11-13-04 / 11-14-04

Reworked the TB air inlet in the right radiator duct.  Before, it was just a rectangular hole in the bottom, forcing the air to make a hard 90 degree turn.  I reshaped this to make it a much smoother curved entry into the TB pipe.  I also got carried away, and made a scoop for the inlet, so that about a third of the right radiator duct is not dedicated to the TB only.  This will have to have an effect on ram air pressure, which I basically didn’t have before. 

Reshaped the rear of the oil cooler scoop.  Before, it had a flat wall in the rear of the scoop, but now I’ve sloped the rear so that it’s a smooth transition into the back of the oil cooler.  I wish I had tested this before, but I set up a test with the new scoop shape.  Basically, I set the cowl on the floor, and pointed a leaf blower at the scoop from about 10 feet away.  I set a spare evap core on the top side of the scoop, just like it would be on the plane.  Finally, I used a handheld wind meter to measure the speed of the air through various portions of the core.  There was no significant difference between the left, right, and center of the core, however, there was a difference from front to rear.  I recorded speeds for the front edge, 25% back, 50% back, 75% back, and the rear edge.  Next, I made an aluminum divider to try to force air to the front of the core.  It didn’t really work, so I just left it out.  With any luck, the flow is already improved with the new scoop contour.  I probably won’t really know until Summer.   

Air speed going into the oil cooler scoop = 18 mph

Position from front to rear                  Speed without divider         speed with divider

Front                                                      5.6 mph                                  5.5 mph

25% back                                               6.3 mph                                  5.9 mph

50% back                                               6.8 mph                                  6.1 mph

75% back                                               7.6 mph                                  7.4 mph

Rear                                                        7.4 mph                                  8.0 mph

I riveted the cowl cheek extensions in place, and added a platenut to the front of the cowl to retain the cowl pins.  I decided not to install the plate that was meant to deflect air past the muffler,  I’m thinking that’s not worth messing with at the moment, since I’ll likely end up reshaping the lower edge of the cowl for more air exit. 

Finally, I got a chance to test my EWP without the mechanical pump.  I removed the alternator belt, and tied the plane down for a static rpm test.  I then proceeded to stress test my battery, by cranking and cranking without turning on the EC-2 (Doh!)      Finally, the brain kicked in, and I cranked the engine.  It was much cooler than usual today, about 70 rather than 85 or so like it’s been recently.  My impression was that the EWP was doing a reasonably good job by itself.  It took quite a while to warm up enough to make a full throttle run, and during that run, the water didn’t seem be heating much faster than normal.  I would say that it probably WAS heating faster than normal, but not at any sort of alarming rate.  Lower power settings were just fine, and I have no doubt the EWP will work as intended if I ever lose a belt on the mechanical pump.  Unfortunately, (or fortunately, depending on how you look at it), I couldn’t tell any difference in static rpm between having he EWP only, and the mechanical pump.  Both measured 5960 static.  This means I can leave my system alone.