|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

12-13-2010, 10:39 PM
|
|
|
|
Join Date: Aug 2010
Location: Guthrie Oklahoma
Posts: 65
|
|
Take off RPM
What RPM's should I be seeing on take off? I just started flying my new 6 with an IO 320 airboat mod engine, fixed pitch wooden prop. Right now best I can do is 2,240 rpm on take off. Goes like stink when I get some altitude. I know I'm over pitched and the prop is going back for rework. Just need some ballpark figures on what I should expect when dialed in. Thanks! 
__________________
"Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the vote!"
Benjamin Franklin
|

12-14-2010, 12:48 AM
|
 |
|
|
Join Date: Jan 2005
Location: MKE
Posts: 1,519
|
|
A little more info is needed to make an informed comparison. What kind of prop/ what pitch do you have? At what point in the takeoff is the 2240? Static, start of t/o roll, after liftoff, etc. What kind of RPM do you get wide open, leaned for best power at 8000 feet? These are all important data points.
As a point of reference, 2240 static is about right for a fixed pitch RV, if that is what you are seeing.
__________________
Jeff Point
RV-6, RLU-1 built & flying
Tech Counselor, Flight Advisor & President, EAA Chapter 18
Milwaukee
|

12-14-2010, 06:38 AM
|
 |
|
|
Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
|
|
Sounds like you're in the ballpark, Joe
....our -6A turned 2200 with Catto's three blade and turned 2760 wide open for a near 200 MPH true.
Best,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
|

12-14-2010, 07:56 AM
|
|
|
|
Join Date: Nov 2006
Location: Albuquerque
Posts: 297
|
|
same here..
2200 -2250 is about what I get with my wood cruise prop & 150 HP engine.
I'm overpitched but I am going to withhold final judgement until I get my
wheel fairing on.
Dave
-9A flying
|

12-14-2010, 08:53 AM
|
 |
been here awhile
|
|
Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
|
|
Quote:
Originally Posted by 1Oldguy
What RPM's should I be seeing on take off? I just started flying my new 6 with an IO 320 airboat mod engine, fixed pitch wooden prop. Right now best I can do is 2,240 rpm on take off. Goes like stink when I get some altitude. I know I'm over pitched and the prop is going back for rework. Just need some ballpark figures on what I should expect when dialed in. Thanks! 
|
Don't touch that prop!
You are most likely right in the middle of the sweet spot, the ideal combination of climb and cruise performance. I see 2270 at rotation with my RV-6 (O-320, FP Sensenich).
The low takeoff rpm is a little startling to someone whose experience is with fixed-pitch 172's, etc. There is a huge gap between stall speed and cruise on our planes, and the steep pitch is necessary to prevent the engine from overspeeding at max cruise. Makes our planes go fast, too! 
Last edited by Sam Buchanan : 12-14-2010 at 08:56 AM.
|

12-14-2010, 09:15 AM
|
|
|
|
Join Date: Dec 2006
Location: Arroyo Grande, CA
Posts: 938
|
|
Some propellers have an unusual characteristic that the rpm will be higher at the start of the take-off run, and as they pick up speed, the rpm will drop 50-150 rpm, then be back at the same rpm as when they started. This is due to the inner part of the blade being past stall AOA and not generating as much lift. This means its induced "drag", a measure of its torque load, is not as much and so the rpm goes up. Then when the forward speed increases, the blade will come un-stalled, absorbing more engine power.
|

12-14-2010, 11:41 AM
|
 |
|
|
Join Date: Nov 2006
Location: Oklahoma
Posts: 672
|
|
Quote:
Originally Posted by 1Oldguy
What RPM's should I be seeing on take off? I just started flying my new 6 with an IO 320 airboat mod engine, fixed pitch wooden prop. Right now best I can do is 2,240 rpm on take off. Goes like stink when I get some altitude. I know I'm over pitched and the prop is going back for rework. Just need some ballpark figures on what I should expect when dialed in. Thanks! 
|
Joe,
Tell these guys a bit more about your airplane. What top speed you are seeing? Also, they should know about the interesting build background. This is one special airplane. Trust me! Post some pics!
Congrats on the first flight!
The other Joe
__________________
Joe Schneider
RV-7, IO-360, BA Hartzell, N847CR
Flying since 2008
|

12-14-2010, 07:52 PM
|
|
|
|
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
|
|
Quote:
Originally Posted by elippse
Some propellers have an unusual characteristic that the rpm will be higher at the start of the take-off run, and as they pick up speed, the rpm will drop 50-150 rpm, then be back at the same rpm as when they started. This is due to the inner part of the blade being past stall AOA and not generating as much lift. This means its induced "drag", a measure of its torque load, is not as much and so the rpm goes up. Then when the forward speed increases, the blade will come un-stalled, absorbing more engine power.
|
Thanks for that bit of information.
It explains what is going with my prop in that it turns nearly 2200 static and stays that way up to about 110 knots. I never understood why rpm isn't increasing as speed builds up on the roll.
What you say makes perfectly good sense.
__________________
RV-12 Build Helper
RV-7A...Sold #70374
The RV-8...Sold #83261
I'm in, dues paid 2019 This place is worth it!
|

12-17-2010, 09:42 AM
|
|
|
|
Join Date: Jul 2008
Location: Camas, WA
Posts: 481
|
|
Light bulb.... <BG>
This explains what I've been seeing... Happens pretty quick though...
DM
RV-4 MT F/P Prop.
Quote:
Originally Posted by elippse
Some propellers have an unusual characteristic that the rpm will be higher at the start of the take-off run, and as they pick up speed, the rpm will drop 50-150 rpm, then be back at the same rpm as when they started. This is due to the inner part of the blade being past stall AOA and not generating as much lift. This means its induced "drag", a measure of its torque load, is not as much and so the rpm goes up. Then when the forward speed increases, the blade will come un-stalled, absorbing more engine power.
|
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 12:54 AM.
|