why so slow??!!

I have a Stitts SA-3A playboy I picked up recently. It has an A-75
Continental and a 67" Fottorp prop with a 47 pitch. The plans indicate this
machine should fly around 120 mph with this engine; no mention of prop. A
previous owner I spoke to said it cruised around 118mph for him. For me, it
cruises around 95mph; I verified this with GPS. On run-up, I get about 2250
max RPM. On take-off it easily red-lines, suggesting to me the prop is not
a good match, but then I know next to nothing about this. It flies
beautifully, feels very well rigged. I won't pretend I know what the
problem could be; but I do know it is flying a lot slower than it should.
Any suggestions would be greatly appreciated!!
Thank you
Heino

"Heino & Deanne Weisberg" wrote in message ...
I have a Stitts SA-3A playboy I picked up recently. It has an A-75 Continental and a 67" Fottorp prop with a 47 pitch.
The plans indicate this machine should fly around 120 mph with this engine; no mention of prop. A previous owner I
spoke to said it cruised around 118mph for him. For me, it cruises around 95mph; I verified this with GPS. On run-up,
I get about 2250 max RPM. On take-off it easily red-lines, suggesting to me the prop is not a good match, but then I
know next to nothing about this. It flies beautifully, feels very well rigged. I won't pretend I know what the
problem could be; but I do know it is flying a lot slower than it should. Any suggestions would be greatly
appreciated!!
Thank you
Heino


Is it knots on the GPS?

(".Blueskies." wrote)
Is it knots on the GPS?


95 knots = 109 mph

....which would help (half way to the wall) but he's still then missing
another 10%, from 109 mph up to 118 mph -120 mph.


Montblack

ASI is calibrated in mph, GPS is set to mph.
Heino

"Montblack" wrote in message
...
(".Blueskies." wrote)
Is it knots on the GPS?


95 knots = 109 mph

...which would help (half way to the wall) but he's still then missing
another 10%, from 109 mph up to 118 mph -120 mph.


Montblack

The prop should be pitched to achieve redline RPM at full
throttle in level flight. Redlining in takeoff is not a good sign of a
suitable prop. And check that tach; most tachs any more than a few
years old tend to under-read as the magnet within tends to weaken as it
ages.

Dan

Before you start messing with the prop, I'd recommend making sure that
your tach is reading right.
--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR

The A-75 gets its 75 HP by turning 2600. The Manual recommended cruise rpm
is 2350. I would check the timing as it is 29° for the top plugs (right
mag) and 32° for the bottom plugs. It is NOT timed the same as the A-65.
--
Cy Galley - Aeronca Aviators Club
Newsletter Editor & EAA TC
www.aeronca.org
Actively supporting Aeroncas every day

"Heino & Deanne Weisberg" wrote in message
...
I have a Stitts SA-3A playboy I picked up recently. It has an A-75
Continental and a 67" Fottorp prop with a 47 pitch. The plans indicate
this machine should fly around 120 mph with this engine; no mention of
prop. A previous owner I spoke to said it cruised around 118mph for him.
For me, it cruises around 95mph; I verified this with GPS. On run-up, I
get about 2250 max RPM. On take-off it easily red-lines, suggesting to me
the prop is not a good match, but then I know next to nothing about this.
It flies beautifully, feels very well rigged. I won't pretend I know what
the problem could be; but I do know it is flying a lot slower than it
should. Any suggestions would be greatly appreciated!!
Thank you
Heino