|
-
POSTING RULES

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

04-21-2006, 12:36 PM
|
 |
Senior Curmudgeon
|
|
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
|
|
Crude but simple analogy----------------imagine a car with only one forward gear in the transmission--------you have to use it for acceleration, cruse, hill climbing, and top speed. Now think how much better the 4,5,or 6 speed you drive is.
Mike
|

04-21-2006, 01:38 PM
|
|
|
|
Join Date: Jan 2005
Location: Kirland, WA
Posts: 200
|
|
Mel:
Thanks for the note about glide and stopped prop. I'm going to play with that this weekend. My engine out emergency proceedures have me pull to coarse pitch but not to stop the prop. Can't recall an engine out procedure on any airplane telling me to stop the windmilling.
Is the effect dramatic? If it's the area ratio of the full disk to just the prop it sounds like it would be very large.
Chuck
|

04-21-2006, 01:58 PM
|
|
|
|
Join Date: May 2005
Location: Utah
Posts: 274
|
|
"...During the same RV-4 flight we bumped the speed up to 175 mph indicated. The RPM was nudging 2600 at this point. It was obvious the airplane wanted to go faster but the engine RPM was getting into the limiting range."
Serious question: If the engine/prop were able to safely spin faster, to say 3200 rpm assuming the tips stay less than sonic speed, is your argument still valid?
__________________
Mike Parker
RV-9a under construction
w/Mazda rotary- Renesis
|

04-21-2006, 02:29 PM
|
 |
|
|
Join Date: Jul 2005
Location: Clearwater, FL
Posts: 287
|
|
What about Maint?
One thing I'm not seeing mentioned here is prop maint.
I don't know much about which prop uses more or less fuel. However the issue of a constant speed saving enough fuel in 2000 hours has too many variables. For example if the CS costs 6K more than the FP than you would have to save $3 an hour in fuel pay for the differance. This does not take into account the cost for overhaul. Most planes never make it to TBO before the prop reaches the reccomended overhaul based on age.
Lets face it a CS prop and gov overhaul is much more costly than a FP service.
Also what about insurance? I havn't checked into this and it may not even be a factor. Do insurance companies charge more or less depending on what prop?
I'm not taking either side here. Just giving some food for thought.
__________________
Bruce Smith
Clearwater, FL
RV-7A Fuse
N27DB reserved
web.tampabay.rr.com/flrv7a
"Political correctness is tyranny with manners."
Charlton Heston
|

04-21-2006, 02:58 PM
|
 |
|
|
Join Date: Mar 2005
Location: Dallas area
Posts: 10,769
|
|
The increase in glide is pretty dramatic, but stopping the prop is not usually practical. If the prop has lost some mass or is out of balance causing a lot of vibration, then yes, stop the prop if you can. Otherwise, to stop the prop usually requires almost stalling the airplane. You already have a problem. Don't push for another one.
Mel...DAR
|

04-21-2006, 08:28 PM
|
|
|
|
Join Date: Apr 2005
Posts: 129
|
|
200HP RV-4, fixed pitch, 170 MPH 1700 FPM climb...the only thing a CS would benefit me is slowing this darn thing down on landing, and with aerobatics...the climb performance is fine for me.
|

04-21-2006, 08:48 PM
|
|
|
|
Join Date: Jan 2005
Location: SoCal
Posts: 2,061
|
|
Fixies Unite! 
__________________
Steve Zicree
Fullerton, Ca. w/beautiful 2.5 year old son 
RV-4 99% built  and sold 
Rag and tube project well under way
paid =VAF= dues through June 2013
|

04-21-2006, 11:29 PM
|
|
|
|
Join Date: Feb 2005
Location: Apollo Beach, FL
Posts: 10
|
|
care to guess?
Quote:
|
Originally Posted by pbesing
200HP RV-4, fixed pitch, 170 MPH 1700 FPM climb...the only thing a CS would benefit me is slowing this darn thing down on landing, and with aerobatics...the climb performance is fine for me.
|
Assuming a limited amount of capital to invest - does anyone want to guess at the climb rates of say, a 160 HP CS vs maybe a 210 HP fixed set up for max cruise? In other words, where should I put my first "extra" $6K?
Newbee w/ -7 plans, but still thinking about the -8
|

04-22-2006, 12:36 AM
|
|
|
|
Join Date: Apr 2006
Posts: 22
|
|
Quote:
|
Originally Posted by B. Hoover
Assuming a limited amount of capital to invest - does anyone want to guess at the climb rates of say, a 160 HP CS vs maybe a 210 HP fixed set up for max cruise? In other words, where should I put my first "extra" $6K?
Newbee w/ -7 plans, but still thinking about the -8
|
Personally I would say put in the prop. Increase in speed will be at the cube root of the added power, which is not a good return on $$, not even factoring in added weight. Increasing prop performance seems to be a good idea unless you intend to fly mostly at the optimum speed your FP is configured for (i.e. cruise). If that is the case invest the money instead, or buy snazzier avionics. From what I have read, it is a personal preference question where it would be nice to have C/S but is it worth it based on your intended flying.....
Advice from one who has never flown an RV....
You know what they say about advice!
I don't have an ore in the water on this race, so I think I am fairly objective.
__________________
Ward Johnson
RV-??/Pre-empennage
Germantown, Tn.
Last edited by Rosie : 04-25-2006 at 11:39 PM.
Reason: Fixed quote
|

04-22-2006, 06:10 AM
|
 |
|
|
Join Date: Jan 2005
Location: NC25
Posts: 3,508
|
|
Quote:
|
Originally Posted by wingtime
One thing I'm not seeing mentioned here is prop maint.
I don't know much about which prop uses more or less fuel. However the issue of a constant speed saving enough fuel in 2000 hours has too many variables. For example if the CS costs 6K more than the FP than you would have to save $3 an hour in fuel pay for the differance. This does not take into account the cost for overhaul. Most planes never make it to TBO before the prop reaches the reccomended overhaul based on age.
Lets face it a CS prop and gov overhaul is much more costly than a FP service.
Also what about insurance? I havn't checked into this and it may not even be a factor. Do insurance companies charge more or less depending on what prop?
I'm not taking either side here. Just giving some food for thought.
|
I hit 1,842 hours last weekend. My CS prop has cost around $15 for maintenance over the 8.5 years I have been flying. I am on my second tube of grease. My insurance is $311 per year for $1 Million coverage through NationAir. Am expecting an increase this year.
I do NOT want an RV without a constant speed prop. Ken Scott once said that you can only get 85% of the performance out of an RV without the constant speed prop.
There is a fuel savings enough to more than pay for the constant speed prop. See another post that I have in the forums that show it will pay for itself and the overhaul costs over it life time.
Gary A. Sobek
|
| 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 07:07 AM.
|