thomas rubino wrote:Hi Kees; Welcome to permies!
I will try to answer your questions as best as I understand them. Please forgive me if I misinterpret your questions.
Your sketch up of the base looks very good. I think that looks like a properly built safe base.
Your design of a rocket core and riser also looks good (must be sized properly)
Your last sketch up is the most confusing for me. This looks to be a chimney cap ? Hand made, possibly a revolving cap ? Do I see a size change in the construction?
If I understand your question) you are wondering if you need a fan (blower) on the chimney stack ? If that is the question the answer is No.
Of course there are exceptions where a fan might be needed to start a draft. But as a general rule in most builds , a properly built rmh with a proper warm chimney stack , will have no need of mechanical assistance.
Glenn Herbert wrote:What is the length of the 11 cm portion of chimney? How much of it can not be made bigger due to existing holes or whatever?
If you can make most of the chimney bigger, you may be able to work with a constricted part of the chimney... this will depend on a lot of factors in your situation, so the more detail you can give about your house, the better the answers we can give.
With a restricted chimney size and thus system size, I would recommend you look into a batch box instead of a J-tube core. A batch box delivers heat much faster for the same system size compared to a J-tube, and the firebox of a batch box will be significantly bigger than a J-tube feed. Peter van den Berg is a world leader in batch box research and design, so you can get the best information directly from him, as well as from his website batchrocket.eu.
Glenn Herbert wrote:Note that the diagram says that C can be less than OR EQUAL to A and F... just not larger.