Cutting a hole in my roof

[blackrose]

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

 

Why would that be a problem? I've done the job several times and never had a problem using a good high-temperature silicone sealant.

 

Edit: Unless you mean that using wood which can rot brings an additional problem? Yes, that's true. Because the wood will expand and contract at a different rate to steel or iron, any paint around the joint will crack, but the sealant between the different materials should still be fine. If I were using a hardwood spacer I'd smear black high-temp silicone over the outside of the wood too.

Edited October 28, 2012 by blackrose

[Guest]

Why would that be a problem? I've done the job several times and never had a problem using a good high-temperature silicone sealant.

 

Edit: Unless you mean that using wood which can rot brings an additional problem? Yes, that's true. Because the wood will expand and contract at a different rate to steel or iron, any paint around the joint will crack, but the sealant between the different materials should still be fine. If I were using a hardwood spacer I'd smear black high-temp silicone over the outside of the wood too.

 

I just think you would get a chance of a better seal if you had less of a gap to fill - overall a collar that better matches the angle/curve of the roof is better - ??

[blackrose]

I just think you would get a chance of a better seal if you had less of a gap to fill - overall a collar that better matches the angle/curve of the roof is better - ??

 

Yes, it's better if you don't have to use a spacer at all, but sealing shouldn't really be an issue as long as sealant is used on both sides of the spacer.

[dmr]

Ours has a wedge shaped spacer fitted. The only possible problem is that this gives two joints to seal.

We got blacked at Stone Boatyard this year and I saw the welder there repairing a roof where it has rusted out under the collar.

He made a wedge shaped "repair" spacer that he welded to the roof.

It had tapped holes for the collar to bolt to, gave a vertical chimney, and I assume that because the collar joint is now set slightly proud of the roof is much less prone to water leakage. Looked to be the perfect way to do it to me!

 

.........Dave

[blackrose]

Ours has a wedge shaped spacer fitted. The only possible problem is that this gives two joints to seal.

We got blacked at Stone Boatyard this year and I saw the welder there repairing a roof where it has rusted out under the collar.

He made a wedge shaped "repair" spacer that he welded to the roof.

It had tapped holes for the collar to bolt to, gave a vertical chimney, and I assume that because the collar joint is now set slightly proud of the roof is much less prone to water leakage. Looked to be the perfect way to do it to me!

 

.........Dave

 

Sounds like someone had skimped on the sealant and just gone around the edges. Any fitting you put on a boat has to be bedded in properly.

[Phil Ambrose]

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

 

 

Agreed, I fitted a stove to my boat this summer and used a jig saw running at slow speed with a bit of lube, took me about 20 mins and just the one blade, fine toothed for metal cutting.

 

Phil

[LEO]

Sounds like someone had skimped on the sealant and just gone around the edges. Any fitting you put on a boat has to be bedded in properly.

Hi,

 

And it helps if the sealant can be allowed to cure for 12 or preferably 24 hours before fitting the parts together.

 

L.

[Wanted]

Success! I used a jigsaw with a bosch blade, bought 4 but only needed one. Used olive oil as that's the only coolant I had, the angle of the collar was pretty close to my roof so I put some washers underneath as spacers and then used p38 filler as Bizz describes. I then used the black heat sealant around that and on the inside.

 

Where the flu enters the collar there was a half inch gap all around because of a stupid reducer on my flue, I packed this out with really thick glass fibre lagging and then used the heat resistant mastic to seal the top of this. The idea being that anything running back down will not enter the boat.

 

One question, how long should I leave the mastic to go off before I light the fire?

 

Thanks all for the advice. Appreciated.

 

Rob

[blackrose]

Hi,

 

And it helps if the sealant can be allowed to cure for 12 or preferably 24 hours before fitting the parts together.

 

L.

 

Not with a silicone sealant surely? It starts to go off in about 10 minutes.

 

Success! I used a jigsaw with a bosch blade, bought 4 but only needed one. Used olive oil as that's the only coolant I had, the angle of the collar was pretty close to my roof so I put some washers underneath as spacers and then used p38 filler as Bizz describes. I then used the black heat sealant around that and on the inside.

 

Where the flu enters the collar there was a half inch gap all around because of a stupid reducer on my flue, I packed this out with really thick glass fibre lagging and then used the heat resistant mastic to seal the top of this. The idea being that anything running back down will not enter the boat.

 

One question, how long should I leave the mastic to go off before I light the fire?

 

Thanks all for the advice. Appreciated.

 

Rob

 

I hope you thouroughly cleaned the surfaces before applying the sealant Rob - any oil will stop the sealant sticking.

 

I think you can pretty much use your stove within a couple of hours. Is it a silicone-based sealant?

[Wanted]

Not with a silicone sealant surely? It starts to go off in about 10 minutes.

 

 

 

I hope you thouroughly cleaned the surfaces before applying the sealant Rob - any oil will stop the sealant sticking.

 

I think you can pretty much use your stove within a couple of hours. Is it a silicone-based sealant?

 

Yes to both, I used a spray degreaser from the cycle shop before applying the silicone.

 

The whole job wasn't as bad as I expected although I feel as if I have earned a pint!