Baffle plate / Chinese hat?

[ytre]

Hello folks
Ive just been working on my first woodburner, using a 11kg gas cylinder and welded on a 4ft 4inch flue. After lighting it there is about 8inches of flame above the flue, should i fit a baffle plate near the bottom of the flue or into the cylinder itself?
Secondly id thought about fitting a chinamans hat about a foot from the top of the flue to deflect the heat downwards.
How do i go about making a chinamans hat? Any help or advise greatly appreciated

 

[Sam]

If you are fitting a baffle plate feep it a half inch or so above the bottom of the flue eg. 4" pipe 2 1/2" up from bottom that way when you fill it with wood it cannot catch the baffle plate and stop it closing.

If you seal the burner well enough you should be able to control the burn by the amount of air you let into the fire by means of a spinner ideally you dont want to keep the burnt gasses back some air above the flame helps as well.

As for the chinamans hat draw a circle and make a slit from the outer edge to the centre and gently form with your hands as you go around the circumference. Another thought is if you use a smaller cone inverted within the outer cone that may help as well.
Ask your mum for the empty cornflake's box to practice on. p.s. remember to use steel or preferably stainless as the card will burn.

 

[Omniata]

I thought the "chinaman's hat" was to stop rain going down the flue

And that to increase the burning in the stove you put a baffle just before the flue with a feed of fresh air over it to burn what hadn't already been burnt
The baffle in the flue merely to restrict the air flow?

 

[ytre]

The chinamans hat is for stopping rain going down the flue but i was gonna make one to fit the circumference of the flue so it'll act as a heat reflector, bit like a gas patio heater.

 

[Omniata]

I get what you mean

 

[Sam]

I thought the "chinaman's hat" was to stop rain going down the flue

And that to increase the burning in the stove you put a baffle just before the flue with a feed of fresh air over it to burn what hadn't already been burnt
The baffle in the flue merely to restrict the air flow?

On a short piece of flue and with a cap fitted it will direct heat downward and yes it will stop rain going down he chimney and also help with blowback.

In my opinion you dont want to restrict gases going up the flue carbon monoxide kills you are better adjusting the flow with a spinner on the stove than restricting the flue but I am sure someone will disagree, there again you are only using it in open spaces.

 

[ytre]

What do you mean by a "spinner"?

 

[Omniata]

I was only querying it

Just wasn't sure at the time from what was being said

Previously I'd picked up that a baffle with it's own free air flow was ideal so that as the unburnt gases went up the flue that mixed with fresh air and burnt just before leaving the stove to release more heat instead of burning in the flue?
Not so small to restrict flow but quite big over a larger area to ensure complete combustion with a free air feed up the back?

Something like this:

The blue arrows being fresh air, red being just burnt/partially unburnt and the orange almost completely burnt...

 

[Omniata]

What do you mean by a "spinner"?

Something like this:

A flue "damper"

 

[Sam]

What do you mean by a "spinner"?

A simple disc covering a hole in the heater with a bolt or screwed rod attached so you can adjust the flow of air by screwing the disc closer or farther apart.

 

[Omniata]

A simple disc covering a hole in the heater with a bolt or screwed rod attached so you can adjust the flow of air by screwing the disc closer or farther apart.

ie: an air vent?

Not the one mounted in the flue

 

[Sam]

Have never been in favour of a balance vent or baffle in a flue if it has been installed properly outwith any negative pressure zone there should not be any reason for one. Why anyone would want a vent in a flue still baffles me p.s. no pun intended! but this is only for a patio heater depending on what he is burning they will still smell like kippers next morning!

 

[ytre]

Thanks for the help folks, much appreciated