From what I can see Mike Heywood must have had a cheap supply of thick steel!

 

Happy to use jig saw, means I can go tool shopping in the morning!

[alan_fincher]

Same builder I believe (if you are talking about Chalice) From what I can see Mike Heywood must have had a cheap supply of thick steel!

Don't panic if the front projection of cabin-sides and steel beyond front bulkhead looks frighteningly thick. Certainly on ours, all this is two sheets welded together. The bit one would have to cut through should only be half that!

[Wanted]

Don't panic if the front projection of cabin-sides and steel beyond front bulkhead looks frighteningly thick. Certainly on ours, all this is two sheets welded together. The bit one would have to cut through should only be half that!

 

I might buy a few spare blades anyhow....

 

Cheers

[Pie Eater]

I might buy a few spare blades anyhow....

 

Cheers

Drill holes along the line first,cut through with jigsaw and then finish off with a file. (saves on blades)

 

Steve

[LEO]

Hi,

 

I cut a square hold in my boats roof with a jig saw, used 2 blades, slow speed setting, did not take long.

 

L.

[gary4lw]

When your blades worn put a piece of wood under your jigsaw and then you can use a bit of unworn blade !

[fudd]

When your blades worn put a piece of wood under your jigsaw and then you can use a bit of unworn blade !

Not too thick though. Don't half go bang if you do.

[RLWP]

Do make sure you haven't confused the roof for the floor

 

Richard

[Timleech]

Do make sure you haven't confused the roof for the floor

 

Richard

 

There can be real confusion for the uninitiated if you start to talk about ceilings on a boat.

Of course, a floor is not a floor either

 

Tim

[Wanted]

I will look up before cutting, if I see t&g I am in the wrong place right?

[RLWP]

I will look up before cutting, if I see t&g I am in the wrong place right?

 

Drill a small pilot hole first. If water comes out:

 

• It is raining
  
• you have drilled into a water tank
  
• that's the floor
  

 

Richard

[Wanted]

Drill a small pilot hole first. If water comes out:

 

• It is raining
  
• you have drilled into a water tank
  
• that's the floor
  

 

Richard

 

And This is why you do what you do!

 

Thank you Richard

[blackrose]

 

Also, the new collar has a slant to allow for the roof but I don't think it's enough, what should I use to pack it out?

 

 

Uxbridge sells angled hardwood spacers. I think they make them to order.

 

I don't know how you're supposed to stop them getting charred on the inside? The flue should go right through into the collar of course, so perhaps I'd smear the inside of the spacer with plumbaflue and let it go off before fitting the flue. You can bed it in (top and bottom) with the same stuff too.

 

The yard that fitted our stove used a block of shaped hardwood, teak I think to enable the chimney to be mounted vertically. They cut the hole in the wood former about an 1/2" diameter larger than the chimney collar and filled the void with fire resistant expanding foam.

 

I don't think fire-resistant expanding foam is the stuff to use. It's fire-retardant properties simply mean that ignition time is retarded compared to the standard PU foam, so it can still catch fire.

Edited October 28, 2012 by blackrose

[alan_fincher]

No help to "Wanted", but I have often wondered why when the chimney collars sold don't seem to match the required angle on a huge number of boats, the manufacturers don't seem to have had the wit to supply a number of different castings to suit different roof profiles and pipe angles.

 

Stuffing a bit of hardwood, (something that can both rot and burn), to fill the gap between roof and collar may work, but it doesn't exactly seem an appealing engineering solution, does it ?

[blackrose]

No help to "Wanted", but I have often wondered why when the chimney collars sold don't seem to match the required angle on a huge number of boats, the manufacturers don't seem to have had the wit to supply a number of different castings to suit different roof profiles and pipe angles.

 

Yes, you can buy collars with shallow angles, but you'd think the manufacturers could just make collars with flat bases and a range of say 5 different angled spacers made of cast iron.

[alan_fincher]

Yes, you can buy collars with shallow angles, but you'd think the manufacturers could just make collars with flat bases and a range of say 5 different angled spacers made of cast iron.

I have in the past seen cast spacers, but only with a very shallow additional angle on.

[RLWP]

I have in the past seen cast spacers, but only with a very shallow additional angle on.

 

Use more than one angled spacer?

 

Richard

[Guest]

No help to "Wanted", but I have often wondered why when the chimney collars sold don't seem to match the required angle on a huge number of boats, the manufacturers don't seem to have had the wit to supply a number of different castings to suit different roof profiles and pipe angles.

 

Stuffing a bit of hardwood, (something that can both rot and burn), to fill the gap between roof and collar may work, but it doesn't exactly seem an appealing engineering solution, does it ?

 

and brings the additional problem of getting an effective seal between the roof and collar.