Can somebody clear this dimention fog I have ..

This is a drawing from the "Rocket Mass Heaters  (Superefficient WoodstovesYOU Can Build) by Ianto Evans & Leslie Jackson".
I explain in the image where I cannot get my head around ..

Thanks

Yeah, ignore the wording and just look at the letters. Also, experiment if you can. The taller the heat riser, the better draft you should get.

petra sips wrote:This is a drawing from the "Rocket Mass Heaters  (Superefficient WoodstovesYOU Can Build) by Ianto Evans & Leslie Jackson".
I explain in the image where I cannot get my head around ..

Thanks

Yes, that is confusing since the description is inconsistent with the diagram/drawing. There is a correction of the wording in the 3rd edition of the book, and I quote:  "E is the most important single dimension: the height of the Heat Riser from the top of Burn Tunnel to the top of the enclosed Heat Riser stack. (Measure this distance from the dotted line in the drawing..."

HTH

thanks ron. So did I understand it right (not so much in this topic but in general ..) that the heat riser should be AT LEAST twice the length of the burn canal! But longer is all right  too?!

Ideally the Burn Tunnel should be as short as possible, and constructed so that it will be less than one half the height of the Heat Riser.

petra sips wrote:thanks ron. So did I understand it right (not so much in this topic but in general ..) that the heat riser should be AT LEAST twice the length of the burn canal! But longer is all right  too?!

I think yes, the heat riser can be longer than that.

One thing I think is at least theoretically possible is that if you make the heat riser too long/tall then the draft will be so strong that it will result in too much heat being removed from the burn tunnel, making the burn less all-consuming. But in practice, that isn't very likely.

I think the most important ratio is feed tube height to riser height. If the riser is not at least 3 times the feed tube, it may not have enough greater draw to pull the flames to it instead of coming back up the feed tube.

hi Glenn, thats a very usefull comment. I've build one rocket before and it works really well.
I was wondering why it worked so well when I red that the feeding tube needs to be low, while mine is about 12". But my first Rocket might wirk so well because my riser is about 36" .
Thanks for the use full comment!
It great having a forum like this!