Narrowboat flue collar attachment

[gbclive]

Having finally identified the rear chimney collar as the source of a pesky rain leak and my initial attempt at just sealing round the edge having failed, I need to man up and remove the collar to do the job properly.

Can I ask please whether the convention is to tap threads into the roof for the two bolts, or am I likely to be faced with inaccessible nuts?

Many thanks,

Clive.

 

[rusty69]

Took ours off last year and re-gunked as it was leaking. Through bolted and cut some holes in the internal woodwork.

I think you will be hard pushed to tap the holes.

I think having some nuts welded internally would work if starting out with an unlined boat.

Good luck.

[dmr]

Tapped holes are much better than free nuts on the inside, but the roof is 4mm and the bolts will likely be m10 or m12 so you wont really get enough threads in 4mm steel. Captive nuts welded on the inside are best, if you drill out the holes a bit a good welder might just be able to weld them in place from the outside. You should be able to get your fingers down the big hole to get the nuts into place, but you will need to devise a way of holding them whilst they are welded else you will burn yer fingers.

.............Dave

[gbclive]

58 minutes ago, rusty69 said:

Took ours off last year and re-gunked as it was leaking. Through bolted and cut some holes in the internal woodwork.

I think you will be hard pushed to tap the holes.

I think having some nuts welded internally would work if starting out with an unlined boat.

Good luck.

Thanks - it’s an oldish boat with a scumbled liner and a wooden bulkhead in just the wrong place to access one the nuts by cutting a hole.

My thinking cap is on

41 minutes ago, dmr said:

Tapped holes are much better than free nuts on the inside, but the roof is 4mm and the bolts will likely be m10 or m12 so you wont really get enough threads in 4mm steel. Captive nuts welded on the inside are best, if you drill out the holes a bit a good welder might just be able to weld them in place from the outside. You should be able to get your fingers down the big hole to get the nuts into place, but you will need to devise a way of holding them whilst they are welded else you will burn yer fingers.

.............Dave

Thanks Dave - that all makes sense.

Not the relatively straightforward job I was hoping for

Access from below will be tricky.

[dmr]

33 minutes ago, gbclive said:

Thanks - it’s an oldish boat with a scumbled liner and a wooden bulkhead in just the wrong place to access one the nuts by cutting a hole.

My thinking cap is on

Thanks Dave - that all makes sense.

Not the relatively straightforward job I was hoping for

Access from below will be tricky.

The hardest part will likely be getting the old bolts undone. If they are non captive nuts on the inside and you don't wan't to cut away at the lining then drilling them out might be the best option. Welding is a surprisingly quick and easy process, finding the right welder is the hardest bit.  Be emotionally prepared to find quite a bit of rust in the roof when you take the collar off, and spend time grinding it right back to bare metal and painting it well.

Ive done both my collars in the last few years, though one needs doing again soon. Most recently I bolted one down using a home made neoprene gasket rather than sealant and that has worked very well. The flue should not touch the collar so the collar should not get any more than slightly warm.

............Dave

[gbclive]

53 minutes ago, dmr said:

The hardest part will likely be getting the old bolts undone. If they are non captive nuts on the inside and you don't wan't to cut away at the lining then drilling them out might be the best option. Welding is a surprisingly quick and easy process, finding the right welder is the hardest bit.  Be emotionally prepared to find quite a bit of rust in the roof when you take the collar off, and spend time grinding it right back to bare metal and painting it well.

Ive done both my collars in the last few years, though one needs doing again soon. Most recently I bolted one down using a home made neoprene gasket rather than sealant and that has worked very well. The flue should not touch the collar so the collar should not get any more than slightly warm.

............Dave

Thanks again Dave - valuable information.

As we are currently on a bit of a epic from the Wey to the Fens and back, I decided as a short term fix to re-do my first effort (bodge) of sealing round the edge of the collar, but with more careful preparation and using a dry finger to smooth. Soapy water contaminated the PU sealant even though that was what it said to do 

Looks a better job this time, so we will see - I’ll do the same with the bolts.

Your advise will be very helpful when I get time to do a proper job.

 

[Jen-in-Wellies]

On a friends boat we ended up working out where the nuts were and drilled through the lining with a hole saw to reach each one so we could get a socket to them. Fitted a trim panel over the holes after. On my boat there is a ply panel that is screwed on and easily removed to reach the collar nuts from inside. I think I am going to have to remove the roof collar this summer to deal with rust around it and probably underneath. As others have said, on 3, or 4 mm thick roof you would only get a thread or two tapping for M10, or 12.

Jen

[rusty69]

23 minutes ago, Jen-in-Wellies said:

On a friends boat we ended up working out where the nuts were and drilled through the lining with a hole saw to reach each one so we could get a socket to them. Fitted a trim panel over the holes after.

That's the method i used too

[bizzard]

After the collars removed and everythings been cleaned up place the collar back on and draw all around it on the roof with chalk or felt tipped pen. Remove collar and run a heavy bead of Sikaflex or Marineflex all around the drawing. Sometimes collars have an inner ring rib underneath as well, if so run a heavy bead of the goo around that too.  Place the coach bolts in the collar with plenty of Sikaflex-Marineflex under their heads. Lower the collar carefully into place feeding the bolts into the holes, to settle onto the goo. Nut up inside equally, not too tight, just so, so. Trim off goo around the collar on the roof leaving enough to smooth round with a lolly stick or finger.  To be honest Sikaflex and Marineflex stick things very powerfully indeed and really don't need bolting at all.  Some older collars have plain flat bottoms, but the same holds good. Roofs with heavy curvature like Liverpool boats have apply extra thick beads of goo.

[koukouvagia]

On the old cabin on Hampton I cut a hole in the lining and after dealing wih the nuts, covered the hole with a brass plate.

 

On the rebuilt back cabin I can more easily reach the nuts.

[gbclive]

12 hours ago, Jen-in-Wellies said:

On a friends boat we ended up working out where the nuts were and drilled through the lining with a hole saw to reach each one so we could get a socket to them. Fitted a trim panel over the holes after. On my boat there is a ply panel that is screwed on and easily removed to reach the collar nuts from inside. I think I am going to have to remove the roof collar this summer to deal with rust around it and probably underneath. As others have said, on 3, or 4 mm thick roof you would only get a thread or two tapping for M10, or 12.

Jen

Thank Jen - all helping to improve my understanding of chimney collars 

[Neil Smith]

You will find it difficult to get an exact measurement from outside to inside to locate the 2 nuts so make the holes large enough for wiggle room or just use a jig saw to cut a big hole and over clad after, then do as biz said with sika flex as I did that and no problems yet.

Neil

[gbclive]

Thanks Bizzard and thanks Koukouvagia,

I’m now just about ready to take my City and Guilds in advanced chimney collar refurbishment 

Cracking advice.

[Detling]

Captain Tolley’s Creeping Crack Cure would probably creep in and do the job (I think it is thin PVA )

[gbclive]

31 minutes ago, Neil Smith said:

You will find it difficult to get an exact measurement from outside to inside to locate the 2 nuts so make the holes large enough for wiggle room or just use a jig saw to cut a big hole and over clad after, then do as biz said with sika flex as I did that and no problems yet.

Neil

OK, I’ll probably use a largish hole saw that I have and I like the concept of wriggle room 

Thank you Neil.

[gbclive]

11 minutes ago, Detling said:

Captain Tolley’s Creeping Crack Cure would probably creep in and do the job (I think it is thin PVA )

Thanks - It’s a shame that I did not have any crack cure, but my second go at running a bead of PU sealant around the edge of the collar seems have been much more successful than my first go. If so I’ll leave the proper job until the late autumn when we finish this years cruising.

I’m going to order some Captain Trolley’s to add to my other useful “stuff”.

 

[nbfiresprite]

Use a pair of rivet nuts instead of tapping the roof.

[ditchcrawler]

14 hours ago, koukouvagia said:

On the old cabin on Hampton I cut a hole in the lining and after dealing wih the nuts, covered the hole with a brass plate.

 

On the rebuilt back cabin I can more easily reach the nuts.

I used a piece of Masterboard painted black so its heat resistant

[gbclive]

20 hours ago, nbfiresprite said:

Use a pair of rivet nuts instead of tapping the roof.

Thanks for the thought, but the bolts are existing ones, so probably easiest to achieve access to the nuts from below, then hide the holes in the T&G with a cover plate as suggested above.

19 hours ago, ditchcrawler said:

I used a piece of Masterboard painted black so its heat resistant

Thanks Brian - good idea 

[james46]

Hi everyone, im fitting my chimney collar, what is best fire rope with fire cement around the flue or hi temp sealant thanks in advance.

[Tracy D'arth]

8 minutes ago, james46 said:

Hi everyone, im fitting my chimney collar, what is best fire rope with fire cement around the flue or hi temp sealant thanks in advance.

Fire rope and flaunched with silicone. Then if you want it out ever you stand a chance.

[james46]

Hi tracy thanks. I did see someone who cemented theres in. he looked like he was having a nightmare.

[ditchcrawler]

It needs to be able to move, the flue will get longer as it heats up.

[Jen-in-Wellies]

15 minutes ago, ditchcrawler said:

It needs to be able to move, the flue will get longer as it heats up.

Which will put pressure on the stove top plate, if there is no compliance at the collar end and has been known to crack said top plates. Silicone + fibreglass rope is the way to go.

[Tony Brooks]

2 hours ago, james46 said:

Hi everyone, im fitting my chimney collar, what is best fire rope with fire cement around the flue or hi temp sealant thanks in advance.

 

I am not clear as to which collar you are talking about. For the roof collar ordinary silicon will probably be OK but if you are talking stove collar then I think it needs a higher temperature one. You will probably have plenty left over to do the roof collar as well.