During our 2010 round the world flight our CTLS were capable of staying airborne for 22 hours and travel 1/10th of Earth circumference in one leap ! Extended Range, the goal of this “project within the project” is to double the range of our RV-10 and enable him to achieve such leap if we were, in a few years, to set off on a new adventure.

It has been several years since I am interested in this modification consisting of adding a pair of fuel tanks in-line with the main tanks. Tens of RV’s fly already in the world with such a configuration and contacts with several builders such as Brian Foster in South Africa, Ashley Miller in Australia or Michel Gordillo in Spain greatly help me to finalize this project. A full technical study has been submitted to the authorities and approved, Sine qua none condition to start working on this major modification.

September 14 2019, the main tanks building starts and few weeks later the battle plan to fabricate the auxiliary tanks is ready. The builder’s manual is stowed, it will be of no use for some months, big jump in the unknown ! The 3 main challenges are : the fabrication of the tanks themselves based on a pre bent but undrilled skin, the mounting on the spar web and the mounting on the spar flanges by transforming holes initially planned for rivets to bigger holes for screw (in order to have a removable tank). The major difficulty is the accuracy one has to achieve this job : 2 or 3/10 of a millimeter to align the 42 mounting holes on the spar web, the same for the 140 holes between the spar flange and the tank itself. It’s less than a pencil line !

Several months of work will be necessary, for sure.   

2020 starts painfully with the passing of Daniel Koblet. Daniel was an outstanding aviator and mechanic from Switzerland, well-known and recognized in the historical aircraft scene. He had accepted to be my advisor despite a busy schedule and several projects in mind. We spent some great time together during this first year of building in the workshop or around a good drink. We were already speaking about the first flight of “Spirit of Sion” and I was looking forward to share this adventure with an engaging person having such an experience. Destiny decided otherwise.    

Have a good flight Daniel, and thank you.  

Days are going, the mind is somewhere else, I finally make it to the workshop and enjoy, little by little, building again. Then it’s the Coronavirus ! Lots of free time but the motivation is at its lowest level. This modification is a big chunk, progress are very slow and I suddenly realize how complex the task is. 

To insist is to exist ! In a few months, biting the bullet, the 4 tanks are finally done (still temporarily put together) and in April the spars are modified with success ! A major step is behind us. We can see light at the end of the tunnel, starts the tank’s final assembly and discover the last challenge : the use of Proseal, a black sealant that stinks, that sticks everywhere but is essential in sealing the integral type of tank where fuel is directly in contact with the structure. Each rivet, each join, each gap where the fuel could possibly leak must be treated… Vasita is there, her help precious. We will use 30 cartridge of the goop in as much sessions of 2 to 4 hours !

By mid-May we can proceed with the leak test number 1. Tanks are filled with 110 litres of water to detect possible leaks before definitely and fully closing them, that’s done in June. Then it’s the moment of truth, the final test : the tanks are slightly pressurized and soapy water sprayed on the outside as we would do it with a bike inner tube. The slightest leak producing air bubbles.

Results : not a single leak in any of the 4 tanks… Alleluia !!

What an adventure ! It took 8 months to think and fabricate those 4 tanks, it has been a fantastic journey, off the beaten track, with its ups and downs but fortunately, all’s well that ends well.

The builder manual and its reassuring instructions has been reopened !