VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > RV Firewall Forward Section > Propellers
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #51  
Old 03-11-2019, 11:35 PM
paul330 paul330 is offline
 
Join Date: Feb 2007
Location: Mpumalanga, South Africa
Posts: 1,027
Default

Quote:
Originally Posted by rv6ejguy View Post
Just another point of interest in this discussion about numbers of blades- the Phantom biplane racer at Reno gained over 30mph going to a 4 blade Paul Lipps design compared to the original 2 blade. Absolutely huge.

This shows that with proper design, more blades does not always have to be slower.

I submit that some of the 3 blade props available for RVs could be improved on.
Assuming the prop is properly designed and optimized for the aircraft.....

I believe the theory is that less blades are optimal because each blade has more time to clear the turbulent air from the previous blade sweep. This works up to the point where the blades cannot support the power of the engine. They either have to become too thick or too long or run too fast. Then you have to shift up to more blades to effectively absorb the power.

Because the RV-10 is a relatively fast aircraft with a powerful engine, I suspect that the 2 vs 3 blades argument is finely balanced.
__________________
Paul
Mercy Air, White River FAWV
RV-10 ZU-IIZ - "Zeus"
Building Bearhawk Bravo - RV-18 not available
2019 Donation Made
Reply With Quote
  #52  
Old 03-12-2019, 06:32 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,021
Default

Quote:
Originally Posted by paul330 View Post
Assuming the prop is properly designed and optimized for the aircraft.....

I believe the theory is that less blades are optimal because each blade has more time to clear the turbulent air from the previous blade sweep. This works up to the point where the blades cannot support the power of the engine. They either have to become too thick or too long or run too fast. Then you have to shift up to more blades to effectively absorb the power.

Because the RV-10 is a relatively fast aircraft with a powerful engine, I suspect that the 2 vs 3 blades argument is finely balanced.
At 150 knots, each blade describes its own helix through the air so no blade is in the turbulent air from the preceding one. Running up on the ground, yup, blades are in disturbed air.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 428.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


Reply With Quote
  #53  
Old 03-13-2019, 04:20 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,154
Default

Because I know none of us are patient, and I have not had the chance yet for side by side, same day same location tests yet, here is what we found yesterday.

Bare in mind this is subject to some validation, but nothing beats a side by side test, because that takes out a lot of variables.

Observation yesterday is at least 4 knots, I am edging towards 5 maybe 6. Certainly not 10 knots as someone originally was fearing.

Another observation (no real data here), but the take off distance I would have expected to be a bit shorter, but when flown from my home airfield, where markings are available for reference, it appeared to be the same. Maybe it felt quicker, but there ya go. Thats why data beats what it feels like every day.

As we know more I will share it, especially if we get a comparison with an almost identical air-conditioned plane we have that is two blade, that we do have on hand :-)
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #54  
Old 03-13-2019, 04:48 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,436
Default Thanks!

It's nice when the data agrees with the math!
__________________
Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues Paid 2018,...Thanks DR+
Reply With Quote
  #55  
Old 03-13-2019, 04:52 PM
tomww tomww is offline
 
Join Date: Jan 2015
Location: uk
Posts: 41
Default

I have the MT prop. My aircraft has two radios and two GPS antenna. But is generally fairly smooth apart from that. As long as she is clean and the air filter is clean with clean plugs etc she will almost meet the VANS performance numbers for top speed and for cruise. However the one area where she really impresses is the take off and climb. One up and lightly loaded she will easily hold 3000ft min climb. Fully loaded she will do over 2000ft min.

So I would agree with the general feeling that she is down a touch on top speed and maybe on cruise, but that's less easy to be sure of. However the performance benefit is great take off and fantastic climb.

Over all she is quite light and the prop helps with that of course. She is also smooth and quiet. These are less easy to quantify but people often mention how smooth she is, but that comes after amazement at the performance.

EDIT to add: If top speed is your priority then 2 blade is probably best. If climb is more important I would say go for the MT 3 blade. BUT ALL THIS IS SPLITTING HAIRS, THESE ARE ALL GREAT AIRCRAFT WHATEVER THE PROP.

Last edited by tomww : 03-13-2019 at 04:56 PM.
Reply With Quote
  #56  
Old 03-13-2019, 05:14 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,021
Default

Quote:
Originally Posted by rocketman1988 View Post
It's nice when the data agrees with the math!
Bob, can you show us those calcs? I'm most interested.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 428.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


Reply With Quote
  #57  
Old 03-13-2019, 05:58 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,436
Default Calcs

Actually in training for a new aircraft for the next four weeks but I will try and get a print out for you...
__________________
Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues Paid 2018,...Thanks DR+
Reply With Quote
  #58  
Old 03-13-2019, 07:02 PM
Michael Henning Michael Henning is offline
 
Join Date: Jun 2011
Location: Nashua, NH
Posts: 518
Default Cold

You can have my 3 blade prop when you pry it from my cold, dead hands. VNE at sea level, 4K fpm when light on a cold day, 170 knots abeam the numbers on the downwind, a 180 degree turn to the runway, and off at the first taxiway. Iíll give up the few extra knots at top speed because I would be over VNE anyways. 2350 Rpms, wot, 10,500 gives me 167 ktas, 7.8gph. Oh, it looks darn good just sitting there too.
__________________
Mike
RV-4 #2750
N654ML
IO-360
WW150C Prop
1018 lbs
Flying
Reply With Quote
  #59  
Old 03-15-2019, 05:38 PM
N49ex N49ex is offline
 
Join Date: Apr 2015
Location: Wheaton, Illinois
Posts: 42
Default Same plane comparison

To throw my 2 cents into this fray, here's my experience with a move from a 2 blade to a 3 blade on the same airplane. (Sorry, no MT info here though...)

- Engine - custom built balanced components I/O-390 210Hp
- Original 2 blade prop - Hartzell HC-E2YR-1B/7666A-2R (common on many Vans)
- New 3 blade - Harzell "Top Prop" scimitar HC-E3YR-1RF/F7392

Performance result - noticeable climb performance improvement, as expected, with the 3 blade AND (the big surprise) exactly the same cruise speed. So, this is a demonstration of how efficiency and design come to play - the scimitar 3 blade is apparently a significant design improvement over the older 7666 blades, compensating for the usual cruise performance reduction of a 3 blade. Interesting also was that the dynamic balance delivered some exciting news - 0.02"/sec. right out of the box, no balance weights required at all! Speaks well for both Hartzell and Lycoming. And I also have to heap praise on the Hatzell customer support. Since this was a Top Prop meant for a Commander, the spinner was wrong, and the customer support folks were incredible in finding me a spinner in their line that fit.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 11:28 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.