This process of pressure testing has taken a significant amount of time. The task was started at the end of April. A tee was installed in the vent manifold that ties the two tanks vent lines together. One side of the tee was connected to a tubing. The other side was connected to a water manifold constructed of tubing and mounted on a 2x4. During the middle of testing I decided to isolate the two tanks. I did this by capping the flared fittings to the port and then the starboard tanks.
At first, I pressured the tanks to 20 in H2O which is about 1500 ft altitude as indicated in the plans. I eventially have taken it up to as high as 36 in H2O. For the 3.8 G loading that the plane is designed to be able to operate, the tank bottom could see as much as 43.1 in H2O , the basis for this is full ram air at 190 Knots (Vne) or 24 in H2O, a full tank at 7" of fuel. The fuel SG is .71, so at 1 G that is about 5 in H2O pressure. At 3.8 G, this is about 19.1 in H2O.
Over several pressure tests there were many leaks found and fixed. I have listed all of the locations that I found leaks below and all of the suspected leak sources that actually did not leak. Currently, the port tank is esentially tight, the measured leak rate over 8 hours is less than 0.05 in H2O/hr.
Leak testing was primarily completed using soap and water. R-134A was also used to find leaks. This method did not appear to be more sensitive than the bubble method. In fact, the refrigerant detector that I bought from Harbor Freight seems to alert on epoxy in general. This lead to some false findings. Another method that was considered but rejected was using ammonia in the tank and then use pH indicator to find a leak. Preliminary tests indicate that ammonia will corrode the aluminum metals.
The leaks found and fixed were: 1. Tubing fittings on the vent manifold. 2. Tubing fittings at the fuel valve. 3. The LE drain valve on the starboard tank was still covered with fiberglass. The glass had a small pin hole. I decided to open the hole and install t
