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Metal Prop vs. Wood Prop



 
 
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  #1  
Old September 21st 03, 12:21 AM
Larry Smith
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Default Metal Prop vs. Wood Prop

I have a wood prop on my Taylorcraft and the GPS says it's slow, at around
65 kts. How about a discussion on the relative merits of wood and aluminum
props. I understand that wood is easier on your engine but the aluminum
prop is more efficient. Another thing I notice too, especially on the
O-320 and O-360-powered RV's is that the wood prop is so light it has little
flywheel effect and if you don't have your timing retarded, it will kick
back in a heartbeat. I figure the wood prop on a Van's aircraft is for CG.

I think what I'll do is buy an aluminum prop and try it for a while. I
couldn't keep up with a DCO-75 last week and it was a little embarrassing,
since his engine was sick. But he had an aluminum prop.


  #2  
Old September 21st 03, 12:39 PM
Barnyard BOb --
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One simple improvement you can make is to clean the prop and give it
some polish. It really is the most critical aerofoil on your aircraft
and should be kept clean and smooth.


Stealth Pilot

++++++++++++++++++++++++++++++++++++++++++++++++

MIRROR FINISHED POLISHED PROPS

It is being rumored here in Kansas City, USA, that the local FAA
is taking a very dim view concerning polished props. Unless the
prop comes that way from the manufacturer.... it's considered a
modification requiring an STC - Supplemental Type Certificate.

Barnyard BOb -- what next?
  #3  
Old September 21st 03, 02:23 PM
Eric Miller
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"Barnyard BOb --" wrote in message
...
MIRROR FINISHED POLISHED PROPS

It is being rumored here in Kansas City, USA, that the local FAA
is taking a very dim view concerning polished props. Unless the
prop comes that way from the manufacturer.... it's considered a
modification requiring an STC - Supplemental Type Certificate.

Barnyard BOb -- what next?


Obviously, next you'll be require an A&P with IA to wash and wax your
airplaine.
And don't even think about cleaning the plexiglass!

Eric


  #4  
Old September 21st 03, 02:30 PM
Jan Carlsson
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The right metal propeller will make your plane go faster, climb better, but
just marginally compered to the right wood prop. (with this kind of draggy
planes) if you have a bad choosen propeller on now, you will pick up some
speed to the cost of extra fuel.

Every speed, RPM and power setting have its own optimal propeller diameter,
pitch, blade area.....
The diameter and pitch have the biggest influence on the performance One
inch on the diameter change the RPM as much as 2 inch pitch change.

A Climb prop should not turn faster then the redline with WOT during a climb
(Vy)
A Cruise prop should not turn faster then redline with WOT at your cruise
alt.
A Standard prop fall in between the two above!

A Cub or Champ with a A-65 or C-90 both have a 72"X42" as Standard prop
(wood) (the C-90 will be about 9 MPH faster at cruise, using 30% more fuel)

Jan Carlsson
www.jcpropellerdesign.com


To some extent it is nothing to do with the wood or aluminium that the
prop is made from.
More likely it is the pitch and diameter of the prop you have.

Diameter is set by ground clearance requirements, broadly speaking, so
you can look beyond tinkering there.

Propellor Pitch is what will directly affect the airspeed for any
given engine RPM. (that and the winds)

On the Aluminium props intended for the old Cessna 150 the typical
prop supplied has a 52" pitch.The standard climb prop was 48" pitch
and the standard cruise prop was 54" pitch. (all the same diameter)
You picked the prop to use depending on whether you wanted steep climb
outs, typical around the patch performance, or you were out for long
distance flying.

In your case you really need to find out what props (particularly
their pitch values) were certified for the design. You may actually
have the optimum for your aircraft already and improvements will only
be seen by changing aircraft.

One simple improvement you can make is to clean the prop and give it
some polish. It really is the most critical aerofoil on your aircraft
and should be kept clean and smooth.
My own aircraft had a pretty grotty paint job on the prop when I
bought it, Cleaning this up and getting the surface finish nice and
smooth got me an immediate 4 knots improvement.
In my case the only improvement in cruise speed I can forsee is by
changing to a higher pitched prop.

If you cant garner an improvement buy a better camera and enjoy the
view, either that, or only fly in a tailwind.
Stealth Pilot




  #5  
Old September 21st 03, 04:16 PM
Larry Smith
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Default


"Jan Carlsson" wrote in message
...
The right metal propeller will make your plane go faster, climb better,

but
just marginally compered to the right wood prop. (with this kind of draggy
planes) if you have a bad choosen propeller on now, you will pick up some
speed to the cost of extra fuel.

Every speed, RPM and power setting have its own optimal propeller

diameter,
pitch, blade area.....
The diameter and pitch have the biggest influence on the performance One
inch on the diameter change the RPM as much as 2 inch pitch change.

A Climb prop should not turn faster then the redline with WOT during a

climb
(Vy)
A Cruise prop should not turn faster then redline with WOT at your cruise
alt.
A Standard prop fall in between the two above!

A Cub or Champ with a A-65 or C-90 both have a 72"X42" as Standard prop
(wood) (the C-90 will be about 9 MPH faster at cruise, using 30% more

fuel)

Jan Carlsson
www.jcpropellerdesign.com



Thanks for the link, Jan. I get 2100 rpm on static runup with a 72-42
Sensenich wooden climb prop. It will easily over-rev in straight and level
flight. Now what should I get static with a 72-44 prop? More or less?
Less, I would think. I haven't tried it on yet, but plan to just to see.
The engine has recently been rebuilt and so the old numbers, which were
lower at static, iirc, are no longer valid.


  #6  
Old September 21st 03, 04:55 PM
Jan Carlsson
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HI Larry,

I got about 2150 static and 2240 climbing at 60 MPH on a 72x42 wood
Cruise is 80-85 MPH 2150 rpm
The plane is a Champ 7AC 1945 (A-65)

The static rpm should not be under 1960 !

A metal might be a bit longer (73")

Jan Carlsson
www.jcpropellerdesign.com

A Climb prop should not turn faster then the redline with WOT during a

climb
(Vy)
A Cruise prop should not turn faster then redline with WOT at your

cruise
alt.
A Standard prop fall in between the two above!

A Cub or Champ with a A-65 or C-90 both have a 72"X42" as Standard prop
(wood) (the C-90 will be about 9 MPH faster at cruise, using 30% more

fuel)

Jan Carlsson
www.jcpropellerdesign.com



Thanks for the link, Jan. I get 2100 rpm on static runup with a 72-42
Sensenich wooden climb prop. It will easily over-rev in straight and

level
flight. Now what should I get static with a 72-44 prop? More or less?
Less, I would think. I haven't tried it on yet, but plan to just to see.
The engine has recently been rebuilt and so the old numbers, which were
lower at static, iirc, are no longer valid.




  #7  
Old September 22nd 03, 10:14 AM
Stealth Pilot
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Default

On Sun, 21 Sep 2003 06:39:37 -0500, Barnyard BOb --
wrote:


One simple improvement you can make is to clean the prop and give it
some polish. It really is the most critical aerofoil on your aircraft
and should be kept clean and smooth.


Stealth Pilot

+++++++++++++++++++++++++++++++++++++++++++++++ +

MIRROR FINISHED POLISHED PROPS

It is being rumored here in Kansas City, USA, that the local FAA
is taking a very dim view concerning polished props. Unless the
prop comes that way from the manufacturer.... it's considered a
modification requiring an STC - Supplemental Type Certificate.

Barnyard BOb -- what next?


I was referring to wooden props in my comments, though your point is
interesting re the 2025 props. if the anodised phlogiston spars (used
on RV's) have half the fatigue life of an alodined spar why is it that
props with an anodised finish dont seem to suffer a reduced fatigue
life?
beats me
Stealth Pilot

  #8  
Old September 22nd 03, 02:46 PM
Ed Wischmeyer
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Default

If the anodised phlogiston spars (used
on RV's) have half the fatigue life of an alodined spar



My newsreader doesn't get all the messages, so I may have missed the
antecedent referenced -- but what's the source that the anodized spars
have half the fatigue life? and why? Is that true in general, or only
for these spars?

thanks

Ed Wischmeyer
  #9  
Old September 22nd 03, 06:47 PM
Bob Kuykendall
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Earlier, Ed Wischmeyer wrote:

what's the source that the anodized spars
have half the fatigue life? and why? Is
that true in general, or only for these
spars?


http://www.matronics.com/rv-list/hov...s/AlAnDef.html

Search this page on "Fatigue." It references a 1991 RVator article by Van:

http://www.matronics.com/rv-list/hov...s/AlAnDef.html

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24
  #10  
Old September 23rd 03, 12:54 AM
Ed Wischmeyer
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Default

Bob Kuykendall wrote:

Earlier, Ed Wischmeyer wrote:

what's the source that the anodized spars
have half the fatigue life? and why? Is
that true in general, or only for these
spars?


http://www.matronics.com/rv-list/hov...s/AlAnDef.html


Thanks, Bob! Learned something new.

Ed Wischmeyer
 




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