The 2019 Stirling Rally... We have started running engines using Helium. The revs SOAR!

This year we extended the rally to two days.
The first day we cruised upstream to Brunel's bridge at Maidenhead.
The next day, downstream to Windsor.
Two of the three boats were pressurised, and one was using Helium.
Pressurisation is the big factor in getting more power out of a Stirling.
Helium makes the engine run faster (about 50%) and the higher revs raise the power.
Helium gas heats more quickly than air - thus the higher speed.