Sorry. Not been on this thread for a while.
I guess it all comes down to fuel. I use nothing but Tygon and felt clunks. Oldest still in my possession is the Instruction manual Classic Flash, I finished the tank for flight in July 2006 and it still has the same Tygon and felt clunks on main and wing tank today. The fuel system works flawlessly with the BVM bubble trap (No MAP at that time!) landing with almost zero air after 8 minutes. CARF Hawk from 2009 same Tygon and felt clunk from day one, also on a BVM trap as it was late that year I got my first MAP Bubble trap, again lands with no air in the UAT. This goes through all my models since I have never changed a clunk line, I’m not aware of any of my team having to either. Several have models in the 10-12 year age still with same Tygon clunk line.
We all use the same Paraffin (Kerosene) green house heater type 28second heating oil bought from the same refinery for 20 years. It’s super clean and water free. It’s expensive compared to JetA and other Kero options...but none of us have turbine issues, I have several JetCat turbines run into 35-40 hours with no service.
Clunk line hard tube. I’m talking about un-baffled open tanks. Anything from 50oz Dubro to the CARF cylinder tanks without a baffle, coke bottles, Derjet Cougar and Vampire all just have a length of Tygon that when hung vertically the clunk sits 10-15mm from the rear of the tank. I always Felt clunks (which should be thought of ‘wet weight’ not dry as they are installed. I have never had a tank clunk line hang up/kink. Yes I want the clunk line to have the chance of following the fuel when nose down (remember G force not static workshop testing) I only use 1/8” (3.2mm) bore Tyron for the clunk lines right up to 220N twin tank set ups like my Mephisto/Bolt.
I buy genuine Tygon 4040 not the half dozen lookalike types.
Dave