Flue and chimney fitting

[Phil F]

Hi, looking to install a stove on my boat which means cutting a 6+ inch hole in the roof for the flue (4inch twinwall ??) and chimney. My boat is just over 2 years old and has diesel blown air heating which is OK but doesn't cope too well when really cold. I am not a liveaboard so am doing this mainly as a project and will not be dependent on the stove as permanent heat source. I feel OK with insulating around the stove etc but am struggling to understand the dynamics re flue, chimney etc. My stove (Hamlet Hardy 4) has a 4inch opening at the top. After a lot of searching on the internet, Youtube, forums etc it seems the traditional approach is to use flue which goes into a cast iron deck plate bolted and sealed on the roof with a removeable chimney on top of the plate.  Recent regulations seem to indicate that twin wall flue has to be used. Is it possible for me to do the following ? Can I use 4inch twin wall attached to the stove by an adapter  which exits the roof about 100mm above a Dektite heat proof roof flashing then attach to that a 500mm length of 4inch twin wall (+ cowl) secured by a locking band as a chimney ? Could this work as a removeable chimney ? or is it not possible to undo the locking band once fitted ? I would protect the ceiling internally with a firestop collar and pack around the flue inside the roof space with fire rope or similar. So, what I really need to know - is 4inch twin wall too small ? If so, what is the minimum I can use safely on a boat. I cannot find anywhere where minimum flue size is mentioned. And, more importantantly, is what I want to do possible, or is there a reason why a  cast iron deck plate has to be used rather than a Dektite, and, would what I want to do work and pass a BSS ?. All comments/advice welcome - thanks Phil

[mrsmelly]

In short, you DO NOT need twin wall flue. It will pass the bss with single provided the instalation is safe. Get a flue and collar etc from Limekiln chandlers for peanuts delivered.

[Alan de Enfield]

It would be a lot easier to get a bigger blown air heater.

I have an 8Kw Eberspacher blown-air and it gets the boat way too hot, even in the middle of the 2010 Winter when the marina was frozen so hard you could walk across the ice we had to open the doors to let some heat out.

[matty40s]

It doesnt Have to be used, it is a recommendation as best practice, most modern boat builders will do it if installing from new, however, as a post build install, you can do it with a single wall flue, so long as this is installed  correctly.

 

[LadyG]

The heat from stove must mostly be radiation, it makes little sense to insulate the flue unless kiddies or elderly could fall against it, but really, placement of the stove must be the main thing, and insulation at the deckhead (ceiling).

[Ally]

If you google Soliftec, you should come up with the recommendations for a new stove fit. Some, but only a few surveyors,  will "want" you to fit accordingly, most will check simply that it is a safe fitting and installation,  so fixed to the floor, no cracks or leakage or scorching apparent.  8t will be clear its a new installation from the cross on the previous bss cert by stoves.

So whilst recommended,  you could fit a standard flue, single wall. If you prefer to go with recommendations however, the 4" internal, 6" external flue is fine. Usually attached via a short length of single 4" from the stove. Various makes of flue kits are available fa pretty penny, Morso being the obvious. 

Personally I think the traditional cast roof fitting is best, but never having used anything else, I couldn't comment,  but I remember reading another thread where the decktite fitting wasn't popular...try the search engine?

In theory, you should also have an insulated chimney to complete the "ideal" set up. They do draw extremely well.

 

[matty40s]

This passed a BSS

[ditchcrawler]

1 hour ago, matty40s said:

This passed a BSS

And why not, the BSS don't care if the rain gets in just so long as the smoke and CO goes out

[Phil F]

Thanks to you all for replies. 

[Ray T]

Bit late to the party but I has this made for our boat when we had a stove retrospectively fitted.

The measurements are of course for our boat, a Reeves Hull.

Still in good condition 8 years on. Although, as we don't live aboard the stove doesn't get a lot of use.

 

As I used a woodworking shop it wasn't cheap.

Edited November 30, 2020 by Ray T

[Slim]

4 minutes ago, Ray T said:

Bit late to the party but I has this made for our boat when we had a stove retrospectively fitted.

The measurements are of course for our boat, a Reeves Hull.

 

As I used a woodworking shop it wasn't cheap.

 

I made something almost identical out of African mahogany when I fitted out my boat 20 + years ago. My design was drawn up on the back of a fag packet. (a little poetic licence used).
















 

 

 

 

 

 

 

[PD1964]

A lot of boaters seam to be in the same situation as yourself from what I’m seeing at the minute buying boats without solid fuel fires. If your a livaboard it’s not the best idea.

  Don’t get confused with the Soliftec site as they state Requirements and Recommendations, you need to do the Requirements for the BSS the Recommendations are only that.

  Just fit a 4” flu and coller to fit. Remember to buy an angled coller to compensate for the roof curvature so your chimney is vertical. 

[OldGoat]

6 hours ago, PD1964 said:

A lot of boaters seam to be in the same situation as yourself from what I’m seeing at the minute buying boats without solid fuel fires. If your a livaboard it’s not the best idea.

  Don’t get confused with the Soliftec site as they state Requirements and Recommendations, you need to do the Requirements for the BSS the Recommendations are only that.

  Just fit a 4” flu and coller to fit. Remember to buy an angled coller to compensate for the roof curvature so your chimney is vertical. 

These can be difficult to find - I tried two chandlers in the midlands (see what I did?) before I found 'the last one' - 'no demand' .

There's no joy in havind one's chimney canted over at a ridiculous angle, methinks. Perhaps I've been boating for too many years....

[PD1964]

I would say “No Demand” means they are too expensive to stock and people don’t know there is a difference in roof collers.

[Ally]

We used to have collars made up by Roy Willoughby.  Always specific for the boat roof curve. He has, I believe, sadly passed, but his business may have continued? 

Any decent welder /engineer should otherwise be able to form a correctional lift to straighten a chimney. We had ours built up to straighten. Photo is of one of the ones Roy made for us.

 

Incidentally,  Eddie at Northern Fabrications has offset collars.

Edited November 30, 2020 by Ally