Poor man's tach check

[Mike Kimball]

I know the "check the tach" comment was a joke but it reminded me of a
quick, easy, cheap way of checking the tach on my Piper Arrow ages ago. My
tach was placarded as reading 100RPM low and I was curious. I put some duct
tape on the back of one of the blades on my two blade prop, waited for night
to fall, then put the airplane near a light on a building with the tail
facing the building. In the US AC power is supplied at 60HZ so if my tach
is accurate, the blade with the tape will appear to stop at multiples of 60.
So I tried 1200, and 1800 RPM and discovered that, just as my tach was
placarded, my tach was off by 100 RPM. The prop appeared to stop at 1100
and 1700 RPM. If Canada is 50Hz then just use multiples of 50. Some
mechanic placarded my tach as reading 100RPM low and my test confirmed it.

Mike
044SR

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Rebflyer@aol.com
Sent: Monday, August 28, 2006 4:45 AM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] New Prop

Hi all,
Well it's time to admit I have now purchased prop #3. I vowed in the
beginning that I would not do that, but here I am anyway.
Short history is this. When first certified I installed a McCauley 76".
Great prop on wheels. It spun at about 2300 rpm on initial roll. I felt it
was
to coarse a pitch for the floats and it could not be repitched any more.
Then
came the Warp drive 3 blade sq tip 72". I really enjoyed that prop. I flew
that for almost 300 hrs prior to the cracks in the blade clamping area.
Pitched
for 2300 rpm on the initial roll it was a bit slow off the water for my
liking, but cruise ok. (as a side note, each 10 rpm change seemed to relate
to 1
mph). Pitched for 2450 on the initial roll it smoked off the water,
especially light with cool temps( 60ish f) but 85mph for cruise.
I shipped the prop and hub back to Warp. For the cost of 1 blade they
sent
me a new hub and 4 blades. 70" sq tip. The performance from the 3 to the 4

is the same as far as I could tell.
The rpm range on the Warps was about 600 rpm. More to come on this.
Well after waiting for 8 mo I now have a three blade 68" 46 pitch Catto
prop. Very well known in the canard community for speed and durability. I
figured if it can take nuts, bolts and exhaust systems going thru the prop
without
catastrophic failure it should do fine on the front of a float plane.
After several conversations with Catto the numbers based on the engine
I'm
using and the hp it produces I decided on 2450 for the initial roll with
125mph cruise at full throttle. 2750 rpm.
We hit those numbers right on the money. At 2450 it comes of the water in

90 deg f like the Warp did in 60 deg f !!! I can't wait till it gets cool
again! Cruise at full throttle shows 2775. 300 rpm range. I think I need to

check my tack(grin). Again in 90 deg f temps I'm indicating 115mph. That's
the
fastest I've been on floats. At 2500 it is very close to 100mph. We also
shot
for that number and hit it right on!
Out of all the differences between the props the one that I cannot put a
number to, but the seat of my pants and the size of the trees on the
shoreline
attest to, is when the floats break water this prop really keeps pulling.
Hard!
And last but not least unlike the warps It looks like a real prop!
So at this time the only complaint I have is the wait I had for the prop.

It is better than I hoped for in performance!
Cost? 1775.00
More to come, but I'm going flying, so see ya later!
Curt N97MR





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[eric.r]

Or take the metronome off the piano, set it to 60 and blink your eyes in sync
with the metronome ... too many engineer types on this thread!
On 8/28/2006 7:59 PM, mkimball@gci.net wrote to rebel-builders:

-> I know the "check the tach" comment was a joke but it reminded me of a
-> quick, easy, cheap way of checking the tach on my Piper Arrow ages
ago. My
-> tach was placarded as reading 100RPM low and I was curious. I put some
duct
-> tape on the back of one of the blades on my two blade prop, waited for
night
-> to fall, then put the airplane near a light on a building with the tail
-> facing the building. In the US AC power is supplied at 60HZ so if my tach
-> is accurate, the blade with the tape will appear to stop at multiples of 60.
-> So I tried 1200, and 1800 RPM and discovered that, just as my tach was
-> placarded, my tach was off by 100 RPM. The prop appeared to stop at
1100
-> and 1700 RPM. If Canada is 50Hz then just use multiples of 50. Some
-> mechanic placarded my tach as reading 100RPM low and my test
confirmed it.
->
-> Mike
-> 044SR
->
-> -----Original Message-----
-> From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
-> Rebflyer@aol.com
-> Sent: Monday, August 28, 2006 4:45 AM
-> To: rebel-builders@dcsol.com
-> Subject: [rebel-builders] New Prop
->
-> Hi all,
-> Well it's time to admit I have now purchased prop #3. I vowed in the
-> beginning that I would not do that, but here I am anyway.
-> Short history is this. When first certified I installed a McCauley 76".
-> Great prop on wheels. It spun at about 2300 rpm on initial roll. I felt it
-> was
-> to coarse a pitch for the floats and it could not be repitched any more.
-> Then
-> came the Warp drive 3 blade sq tip 72". I really enjoyed that prop. I flew
-> that for almost 300 hrs prior to the cracks in the blade clamping area.
-> Pitched
-> for 2300 rpm on the initial roll it was a bit slow off the water for my
-> liking, but cruise ok. (as a side note, each 10 rpm change seemed to
relate
-> to 1
-> mph). Pitched for 2450 on the initial roll it smoked off the water,
-> especially light with cool temps( 60ish f) but 85mph for cruise.
-> I shipped the prop and hub back to Warp. For the cost of 1 blade they
-> sent
-> me a new hub and 4 blades. 70" sq tip. The performance from the 3 to
the 4
->
-> is the same as far as I could tell.
-> The rpm range on the Warps was about 600 rpm. More to come on this.
-> Well after waiting for 8 mo I now have a three blade 68" 46 pitch Catto
-> prop. Very well known in the canard community for speed and durability. I
-> figured if it can take nuts, bolts and exhaust systems going thru the prop
-> without
-> catastrophic failure it should do fine on the front of a float plane.
-> After several conversations with Catto the numbers based on the engine
-> I'm
-> using and the hp it produces I decided on 2450 for the initial roll with
-> 125mph cruise at full throttle. 2750 rpm.
-> We hit those numbers right on the money. At 2450 it comes of the
water in
->
-> 90 deg f like the Warp did in 60 deg f !!! I can't wait till it gets cool
-> again! Cruise at full throttle shows 2775. 300 rpm range. I think I need to
->
-> check my tack(grin). Again in 90 deg f temps I'm indicating 115mph. That's
-> the
-> fastest I've been on floats. At 2500 it is very close to 100mph. We also
-> shot
-> for that number and hit it right on!
-> Out of all the differences between the props the one that I cannot put a
-> number to, but the seat of my pants and the size of the trees on the
-> shoreline
-> attest to, is when the floats break water this prop really keeps pulling.
-> Hard!
-> And last but not least unlike the warps It looks like a real prop!
-> So at this time the only complaint I have is the wait I had for the prop.
->
-> It is better than I hoped for in performance!
-> Cost? 1775.00
-> More to come, but I'm going flying, so see ya later!
-> Curt N97MR
->
->
->
->
->
-> -----------------------------------------------------------------
-> List archives located at: https://www.dcsol.com/login
-> username "rebel" password "builder"
-> Unsubscribe: rebel-builders-unsubscribe@dcsol.com
-> List administrator: mike.davis@dcsol.com
-> -----------------------------------------------------------------
->
->
->





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