At last I've finished the Geodesic tunnels plans! These will be available from 3m diameter (10 ft) to 6m (20 ft) This is the metric version but I can make an imperial set if required.
These plans are based on the GD5 garden dome but can be extended as much as you need to form a tunnel, there is only one more triangle shape to make so it's pretty simple to build. Great for covering swimming pools and if you run out of space in your greenhouse just add another section to make it bigger.
Sketch below shows extended version.
Plans are delivered in PDF format, please allow 24hrs for delivery. If you have any questions please feel free to contact me.