Questions about building my first J-tube RMH for a tiny house

Thanks for prompt reply.
That's a very fine looking RMH! Great job from plans to finish. Hope it performs to your satisfaction.

Will be very much appreciated if you can share your custom made bypass valve.
Have been perplexed, if not stumbled at it. The available around (ventilation) ones are from pretty thin tin, which the manufacturers say will deform above 40-50C.

Here are the pictures of the bypass damper. It is build like the ordinary throttle valves used in stove pipes but from a full round piece of metal and some CMS (calcium magnesium silicate) fibre sealing. The sealing is not visible on the pictures because I added them later and I'm not shure wheter they were neccesary because I think the passage through the bypass doesn't need to be closed almost airtight for the hot gases to get forced into the bench bell when closed. So I think maybe a well fitted piece of thick round metal screwed on a round bar of metal could work aswell. Other people in this forum may have more experience on that.

Hi Jonas
Matt Walker describes bypasses in this video.
At about 3:20 he talks about how sealed they need to be.
stove chat

Brilliant start to finish job, very fruitful systematic approach!
Hope the RMH works well for you for many cozy winters ahead.

I thought I posted a reply earlier but it hadn't registered.

If you get a chance to share your custom bypass, that will be much appreciated.
I can find around from the pre-made ones only either ventilation tube or flue types which do not fit tightly and/or deform above 50C

This Rocket Mass Heater is finally finished. You find some pictures and thanks here: https://permies.com/t/372751/RMH-completed-fotos-big#3771354