Phil Stevens

Echo what MK just said...we dry lots of fruit and put lots of the apple slices away in jars with locking lids. If the dehydrator runs a bit longer than planned, they get so  dessicated that they're crispy. The first time the jar is opened they're still super dry and you can just tip out the dry pieces like massive cornflakes, but in humid weather they swell up in a day or so and you need to dig to get them out...and they're no longer crispy, just more like "normal" dried apples.

Not much can go wrong with fruit as long as it's got decent sugar levels and the moisture content is low enough.

Coydon Wallham wrote:Does shiny ductwork not read properly on pointer thermometer guns? I noticed the few sections of duct that I have with a more mottled appearance read a few dozen degrees higher than the shiny ones.

Yep. Reflections work the same way at infrared as they do in visible. I often hit shiny galv or stainless flue pipe with a spot of flat black paint so that my temp gun gives me more accurate readings. Or you could wait for it to get dirty and oxidised. White or very light-coloured surfaces will read cooler than dark ones, as a general rule, and the same goes for shiny versus not shiny.

The cross section is the important constant in RMH design. What we have learned from all the years of trial and error is that a J-tube system with a given diameter that is pretty much equivalent across the burn tunnel, riser, and flue will perform well as long as other dimensions are in alignment with the ratios that are known to work. I'm intentionally citing diameter as the constant, instead of cross sectional area, because another thing we've learned is that as you get farther away from cylindrical sections, the effects of friction on the fluid dynamics are amplified.

This is not to say that you can't push the envelope in one or more directions. But the riser is quite possibly the least tolerant of diameter variance out of all the main parts of the system...the gases in there are at their most expansive point in the process. A riser that is too constricting will impede the flow of combustion gases, choke the draft, and inhibit clean burning. At the other extreme, a riser that is too wide will decrease the velocity and turbulence at the critical stage where the highest temperatures are developed, and this is also likely to limit mixing, efficiency, and clean performance.

Keep running it to dry out that mass. When you finally chase all the water out of the cob things will get better. Extending that chimney would really help as well, but when the mass is fully dry you might get away with it as is.

A properly designed and built RMH burning dry wood will be putting out warm steam, for the most part. So a fan-forced exhaust is certainly a possibility, as long as it doesn't mind the humidity and mildly acidic nature of the flue gas. Forcing air into the system is also an option, and some have done it, but this would make me a little more nervous about overpressurising the system and driving combustion gases into your living space.

I grow it in the glasshouse. In fact, I should go out this week and put the rhizomes into pots...they're currently sitting in some barely damp wood shavings and it's time to start them. They seem to be more likely to start growing when the days are at their longest, and some years I didn't get them going until solstice. They'll grow until end of autumn and then go dormant again, so I tip the pots out in June and store them in sawdust or shavings in a dry corner of the glasshouse. If I put them anywhere cold they rot, but if I bring them indoors they dry out too much.

Good to know it was a problem that could be found and fixed. Have you had any sunny days to see if there's an improvement in performance?