January Flight Log - Flight Hour 95 and counting

The IVO prop governor continues to be complete crap! In December I had to take it back due to a broken rheostat. After putting it back in it worked one flight. Now it pops the C/B in about 3 sec after turning it on. They found a bad relay and I will try it again next flight. It has never worked very well. It allows RPM to wander. One day the max setting will be 5400 and the next 4300. It frequently causes the C/B to pop seemingly due to hitting the limits of the spool. Since there are no limit switches, it relies on the current rise when hitting the stop to turn off. This is highly dependant on the supply voltage and wire length. The wire length must be as sent from the factory which I did not have at first. after fixing that it was a little better but if I turn on a high electrical load for night flight and the voltage drops a bit the C/B pops. I've gotten used to flying in manual and am about to chuck the governor if this next try does not work.

I flew again with the Prop governor and it is operating better. It still hunts in RPM a little and still pops it's breaker occasionally but is much better. Perhaps now it is a matter of adjustment.

I also took data of the pressure in front of and behind the radiator compared to a static port I put in the side of the cowl. This indicated that at 160 KIAS the pressure in front was 20.1" while behind it was 10.4" with similar ratios through out the speed range. This indicates that the exit to the prop disk is a poor exit. At this time a chain of ideas came into play. First, I want to repaint the plane. But before that I want to remake the cowl because it is too heavy. If  I'm going to remake it,  then it ought to be a better design for air flow. So now I'm into a major redesign of the cowl. I decided to close off the prop disk exit all together and make the exit more of a standard cowl flap type exit. This is now below and forward of the prop. In the process I very much wanted to get the radiator more vetical so the air would not have to turn sharply into and out of the radiator. So I cut the entire center bottom out of the cowl and lowered the bottom edge of the radiator 4". This put the radiator at about a 70 deg angle, The bottom of the lowered cowl is now at the same level as the inlet lip so the frontal area is about the same. With the new exit behind the radiator, there is not a sharp curve either. Here are some photos

               NewCowlRear.jpg (120220 bytes)            NewCowlSide.jpg (93302 bytes)


                                            NewCowlFront.jpg (94738 bytes)

I still have a couple of week of work to glass the inside and reposition the radiator and ducting so it will be lat Feb before I know if it worked. If it does then I will make a mold and then a light weight graphite cowl.


The mods are complete but instead of 6 weeks it took me 10. I got a test flight off yesterday April 3. My freinds are now refering to the new cowl as Frankencowl. I must admit it looks like it came back from the dead. But the good news it that it works! I lowered the oil temps by about 17 deg and the water temp by about 10 deg. This puts me in an acceptable range for even a 110 deg day at sea level. The Perfomance Data spread sheet has been updated.


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