With the stove working daily for almost two months now on damp wood (all we could get at the time), it was obvious the flue was becoming obstructed with creosote deposits. When it got to the stage of smoking the yurt out every time we opened the stove door to add more wood, it was time to do something about it.
I also wanted to make a slight modification to my earlier modifications. (The upside-down flue pipe has been working perfectly. No leakage of creosote or smoke.)
The greatest amount of build-up was in the top section of pipe outside the yurt. Logical enough. The air outside is colder and the cooler flue pipe will cause much more condensation. Thanks to João (and whoever it was gave him the advice), I’d purchased a single section of 150mm flue and a chapéu to go with it. This is now fitted over the top section of 110mm pipe from the stove, but the right way up this time, so the chapéu fits the way it should. No cutting. No messing about with bolts (which start to corrode in the creosote and become very hard to remove). Since the flue conveniently exits the yurt at a joint between pipe sections, the outer pipe section is a perfect match lengthwise and simply rests on the silicon flue collar.
At the moment the two sections of pipe are held apart and in place with aluminium foil. However I’m going to find a small amount of mineral wool insulation and use this to fill the entire gap between the two pipes instead. (Mineral wool insulation can tolerate temperatures up to 1,000°C. Fibreglass to only 540°C which is not sufficient.) The insulation will help stop condensation of flue gases by maintaining the internal flue temperatures and hopefully mean we have to dismantle and clean the flue pipe less often.