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Here's another interesting mystery for the tribe to play with...
Because I was suffering from Cranial Rectalitis, I made a bad decision during my recent maintenance downtime. I removed about three pounds of tiny 1/8" copper tubing and duct tape inside the port wing, which was being used for pitot and static lines. I replaced the pitot line with a nice light piece of aluminum tube. So far so good.
But I made the brilliant decision that the static tube, with its tiny hole being an invitation to mud daubers and bugs, should not be outside the airplane. On a non-pressurized plane, I postulated, you could just use the inside of the cabin as a static source. Surely I'd win the Nobel Prize for aerospace !
Well, not exactly. I won the No-Brain prize.
On the first flight I came to the conclusion that I had created the world's fastest 65 horse Taylorcraft, with an astonishing cruise speed of 115 miles an hour at 2150 RPM. By the time it dawned on me that the air pressure inside the cabin was not ambient static pressure, I also realized that I had covered and sewn up the wing without the static line installed.
So I routed a static line from the ASI up the door post and shoved it into the inside of the left wing, hoping that the air inside the wing would be pretty close to ambient. I flew it that way for ten or fifteen flights, but in my heart I knew it wasn't really accurate. The airplane would indicate about 90 on average at 2150, which is a little less than it did before.
The other day I was trying to scrape off about 15 years of rust and corroded flying skills by making slower, more precision landing approaches. On one approach indicating about 52-53 mph, the airplane started complaining and making noises like it was about to quit flying. I had to goose it a little on short final even though it was reading 50 or better. I made pretty close to a full stall landing (on the numbers, thank you), and looked over to see the ASI indicating 45 mph just after touchdown. It SHOULD have been 35 or 37 in my opinion, a 775 pound empty weight pre-war airplane with 1.3 people on board and not much fuel.
Today I wrestled and fought and argued another piece of plastic tube back through the wing, made up an aluminum static probe (what I believe it should look like), and more or less went back to the stock type static... but this whole exercise has raised my curiosity.
I have heard the stories about CG Taylor and his sales staff "adjusting" the static probe with a file to insure the airplane met it's performance numbers before a buyer showed up. I have no idea of the actual details. I know of one sailplane manufacturer who put the static ports in a position that purposely made the ASI read higher at high speed and lower at low speed.
So, after the whole long-winded back story, I now put these questions out to the group in hopes someone knows the real answer:
1: How would you calibrate your static source on a Taylorcraft so you had it exactly right instead of 90% right, if you wanted to do that for total accuracy in ASI and ALT readings?
2: Is there a known, accurate, no BS static port location on a Taylorcraft OTHER than the little probe under the pitot? Cessna has them on the rear fuselage sides and occasionally on the boot cowl. Piper Cherokees use the rear fuselage. On the competition sailplanes we had some very sophisticated pitot and static probes that were highly accurate, that stuck out of the leading edge of the fin. Has the factory or anyone else done a pressure distribution survey on a T-craft airframe to find a locaiton that will give you a really good reading?
The static probe I made today was a piece of 1/4" aluminum tube with an AN 470 round head rivet glued in the end, and two holes drilled through the tube about half an inch behind the rivet. In case the holes get clogged or bugs get in, I can pull the rivet out and have access to clean out the tube from the front.
Because I was suffering from Cranial Rectalitis, I made a bad decision during my recent maintenance downtime. I removed about three pounds of tiny 1/8" copper tubing and duct tape inside the port wing, which was being used for pitot and static lines. I replaced the pitot line with a nice light piece of aluminum tube. So far so good.
But I made the brilliant decision that the static tube, with its tiny hole being an invitation to mud daubers and bugs, should not be outside the airplane. On a non-pressurized plane, I postulated, you could just use the inside of the cabin as a static source. Surely I'd win the Nobel Prize for aerospace !
Well, not exactly. I won the No-Brain prize.
On the first flight I came to the conclusion that I had created the world's fastest 65 horse Taylorcraft, with an astonishing cruise speed of 115 miles an hour at 2150 RPM. By the time it dawned on me that the air pressure inside the cabin was not ambient static pressure, I also realized that I had covered and sewn up the wing without the static line installed.
So I routed a static line from the ASI up the door post and shoved it into the inside of the left wing, hoping that the air inside the wing would be pretty close to ambient. I flew it that way for ten or fifteen flights, but in my heart I knew it wasn't really accurate. The airplane would indicate about 90 on average at 2150, which is a little less than it did before.
The other day I was trying to scrape off about 15 years of rust and corroded flying skills by making slower, more precision landing approaches. On one approach indicating about 52-53 mph, the airplane started complaining and making noises like it was about to quit flying. I had to goose it a little on short final even though it was reading 50 or better. I made pretty close to a full stall landing (on the numbers, thank you), and looked over to see the ASI indicating 45 mph just after touchdown. It SHOULD have been 35 or 37 in my opinion, a 775 pound empty weight pre-war airplane with 1.3 people on board and not much fuel.
Today I wrestled and fought and argued another piece of plastic tube back through the wing, made up an aluminum static probe (what I believe it should look like), and more or less went back to the stock type static... but this whole exercise has raised my curiosity.
I have heard the stories about CG Taylor and his sales staff "adjusting" the static probe with a file to insure the airplane met it's performance numbers before a buyer showed up. I have no idea of the actual details. I know of one sailplane manufacturer who put the static ports in a position that purposely made the ASI read higher at high speed and lower at low speed.
So, after the whole long-winded back story, I now put these questions out to the group in hopes someone knows the real answer:
1: How would you calibrate your static source on a Taylorcraft so you had it exactly right instead of 90% right, if you wanted to do that for total accuracy in ASI and ALT readings?
2: Is there a known, accurate, no BS static port location on a Taylorcraft OTHER than the little probe under the pitot? Cessna has them on the rear fuselage sides and occasionally on the boot cowl. Piper Cherokees use the rear fuselage. On the competition sailplanes we had some very sophisticated pitot and static probes that were highly accurate, that stuck out of the leading edge of the fin. Has the factory or anyone else done a pressure distribution survey on a T-craft airframe to find a locaiton that will give you a really good reading?
The static probe I made today was a piece of 1/4" aluminum tube with an AN 470 round head rivet glued in the end, and two holes drilled through the tube about half an inch behind the rivet. In case the holes get clogged or bugs get in, I can pull the rivet out and have access to clean out the tube from the front.
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