If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
"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
|
|||
|
|||
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
|
|||
|
|||
"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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Right prop, wrong prop? Wood prop, metal prop? | Gus Rasch | Aerobatics | 1 | February 14th 08 10:18 PM |
Direction of warping wood? | BllFs6 | Home Built | 2 | September 1st 03 10:52 AM |
Homebuilt Aircraft Frequently Asked Questions (FAQ) | Ron Wanttaja | Home Built | 4 | August 7th 03 05:12 AM |
Homebuilt Aircraft Frequently-Asked Questions (FAQ) | Ron Wanttaja | Home Built | 0 | July 4th 03 04:50 PM |