I needed a windscreen and a pot cosy on my last outing to combat the wind and heat loss whilst cooking so I decided to make a caldera cone/clone
this is my first attempt with tray foil.


Untitled by MM-on-POINT, on Flickr



Untitled by MM-on-POINT, on Flickr

before I finesse this and apply it to some aluminum sheet I have a few things I need to work out.
1 does it need to be a tight fit around the pot even though I am not using the cone as a pot holder?
2 how high does the air in take holes need to be and do I need the vent holes in the top?

please have a look the pictures and scrutinize.
thanks

1 does it need to be a tight fit around the pot even though I am not using the cone as a pot holder?

No, not really. The tighter the fit the more efficient it'll be but the more important your venting becomes.

2 how high does the air in take holes need to be and do I need the vent holes in the top?

Some will depend on what stove you're using. The height you've got them at in the pic looks okay but you need more / bigger holes. Top vents are at least as important as the bottom intakes, remember that there's a much bigger volume of gas trying to escape from the top than went in the bottom. Slots tend to work better than round holes for both top and bottom ... they don't distort the flame pattern quite as much.

EDIT: I've just realised you're on solid fuel (I think) with an Esbit holder. If that's the case, raise the air intake holes 1/2 inch and bring the vent holes down so they're just a bit higher than the bottom of your pot.

Thanks, I am using this set up solely with esbit.
I did notice the flames seemed a little starved of oxygen so I will turn those bottom vents in to diagenal slots to raise and enlarge them.

Thanks s8tannorm